He has a clinical focus in inherited metabolic diseases, hereditary eye diseases, and neurogenetic conditions, and a particular research focus on clinical outcomes in patients with homocystinurias, especially the cobalamin C (cblC) defect and other inherited disorders of intracellular cobalamin (B12) metabolism. He takes care of patients of all ages with homocystinurias, cobalamin disorders, and remethylation defects as well as dozens of other inherited metabolic disorders.