Abstract
Sickle cell (SS) disease is a complex of various genetic conditions. In some, homozygosity for the βS gene may be present alone or in combination with the heterozygous or homozygous α‐thalassemia‐2 condition. Such combinations might ameliorate the clinical and hematological condition of the patient. The same may be true for the high levels of Hb F and F‐cells observed in many Hb S homozygotes. However, the chemical heterogeneity of Hb F appears not to be related to the clinical status of the Hb S homozygote. Combinations of a Hb S heterozygosity with a heterozygosity for a Hb D‐type of variant, for either one of two types of β‐thalassemia, two types of δβ‐thalassemia, and five types of HPFH are discussed, and data are compared with those obtained for Hb S homozygotes. The use of advanced laboratory procedures and family studies is often necessary for an accurate diagnosis.