Late Infantile Neuronal Ceroid Lipofuscinosis: A New Mutation in Arabs

Late Infantile Neuronal Ceroid Lipofuscinosis: A New Mutation in Arabs Hadassa Goldberg-Stern, MD*†§1, Ayelet Halevi, MD†§1, Dafna Marom, MD‡§, Rachel Straussberg, MD†§, and Aviva Mimouni-Bloch, MD¶ The neuronal ceroid lipofuscinoses are a group of dominant neurodegenerative, progressive, and fatal disorders characterized clinically by myoclonic epilepsy, in variable association with dementia, ataxia, and visual loss. Neuronal ceroid lipofuscinoses were classified into several phenotypes according to their age of onset: infantile, late infantile, juvenile, and adult. A specific phenotype was named ‘‘northern epilepsy,’’ and its onset of signs occurs between ages 5-10 years. Deficiencies in the lysosomal activity of two specific enzymes were found in several types of neuronal ceroid lipofuscinosis: palmitoyl-protein thioesterase 1, encoded by the CLN1 gene, and tripeptidyl-peptidase 1, encoded by the CLN2 gene. Several mutations in CLN2 were described previously. We describe a novel mutation in two siblings of Israeli-Arab origin, with a clinical picture compatible with late infantile neuronal ceroid lipofuscinosis. Both siblings were found to be homozygous for a deletion of a C nucleotide at position 775 in exon 7 of the CLN2 gene. These findings have implications for the worldwide epidemiology of neuronal ceroid lipofuscinosis. Ó 2009 by Elsevier Inc. All rights reserved. Goldberg-Stern H, Halevi A, Marom D, Straussberg R, Mimouni-Bloch A. Late infantile neuronal ceroid lipofuscinosis:A new mutation in Arabs. Pediatr Neurol 2009;41:297-300.

From the *Epilepsy Center, †Department of Child Neurology, and ‡ Department of Genetics, Schneider Children’s Medical Center of Israel, Petah Tiqwa, §Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel, and ¶Neuropediatric Unit, Levinstein Rehabilitation Hospital, Raanana, Israel. 1 Both authors contributed equally to this work.

Ó 2009 by Elsevier Inc. All rights reserved. doi:10.1016/j.pediatrneurol.2009.04.022  0887-8994/09/$—see front matter

Introduction Neuronal ceroid lipofuscinosis is the general name for a group of inherited, neurodegenerative disorders caused by an enzyme or membrane dysfunction resulting in lysosomal storage. Neuronal ceroid lipofuscinosis is characterized clinically by seizures, mainly myoclonic, in association with motor and mental deterioration (cerebral ataxia and dementia) and usually visual loss [1]. The course is progressive, and leads to early death. The disorder is divided into several phenotypes by age of onset and order of occurrence of signs (Table 1): In infantile neuronal ceroid lipofuscinosis, also known as Santavuori-Haltia disease, no abnormalities are evident at birth. Retinal blindness and seizures develop by age 2 years, followed by mental deterioration [2]. Magnetic resonance imaging studies of the brain indicate cerebral atrophy, strong thalamic hypointensity and hyperintensity, and periventricular high-signal rims of white matter [3]. Death usually occurs between ages 8-11 years [3]. Late infantile neuronal ceroid lipofuscinosis, also known as Jansky-Bielschowsky disease, typically manifests as epilepsy at ages 2-4 years. Seizures are usually myoclonic, although generalized tonic-clonic seizures and absence or partial seizures with secondary generalization may also be evident. These are soon followed by a regression of developmental milestones and then dementia, ataxia, and extrapyramidal and pyramidal signs. Affected children are usually bedridden before age 6 years. Life expectancy ranges from 6-30 years [1]. Visual loss is a late sign, typically appearing at ages 4-6 years and rapidly progressing to blindness. Ophthalmologic examinations indicate macular degeneration and pigmentary aggregates. Electroencephalograms demonstrate spikes in the occipital region, in response to a photic stimulation of 1-2 Hz. Responses on an electroretinogram are usually abnormal at presentation, and become undetectable. On occasion, the electroretinogram results may be normal at presentation [4]. Visual-evoked potentials are enhanced for a long period, and diminish in the final stages of the disease. Magnetic resonance imaging of the brain reveals progressive cerebral and cerebellar atrophy, with normal basal ganglia and thalami [1]. Classic juvenile neuronal ceroid lipofuscinosis, also known as Batten disease or Spielmeyer-Vogt disease,

