SCD is a hereditary chronic hemolytic anemia resulting from mutations in the subunit β-chain gene of hemoglobin (Hb) that cause stiff, sickle-shaped red blood cells that are involved in a complex series of adhesive events among blood cells, leading to small blood vessel obstruction, which reduces the oxygen supply to body tissues. The gene discussed is GSTM1; the disease is Schnyder corneal dystrophy.