A case of Hb-SC disease presenting as priapism.

Priapism is a common symptom in Haemoglobin SC and SS disease, which results from thrombosis in the vascular spaces in the cavernous tissue of penis. Thrombosis is due to altered physico-chemical properties of HbS which has glutamic acid substituted for valine in the sixth position from N-terminal in Beta Chain. When deoxygenated, HbS is less soluble and tactoids form in red cells which cause distortion and damage to the red cell membrane. Sickled red cells become rigid and mechanically fragile resulting in haemolysis, repeated vascular occlusions and infarction of various interbak organs like kidneys, mesentery, intestine, lungs, brain and bones.