Résumé :
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OBJECTIVES: We present a new phenotype associated to CoQ10 deficiency characterised by a late-onset recurrent myoglobinuria and exercise intolerance without muscle weakness nor CNS involvement. CoQ10 supplementation was introduced and by now the patient remains asymptomatic. METHODS: A 24-year old man was followed up because of episodes characterised by myalgias and myoglobinuria associated to long-duration physical exercises in the last two years. These symptoms disappeared after hours remaining asymptomatic. There was not neurological family history nor consanguinity. RESULTS: Neurological examination was normal. A high CK level was detected in one of the episodes (18.000 IU/L) being normal in asymptomatic periods. The aerobic forearm exercise test was normal. An open muscle biopsy taken from biceps brachii was performed but routine and immunohistochemical stainings did not show morphological abnormalities. Carnitine palmitoyl transferase deficiency was ruled out. The measurement of the activities of the mitochondrial chain respiratory enzymes in muscle extracts, as well as in fibroblasts, revealed that the activity of II, I-III and II-III complexs and CoQ10 were markedly reduced. This patient is receiving 1500 mg daily of CoQ10. He has not referred exercise intolerance any more and routine analyses have not demonstrate high CK level since then. CONCLUSIONS: - Late-onset and isolated recurrent myoglobinuria constitutes a new phenotype associated to a CoQ10 deficiency. Unlike other reports, this patient has not developed muscle weakness nor CNS abnormalities. We do not know if the early-onset CoQ10 treatment has played a key role avoiding the presence of other symptoms. - Mitochondrial chain respiratory enzymes study should be performed in patients with an undefined exercise intolerance because if a CoQ10 deficiency is confirmed, CoQ10 supplementation is recommended. Skin biopsy could be an alternative to muscle biopsy to confirm a CoQ10 deficiency.
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