Maple Syrup Urine Disease
- Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder of branched chain amino acids caused by a defect in the oxidative decarboxylation of branched-chain -keto acids (BCKA). Resultant accumulation of branched chain amino acids including leucine, isoleucine and valine, with their subsequent excretion give the urine a characteristic maple odor, hence the name.
- Patients are usually normal at birth but become symptomatic in the first week of life and present with difficulty feeding, hypertonia, failure to thrive, seizures and hypoglycemia. Early intervention with dialysis, dietary restrictions and support of anabolic stat is helpful, though most surviving children remain impaired and demonstrate spasticity and mental retardation.
- Key Diagnostic Features: Restricted diffusion in the deep cerebellar white matter, dorsal brainstem, cerebral peduncles, posterior limb of internal capsule and centrum semiovale. Cerebral edema is also seen. Inadequate therapy results in generalized volume loss and periventricular hyperintensities on T2-weighted MRI.
