A rare organic aciduria characterized by impaired isoleucine degradation with increased plasma or whole blood C5 acylcarnitine levels (typically observed in newborn screening) and increased urinary excretion of N-methylbutyrylglycine. The condition is usually clinically asymptomatic, although patients with muscular hypotonia, developmental delay, and seizures (among others) have been reported. The disease is 2-methylbutyryl-CoA dehydrogenase deficiency (MONDO_0012392). Also known as: 2-methylbutyric aciduria, 2-methylbutyrylglycinuria, SBCAD deficiency, butyryl-CoA dehydrogenase deficiency, developmental delay due to 2-methylbutyryl-CoA dehydrogenase deficiency, short/branched-chain acyl-coA dehydrogenase deficiency.