ITGA4 and avascular necrosis: Polymorphisms associated with the DARC receptor (Duffy antigen/chemokine receptor), the ITGA4 gene (in exons 4, 5 and 6), the CD36 adhesion molecule gene (rs198412) and the thrombophilia protein genes (a-fibrinogen, b -fibrinogen, platelet glycoprotein, factor VII, plasminogen activator inhibitor-1, prothrombin and factor V genes) did not show association with AVN in SCD in any of the studies.