- Email: [email protected]
Tubular aggregates in autoimmune Lambert–Eaton myasthenic syndrome
Accepted Manuscript Title: Tubular aggregates in autoimmune Lambert-Eaton myasthenic syndrome Author: Isabell Cordts, Fabian Funk, Jörg B. Schulz, Joachim Weis, Kristl G. Claeys PII: DOI: Reference:
S0960-8966(16)30253-X http://dx.doi.org/doi: 10.1016/j.nmd.2016.09.011 NMD 3255
To appear in:
Neuromuscular Disorders
Received date: Revised date: Accepted date:
22-5-2016 31-8-2016 12-9-2016
Please cite this article as: Isabell Cordts, Fabian Funk, Jörg B. Schulz, Joachim Weis, Kristl G. Claeys, Tubular aggregates in autoimmune Lambert-Eaton myasthenic syndrome, Neuromuscular Disorders (2016), http://dx.doi.org/doi: 10.1016/j.nmd.2016.09.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Tubular aggregates in autoimmune Lambert-Eaton myasthenic syndrome
Isabell Cordtsa,b, Fabian Funkb,c, Jörg B. Schulza,d, Joachim Weisb, Kristl G. Claeysa,b,e
a
Department of Neurology, RWTH Aachen University, Aachen, Germany
b
c
Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
Department of Internal Medicine, Sankt Marien-Hospital Düren, Düren, Germany
d
JARA - Translational Brain Medicine, JARA Brain Institute II, FZ Jülich and RWTH,
Aachen, Germany e
Department of Neurology, University Hospitals Leuven and University of Leuven (KU
Leuven), Leuven, Belgium
E-mail addresses of authors: [email protected] [email protected] [email protected] [email protected] [email protected]
Corresponding author: Prof. Dr. Kristl G. Claeys, MD PhD Department of Neurology University Hospitals Leuven and University of Leuven (KU Leuven) Herestraat 49 3000 Leuven
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Belgium Phone: +32 16 34 42 78 Fax: +32 16 34 42 85 E-mail: [email protected]
ABBREVIATIONS: AMPD A
adenosine monophosphate deaminase
ATPase
adenosine triphosphatase
CMAP
compound muscle action potential
CMS
congenital myasthenic syndrome
COX
cytochrome oxidase
GT
Gomori’s trichrome
HE
hematoxylin and eosin
NADH-TR nicotinamide adenine dinucleotide-tetrazolium reductase RNS
repetitive nerve stimulation
SDH
succinate dehydrogenase
VGCC
voltage-gated calcium channel
Highlights
Tubular aggregates can occur in diverse hereditary and acquired disorders
Tubular aggregates have been described in muscles biopsies of hereditary myasthenic disorders
This is the first report about a patient with tubular aggregates and autoimmune LambertEaton myasthenic syndrome
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The diagnostic difficulties associated with the presence of tubular aggregates are demonstrated
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ABSTRACT: Tubular aggregates are accumulations of densely packed tubules in muscle fibers, occurring in distinct hereditary and acquired disorders. We present a patient with tubular aggregates and autoimmune Lambert-Eaton myasthenic syndrome. Initially, he showed mild proximal weakness, borderline decrement on 3 Hz stimulation, and slightly elevated creatine kinase. Muscle biopsy revealed tubular aggregates in type II fibers. Due to a good response to pyridostigmine, a limb-girdle myasthenia with tubular aggregates was suspected, but genetic analyses of GFPT1, DPGAT1, and ALG2 were normal. Two years later, the patient presented with progressive weakness and autonomic dysfunction. 17% decrement on 3 Hz stimulation and 100% increment after brief exercise were revealed. Autoantibodies to voltage-gated calcium-channels confirmed the diagnosis of Lambert-Eaton myasthenic syndrome. Steroids, azathioprine, and 3,4-diaminopyridine significantly improved symptoms. No tumor was found during follow-up. This is the first report about tubular aggregates associated with an acquired myasthenic syndrome. Our findings are important because of the therapeutic implications.
KEY WORDS: Lambert-Eaton myasthenic syndrome, muscle biopsy, acquired, tubular aggregates
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INTRODUCTION: Tubular aggregates are accumulations of densely packed membranous tubules within skeletal muscle fibers that are most probably derived from the sarcoplasmic reticulum [1]. They are the predominant histopathological finding in tubular aggregates myopathies, for which causative mutations in STIM1 or ORAI1 have recently been identified [2]. However, tubular aggregates can also occur in several hereditary disorders including congenital myasthenic syndromes (CMS) and in a variety of acquired conditions (Table 1). CMS associated with tubular aggregates include hereditary limb-girdle myasthenia with tubular aggregates caused by mutations in GFPT1, DPGAT1, or ALG2 [3] . Lambert-Eaton myasthenic syndrome is a rare acquired autoimmune myasthenic disorder caused by antibodies directed against presynaptic P/Q-type voltage-gated calcium channels (VGCC), leading to an impaired transmission across the neuromuscular junction. The condition can occur as a paraneoplastic syndrome, mostly associated with small cell lung carcinoma, or as an autoimmune disease without underlying tumor. Clinical characteristics are proximal muscle weakness and autonomic dysfunction. Repetitive nerve stimulation (RNS) in Lambert-Eaton myasthenic syndrome usually shows a low compound muscle action potential (CMAP), a decrement >10% with stimulation at low frequency (1-5 Hz), and an increment >100% after maximum voluntary contraction or with high stimulation frequencies (50 Hz) [4]. Here, we present for the first time the occurrence of tubular aggregates in the muscle of a patient with an acquired myasthenic syndrome. We highlight the diagnostic difficulties associated with the presence of tubular aggregates in the muscle biopsy.
