We report 12 patients from 8 families with mutations in ECHS1 and demonstrate the large phenotypic spectrum of this defect.
In all patients severe dystonia, mental retardation and deafness were the leading symptoms. In 7/12 epilepsy was described; in 4/12 there was cardiomyopathy. No other inner organs were involved. The beginning of symptoms varies from birth to 3 years of age. The oldest patient is 32 years old. 4/12 died between 4 months and 8 years of age. In 7/12 patients brain MRI revealed symmetrical changes of the basal ganglia and in 3/11 white matter disease. Elevated lactate in blood/CSF was found in 7/12 patients. Only 2/8 patients showed abnormal results in the activity of pyruvate dehydrogenase complex (PDHc) and respiratory chain complexes (RCC)in muscle.
ECHS1-deficiency is a newly recognized metabolic disorder with a “mitochondrial” phenotype but frequently normal activity of PDHc and RCC. This combination should prompt to investigate S-(2-carboxypropyl)cysteine, methacrylyl-CoA and acryloyl-CoA for early diagnosis. This will be particularly important, if a treatment is available: a diet reduced in valine and isoleucine, the precursors of the potentially toxic metabolites might be a promising approach.