In its classical form this disease presents in the first week with anorexia, vomiting and apathy. There is hypertonicity, abnormal movements and death if the patient is untreated. Survivors usually suffer severe brain damage. With early treatment there is longer survival, but treatment needs to be vigorous and life long. Variant forms of the disease include an “intermittent” form where there may be transient episodes of ataxia and convulsions, and “intermediate” forms characterised by later onset but a non-episodic course. These variant types have higher residual enzyme activity than the classical form.
Enzyme Test: a-ketoacid decarboxylase is assayed to diagnose the disease.