CASE REPORT:
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The 36-year-old Portuguese man presented with a five-month history of non-fluctuating exercise-induced proximal weakness of both upper and lower limbs. He complained of difficulties to climb stairs. Myalgia, cramps, or stiffness as well as sensory, bulbar, or autonomic symptoms were denied. Due to struma nodosa, he underwent a thyroidectomy at the age of 34 years and has since then been treated with L-thyroxine. Family history for neurologic and neuromuscular disorders was negative. The endurance test in which the lower limbs are maintained above the bed plane while lying on the back was abnormal (60 s, normal 75 s). Further neurological examination was normal, including muscle strength and tone, deep tendon reflexes, and sensory testing. In particular, there was no evidence for extraocular muscle dysfunction or bulbofacial weakness. Serum analysis showed slightly elevated creatine kinase levels (281 U/l, normal <190). Antibodies against acetylcholine receptor and muscle-specific receptor tyrosine kinase in serum were both negative. Nerve conduction velocity studies and electromyography were normal. 3 Hz RNS of the ulnar and accessory nerves, recorded at the abductor digiti minimi and trapezius muscle, induced a 9% and 11% borderline decrease of CMAP, respectively. The amplitudes for resting CMAP were normal and no increment after 10s of maximum voluntary muscle contraction was detected. A chest computed tomography scan as well as magnetic resonance imaging of the brain and spinal cord revealed no abnormalities. Due to the inconclusive findings, an open muscle biopsy of the right vastus lateralis muscle was performed and processed according to standard procedures [5], after obtaining the patient’s written informed consent. Light microscopy revealed the presence of inclusions that stained dark blue on nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR), red on modified Gomori’s trichrome (GT), and blue on adenosine monophosphate deaminase (AMPDA) stains, compatible with tubular aggregates (Figure 1). The aggregates appeared basophilic on hematoxylin and eosin (HE) and red-brown on esterase stains, and showed a
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positive reaction for periodic acid Schiff and acid phosphatase (Figure 1). Although the inclusions stained dark blue on succinate dehydrogenase (SDH), they only partially reacted on cytochrome-c-oxidase (COX) (Figure 1G-1H). Adenosine triphosphatase (ATPase) staining at pH 4.2 and 9.4 confirmed that the aggregates were present exclusively in type 2 muscle fibers. Tubular aggregates were distributed unevenly across the biopsy and were present in approximately 4% of the muscle fibers. The biopsy showed a slightly increased variation in fiber size diameter. The number of internalized nuclei was not increased. Fibrotic, necrotic, neurogenic, or inflammatory changes were not present. No ragged red fibers or COXnegative/SDH-positive muscle fibers were detected. Electron microscopy confirmed the inclusions to be tubular aggregates (Figure 1I-1J). They were located underneath the sarcolemma or between the myofibrils. The diameter of tubular aggregates varied from 1 to 114 µm and the tubules showed diameters ranging from 40 to 160 nm. Some tubules appeared empty, while others contained amorphous material or a smaller inner core. Few tubules were connected with filaments. A small number of vacuoles, which might be derived from sarcoplasmic reticulum, were present, most of them located nearby the tubular aggregates. The nuclei, mitochondria, and myofibrillar organization showed no abnormalities and the size and amount of lipid droplets and glycogen were normal. A few normal isolated (no aggregation of) mitochondria were present around the tubular aggregates, but not inside them. No lysosomes were identified among or around the tubular aggregates. Considering all clinical and paraclinical findings, a genetic limb-girdle myasthenia with tubular aggregates was primarily suspected, but molecular genetic analyses of the GFPT1, DPGAT1, and ALG2 genes did not reveal abnormalities. However, a therapy with pyridostigmine resulted in a significant amelioration of exercise-induced weakness. Two years later, the patient consulted again because of progressive fluctuating proximal muscle weakness with tendency to fall. He also complained of erectile problems, dry mouth,
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episodic dysarthria, and dysphagia. Neurological examination revealed prolonged swallowing of 100 ml water (9.65 s, normal < 8 s), but was further normal, including endurance tests of the proximal muscles in the four limbs at the time of examination. In particular, no postexercise facilitation of muscle strength was observed at the time of examination. The electrophysiological examination was repeated and stimulation of the ulnar nerve with recording at abductor digiti minimi muscle showed a reduced resting CMAP (3.4 mV, normal >8 mV), a 17% decrement of CMAP amplitude on 3 Hz RNS, and an almost 100% increment after 10s of maximum voluntary contraction. Serological tests disclosed the presence of antibodies directed against P/Q-type VGCC (111.5 pmol/l, normal <40). Based on the clinical, electrophysiology, and laboratory results, the diagnosis of Lambert-Eaton myasthenic sydrome was established. An extensive search for other acquired and genetic causes of tubular aggregates revealed no abnormalities (Table 1, genetic analysis: CeGat, Tübingen, Germany). Both immunosuppressive treatment with steroids and azathioprine and symptomatic therapy with 3,4-diaminopyridine and pyridostigmine were initiated. Due to side effects, steroids and pyridostigmine were discontinued. Shortly after medication was started, the patient no longer suffered from proximal muscle weakness or dysphagia and experienced an amelioration of autonomous symptoms. Serum antibodies directed against P/Q-type VGCC normalized. A yearly performed tumor screening up to 5 years after diagnosis disclosed no malignancy.
