- Email: [email protected]
Neonatal presentation of coenzyme Q10 deficiency
Neonatal presentation of coenzyme Q10 deficiency Shamima Rahman, MRCP, Iain Hargreaves, PhD, Peter Clayton, MD, FRCP, and Simon Heales, PhD, MRCPath
We report a neonate with ubiquinone deficiency. Skeletal muscle analysis revealed markedly diminished mitochondrial complex II + III activity that could be restored by addition of a ubiquinone analogue. Ubiquinone deficiency was confirmed by high-performance liquid chromatography. Oral ubiquinone therapy was not associated with clinical improvement; the patient died at 2 years. (J Pediatr 2001;139:456-8)
Defects of the mitochondrial respiratory chain represent a relatively common group of inborn errors of metabolism.1 Respiratory chain defects are not amenable to treatment; a possible exception is ubiquinone (CoQ10) deficiency.2 CoQ10 acts as a redox carrier, transferring reducing equivalents from respiratory chain complexes I and II to complex III.3 CoQ10 deficiency appears to be extremely rare. Four patients from 3 families presented with mitochondrial encephalomyopathies4-6; systemic features have been described in only one family.2 We now report a severe neonatal presentation of CoQ10 deficiency with systemic features and poor clinical response to CoQ10 therapy. From the Biochemistry, Endocrinology and Metabolism Unit, Institute of Child Health, and Departments of Neurochemistry and Clinical Biochemistry, Institute of Neurology and National Hospital, London, United Kingdom.
Submitted for publication Dec 29, 2000; revisions received Mar 6, 2001, and May 4, 2001; accepted May 25, 2001. Reprint requests: Simon Heales, PhD, Department of Clinical Biochemistry (Neurometabolic Unit), 9th Floor–Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom. Copyright © 2001 by Mosby, Inc. 0022-3476/2001/$35.00 + 0 9/22/117575 doi:10.1067/mpd.2001.117575
456
PATIENT AND METHODS Clinical Details and Initial Investigations The patient, a boy, was the seventh child of healthy unrelated Pakistani parents and was delivered by elective cesarean section after a normal pregnancy, possibly complicated by reduced fetal movements in the last trimester. Five older siblings, 4 girls and 1 boy, are well but another sibling died on day 1 of life with seizures, aminoaciduria, and acidosis. The mother had previously had 5 first-trimester miscarriages. The patient presented at 6 hours of age with poor feeding, hypothermia, and “shaking of both arms.” Examination revealed a passive neonate, unresponsive to his immediate environment, with a weak cry. There were no dysmorphic features. He had generalized increase of peripheral tone with reduced truncal tone. Initial investigations demonstrated lactic acidosis (plasma lactate 19.4 mmol/L, reference range 0.9 to 1.9 mmol/L), renal tubulopathy (tubular reabsorption of phosphate 60%, reference range >85%), and mild left ventricular hypertrophy with global hypokinesia on echocardiogram. Chest radiograph showed diffuse haze consistent with mild interstitial edema. Mag-
netic resonance imaging of the brain demonstrated generalized cerebral and cerebellar atrophy and abnormal parenchyma, and an electroencephalogram showed bilateral paroxysmal activity. He had mild clotting abnormalities (activated partial thromboplastin time 44.1 seconds, reference range 29 to 40; thrombin time 15.1 seconds, reference range 8 to 12). However, there was no evidence of jaundice; and hepatic transaminase, blood glucose, and ammonia levels were normal. He received formula feeds. Open muscle biopsy was deferred until 10 months. At this time he was more stable, although still requiring continuous administration of oxygen. CoQ10 Ubiquinone CoQ1 Ubiquinone-1
He had a severe seizure disorder, and development continued to be grossly delayed. His head control was poor, he was unable to sit unsupported, and he had minimal fine motor movements. He did not fix and follow, smile, or babble. Weight was on the 91st percentile and head circumference on the 0.4th percentile for age (United Kingdom growth charts). Examination revealed a dystonic movement disorder with generalized hyperreflexia. Repeat plasma lactate level was 4.1 mmol/L.
