Clinical features of mitochondrial disease in a family

Abstract

Mitochondrial disorders, once thought to be relatively rare, are now thought to be the most prevalent metabolic disease. They represent a challenge to clinicians, especially in children, in whom clinical presentation and course show enormous variation. We report a respiratory chain enzyme activity disorder (complex I, III and IV) in a girl, with a severe presentation since the perinatal period. An older female sibling had died at the age of 11 months from an encephalopathy, with a similar clinical presentation. Enzyme activity disorders could not been disclosed. This association has been described only rarely. Mitochondrial disorders associated with defects in the respiratory chain can be attributable to mutations in the mitochondrial genome (mitochondrial DNA) or the nuclear genome (nuclear DNA). The diagnosis is based on the presence of clusters of abnormal mitochondria in muscle cells and a biochemically defined defect in the respiratory chain enzymes or, more recently, also on mutations in the mitochondrial DNA. In our case muscular biopsy to assess enzymatic activity of the respiratory chain complexes disclosed defects in respiratory chain complexes I, III and IV (cytochrome c oxidase). The patients, as our case, usually present early in life and are more severely affected than patients with isolated complex deficiencies. Therapy remains largely ineffective.