Sickle cell crisis presenting as livedo racemosa.

Sickle cell disease is a monogenic hemoglobinopathy that results in the abnormal production of hemoglobin S, which yields the characteristic sickle-shaped red blood cells. Sickle cell vaso-occlusive crisis is a painful complication of sickle cell disease caused by red blood cell entrapment within the microcirculation. The resulting tissue ischemia triggers a secondary inflammatory process involved in the pathogenesis of varying inflammatory skin conditions.