APOL1 and avascular necrosis: Recently, a possible genetic predisposition has been identified: variant alleles of the Apolipoprotein L1 (APOL1) gene, which are involved in innate immune responses and more expressed in African-American patients, are related with an increased risk of progressive kidney disease and atherosclerotic disease, and have been reported to be more prevalent in African-American SLE patients with AVN, supporting a possible role in AVN physiopathology [44,47,56].