Communications should be addressed to: Dr. Goldberg-Stern; Epilepsy Center; Schneider Children’s Medical Center of Israel; 14 Kaplan Street; Petah Tiqwa 49202, Israel. E-mail: [email protected] Received January 26, 2009; accepted April 6, 2009.

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Table 1. Distinguishing clinical features of neuronal ceroid lipofuscinosis phenotypes and their associated genes

Clinical Forms

Late infantile

Classic (Jansky-Bielschowsky) and others Gypsy/Indian, early juvenile variant Turkish variant

Juvenile (Batten)

Percentage of Patients by Genotype Percentage of Patients Gene

Presenting Signs

50% 50%

CLN1

6-24 mo 3-38 yr

80% 8% 12% ?

CLN2 CLN1 Other CLN6

2-8 yr

Cognitive/motor decline, visual loss, seizures Chronic course: all of the above, and behavior abnormalities Motor/cognitive decline, visual loss, seizures

18 mo-8 yr

Motor/cognitive decline, visual loss, seizures

? 21% 7% 72%

CLN7 CLN1 CLN2 CLN3 CLN15 CLN36 CLN47 CLN8

1-6 yr 4-10 yr

Motor decline, visual loss, seizures Visual loss, cognitive/motor decline, seizures

15-50 yr

Type A: motor/cognitive decline, seizures Type B: behavior abnormalities, motor/cognitive decline

5-10 yr

Cognitive decline, seizures

Adult (Kuf’s disease)

Northern epilepsy (progressive epilepsy with mental retardation)

Age of Onset

100%

Modified from Wisniewski and Zhong [17].

presents between ages 4-10 years. The first clinical sign is usually rapidly progressive visual loss, resulting in total blindness within 2-4 years [5]. An ophthalmologic examination early in the course of the disease may reveal only macular changes; an electroretinogram indicates loss of photoreceptor function [5]. Typical signs of panretinal degeneration develop later: pigmentary changes in the retinal periphery, vascular attenuation, and optic-nerve pallor [6]. Visual loss may be the only sign for the first 2-5 years [5]. Epilepsy with generalized tonic-clonic seizures, complex partial seizures, or myoclonic seizures typically appears between ages 5-18 years, and speech disorders with a slow decline in cognition occur between ages 8-4 years. Behavioral problems, extrapyramidal signs, and sleep disorders occur in the second decade. Magnetic resonance imaging at later stages reveals cerebral and (to a lesser degree) cerebellar atrophy. Life expectancy ranges from the late teens to the third decade [5]. In adult neuronal ceroid lipofuscinosis, or Kuf’s disease, initial signs usually appear around age 30 years, with death occurring about 10 years later [7]. Ophthalmologic studies reveal no abnormalities. Clinical findings include either progressive myoclonic epilepsy with dementia, ataxia, and late-occurring pyramidal and extrapyramidal signs, or behavioral abnormalities associated with dementia, ataxia, motor dysfunction, extrapyramidal signs, and suprabulbar signs [7]. There is also a later-onset adult phenotype, presenile neuronal ceroid lipofuscinosis, which first appears after age 50 years and is characterized by dementia, cognitive decline, motor dysfunction, ataxia, and brainstem signs [8]. Northern epilepsy is common in Finland. Its onset is between ages 5-10 years. Signs include tonic-clonic or complex partial seizures, mental deterioration, and motor

