Sickle cell anemia associated with α‐thalassemia in Malaysian Indians

The Indian rubber estate workers in Negri Sembilan, Malaysia, who originated from Orissa in India were found to have a high frequency of Hb S (Joishy SK, Hassan K: Clin Res 28:280, 1980). Unlike the usually severe clinical picture of sickle cell anemia seen in African and American blacks, the clinical picture of the disease in this population was mild and many have reached old age. We studied the leukocyte DNA of 12 patients with sickle cell anemia, ranging in age from 4 to 61 years and 30 sickle cell trait carriers, ranging in age from 7 to 63 years, for the presence of α‐globin gene deletions by gene mapping according to Southern (Southern EM: J Mol Biol 98:503, 1975), using α‐ and ζ‐globin gene probes obtained by nick translation of the α‐ and ζ‐globin genes cloned into plasmid. All 12 sickle cell anemia patients were found to have α‐thalassemia2 (α‐thal2), either in the homozygous or heterozygous condition. Of the Hb S trait carriers, six did not have α‐that2 or or‐thal1 and 24 had α‐thal2 (15 heterozygous, 9 homozygous). Seven of these Hb S trait carriers with α‐thal2 had an additional gene abnormality. Five of them had a fast‐moving Eco RI fragment 5.6 kb long that hybridized with ζ‐specific probe but not with α‐specific probe. An unusual DNA pattern of a different type was further found in the other two. Bgl II restriction analysis showed that the α‐thal2 was mostly of the rightward deletion α‐thal2 genotype. None of the sickle cell anemia patients and Hb S trait carriers had deletion type α‐thal1. The sickle cell anemia patients had very high levels of Hb F and low levels of Hb A2. The Hb S trait carriers with α‐thal2 had relatively low levels of Hb S.