Which of the following is not a feature of sickle cell disease?

Sickle cell disease Caused by missense mutation in the b-globin gene that leads to the replacement of a charged glutamate residue with a hydrophobic valine residue. Mutation promotes the polymerization of deoxygenated hemoglobin, leading to red cell distoion (sickling), hemolytic anemia, microvascular obstruction, and ischemic tissue damage. Sickle cell trait (heterozygosity) confers protective effect against falciparum malaria. In early childhood, spleen is enlarged. However, as disease progresses, there is chronic erythrostasis leading to splenic infarction, fibrosis, and progressive shrinkage, only a small piece of fibrous splenic tissue is left, a process called autosplenectomy. The mainstay of treatment is an inhibitor of DNA synthesis, hydroxyurea.