Objective: To study the clinical and genetic features of the patients with secondary methylmalonic aciduria due to succinate-CoA ligase deficiency.
Method: From February 2011 to April 2014, 4 Chinese patients with succinate-CoA ligase deficiency and mild methylmalonic aciduria were enrolled in this study. The clinical course, biochemical features, brain MRI findings, and mutations were analyzed.
Result: Four patients presented with severe psychomotor retardation, hypotonia, seizures, feeding problems and failure to thrive from the age of one day to 6 months. Three of them had intractable epilepsies. One had hearing defect. Mild methylmalonic aciduria was detected by elevated urine methylmalonic acid and blood propionylcarnitine at the age of 6 months to 2 years and 8 months. Five mutations, c. 550G>A, c. 751C>T, c. 809A>C, c. 961C>G and c. 826-2A>G in SUCLG1 of three patients were identified. On SUCLA2, one novel mutation, c. 970C>T, was found in one patient. After treatment, the disease in all four patients was improved.
Conclusion: Four Chinese patients with succinyl-CoA ligase deficiency caused by SUCLG1 and SUCLA2 mutations were noticed by mild methylmalonic aciduria and diagnosed using high-throughput genomic sequencing. Succinate-CoA ligase deficiency is a rare cause of methylmalonic aciduria. Biochemical and gene studies are necessary for the differential diagnoses.