DISCUSSION: Although tubular aggregates have been described in association with several hereditary myasthenic disorders, this is the first report to our knowledge about the presence of tubular aggregates in a patient with an acquired myasthenic syndrome. Usually a muscle biopsy is not performed in patients with an acquired myasthenic disorder or Lambert-Eaton myasthenic syndrome in particular, especially if the presentation is unambiguous. However, in our
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patient, the clinical presentation at onset was very mild and only non-significant changes were noted at the electrophysiological examination. The finding of tubular aggregates in the patient’s muscle tissue and the multiplicity of hereditary disorders and acquired conditions in which tubular aggregates can occur (Table 1) further contributed to the diagnostic difficulties as demonstrated in our case. Our findings are of particular importance because of the therapeutic possibilities in Lambert-Eaton myasthenic syndrome. All causes of tubular aggregates known so far were excluded in our patient (Table 1), amongst them several hereditary myopathies, multisystemic diseases and different acquired conditions. Tubular aggregates are also reported in familial and sporadic cases of “pure” tubular aggregate myopathies, characterized by the absence of any other underlying disease and presenting tubular aggregates as the main structural pathology on muscle biopsy [6]. In our patient, a genetic analysis of STIM1 and ORAI1 revealed no abnormalities and taken together with the negative family history, the presence of a coincident autosomal dominant (primary) tubular aggregate myopathy, caused by a so far unknown gene, is less probable, but not completely excluded. Tubular aggregates are characterized by defined histochemical and ultrastructural changes. In our patient, the enzymatic reactions typical for tubular aggregates were evident, such as an intense staining on NADH-TR, AMPD, and GT. Interestingly, the tubular aggregates stained strongly on SDH and partially on COX, suggesting the participation of mitochondria or mitochondrial proteins in tubular aggregates. The derivation of tubular aggregates from sarcoplasmic reticulum is widely accepted due to their continuity with sarcoplasmic reticulum membranes [1] and immunochemical evidence of sarcoplasmic reticulum proteins in tubular aggregates [6, 7], but opinions about the participation of mitochondria in tubular aggregates differ largely. While a few studies demonstrated a positive reaction of tubular aggregates on SDH [6] or COX [8, 9], in other studies this observation has not been confirmed [10]. An
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immunohistochemical study in mice disclosed antibodies against the bc1 complex, a protein of the inner mitochondrial membrane, with strong signals in the formation of tubular aggregates, indicating that tubular aggregates may emerge not only from sarcoplasmic reticulum but also from mitochondria [11]. Funk et al. showed that tubular aggregates have a positive reaction for the anti-SDH/IP antibody, demonstrating the presence of this complex II component in tubular aggregates [6]. Apart from mitochondrial participation there might be another explanation for the positive staining of tubular aggregates on SDH and COX, such as a diffusion of mitochondrial enzymes into tubular aggregates or a nonspecific enzymatic reaction, misinterpreted as mitochondrial enzymatic activity [6]. The function and physiological significance of tubular aggregates have not been clarified yet. Several hypotheses about the mechanisms responsible for inducing tubular aggregate formation exist. Salviati et al. suggested tubular aggregates to have a compensating function in damaged muscle fibers due to their ability to sequester calcium [7]. Thus, the aggregates may represent an adaptive response to increased intracellular calcium flux in order to prevent muscle fibers from hypercontraction and necrosis. Schiaffino proposed that tubular aggregates are a special type of protein aggregates caused by misfolding and aggregation of sarcoplasmic reticulum membrane proteins comparable to those in neurodegenerative diseases [12]. In analogy, other authors suggested that mutations in the CMS-associated genes GFPT1 and DPAGT1, that encode proteins required for efficient glycosylation, lead to formation of tubular aggregates due to an altered protein glycosylation with consequential protein misfolding and aggregation in sarcoplasmic reticulum [13]. However, in other CMS, including limb-girdle CMS caused by mutations in DOK7, tubular aggregates are not present in muscle biopsies [3]. Hence, tubular aggregates in CMS do probably not arise as a result of impaired neuromuscular transmission. Considering the large variety of conditions that can be associated with tubular aggregates (Table 1), we hypothesize that the formation of tubular
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aggregates might rather be a general and nonspecific muscle response in our patient with Lambert-Eaton myasthenic syndrome. We conclude that the presence of tubular aggregates in the muscle biopsy should trigger consideration of the diagnosis of Lambert-Eaton myasthenic syndrome.
ACKNOWLEDGEMENTS: We thank the patient for participating in our study. We are grateful for the technical and administrative personnel at the Institute of Neuropathology and the Department of Neurology of the University Hospital Aachen for their support. K.C. received grants of the Deutsche Gesellschaft für Muskelkranke (DGM) e.V. for projects unrelated to this study.
REFERENCES:
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[1]
Engel WK, Bishop DW, Cunningham GG. Tubular aggregates in type II muscle fibers: Ultrastructural and histochemical correlation. J. Ultrastruct. Res. 1970;31:507525.
[2]
Lacruz RS, Feske S. Diseases caused by mutations in ORAI1 and STIM1. Ann. N. Y. Acad. Sci. 2015;1356:45-79.
[3]
Engel AG, Shen X-M, Selcen D, Sine SM. Congenital myasthenic syndromes: pathogenesis, diagnosis, and treatment. The Lancet Neurology 2015;14:420-434.
[4]
Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011;10:1098-1107.
[5]
Dubowitz V, Sewry CA, Oldfors A, Lane RJ, Muscle Biopsy: A Practical Approach, Expert Consult; Online and Print, 4: Muscle Biopsy: A Practical Approach. 2013: Elsevier Health Sciences.
[6]
Funk F, Ceuterick-de Groote C, Martin JJ, et al. Morphological spectrum and clinical features of myopathies with tubular aggregates. Histol. Histopathol. 2013;28:10411054.
[7]
Salviati G, Pierobon-Bormioli S, Betto R, et al. Tubular aggregates: sarcoplasmic reticulum origin, calcium storage ability, and functional implications. Muscle Nerve 1985;8:299-306.
[8]
Meijer AEFH. Histochemical features of tubular aggregates in diseased human skeletal muscle fibres. J. Neurol. Sci. 1988;86:73-82.
[9]
Lewis PD, Pallis C, Pearse AGE. “Myopathy” with tubular aggregates. J. Neurol. Sci. 1971;13:381-388.
[10]
Pavlovicova M, Novotova M, Zahradnik I. Structure and composition of tubular aggregates of skeletal muscle fibres. Gen. Physiol. Biophys. 2003;22:425-440.
Page 12 of 19
13
[11]
Novotová M, Zahradník I, Brochier G, Pavlovičová M, Bigard X, Ventura-Clapier R. Joint participation of mitochondria and sarcoplasmic reticulum in the formation of tubular aggregates in gastrocnemius muscle of CK–/– mice. Eur. J. Cell Biol. 2002;81:101-106.
[12]
Schiaffino S. Tubular aggregates in skeletal muscle: just a special type of protein aggregates? Neuromuscul. Disord. 2012;22:199-207.
[13]
Belaya K, Finlayson S, Slater CR, et al. Mutations in DPAGT1 cause a limb-girdle congenital myasthenic syndrome with tubular aggregates. Am. J. Hum. Genet. 2012;91:193-201.
[14]
Fleury M, Barbier R, Ziegler F, et al. Myopathy with tubular aggregates and gyrate atrophy of the choroid and retina due to hyperornithinaemia. J. Neurol. Neurosurg. Psychiatry 2007;78:656-657.
[15]
Oh SJ, Park K-S, Ryan HF, et al. Exercise-induced cramp, myoglobinuria, and tubular aggregates in phosphoglycerate mutase deficiency. Muscle Nerve 2006;34:572-576.
