Mild or absent clinical signs in twin sisters with short-chain acyl-CoA dehydrogenase deficiency

Two HLA-identical twin sisters are reported, of whom one has remained essentially asymptomatic, and an episode of hypotonia and decreased level of conciousness being the only relevant clinical finding in the other. Organic acid analysis revealed that ethylmalonate was constantly, although sometimes only slightly, increased. No abnormal acylglycines or acylcarnitines could be detected. Enzyme assay in cultured skin fibroblasts confirmed short-chain acyl-CoA dehydrogenase deficiency. Conclusion The lack of appropriate biochemical markers for this deficiency makes the diagnosis difficult and consequently, the low number of patients described may be the result of underdiagnosis.