Enzyme Assays and Coenzyme Q10 Determination The skeletal muscle biopsy specimen (50 mg) was frozen immediately and stored at –70°C until analysis. Analysis of the mitochondrial complexes was conducted as previously described.7 Muscle CoQ10 concentration was de-
RAHMAN ET AL
THE JOURNAL OF PEDIATRICS
VOLUME 139, NUMBER 3 Table. Muscle mitochondrial respiratory chain enzyme activities and ubiquinone concentration
Assay Complex I Complex II + III Complex II + III + CoQ1 Complex IV Complex II Complex III CoQ10 (pmol/mg protein)
Patient value
Pediatric reference range
0.163 <0.001 0.098 0.018 0.151 0.026 37
0.104-0.268 0.040-0.204 0.040-0.204 0.014-0.340 0.052-0.258 0.008-0.028 140-580
termined by high-performance liquid chromatography.6
RESULTS Muscle histologic examination showed type-2B fiber atrophy with excess lipid. There were no ragged red fibers, and cytochrome oxidase staining was normal. Activities of complexes I and IV appeared normal, whereas the combined activity of complexes II and III was below the limit of detection of our assay (Table). However, analysis of complexes II and III revealed normal activity. The effect of exogenous CoQ1 (50 µmol/L) addition on complex II + III activity is also shown in the Table. Mitochondrial complex activities are expressed as a ratio to citrate synthase to account for the mitochondrial enrichment of the muscle homogenate. CoQ10 concentration is related to the protein content of the homogenate. Because the complex II and III assay depends on the endogenous CoQ10 concentration,7 these findings suggested CoQ10 deficiency. Support for this suggestion was provided by the restoration of complex II and III activity after addition of CoQ1, a CoQ10 analogue to the assay system (Table). High-performance liquid chromatography analysis confirmed CoQ10 deficiency (Table). CoQ10 biosynthesis is complex.3,8 Serum cholesterol and transferrin glycoforms (whose production requires
dolichol) were normal in our patient, suggesting that the synthesis of farnesyl-pyrophosphate was intact. Furthermore, no urinary accumulation of metabolites from tyrosine to 4-hydroxy-benzoate could be detected. Oral CoQ10 therapy was commenced at 11.5 months of age (60 mg/d increasing after 6 days to 300 mg/d). At commencement of treatment, the plasma lactate level was 7.6 mmol/L. Eleven days later, the lactate level was 4.4 mmol/L, and by 4 months, it was 2.5 to 2.9 mmol/L. However, the clinical course was marked by severe global developmental delay with microcephaly, dystonia, and a seizure disorder resistant to quadruple anticonvulsant therapy. Renal tubular function had improved before CoQ10 therapy was started, but the cardiomyopathy had worsened. The patient died at 2 years of age after an intercurrent chest infection. Consent was not obtained for a postmortem examination.
DISCUSSION We report a neonatal case of systemic CoQ10 deficiency. Most reported cases had symptoms confined to muscle and the central nervous system.4-6 However, a French family with systemic features, but late onset and slow progression, has been reported.2 Although most of the clinical features of our case can be explained by a failure of cellular energy metabolism,
our patient was noted to be hypothermic at 6 hours. This could relate to the recently attributed role for CoQ10 in brown adipose tissue.9 Our case highlights the need for detailed mitochondrial investigations in the diagnosis of congenital lactic acidosis. Enzymatic analysis is an important tool for identification of defects in one or more of the components of the respiratory chain. Furthermore, inclusion of the complex II and III assay enables identification of CoQ10 deficiency. In this assay, endogenous CoQ10 availability influences activity directly (ie, electrons from succinate are passed by way of complex II onto CoQ10; complex III then removes electrons from reduced CoQ10 and cytochrome C becomes reduced [monitored at 550 nm]).7 The reduction in the blood lactate level observed in our patient after CoQ10 treatment was not accompanied by clinical improvement. The reason for the apparent failure of treatment is not clear but may be related to the severity of neurodevelopmental disturbances before diagnosis or to the nature of the underlying metabolic defect. Early identification of CoQ10 deficiency is important so that appropriate therapy can begin as soon as possible. However, except in cases of proven CoQ10 deficiency, the continued use of CoQ10 therapy in the absence of objective measures of clinical improvement should be discouraged.