[16]
Niakan E, Harati Y, Danon MJ. Tubular aggregates: their association with myalgia. J. Neurol. Neurosurg. Psychiatry 1985;48:882-886.
[17]
Stamboulis E, Manta P, Kararizou E, Grivas I. Whipple's disease with tubular aggregates in asymptomatic muscle. Clin. Neuropathol. 1993;12:121-124.
[18]
Gallai M. Myopathy with hyperaldosteronism. An electron-microscopic study. J. Neurol. Sci. 1977;32:337-345.
[19]
Hurwitz LJ, Carson AJ, Allen IV, Fannin TF, Lyttle JA, Neill DW. Clinical, biochemical and histopathological findings in a family with muscular dystrophy. Brain 1967;90:799-816.
Page 13 of 19
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[20]
Miike T, Ohtani Y, Tamari H, Ishitsu T, Nonaka I. An electron microscopical study of the T-system in biopsied muscles from fukuyama type congenital muscular dystrophy. Muscle Nerve 1984;7:629-635.
[21]
Doriguzzi C, Mongini T, Jeantet A, Monga G. Tubular aggregates in a case of osteomalacic myopathy due to anticonvulsant drugs. Clin. Neuropathol. 1984;3:4245.
[22]
Palmucci L, Doriguzzi C, Anzil AP. Myopathy with tubular aggregates in a patient adrenalectomized for Cushing's syndrome. J. Neurol. 1985;232:374-377.
[23]
Riggs JE, Schochet SS, Jr, Gutmann L. Tubular aggregates in skeletal muscle associated with neoplastic disease. Arch. Neurol. 1990;47:382-383.
[24]
Chariot P, Benbrik E, Schaeffer A, Gherardi R. Tubular aggregates and partial cytochrome c oxidase deficiency in skeletal muscle of patients with AIDS treated with zidovudine. Acta Neuropathol. 1993;85:431-436.
[25]
Gilchrist JM, Ambler M, Agatiello P. Steroid-responsive tubular aggregate myopathy. Muscle Nerve 1991;14:233-236.
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FIGURE CAPTIONS: Figure 1: Enzyme histochemical and ultrastructural features of tubular aggregates in muscle biopsy. A-E) Serial transverse sections through the muscle tissue showing tubular aggregates that are basophilic on HE (A), brownish on acid phosphatase (B), dark blue on NADH-TR (C), brownish in type 2 muscle fiber on ATPase at pH 4,2 (D) and red-brown on esterase (E) stains. F) Tubular aggregates staining dark blue on AMPDA. G-H) Another serial section from the same biopsy, showing tubular aggregates with dark blue staining on SDH (G), that only partially stain with COX (H). I-J) Ultrastructural pictures of tubular aggregates, showing tubules that contain amorphous material (I). Most tubular aggregates are shown in a transverse section (e.g. asterisk in I), however in one region (arrow in I), some longitudinally cut tubules are also visible. (J) Adjacent to a group of tubular aggregates, vacuoles are shown (example indicated with asterisk). Scale bars: A-H) 100 µm; I-J) 1 µm.
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Table 1: Disorders associated with tubular aggregates in human muscle biopsies (literature review) and investigations to exclude the respective condition in our patient.
Conditions
associated
with
tubular Diagnostic assessment in our patient
aggregates Tubular aggregate myopathy [2] Limb-girdle
myasthenia
Genetic analysis normal (STIM1, ORAI1)
with
tubular Genetic analysis normal (GFPT1, DPAGT1,
aggregates [3]
ALG2)
Gyrate atrophy of choroid and retina [14]
Clinical: normal vision
Periodic paralysis [1, 6]
Genetic analysis normal (CACNA1S, KCNE3, KCNJ2, KCNJ5, KJNJ18, SCN4A) Clinical: no paralytic attacks
Malignant hyperthermia [6]
Genetic
analysis
normal
(RYR1,
SCN4A,
CACNA1S) Clinical: no incidents with previous anesthesias Myotonic myopathy [6] , Myotonic dystrophy Genetic analysis normal (CLCN1) [15]
Clinical and EMG: no myotonia, no typical features
Glycogen
storage
diseases
metabolic myopathies [6]
and
other Alpha-glucosidase activity in blood normal Genetic analysis normal (PGAM2) Muscle
biopsy:
no
glycogen
or
lipid
accumulations CADASIL [6]
Brain MRI normal Clinical: no strokes, no headache
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Morbus Fabry [6]
Genetic analysis normal (GLA)
Mitochondrial disorders [6, 11]
Muscle biopsy: no mitochondrial abnormalities
Polyneuropathy [1, 6, 16]
NCV normal Clinical:
no
abnormalities
suggestive
for
polyneuropathy Alcoholic myopathy [6]
No alcohol abuse
Toxic / drug-induced myopathy [1, 6]
No relevant toxins/drugs
Diabetic amyotrophy [6]
Blood analysis: HbA1c normal
Polymyositis, dermatomyositis [6]
Muscle biopsy: no inflammatory infiltrates, no necroses, no perifascicular atrophy Blood analysis: no considerably increased CK, no myositis-associated/-specific antibodies
Porphyria cutanea tarda [1]
Clinical: no skin changes
Whipple’s disease [17]
Clinical: no gastrointestinal symptoms
Hyperaldosteronism [18]
Blood analysis: no elevated aldosterone
Amyotrophic lateral sclerosis [16]
Clinical: no upper and/or lower motor neuron signs, no progressive disease
Facioscapulohumeral
muscular
dystrophy Clinical: no manifestation in face and shoulder
[19]
region, no typical features
Lupus erythematosus [16]
Clinical: no abnormalities of skin or internal organs Blood analysis: no inflammation parameters, ANA negative, no cytopenia
Muscle infarction [9]
Clinical: no acute episode with pain and swelling
Fukuyama congenital muscular dystrophy Clinical: no congenital onset, no typical features
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[20] Osteomalacic
myopathy
due
to No anticonvulsant drugs
anticonvulsant drugs [21] After adrenalectomy [22]
No adrenalectomy
Neoplastic disease [23]
No tumor
Zidovudine therapy for AIDS [24]
No zidovudine
Steroid response myopathy [25]
Tubular aggregates documented in our patient prior to the intake of steroids
