What would you say are major causes of sickle cell disease?

Gene mutation: Sickle cell anemia is caused by a mutation in the gene that tells your body to make hemoglobin.The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected.

It's an inherited...: Blood disorder caused by a nutation in the 6th codon of the beta globin chain, one of the two globins that constitute adult hemoglobin-a. People who are homozygous (2 copies) for the mutation have sickle cell disease. People who are heterozygous for the mutation (1 copy) have sickle cell trait. They have a selective advantage when living in malaria endemic regions (the thalassemia belt).