Down syndrome complicated by hemoglobin S/beta+ thalassemia. Atypical expression of coexistent disease

The chance occurrence of Down syndrome and sickle cell disease is an extremely rare event. The patient presented in this article is the only reported case, based on medical literature review, of Down syndrome coexisting with sickle cell disease due to hemoglobin S/beta+ thalassemia. He had multiple recurrent aplastic crises and severe psychomotor and growth retardation. The physiologic basis for the atypical manifestations of both of his disorders is the subject of this report.