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dysfunction. The frequency of epileptic manifestations decreases after puberty, but slow cognitive decline continues for life. Some patients with northern neuronal ceroid lipofuscinosis have lived beyond age 60 years [9]. Laboratory studies of patients with neuronal ceroid lipofuscinosis reported a deficiency in two lysosomal enzymes: palmitoyl-protein thioesterase 1 and tripeptidyl-peptidase 1. Thus, beyond the clinical and imaging findings, a diagnosis of neuronal ceroid lipofuscinosis is based on an electron microscopy study of white blood cells, skin, conjunctiva, eccrine secretory glands, or other tissues, to detect specific lysosomal storage material: fingerprints (in juvenile neuronal ceroid lipofuscinosis), curvilinear profiles (in late infantile neuronal ceroid lipofuscinosis), granular osmophilic deposits (in infantile neuronal ceroid lipofuscinosis), or their combination (adult and late infantile neuronal ceroid lipofuscinosis). Detection of pathologic inclusions depends on the tissue examined. Biochemical analyses of the deposits indicate that subunit c of the mitochondrial adenosine triphosphate synthase complex is the major storage component of fingerprints and curvilinear profiles, and saponins A and D (sphingolipid activator proteins) are the main storage components of granular osmophilic deposits [10]. At least eight genes play a role in neuronal ceroid lipofuscinosis, and are denoted CLN1 to CLN8. Palmitoyl-protein thioesterase 1 is encoded by the CLN1 gene, and tripeptidyl-peptidase 1 is encoded by the CLN2 gene. Individuals with mutations of the CLN2 gene usually demonstrate no enzymatic activity. In carriers of CLN1 or CLN2 mutations, the normal activity of the respective enzymes is reduced by half [11]. This report describes an Israeli-Arab family with clinical features of late infantile neuronal ceroid lipofuscinosis in whom we identified a new mutation in the CLN2 gene.

Figure 1. Pedigree of unrelated Arab parents. A solid symbol signifies affected. An open symbol signifies unaffected.

Case Reports Case 1 The proband was a 10-year-old girl born to unrelated, healthy parents of Arab origin after a normal pregnancy and delivery (Fig 1). Her birth weight was 2800 g. There was no family history of neurologic disorders. Her perinatal development was normal. The child began to walk at age 1 year. At age 3 years, she began to manifest occasional left-sided focal seizures with vomiting, and secondary generalized seizures. Thereafter, myoclonic jerks appeared, followed by gait ataxia and deterioration of speech. Remarkable findings on neurologic examination included head circumference in the second percentile for age, absence of eye contact, no dysmorphism, increased muscle tone (cogwheel type), hyperreflexia without clonus, and extensor plantar responses. The initial electroencephalogram revealed generalized spike wave discharges, more prominent in the frontal regions, with slow background activity in the theta range. Repeated electroencephalograms in subsequent years revealed deterioration of slow background activity and multifocal epileptiform discharges with generalized spike waves and polyspikes, aggravated by photic stimulation with increased photosensitivity. Magnetic resonance imaging performed at age 3 years revealed diffuse cerebral and cerebellar atrophy (Fig 2). Metabolic and genetic tests excluded other etiologies of progressive myoclonic epilepsy, such as mitochondrial disease, sialidosis, or Unverricht-Lundborg disease. Laboratory findings were within normal range for serum amino acids, vitamins E and B12, serum lactate, pyruvate, carnitine, acylcarnitine, urine organic acids, reduced substances, and oligosaccharides. Cerebrospinal fluid analysis yielded normal chemistry and amino-acid levels. A muscle biopsy with a respiratory enzyme study revealed no abnormalities. Testing for the cystatin B mutation was negative. A diagnosis of neuronal ceroid lipofuscinosis was initially missed because of apparently normal findings in the ophthalmologic examination, electroretinogram, and visual-evoked potentials at presentation. However, when the patient returned at age 7 years for a follow-up visit together with her brother, who was found to exhibit a similar clinical picture, we began to suspect neuronal ceroid lipofuscinosis. At that point, a repeated fundus examination indicated optic atrophy, and enzyme analysis demonstrated a deficiency in tripeptidyl-peptidase 1 activity in her fibroblasts. An electron microscopy study of leukocytes or other tissues was not performed. We proceeded with molecular testing for the CLN genes (performed at the Molecular Genetics Laboratory, Hospital for Sick Children, Toronto, Canada). Direct mutation analysis for common mutations in the CLN1, CLN2, and CLN3 genes produced negative results. Sequencing of CLN2 revealed a homozygous deletion of a C nucleotide at position 775 in exon 7 of the gene. The parents are both heterozygotes for this mutation. This frameshift mutation is novel, and was not previously described. At present, the patient is 10 years old, and is unable to walk or talk. She exhibits continuous myoclonic jerks and intractable partial seizures with secondary generalization that respond partially to levetiracetam and clonazepam. A recent electroencephalogram demonstrated continuous discharges of spike waves and polyspikes, aggravated during photic stimulation at low and high frequencies.

