Hemoglobin sickle-Lepore: report of two siblings and review of the literature.

Hemoglobin Lepore is composed of two normal alpha-globin chains and two delta-beta fusion globin chains that result from nonhomologous crossing over of genetic material during meiosis. The doubly heterozygous condition of sickle hemoglobin with Lepore hemoglobin (Hb S-Lepore) is rare, having been described previously in only nine patients. We report two siblings with Hb S-Lepore who have similar hematologic characteristics but a marked difference in clinical severity.