ABSTRACT
Maple syrup urine disease (MSUD) is a disorder of branched-chain amino acid metabolism in which elevated quantities of leucine, isoleucine, and valine and their corresponding oxo- and corresponding hydroxyacids accumulate in body fluids. The electroencephalogram of the newborn with MSUD has been described as a comb-like rhythm of spindle-like sharp waves over the central regions and multiple shifting spikes and sharp waves with suppression bursts. The usual neuropathologic finding in patients dying of MSUD is a generalized status spongiosus of the white matter similar to that seen in phenylketonuria and nonketotic hyperglycinemia. Oxidation of labeled leucine in vivo served as a much better discriminant than in vitro enzyme activity of variant forms of MSUD. MSUD is transmitted as an autosomal recessive trait. This is true of each of the variants. Classic MSUD has been seen throughout the world and in all ethnic groups.
