Favourable clinical course in an infant with severe deficiency of complex III of the respiratory chain combined with less severe deficiencies of complexes I, II and IV

An infant with severe deficiency of complex III combined with less severe deficiencies of complexes I, II and IV of the mitochondrial respiratory chain in skeletal muscle tissue presented with intra-uterine growth retardation, generalized hypotonia and delayed motor development. In the following 3.5 years muscle tone and motor development gradually normalized whereas the lactic acidosis and enzyme activities did not improve. This report documents a favourable clinical course in a child with combined respiratory chain deficiency despite persistent biochemical abnormalities.