Both are primarily caused by the polymerization of sickle cells in the kidney microvasculature due to the low O2 tension, high osmolarity, and low acidity. This polymerization fills and occludes blood vessels such as the vasa recta in the kidneys leading to microinfarctions, leakage into surrounding tissues and potentially papillary necrosis and renal infarcts. Renal papillae are especially susceptible to damage eventually causing papillary necrosis since these vessels are only supplied with blood by the vasa recta. The sickling of the cells also contribute to two other mechanisms which are chronic hypoxia and chronic hemolysis. Hypoxia is caused from both the insufficient ability for the red blood cells to transport oxygen alongside blood vessel occlusions promoting the activation of Hypoxia Inducible Factor-1𝛂. The hypoxia also causes the over expression of endothelin-1 and functional nitric oxide deficiency and due to the chronic hemolysis, reactive oxygen species are produced leading to vasoconstriction and further medullary hypoxia. This nitric oxide deficiency alongside endothelin-1 overproduction leads to the inability to properly respond to stress and hemodynamic changes which increases the likelihood of experiencing acute kidney injury.The hyperfiltration has multiple contributing factors such as the increased cardiac output caused by the normal physiological response to anemia leading to greater renal blood flow and an increase in glomerular filtration rate (GFR). This is not the only factor because having multiple blood transfusions does not reverse this effect.
Thalassemias are inherited blood disorders characterized by decreased hemoglobin production. Symptoms depend on the type and can vary from none to severe. Often there is mild to severe anemia (low red blood cells or hemoglobin). Anemia can result in feeling tired and pale skin. There may also be bone problems, an enlarged spleen, yellowish skin, and dark urine. Slow growth may occur in children.Thalassemias are genetic disorders inherited from a persons parents. There are two main types, alpha thalassemia and beta thalassemia. The severity of alpha and beta thalassemia depends on how many of the four genes for alpha globin or two genes for beta globin are missing. Diagnosis is typically by blood tests including a complete blood count, special hemoglobin tests, and genetic tests. Diagnosis may occur before birth through prenatal testing.Treatment depends on the type and severity. Treatment for those with more severe disease often includes regular blood transfusions, iron chelation, and folic acid. Iron chelation may be done with deferoxamine, deferasirox or deferiprone. Occasionally, a bone marrow transplant may be an option. Complications may include iron overload from the transfusions with resulting heart or liver disease, infections, and osteoporosis. If the spleen becomes overly enlarged, surgical removal may be required. Thalassemia patients who do not respond well to blood transfusions can take hydroxyurea or thalidomide, and sometimes a combination of both. Hydroxyurea is the only FDA approved drug for thalassemia.