EMG: electromyography, CADASIL: cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy, MRI: magnetic resonance imaging, NCV: nerve conduction velocity, HbA1c: hemoglobin A1c, CK: creatine kinase, ANA: antinuclear antibody, AIDS: acquired immune deficiency syndrome
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S0960-8966(16)30253-X http://dx.doi.org/doi: 10.1016/j.nmd.2016.09.011 NMD 3255
To appear in:
Neuromuscular Disorders
Received date: Revised date: Accepted date:
22-5-2016 31-8-2016 12-9-2016
Please cite this article as: Isabell Cordts, Fabian Funk, Jörg B. Schulz, Joachim Weis, Kristl G. Claeys, Tubular aggregates in autoimmune Lambert-Eaton myasthenic syndrome, Neuromuscular Disorders (2016), http://dx.doi.org/doi: 10.1016/j.nmd.2016.09.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Tubular aggregates in autoimmune Lambert-Eaton myasthenic syndrome
Isabell Cordtsa,b, Fabian Funkb,c, Jörg B. Schulza,d, Joachim Weisb, Kristl G. Claeysa,b,e
a
Department of Neurology, RWTH Aachen University, Aachen, Germany
b
c
Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
Department of Internal Medicine, Sankt Marien-Hospital Düren, Düren, Germany
d
JARA - Translational Brain Medicine, JARA Brain Institute II, FZ Jülich and RWTH,
Aachen, Germany e
Department of Neurology, University Hospitals Leuven and University of Leuven (KU
Leuven), Leuven, Belgium
E-mail addresses of authors: [email protected] [email protected] [email protected] [email protected] [email protected]
Corresponding author: Prof. Dr. Kristl G. Claeys, MD PhD Department of Neurology University Hospitals Leuven and University of Leuven (KU Leuven) Herestraat 49 3000 Leuven
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Belgium Phone: +32 16 34 42 78 Fax: +32 16 34 42 85 E-mail: [email protected]
ABBREVIATIONS: AMPD A
adenosine monophosphate deaminase
ATPase
adenosine triphosphatase
CMAP
compound muscle action potential
CMS
congenital myasthenic syndrome
COX
cytochrome oxidase
GT
Gomori’s trichrome
HE
hematoxylin and eosin
NADH-TR nicotinamide adenine dinucleotide-tetrazolium reductase RNS
repetitive nerve stimulation
SDH
succinate dehydrogenase
VGCC
voltage-gated calcium channel
Highlights
Tubular aggregates can occur in diverse hereditary and acquired disorders
Tubular aggregates have been described in muscles biopsies of hereditary myasthenic disorders
This is the first report about a patient with tubular aggregates and autoimmune LambertEaton myasthenic syndrome
Page 2 of 19
3
The diagnostic difficulties associated with the presence of tubular aggregates are demonstrated
Page 3 of 19
4
ABSTRACT: Tubular aggregates are accumulations of densely packed tubules in muscle fibers, occurring in distinct hereditary and acquired disorders. We present a patient with tubular aggregates and autoimmune Lambert-Eaton myasthenic syndrome. Initially, he showed mild proximal weakness, borderline decrement on 3 Hz stimulation, and slightly elevated creatine kinase. Muscle biopsy revealed tubular aggregates in type II fibers. Due to a good response to pyridostigmine, a limb-girdle myasthenia with tubular aggregates was suspected, but genetic analyses of GFPT1, DPGAT1, and ALG2 were normal. Two years later, the patient presented with progressive weakness and autonomic dysfunction. 17% decrement on 3 Hz stimulation and 100% increment after brief exercise were revealed. Autoantibodies to voltage-gated calcium-channels confirmed the diagnosis of Lambert-Eaton myasthenic syndrome. Steroids, azathioprine, and 3,4-diaminopyridine significantly improved symptoms. No tumor was found during follow-up. This is the first report about tubular aggregates associated with an acquired myasthenic syndrome. Our findings are important because of the therapeutic implications.
KEY WORDS: Lambert-Eaton myasthenic syndrome, muscle biopsy, acquired, tubular aggregates
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INTRODUCTION: Tubular aggregates are accumulations of densely packed membranous tubules within skeletal muscle fibers that are most probably derived from the sarcoplasmic reticulum [1]. They are the predominant histopathological finding in tubular aggregates myopathies, for which causative mutations in STIM1 or ORAI1 have recently been identified [2]. However, tubular aggregates can also occur in several hereditary disorders including congenital myasthenic syndromes (CMS) and in a variety of acquired conditions (Table 1). CMS associated with tubular aggregates include hereditary limb-girdle myasthenia with tubular aggregates caused by mutations in GFPT1, DPGAT1, or ALG2 [3] . Lambert-Eaton myasthenic syndrome is a rare acquired autoimmune myasthenic disorder caused by antibodies directed against presynaptic P/Q-type voltage-gated calcium channels (VGCC), leading to an impaired transmission across the neuromuscular junction. The condition can occur as a paraneoplastic syndrome, mostly associated with small cell lung carcinoma, or as an autoimmune disease without underlying tumor. Clinical characteristics are proximal muscle weakness and autonomic dysfunction. Repetitive nerve stimulation (RNS) in Lambert-Eaton myasthenic syndrome usually shows a low compound muscle action potential (CMAP), a decrement >10% with stimulation at low frequency (1-5 Hz), and an increment >100% after maximum voluntary contraction or with high stimulation frequencies (50 Hz) [4]. Here, we present for the first time the occurrence of tubular aggregates in the muscle of a patient with an acquired myasthenic syndrome. We highlight the diagnostic difficulties associated with the presence of tubular aggregates in the muscle biopsy.
