Hb: hemoglobin; SCD: sickle cell disease; WBC: white blood cell; RBC: red blood cell; MCV: mean corpuscular volume; MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration; RDW: red cell distribution width. The gene discussed is GSTM1; the disease is Schnyder corneal dystrophy.