REFERENCES 1. Skladal D, Bernier FP, Halliday JL, Thornburn DR. Birth prevalence of mitochondrial respiratory chain defects in children [abstract}. J Inherit Metab Dis 2000;23:S138. 2. Rotig A, Appelkvist EL, Geromel V, Chretien D, Kadhom N, Edery P, et al. Quinone-responsive multiple respiratory-chain dysfunction due to widespread coenzyme Q10 deficiency. Lancet 2000;356:391-5. 3. Ernster L, Dallner G. Biochemical, physiological and medical aspects of ubiquinone function. Biochim Biophys Acta 1995;1271:195-204. 457
THE JOURNAL OF PEDIATRICS SEPTEMBER 2001
RAHMAN ET AL
4. Ogasahara S, Engel AG, Frens D, Mack D. Muscle coenzyme Q deficiency in familial mitochondrial encephalomyopathy. Proc Natl Acad Sci U S A 1989;86:2379-82. 5. Sobreira C, Hirano M, Shanske S, Keller RK, Haller RG, Davidson E, et al. Mitochondrial encephalomyopathy with coenzyme Q10 deficiency. Neurology 1997;48:1238-43.
458
6. Boitier E, Degoul F, Desguerre I, Charpentier C, Francois D, Ponsot G, et al. A case of mitochondrial encephalomyopathy associated with a muscle coenzyme Q10 deficiency. J Neurol Sci 1998;156:41-6. 7. Clark JB, Bates TE, Boakye P, Kuimov A, Land JM. Investigation of mitochondrial defects in brain and skeletal muscle. In: Turner AJ, Bachelard HS, editors. Neurochem-
istry: a practical approach. 2nd ed. Oxford University Press: Oxford; 1994. p. 151-74. 8. Szkopinska A. Ubiquinone. Biosynthesis of quinone ring and its isoprenoid side chain. Intracellular localization. Acta Biochim Pol 2000;47:469-80. 9. Echtay KS, Winkler E, Klingenberg M. Coenzyme Q is an obligatory cofactor for uncoupling protein function. Nature 2000;408:609-13.
We report a neonate with ubiquinone deficiency. Skeletal muscle analysis revealed markedly diminished mitochondrial complex II + III activity that could be restored by addition of a ubiquinone analogue. Ubiquinone deficiency was confirmed by high-performance liquid chromatography. Oral ubiquinone therapy was not associated with clinical improvement; the patient died at 2 years. (J Pediatr 2001;139:456-8)
Defects of the mitochondrial respiratory chain represent a relatively common group of inborn errors of metabolism.1 Respiratory chain defects are not amenable to treatment; a possible exception is ubiquinone (CoQ10) deficiency.2 CoQ10 acts as a redox carrier, transferring reducing equivalents from respiratory chain complexes I and II to complex III.3 CoQ10 deficiency appears to be extremely rare. Four patients from 3 families presented with mitochondrial encephalomyopathies4-6; systemic features have been described in only one family.2 We now report a severe neonatal presentation of CoQ10 deficiency with systemic features and poor clinical response to CoQ10 therapy. From the Biochemistry, Endocrinology and Metabolism Unit, Institute of Child Health, and Departments of Neurochemistry and Clinical Biochemistry, Institute of Neurology and National Hospital, London, United Kingdom.