CASE REPORT:
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The 36-year-old Portuguese man presented with a five-month history of non-fluctuating exercise-induced proximal weakness of both upper and lower limbs. He complained of difficulties to climb stairs. Myalgia, cramps, or stiffness as well as sensory, bulbar, or autonomic symptoms were denied. Due to struma nodosa, he underwent a thyroidectomy at the age of 34 years and has since then been treated with L-thyroxine. Family history for neurologic and neuromuscular disorders was negative. The endurance test in which the lower limbs are maintained above the bed plane while lying on the back was abnormal (60 s, normal 75 s). Further neurological examination was normal, including muscle strength and tone, deep tendon reflexes, and sensory testing. In particular, there was no evidence for extraocular muscle dysfunction or bulbofacial weakness. Serum analysis showed slightly elevated creatine kinase levels (281 U/l, normal <190). Antibodies against acetylcholine receptor and muscle-specific receptor tyrosine kinase in serum were both negative. Nerve conduction velocity studies and electromyography were normal. 3 Hz RNS of the ulnar and accessory nerves, recorded at the abductor digiti minimi and trapezius muscle, induced a 9% and 11% borderline decrease of CMAP, respectively. The amplitudes for resting CMAP were normal and no increment after 10s of maximum voluntary muscle contraction was detected. A chest computed tomography scan as well as magnetic resonance imaging of the brain and spinal cord revealed no abnormalities. Due to the inconclusive findings, an open muscle biopsy of the right vastus lateralis muscle was performed and processed according to standard procedures [5], after obtaining the patient’s written informed consent. Light microscopy revealed the presence of inclusions that stained dark blue on nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR), red on modified Gomori’s trichrome (GT), and blue on adenosine monophosphate deaminase (AMPDA) stains, compatible with tubular aggregates (Figure 1). The aggregates appeared basophilic on hematoxylin and eosin (HE) and red-brown on esterase stains, and showed a
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positive reaction for periodic acid Schiff and acid phosphatase (Figure 1). Although the inclusions stained dark blue on succinate dehydrogenase (SDH), they only partially reacted on cytochrome-c-oxidase (COX) (Figure 1G-1H). Adenosine triphosphatase (ATPase) staining at pH 4.2 and 9.4 confirmed that the aggregates were present exclusively in type 2 muscle fibers. Tubular aggregates were distributed unevenly across the biopsy and were present in approximately 4% of the muscle fibers. The biopsy showed a slightly increased variation in fiber size diameter. The number of internalized nuclei was not increased. Fibrotic, necrotic, neurogenic, or inflammatory changes were not present. No ragged red fibers or COXnegative/SDH-positive muscle fibers were detected. Electron microscopy confirmed the inclusions to be tubular aggregates (Figure 1I-1J). They were located underneath the sarcolemma or between the myofibrils. The diameter of tubular aggregates varied from 1 to 114 µm and the tubules showed diameters ranging from 40 to 160 nm. Some tubules appeared empty, while others contained amorphous material or a smaller inner core. Few tubules were connected with filaments. A small number of vacuoles, which might be derived from sarcoplasmic reticulum, were present, most of them located nearby the tubular aggregates. The nuclei, mitochondria, and myofibrillar organization showed no abnormalities and the size and amount of lipid droplets and glycogen were normal. A few normal isolated (no aggregation of) mitochondria were present around the tubular aggregates, but not inside them. No lysosomes were identified among or around the tubular aggregates. Considering all clinical and paraclinical findings, a genetic limb-girdle myasthenia with tubular aggregates was primarily suspected, but molecular genetic analyses of the GFPT1, DPGAT1, and ALG2 genes did not reveal abnormalities. However, a therapy with pyridostigmine resulted in a significant amelioration of exercise-induced weakness. Two years later, the patient consulted again because of progressive fluctuating proximal muscle weakness with tendency to fall. He also complained of erectile problems, dry mouth,
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episodic dysarthria, and dysphagia. Neurological examination revealed prolonged swallowing of 100 ml water (9.65 s, normal < 8 s), but was further normal, including endurance tests of the proximal muscles in the four limbs at the time of examination. In particular, no postexercise facilitation of muscle strength was observed at the time of examination. The electrophysiological examination was repeated and stimulation of the ulnar nerve with recording at abductor digiti minimi muscle showed a reduced resting CMAP (3.4 mV, normal >8 mV), a 17% decrement of CMAP amplitude on 3 Hz RNS, and an almost 100% increment after 10s of maximum voluntary contraction. Serological tests disclosed the presence of antibodies directed against P/Q-type VGCC (111.5 pmol/l, normal <40). Based on the clinical, electrophysiology, and laboratory results, the diagnosis of Lambert-Eaton myasthenic sydrome was established. An extensive search for other acquired and genetic causes of tubular aggregates revealed no abnormalities (Table 1, genetic analysis: CeGat, Tübingen, Germany). Both immunosuppressive treatment with steroids and azathioprine and symptomatic therapy with 3,4-diaminopyridine and pyridostigmine were initiated. Due to side effects, steroids and pyridostigmine were discontinued. Shortly after medication was started, the patient no longer suffered from proximal muscle weakness or dysphagia and experienced an amelioration of autonomous symptoms. Serum antibodies directed against P/Q-type VGCC normalized. A yearly performed tumor screening up to 5 years after diagnosis disclosed no malignancy.
