2-Methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency: impaired catabolism of isoleucine presenting as neurodegenerative disease.

We describe a further case of recently reported 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiency, a disorder of isoleucine metabolism. The development of pronounced brain atrophy and symmetrical alterations of the basal ganglia were observed and the importance of specific enzymatic tests is emphasized, which should be performed if urinary metabolites suggest impaired catabolism of isoleucine.