GAMT and hyperinsulinemic hypoglycemia, familial, 4: Aside from classical homocystinuria disease, 2 patients were identified with a suggestive phenotype of MPS, a group of rare IEMs in which the accumulation of glycosaminoglycans (GAGs) occur due to enzyme deficiencies (WES data is in progress to find causative mutations).Two more patients were found with GAMT deficiency, which is a disorder of creatine metabolism amenable to high dose creatine and an arginine restricted diet (47).