Dystonia and deafness due to SUCLA2 defect; Clinical course and biochemical markers in 16 children.

Patients with SUCLA2 gene defects characteristically develop the trias of early hypotonia, progressive dystonia and sensori-neural deafness. We describe the clinical course and biochemical phenotype in 16 children from the Faroe Islands with a homozygous SUCLA2 splice site mutation. Elevated urinary 3-hydroxyisovaleric acid is a novel biochemical feature in patients. Progressive hearing loss, in combination with a characteristic metabolite profile (increased lactate, methylmalonic acid, C4-dicarboxylic carnitine, 3-hydroxyisovaleric acid) should lead the clinician to the correct diagnosis even in patients with only intermittent lactic acidemia. Direct SUCLA2 sequence analysis is suggested instead of an invasive muscle biopsy to obtain the diagnosis. Nutritional intervention may be considered in SUCLA2 patients.