KL and avascular necrosis: Based on the articles included in this review, the researched data associated AVN in SCD with polymorphisms in the BMP6, KL and ANXA2 genes, which are involved in bone metabolism.14 Chaouch et al.18 reported that the polymorphisms rs267196 and rs267201 do BMP6 are reliable biomarkers to predict patients at high risk for osteonecrosis.