Our data showed a direct correlation of plasma extracellular Hb with platelet activation markers such as surface P-selectin expression and PAC1 binding, and also with platelet-derived microparticles in plasma (Fig 5) of sickle patients, similar to the phenomenon described recently by us in PNH patients [13]. The gene discussed is GSTM1; the disease is paroxysmal nocturnal hemoglobinuria.