CLINICAL HETEROGENEITY IN RESPIRATORY-CHAIN COMPLEX-III DEFICIENCY INCHILDHOOD

Six children are presented with an isolated complex III deficiency in muscle tissue. More specifically, oxidation rates and ATP + CrP produc tion rates from both pyruvate and succinate as substrates and/or the a ctivity of decylubiquinol:cytochrome c oxidoreductase were all markedl y reduced. Complex III deficiency was also present in liver of two pat ients tested, but could not be demonstrated in cultured fibroblasts of four patients tested. Mitochondrial DNA, extracted from muscle, was a nalyzed; no deletions or common point mutations were found. Four patie nts presented with a multi-organ disorder. Among these patients three presented at neonatal age with neurological signs and lactate elevatio n in blood and CSF, of whom two had severe neonatal Fanconi syndrome. One child, aged seven years, had encephalomyopathy, ophthalmoplegia, r etinopathy and Wolff-Parkinson-White syndrome. The remaining two patie nts exhibited myopathy only, within the first year of life. Thus, like in other respiratory chain disorders, patients with complex III defic iency may present at any age and show variable symptoms and outcome, r anging from neonatal death to failure to thrive only. Apparently there are no clinical findings which are specific for complex III deficienc y. (C) 1997 Elsevier Science B.V.