Children with this defect commonly present with
failure to thrive, recurrent episodes of severe ketoacidosis with
hyperventilation (caused by metabolic acidosis), vomiting, diarrhea (often
bloody), and coma during the course of intercurrent infections or after
excessive protein intake. Onset is rarely before age 4 months. Most patients
(approximately 60%) can have normal mental development if severe
metabolic decompensations can be prevented. However, ataxia and frequent
headaches have been reported. One case with congestive cardiomyopathy has
been described. Mainstay of therapy is moderate restriction of isoleucine
intake, intravenous glucose, and sodium bicarbonate during decompensations
and avoidance of fasting.