We describe a new deletional form of alpha thalassemia segregating in three generations of a family of northern European origin. A full-term female girl had hypochromic, microcytic anemia since early infancy associated with delayed language development, slow growth and weight gain. Hematologic studies suggested the presence of alpha thalassemia. Gene-blotting studies showed no abnormal alpha-like globin gene fragments; however, studies of inheritance of informative polymorphic restriction fragments using zeta, alpha and 3'-alpha-hypervariable region (3'-HVR) probes showed evidence for an extensive deletion encompassing the entire alpha-like globin gene cluster. The 3' breakpoint of this deletion maps beyond the 3'-HVR, a region implicated as a hot spot for the generation of other large deletional events within the alpha-like cluster. The 5' breakpoint maps at least 10 kilobases (kb) 5' to the zeta-globin gene. The minimum size estimate for this deletion is greater than 47 kilobases