Submitted for publication Dec 29, 2000; revisions received Mar 6, 2001, and May 4, 2001; accepted May 25, 2001. Reprint requests: Simon Heales, PhD, Department of Clinical Biochemistry (Neurometabolic Unit), 9th Floor–Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom. Copyright © 2001 by Mosby, Inc. 0022-3476/2001/$35.00 + 0 9/22/117575 doi:10.1067/mpd.2001.117575
456
PATIENT AND METHODS Clinical Details and Initial Investigations The patient, a boy, was the seventh child of healthy unrelated Pakistani parents and was delivered by elective cesarean section after a normal pregnancy, possibly complicated by reduced fetal movements in the last trimester. Five older siblings, 4 girls and 1 boy, are well but another sibling died on day 1 of life with seizures, aminoaciduria, and acidosis. The mother had previously had 5 first-trimester miscarriages. The patient presented at 6 hours of age with poor feeding, hypothermia, and “shaking of both arms.” Examination revealed a passive neonate, unresponsive to his immediate environment, with a weak cry. There were no dysmorphic features. He had generalized increase of peripheral tone with reduced truncal tone. Initial investigations demonstrated lactic acidosis (plasma lactate 19.4 mmol/L, reference range 0.9 to 1.9 mmol/L), renal tubulopathy (tubular reabsorption of phosphate 60%, reference range >85%), and mild left ventricular hypertrophy with global hypokinesia on echocardiogram. Chest radiograph showed diffuse haze consistent with mild interstitial edema. Mag-
netic resonance imaging of the brain demonstrated generalized cerebral and cerebellar atrophy and abnormal parenchyma, and an electroencephalogram showed bilateral paroxysmal activity. He had mild clotting abnormalities (activated partial thromboplastin time 44.1 seconds, reference range 29 to 40; thrombin time 15.1 seconds, reference range 8 to 12). However, there was no evidence of jaundice; and hepatic transaminase, blood glucose, and ammonia levels were normal. He received formula feeds. Open muscle biopsy was deferred until 10 months. At this time he was more stable, although still requiring continuous administration of oxygen. CoQ10 Ubiquinone CoQ1 Ubiquinone-1
He had a severe seizure disorder, and development continued to be grossly delayed. His head control was poor, he was unable to sit unsupported, and he had minimal fine motor movements. He did not fix and follow, smile, or babble. Weight was on the 91st percentile and head circumference on the 0.4th percentile for age (United Kingdom growth charts). Examination revealed a dystonic movement disorder with generalized hyperreflexia. Repeat plasma lactate level was 4.1 mmol/L.
Enzyme Assays and Coenzyme Q10 Determination The skeletal muscle biopsy specimen (50 mg) was frozen immediately and stored at –70°C until analysis. Analysis of the mitochondrial complexes was conducted as previously described.7 Muscle CoQ10 concentration was de-
RAHMAN ET AL
THE JOURNAL OF PEDIATRICS
VOLUME 139, NUMBER 3 Table. Muscle mitochondrial respiratory chain enzyme activities and ubiquinone concentration
Assay Complex I Complex II + III Complex II + III + CoQ1 Complex IV Complex II Complex III CoQ10 (pmol/mg protein)
Patient value
Pediatric reference range
0.163 <0.001 0.098 0.018 0.151 0.026 37
0.104-0.268 0.040-0.204 0.040-0.204 0.014-0.340 0.052-0.258 0.008-0.028 140-580
termined by high-performance liquid chromatography.6
RESULTS Muscle histologic examination showed type-2B fiber atrophy with excess lipid. There were no ragged red fibers, and cytochrome oxidase staining was normal. Activities of complexes I and IV appeared normal, whereas the combined activity of complexes II and III was below the limit of detection of our assay (Table). However, analysis of complexes II and III revealed normal activity. The effect of exogenous CoQ1 (50 µmol/L) addition on complex II + III activity is also shown in the Table. Mitochondrial complex activities are expressed as a ratio to citrate synthase to account for the mitochondrial enrichment of the muscle homogenate. CoQ10 concentration is related to the protein content of the homogenate. Because the complex II and III assay depends on the endogenous CoQ10 concentration,7 these findings suggested CoQ10 deficiency. Support for this suggestion was provided by the restoration of complex II and III activity after addition of CoQ1, a CoQ10 analogue to the assay system (Table). High-performance liquid chromatography analysis confirmed CoQ10 deficiency (Table). CoQ10 biosynthesis is complex.3,8 Serum cholesterol and transferrin glycoforms (whose production requires
dolichol) were normal in our patient, suggesting that the synthesis of farnesyl-pyrophosphate was intact. Furthermore, no urinary accumulation of metabolites from tyrosine to 4-hydroxy-benzoate could be detected. Oral CoQ10 therapy was commenced at 11.5 months of age (60 mg/d increasing after 6 days to 300 mg/d). At commencement of treatment, the plasma lactate level was 7.6 mmol/L. Eleven days later, the lactate level was 4.4 mmol/L, and by 4 months, it was 2.5 to 2.9 mmol/L. However, the clinical course was marked by severe global developmental delay with microcephaly, dystonia, and a seizure disorder resistant to quadruple anticonvulsant therapy. Renal tubular function had improved before CoQ10 therapy was started, but the cardiomyopathy had worsened. The patient died at 2 years of age after an intercurrent chest infection. Consent was not obtained for a postmortem examination.