Case 2 The younger brother of the proband was born after a normal pregnancy and delivery. His birth weight was 2500 g. His perinatal development was

Figure 2. Coronal T2-weighted magnetic resonance image (TR/TE = 4500/100 ms) demonstrates diffuse cerebral and cerebellar atrophy. normal, and the child was walking independently at age 1 year, and was talking in sentences around age 2 years. The first seizure occurred at age 3 years, and was followed by gradual neurologic deterioration. The child stopped walking and talking, and began to manifest involuntary movements. Degenerative ocular changes were evident on fundus examination, and an electroencephalogram revealed generalized epileptiform discharges with spike and polyspike waves. An enzyme analysis of his fibroblasts indicated an absence of tripeptidyl-peptidase 1 activity, compatible with a CLN2 gene defect. Molecular genetic analysis yielded homozygosity for the same novel mutation as in his sister, i.e., a deletion of a C nucleotide at position 775 in exon 7 of the CLN2 gene.

Discussion The neuronal ceroid lipofuscinoses are the most common hereditary progressive neurodegenerative disease (1:25,000). The incidence ranges in different countries from 0.1 per 10,000 to 7 per 100,000 live births. About half the reported cases of infantile neuronal ceroid lipofuscinosis have been diagnosed in Finland, where the incidence is 1 per 20,000 live births. The incidence of late infantile neuronal ceroid lipofuscinosis in Finland is 0.36-0.46 per 100,000 [12]. Neuronal ceroid lipofuscinosis is associated with defects in eight different genes (CLN1-CLN8) [11]. Several recurrent mutations account for 80% of all cases of the disease. In addition, more than 100 rare CLN gene mutations causing neuronal ceroid lipofuscinosis were reported. At present, molecular genetic testing is available on a clinical basis for CLN1, CLN2, and CLN3, and on a research basis only for CLN5 and CLN [13]. The CLN1 gene, which encodes for palmitoyl-protein thioesterase 1, is located on chromosome 1p32. More than 38 mutations are known. The CLN2 gene, which encodes for tripeptidyl-peptidase 1, is located on chromosome 11p15; more than 40 mutations are known. The most common CLN2 mutations are c.622C > T(R208X) and IVS5-1 G > C(G.3556

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G > C) [13]. The CLN3 gene is located on chromosome 16p12.1. The common CLN3 mutation in neuronal ceroid lipofuscinosis is a 1-kilobase deletion that removes exons 7 and 8 [11]. The CLN4 gene has not yet been identified. The CLN5 gene resides on chromosome 13q22, and is specific to the Finnish variant of late infantile neuronal ceroid lipofuscinosis, characterized by delayed onset at ages 4.5-7 years. In addition, a missense mutation identified on the CLN8 gene on chromosome 8p23 is exclusive to patients of Finnish origin [12]. The CLN6 gene was mapped to a 4-cM region on chromosome 15q21-23. Mutations in CLN6 account for 10-15% of cases of neuronal ceroid lipofuscinosis and all cases of a Gypsy/Indian variant of late infantile neuronal ceroid lipofuscinosis, in which visual loss and seizures may be the initial signs [14]. A mutation in CLN7, which has not yet been identified, causes a Turkish variant of late infantile neuronal ceroid lipofuscinosis, with onset at ages 1-6 years [15]. Neuronal ceroid lipofuscinosis is inherited in an autosomal-recessive mode. Carrier parents have a normal phenotype, and never acquire progressive myoclonic epilepsy. In the family described here, the parents are nonconsanguineous. However, their children are homozygotes for the same mutation. This finding suggests the possibility of a high carrier frequency for CLN2 in the Arab-Muslim population in Israel. A previous Arab-Muslim family with neuronal ceroid lipofuscinosis was described in Israel, but with a mutation in CLN8 [16]. To the best of our knowledge, this is the first report of homozygous CLN2 in a nonconsanguineous Israeli-Arab family. This novel mutation in the CLN2 gene in a family of Arab origin from Israel sheds further light on the epidemiology of neuronal ceroid lipofuscinosis as a worldwide disease. References [1] Wisniewski KE, Zhong N, Philippart M. Pheno/genotypic correlations of neuronal ceroid lipofuscinoses. Neurology 2001;57:576-81.

