title: Alpha thalassaemia and extended alpha globin genes in Sri Lanka.
abstract: The α-globin genes were studied in nine families with unexplained hypochromic anaemia and in 167 patients with HbE β thalassaemia in Sri Lanka. As well as the common deletion forms of α(+) thalassaemia three families from an ethnic minority were found to carry a novel form of α(0) thalassaemia, one family carried a previously reported form of α(0) thalassaemia, --(THAI), and five families had different forms of non-deletional thalassaemia. The patients with HbE β thalassaemia who had co-inherited α thalassaemia all showed an extremely mild phenotype and reduced levels of HbF and there was a highly significant paucity of α(+) thalassaemia in these patients compared with the normal population. Extended α gene arrangements, including ααα, αααα and ααααα, occurred at a low frequency and were commoner in the more severe phenotypes of HbE β thalassaemia. As well as emphasising the ameliorating effect of α thalassaemia on HbE β thalassaemia the finding of a novel form of α(0) thalassaemia in an ethnic minority, together with an unexpected diversity of forms of non-deletion α thalassaemia in Sri Lanka, further emphasises the critical importance of micro-mapping populations for determining the frequency of clinically important forms of the disease.
authors.affiliation: National Cancer Institute, Maharagama, Sri Lanka.
authors.forename: Sasikala
authors.initials: S
authors.lastname: Suresh
authors.forename: Christopher
authors.initials: C
authors.lastname: Fisher
authors.forename: Helena
authors.initials: H
authors.lastname: Ayyub
authors.forename: Anuja
authors.initials: A
authors.lastname: Premawardhena
authors.forename: Angela
authors.initials: A
authors.lastname: Allen
authors.forename: Ashok
authors.initials: A
authors.lastname: Perera
authors.forename: Dayananda
authors.initials: D
authors.lastname: Bandara
authors.forename: Nancy
authors.initials: N
authors.lastname: Olivieri
authors.forename: David
authors.initials: D
authors.lastname: Weatherall
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D003241:Consanguinity; D003434:Crossing Over, Genetic; D005260:Female; D005838:Genotype; D006446:Hemoglobin E / Q000235:genetics; D006455:Hemoglobins, Abnormal / Q000235:genetics; D006801:Humans; D007514:Islam; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D010641:Phenotype; D017354:Point Mutation; D026723:Polyadenylation / Q000235:genetics; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000235:genetics; D022821:RNA Splice Sites / Q000235:genetics; D017384:Sequence Deletion; D013188:Sri Lanka / Q000453:epidemiology; D055542:alpha-Globins / Q000172:deficiency / Q000235:genetics*; D017085:alpha-Thalassemia / Q000453:epidemiology / Q000208:ethnology / Q000235:genetics*
chemical_list: D006455:Hemoglobins, Abnormal; D022821:RNA Splice Sites; D055542:alpha-Globins; C581983:hemoglobin Koya Dora; C039216:hemoglobin Evanston; D006446:Hemoglobin E