glutaric acidemia, type i (ga i), was first described in 1975. the disease is caused by a genetic deficiency of the enzyme, glutaryl-coa dehydrogenase (gcd), which leads to the buildup of glutaric acid in the tissues and its excretion in the urine of affected patients. gcd is involved in the catabolism of the amino acids, lysine, hydroxylysine, and tryptophan. over 200 cases of ga i have been r...