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[2] Santavauori P. Neuronal ceroid lipofuscinoses in childhood. Brain Dev 1980;10:80-3. [3] Vanhanen SL, Raininko R, Autti T, Santavuori P. MRI evaluation of the brain in infantile neuronal ceroid-lipofuscinosis. Part 2: MRI findings in 21 patients. J Child Neurol 1995;10:444-50. [4] Weleber RG. The dystrophic retina in multisystem disorders: The electroretinogram in neuronal ceroid lipofuscinosis and its variants. J Med Genet 1999;36:471-4. [5] Wisniewski KE, Zhong N, Kaczmarski W, et al. Compound heterozygous genotype is associated with protracted juvenile neuronal ceroid lipofuscinosis. Ann Neurol 1998;43:106-10. [6] Spalton DJ, Taylor DS, Sanders MD. Juvenile Batten’s disease: An ophthalmological assessment of 26 patients. Br J Ophthalmol 1980; 64:726-32. [7] Burneo JG, Arnold T, Palmer CA, Kuzniecky RI, Oh SJ, Faught E. Adult-onset neuronal ceroid lipofuscinosis (Kufs disease) with autosomal dominant inheritance in Alabama. Epilepsia 2003;44:841-6. [8] Constantinidis J, Wisniewski KE, Wisniewski TM. The adult and a new late adult forms of neuronal ceroid lipofuscinosis. Acta Neuropathol (Berl) 1992;83:461-8. [9] Zupanc ML, Legros B. Progressive myoclonic epilepsy. Cerebellum 2004;3:156-71. [10] Goebel HH, Wisniewski KE. Current state of clinical and morphological features in human NCL. Brain Pathol 2004;141:61-9. [11] Mole SE, Zhong NA, Sarpong A, et al. New mutations in the neuronal ceroid lipofuscinosis genes. Eur J Paediatr Neurol 2001;5(Suppl. A): 7-10. [12] Uvebrant P, Hagberg B. Neuronal ceroid lipofuscinoses in Scandinavia. Epidemiology and clinical pictures. Neuropediatrics 1997;28:6-8. [13] Claussen M, Heim P, Knispel J, Goebel HH, Kohlschu¨tter A. Incidence of neuronal ceroid-lipofuscinoses in West Germany: Variation of a method for studying autosomal recessive disorders. Am J Med Genet 1992;42:536-8. [14] Cismondi IA, Kohan R, Ghio A, Ramirez AM, Halac IN. Gene symbol: CLN6. Disease: Neuronal ceroid lipofuscinosis, late infantile. Hum Genet 2008;124:324. [15] Ranta S, Topcu M, Tegelberg S, et al. Variant late infantile neuronal ceroid lipofuscinosis in a subset of Turkish patients is allelic to northern epilepsy. Hum Mutat 2004;23:300-5. [16] Zelnik N, Mahajna M, Iancu TC, Sharony R, Zeigler M. A novel mutation of the CLN8 gene: Is there a Mediterranean phenotype? Pediatr Neurol 2007;36:411-3. [17] Wisniewski KE, Zhong N, eds. Batten disease: diagnosis, treatment, and research, Vol 45. London: Academic Press, 2001.