Sudden pain onset, sharp and throbbing, lasting up to 6–7 days before resolvingCommon in the lower back and extremitiesPain crises can begin as early as the first year of lifeVariable number of VOCs and pain crises during lifetime (up to 18.2 VOCs/year)Common in women during pregnancyTriggered by patient features (DNA variants of Hb, ethnic group) and environmental factors (hypoxia, dehydration, cold, prolonged immobility, infection, fever, acidosis)Possible clinical consequences are ACS, hepatic and renal involvement, and cerebrovascular accident. This evidence concerns the gene GSTM1 and acute chest syndrome.