DISCUSSION: Although tubular aggregates have been described in association with several hereditary myasthenic disorders, this is the first report to our knowledge about the presence of tubular aggregates in a patient with an acquired myasthenic syndrome. Usually a muscle biopsy is not performed in patients with an acquired myasthenic disorder or Lambert-Eaton myasthenic syndrome in particular, especially if the presentation is unambiguous. However, in our
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patient, the clinical presentation at onset was very mild and only non-significant changes were noted at the electrophysiological examination. The finding of tubular aggregates in the patient’s muscle tissue and the multiplicity of hereditary disorders and acquired conditions in which tubular aggregates can occur (Table 1) further contributed to the diagnostic difficulties as demonstrated in our case. Our findings are of particular importance because of the therapeutic possibilities in Lambert-Eaton myasthenic syndrome. All causes of tubular aggregates known so far were excluded in our patient (Table 1), amongst them several hereditary myopathies, multisystemic diseases and different acquired conditions. Tubular aggregates are also reported in familial and sporadic cases of “pure” tubular aggregate myopathies, characterized by the absence of any other underlying disease and presenting tubular aggregates as the main structural pathology on muscle biopsy [6]. In our patient, a genetic analysis of STIM1 and ORAI1 revealed no abnormalities and taken together with the negative family history, the presence of a coincident autosomal dominant (primary) tubular aggregate myopathy, caused by a so far unknown gene, is less probable, but not completely excluded. Tubular aggregates are characterized by defined histochemical and ultrastructural changes. In our patient, the enzymatic reactions typical for tubular aggregates were evident, such as an intense staining on NADH-TR, AMPD, and GT. Interestingly, the tubular aggregates stained strongly on SDH and partially on COX, suggesting the participation of mitochondria or mitochondrial proteins in tubular aggregates. The derivation of tubular aggregates from sarcoplasmic reticulum is widely accepted due to their continuity with sarcoplasmic reticulum membranes [1] and immunochemical evidence of sarcoplasmic reticulum proteins in tubular aggregates [6, 7], but opinions about the participation of mitochondria in tubular aggregates differ largely. While a few studies demonstrated a positive reaction of tubular aggregates on SDH [6] or COX [8, 9], in other studies this observation has not been confirmed [10]. An
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immunohistochemical study in mice disclosed antibodies against the bc1 complex, a protein of the inner mitochondrial membrane, with strong signals in the formation of tubular aggregates, indicating that tubular aggregates may emerge not only from sarcoplasmic reticulum but also from mitochondria [11]. Funk et al. showed that tubular aggregates have a positive reaction for the anti-SDH/IP antibody, demonstrating the presence of this complex II component in tubular aggregates [6]. Apart from mitochondrial participation there might be another explanation for the positive staining of tubular aggregates on SDH and COX, such as a diffusion of mitochondrial enzymes into tubular aggregates or a nonspecific enzymatic reaction, misinterpreted as mitochondrial enzymatic activity [6]. The function and physiological significance of tubular aggregates have not been clarified yet. Several hypotheses about the mechanisms responsible for inducing tubular aggregate formation exist. Salviati et al. suggested tubular aggregates to have a compensating function in damaged muscle fibers due to their ability to sequester calcium [7]. Thus, the aggregates may represent an adaptive response to increased intracellular calcium flux in order to prevent muscle fibers from hypercontraction and necrosis. Schiaffino proposed that tubular aggregates are a special type of protein aggregates caused by misfolding and aggregation of sarcoplasmic reticulum membrane proteins comparable to those in neurodegenerative diseases [12]. In analogy, other authors suggested that mutations in the CMS-associated genes GFPT1 and DPAGT1, that encode proteins required for efficient glycosylation, lead to formation of tubular aggregates due to an altered protein glycosylation with consequential protein misfolding and aggregation in sarcoplasmic reticulum [13]. However, in other CMS, including limb-girdle CMS caused by mutations in DOK7, tubular aggregates are not present in muscle biopsies [3]. Hence, tubular aggregates in CMS do probably not arise as a result of impaired neuromuscular transmission. Considering the large variety of conditions that can be associated with tubular aggregates (Table 1), we hypothesize that the formation of tubular
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aggregates might rather be a general and nonspecific muscle response in our patient with Lambert-Eaton myasthenic syndrome. We conclude that the presence of tubular aggregates in the muscle biopsy should trigger consideration of the diagnosis of Lambert-Eaton myasthenic syndrome.
ACKNOWLEDGEMENTS: We thank the patient for participating in our study. We are grateful for the technical and administrative personnel at the Institute of Neuropathology and the Department of Neurology of the University Hospital Aachen for their support. K.C. received grants of the Deutsche Gesellschaft für Muskelkranke (DGM) e.V. for projects unrelated to this study.
REFERENCES:
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[1]
Engel WK, Bishop DW, Cunningham GG. Tubular aggregates in type II muscle fibers: Ultrastructural and histochemical correlation. J. Ultrastruct. Res. 1970;31:507525.
[2]
Lacruz RS, Feske S. Diseases caused by mutations in ORAI1 and STIM1. Ann. N. Y. Acad. Sci. 2015;1356:45-79.
[3]
Engel AG, Shen X-M, Selcen D, Sine SM. Congenital myasthenic syndromes: pathogenesis, diagnosis, and treatment. The Lancet Neurology 2015;14:420-434.
[4]
Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011;10:1098-1107.
[5]
Dubowitz V, Sewry CA, Oldfors A, Lane RJ, Muscle Biopsy: A Practical Approach, Expert Consult; Online and Print, 4: Muscle Biopsy: A Practical Approach. 2013: Elsevier Health Sciences.
[6]
Funk F, Ceuterick-de Groote C, Martin JJ, et al. Morphological spectrum and clinical features of myopathies with tubular aggregates. Histol. Histopathol. 2013;28:10411054.
[7]
Salviati G, Pierobon-Bormioli S, Betto R, et al. Tubular aggregates: sarcoplasmic reticulum origin, calcium storage ability, and functional implications. Muscle Nerve 1985;8:299-306.
[8]
Meijer AEFH. Histochemical features of tubular aggregates in diseased human skeletal muscle fibres. J. Neurol. Sci. 1988;86:73-82.
[9]
Lewis PD, Pallis C, Pearse AGE. “Myopathy” with tubular aggregates. J. Neurol. Sci. 1971;13:381-388.
[10]
Pavlovicova M, Novotova M, Zahradnik I. Structure and composition of tubular aggregates of skeletal muscle fibres. Gen. Physiol. Biophys. 2003;22:425-440.
Page 12 of 19
13
[11]
Novotová M, Zahradník I, Brochier G, Pavlovičová M, Bigard X, Ventura-Clapier R. Joint participation of mitochondria and sarcoplasmic reticulum in the formation of tubular aggregates in gastrocnemius muscle of CK–/– mice. Eur. J. Cell Biol. 2002;81:101-106.
[12]
Schiaffino S. Tubular aggregates in skeletal muscle: just a special type of protein aggregates? Neuromuscul. Disord. 2012;22:199-207.
[13]
Belaya K, Finlayson S, Slater CR, et al. Mutations in DPAGT1 cause a limb-girdle congenital myasthenic syndrome with tubular aggregates. Am. J. Hum. Genet. 2012;91:193-201.
[14]
Fleury M, Barbier R, Ziegler F, et al. Myopathy with tubular aggregates and gyrate atrophy of the choroid and retina due to hyperornithinaemia. J. Neurol. Neurosurg. Psychiatry 2007;78:656-657.
[15]
Oh SJ, Park K-S, Ryan HF, et al. Exercise-induced cramp, myoglobinuria, and tubular aggregates in phosphoglycerate mutase deficiency. Muscle Nerve 2006;34:572-576.
[16]
Niakan E, Harati Y, Danon MJ. Tubular aggregates: their association with myalgia. J. Neurol. Neurosurg. Psychiatry 1985;48:882-886.
