A very rare genetic disorder where an enzyme deficiency prevents the break down of certain proteins into energy and results in a harmful accumulation of acids in the blood and body tissues. More specifically, there is a deficiency of an enzyme (2-methylbutyryl-coenzyme A dehydrogenase) needed to convert the amino acid isoleucine into energy. 2-methylbutyrylglycine levels build up in the body and may cause damage. Symptoms vary according to the degree of enzyme deficiency - can range from asymptomatic to life-threatening. See also 2-methylbutyryl-coenzyme A dehydrogenase deficiency