Maple Syrup Urine Disease (MSUD) is due to an inability to metabolize branched chain amino acids. Intermediate MSUD is associated with symptoms less severe than classic MSUD.

Intermediate MSUD is associated with decreased but present activity of the BCKAD complex (branched-chain alpha-ketoacid dehydrogenase complex). Enzyme activity in fibroblasts range from 3 to 40% of normal (versus less than 3% in the classic form).


Onset: later in infancy or childhood, may not be diagnosed until older


General findings:

(1) anorexia with poor feeding

(2) normal to poor growth

(3) variable developmental delay

(4) variable irritability

(5) encephalopathy and clinical deterioration if acutely ill, dehydrated or fasting


Laboratory findings:

(1) ketonuria when sick

(2) elevated plasma leucine concentration when sick

(3) maple syrup smell to urine and cerumen due to the presence of sotolone (4,5-dimethyl-3-hydroxy-2[5h]-furanone)

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