tThe Klotho protein, whose gene has predominant renal expression, acts in the control ofserum phosphorus and 1,25-dihydroxyvitamin D3 and regulates the function of ion chan-nels. It also participates in the mechanism of protection against oxidative stress and acts onthe vascular endothelium by inducing the production of nitric oxide. Mutations that reflectdefects in the Klotho gene expression may be implicated in the onset of osteonecrosis, pri-apism, and leg ulcers in patients with sickle cell disease, as a result of oxidative stress andendothelial impairment, important factors in the development and severity of this disease.Previous reports regarding the association of Klotho single nucleotide polymorphisms withsickle cell disease subphenotypes have found that these polymorphisms are important toidentify genetic markers of risk in these individuals and allow early and more effectivetherapeutic intervention.