[17]
Stamboulis E, Manta P, Kararizou E, Grivas I. Whipple's disease with tubular aggregates in asymptomatic muscle. Clin. Neuropathol. 1993;12:121-124.
[18]
Gallai M. Myopathy with hyperaldosteronism. An electron-microscopic study. J. Neurol. Sci. 1977;32:337-345.
[19]
Hurwitz LJ, Carson AJ, Allen IV, Fannin TF, Lyttle JA, Neill DW. Clinical, biochemical and histopathological findings in a family with muscular dystrophy. Brain 1967;90:799-816.
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[20]
Miike T, Ohtani Y, Tamari H, Ishitsu T, Nonaka I. An electron microscopical study of the T-system in biopsied muscles from fukuyama type congenital muscular dystrophy. Muscle Nerve 1984;7:629-635.
[21]
Doriguzzi C, Mongini T, Jeantet A, Monga G. Tubular aggregates in a case of osteomalacic myopathy due to anticonvulsant drugs. Clin. Neuropathol. 1984;3:4245.
[22]
Palmucci L, Doriguzzi C, Anzil AP. Myopathy with tubular aggregates in a patient adrenalectomized for Cushing's syndrome. J. Neurol. 1985;232:374-377.
[23]
Riggs JE, Schochet SS, Jr, Gutmann L. Tubular aggregates in skeletal muscle associated with neoplastic disease. Arch. Neurol. 1990;47:382-383.
[24]
Chariot P, Benbrik E, Schaeffer A, Gherardi R. Tubular aggregates and partial cytochrome c oxidase deficiency in skeletal muscle of patients with AIDS treated with zidovudine. Acta Neuropathol. 1993;85:431-436.
[25]
Gilchrist JM, Ambler M, Agatiello P. Steroid-responsive tubular aggregate myopathy. Muscle Nerve 1991;14:233-236.
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FIGURE CAPTIONS: Figure 1: Enzyme histochemical and ultrastructural features of tubular aggregates in muscle biopsy. A-E) Serial transverse sections through the muscle tissue showing tubular aggregates that are basophilic on HE (A), brownish on acid phosphatase (B), dark blue on NADH-TR (C), brownish in type 2 muscle fiber on ATPase at pH 4,2 (D) and red-brown on esterase (E) stains. F) Tubular aggregates staining dark blue on AMPDA. G-H) Another serial section from the same biopsy, showing tubular aggregates with dark blue staining on SDH (G), that only partially stain with COX (H). I-J) Ultrastructural pictures of tubular aggregates, showing tubules that contain amorphous material (I). Most tubular aggregates are shown in a transverse section (e.g. asterisk in I), however in one region (arrow in I), some longitudinally cut tubules are also visible. (J) Adjacent to a group of tubular aggregates, vacuoles are shown (example indicated with asterisk). Scale bars: A-H) 100 µm; I-J) 1 µm.
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Table 1: Disorders associated with tubular aggregates in human muscle biopsies (literature review) and investigations to exclude the respective condition in our patient.
Conditions
associated
with
tubular Diagnostic assessment in our patient
aggregates Tubular aggregate myopathy [2] Limb-girdle
myasthenia
Genetic analysis normal (STIM1, ORAI1)
with
tubular Genetic analysis normal (GFPT1, DPAGT1,
aggregates [3]
ALG2)
Gyrate atrophy of choroid and retina [14]
Clinical: normal vision
Periodic paralysis [1, 6]
Genetic analysis normal (CACNA1S, KCNE3, KCNJ2, KCNJ5, KJNJ18, SCN4A) Clinical: no paralytic attacks
Malignant hyperthermia [6]
Genetic
analysis
normal
(RYR1,
SCN4A,
CACNA1S) Clinical: no incidents with previous anesthesias Myotonic myopathy [6] , Myotonic dystrophy Genetic analysis normal (CLCN1) [15]
Clinical and EMG: no myotonia, no typical features
Glycogen
storage
diseases
metabolic myopathies [6]
and
other Alpha-glucosidase activity in blood normal Genetic analysis normal (PGAM2) Muscle
biopsy:
no
glycogen
or
lipid
accumulations CADASIL [6]
Brain MRI normal Clinical: no strokes, no headache
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Morbus Fabry [6]
Genetic analysis normal (GLA)
Mitochondrial disorders [6, 11]
Muscle biopsy: no mitochondrial abnormalities
Polyneuropathy [1, 6, 16]
NCV normal Clinical:
no
abnormalities
suggestive
for
polyneuropathy Alcoholic myopathy [6]
No alcohol abuse
Toxic / drug-induced myopathy [1, 6]
No relevant toxins/drugs
Diabetic amyotrophy [6]
Blood analysis: HbA1c normal
Polymyositis, dermatomyositis [6]
Muscle biopsy: no inflammatory infiltrates, no necroses, no perifascicular atrophy Blood analysis: no considerably increased CK, no myositis-associated/-specific antibodies
Porphyria cutanea tarda [1]
Clinical: no skin changes
Whipple’s disease [17]
Clinical: no gastrointestinal symptoms
Hyperaldosteronism [18]
Blood analysis: no elevated aldosterone
Amyotrophic lateral sclerosis [16]
Clinical: no upper and/or lower motor neuron signs, no progressive disease
Facioscapulohumeral
muscular
dystrophy Clinical: no manifestation in face and shoulder
[19]
region, no typical features
Lupus erythematosus [16]
Clinical: no abnormalities of skin or internal organs Blood analysis: no inflammation parameters, ANA negative, no cytopenia
Muscle infarction [9]
Clinical: no acute episode with pain and swelling
Fukuyama congenital muscular dystrophy Clinical: no congenital onset, no typical features
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[20] Osteomalacic
myopathy
due
to No anticonvulsant drugs
anticonvulsant drugs [21] After adrenalectomy [22]
No adrenalectomy
Neoplastic disease [23]
No tumor
Zidovudine therapy for AIDS [24]
No zidovudine
Steroid response myopathy [25]
Tubular aggregates documented in our patient prior to the intake of steroids
EMG: electromyography, CADASIL: cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy, MRI: magnetic resonance imaging, NCV: nerve conduction velocity, HbA1c: hemoglobin A1c, CK: creatine kinase, ANA: antinuclear antibody, AIDS: acquired immune deficiency syndrome
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