Sickle Cell Disease and Renal Disease

The kidney of patients with sickle cell disease (SCD) is affected by both haemodynamic changes of chronic anaemia and by the consequences of vaso-occlusion which are especially marked within the renal medulla. There are many abnormalities in renal structure and function as a result of these changes. Functional changes occur with increasing age in subjects with sickle cell disease. Proteinuria, severe anaemia and haematuria are reliable markers and predictors of chronic renal disease in patients with sickle cell disease (Emokpae et al., 2010a). Sickle cell disease is characterized by chronic haemolytic anaemia due to adverse effects of oxygen transport by the red blood cells. This often leads to a decrease in oxygen supply to peripheral tissues. The substitution of valine for glutamic acid at the sixth position of the ┚-globin polypeptide chain made haemoglobin S (HbS) different from normal adult haemoglobin A (HbA) (Reid et al., 1984).The inheritance of HbS gene in the heterozygous state results in sickle cell trait while inheritance in the homozygous state results in sickle cell disease (SCD). The prevalence of Hb S gene in various parts of Africa varies between 20-40% (Arabs, 1970), while in Nigeria the prevalence is put at 20-25percent (Lindner et al., 1974; Ukoli et al., 1988). Sickling phenomenon occurs secondary to intra erythrocytic HbS polymerization because of low oxygen tension which becomes reversible with adequate re-oxygenation of the haemoglobin. But with repeated sickling and resultant deformation, the red cell membranes become fragile and haemolyse. Sickle cell disease often results in a severe disease, with profound anaemia and multiple organ involvement including cerebrovascular events, acute vaso-occlusive episodes, retinopathy, acute chest syndrome and renal damage (Guash et al.,2006).Haemoglobin S may coexist with other mutant beta globin chains (┚c or ┚D) in a mixed heterozygous state leading to haemoglobin SC or SD disease. Haemoglobin SC disease is the most common mixed heterozygous form of sickle haemoglobinopathies occurring in one per 800 births in the African Americans (Guash et al., 2006). Sickle cell anaemia (SCA) affects the kidney, causing defects in tubulomedullary function (Allon, 1990); and also causes proteinuria, progressive renal insufficiency and end stage renal disease (Pham et al., 2000). The glomerulopathy is the cause of the proteinuria and progressive renal insufficiency (Guash et al., 1996).