Sickle Cell Exceptions
Are there any known cases where one parent had the sickle cell trait and the other did not have the sickle cell gene, however the child has the sickle cell disease?
There is no way that one sickle trait in one parent can lead to homozygous sickle cell anemia (hemoglobin SS), but it is possible for the child to have a sickle variant. A child can inherit one sickle cell gene from one parent and an abnormal gene (other than sickle trait) from the other parent that leads to sickle cell disease.
For example, if one parent has sickle trait and the other parent has hemoglobin C trait, then the child has a 25% chance of having sickle-hemoglobin C disease which is a milder form of sickle cell. In another example, if one parent has sickle trait and the other parent has beta thalassemia trait (minor) then the child has a 25% chance of having sickle beta thalassemia which also causes sickle cell diseases.
There are other combinations of sickle trait with abnormal hemoglobin genes that are rare and can lead to sickle cell disease. In order to be sure, both parents have to be tested with blood counts and a hemoglobin electrophoresis.
For more information:
Go to the Sickle Cell Anemia health topic.