GSTM1 and Schnyder corneal dystrophy: Forty-one SCD patients (6 Hb SS, 23 severe Hb S/β+ and 12 Hb S/β0 patients) (68.3%) in our series had a history of at least one pain event (Joint/Abdominal/Chest) in their lifetime, while 19 SCD patients including three Hb SS individuals had not experienced any pain events.