What are possible genotypes for a child who has sickle cell disease but their parents don't?

Simple SS: Most ss sickle cell patients are born to unaffected parents. Sickle trait is common in the african american community and 2 trait parents have a 25% risk with each pregnancy of having a ss kid.Classical sickle cell has only one genotype, although the pairing of a sickle gene with a thallasemia or other abnormal hemoglobin can produce clinical disease.

Most likely....: The parents are both carriers of the sickle cell mutation on one of their two beta globin genes. Their other gene is normal. This condition is called sickle cell trait. These people are usually asymptomatic with normal red cell indices. The child could have two copies of the mutant beta globin gene, one from each parent. Their is a 25% chance of this. More rarely, thalassemia combines with beta-s.