DISCUSSION We report a neonatal case of systemic CoQ10 deficiency. Most reported cases had symptoms confined to muscle and the central nervous system.4-6 However, a French family with systemic features, but late onset and slow progression, has been reported.2 Although most of the clinical features of our case can be explained by a failure of cellular energy metabolism,
our patient was noted to be hypothermic at 6 hours. This could relate to the recently attributed role for CoQ10 in brown adipose tissue.9 Our case highlights the need for detailed mitochondrial investigations in the diagnosis of congenital lactic acidosis. Enzymatic analysis is an important tool for identification of defects in one or more of the components of the respiratory chain. Furthermore, inclusion of the complex II and III assay enables identification of CoQ10 deficiency. In this assay, endogenous CoQ10 availability influences activity directly (ie, electrons from succinate are passed by way of complex II onto CoQ10; complex III then removes electrons from reduced CoQ10 and cytochrome C becomes reduced [monitored at 550 nm]).7 The reduction in the blood lactate level observed in our patient after CoQ10 treatment was not accompanied by clinical improvement. The reason for the apparent failure of treatment is not clear but may be related to the severity of neurodevelopmental disturbances before diagnosis or to the nature of the underlying metabolic defect. Early identification of CoQ10 deficiency is important so that appropriate therapy can begin as soon as possible. However, except in cases of proven CoQ10 deficiency, the continued use of CoQ10 therapy in the absence of objective measures of clinical improvement should be discouraged.
REFERENCES 1. Skladal D, Bernier FP, Halliday JL, Thornburn DR. Birth prevalence of mitochondrial respiratory chain defects in children [abstract}. J Inherit Metab Dis 2000;23:S138. 2. Rotig A, Appelkvist EL, Geromel V, Chretien D, Kadhom N, Edery P, et al. Quinone-responsive multiple respiratory-chain dysfunction due to widespread coenzyme Q10 deficiency. Lancet 2000;356:391-5. 3. Ernster L, Dallner G. Biochemical, physiological and medical aspects of ubiquinone function. Biochim Biophys Acta 1995;1271:195-204. 457
THE JOURNAL OF PEDIATRICS SEPTEMBER 2001
RAHMAN ET AL
4. Ogasahara S, Engel AG, Frens D, Mack D. Muscle coenzyme Q deficiency in familial mitochondrial encephalomyopathy. Proc Natl Acad Sci U S A 1989;86:2379-82. 5. Sobreira C, Hirano M, Shanske S, Keller RK, Haller RG, Davidson E, et al. Mitochondrial encephalomyopathy with coenzyme Q10 deficiency. Neurology 1997;48:1238-43.
458
6. Boitier E, Degoul F, Desguerre I, Charpentier C, Francois D, Ponsot G, et al. A case of mitochondrial encephalomyopathy associated with a muscle coenzyme Q10 deficiency. J Neurol Sci 1998;156:41-6. 7. Clark JB, Bates TE, Boakye P, Kuimov A, Land JM. Investigation of mitochondrial defects in brain and skeletal muscle. In: Turner AJ, Bachelard HS, editors. Neurochem-
istry: a practical approach. 2nd ed. Oxford University Press: Oxford; 1994. p. 151-74. 8. Szkopinska A. Ubiquinone. Biosynthesis of quinone ring and its isoprenoid side chain. Intracellular localization. Acta Biochim Pol 2000;47:469-80. 9. Echtay KS, Winkler E, Klingenberg M. Coenzyme Q is an obligatory cofactor for uncoupling protein function. Nature 2000;408:609-13.