Respiratory chain deficiency presenting as recurrent myoglobinuria in childhood.

Myoglobinuria is an abnormal urinary excretion of myoglobin due to an acute destruction of skeletal muscle fibres. Several metabolic diseases are known to account for myoglobinuria including defects of glycolysis and fatty acid oxidation. Here, we report on respiratory chain enzyme deficiency in three unrelated children with recurrent episodes of myoglobinuria and muscle weakness (complex I: one patient, complex IV: two patients). All three patients had generalized hyporeflexia during attacks, a feature which is not commonly reported in other causes of rhabdomyolysis. Studying respiratory chain enzyme activities in cultured skin fibroblasts might help diagnosing this condition, especially when acute rhabdomyolysis precludes skeletal muscle biopsy during and immediately after episodes of myoglobinuria.