title: Molecular basis of alpha-thalassemia in Portugal.
abstract: We have estimated the incidence and molecular basis of alpha-thalassemia in a Portuguese population, mostly from the Greater Lisbon area. In a group of 100 consecutive cord blood samples, the gene frequency of the rightward deletion (-alpha 3.7) was 0.035, and the leftward deletion (-alpha 4.2) was 0.015. In this group, we have also found four heterozygotes for the triple alpha-globin gene rearrangement (alpha alpha alpha anti 3.7. gene frequency 0.020). We have characterized the subtypes of -alpha 3.7 and alpha alpha alpha anti 3.7 rearrangements. On the whole, these results give an incidence of 10% for deletional alpha-thalassemia carriers in the studied Portuguese population. In a group of 342 subjects presenting beta-thalassemia, or Hb S trait, beta-thalassemia major sickle cell disease or low red blood cell indices, the -alpha 3.7, -alpha 4.2, -SEA, -MED, (alpha alpha)MM, and alpha alpha alpha anti 3.7 haplotypes were found in different combinations. Only one nondeletional alpha-thalassemia determinant (a 5 nucleotide deletion in the alpha 2-globin gene in the second intervening sequence donor site) was detected, which might suggest a low incidence of these defects in the Portuguese population.
authors.affiliation: Departamento de Biologia Médica, Instituto Nacional de Saúde Dr Ricardo Jorge, Lisboa, Portugal.
authors.forename: M J
authors.initials: MJ
authors.lastname: Peres
authors.forename: L
authors.initials: L
authors.lastname: Romão
authors.forename: H
authors.initials: H
authors.lastname: Carreiro
authors.forename: I
authors.initials: I
authors.lastname: Picanço
authors.forename: L
authors.initials: L
authors.lastname: Batalha
authors.forename: H A
authors.initials: HA
authors.lastname: Magalhães
authors.forename: M C
authors.initials: MC
authors.lastname: Martins
authors.forename: J
authors.initials: J
authors.lastname: Lavinha
mesh_terms: D000328:Adult; D000349:Africa / Q000208:ethnology; D000755:Anemia, Sickle Cell / Q000453:epidemiology / Q000235:genetics; D001208:Asia / Q000208:ethnology; D001483:Base Sequence; D005060:Europe / Q000208:ethnology; D005260:Female; D005312:Fetal Blood; D005787:Gene Frequency; D006580:Genetic Carrier Screening; D005820:Genetic Testing; D005838:Genotype; D005914:Globins / Q000235:genetics*; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D008297:Male; D008969:Molecular Sequence Data; D011174:Portugal / Q000453:epidemiology; D011446:Prospective Studies; D017384:Sequence Deletion; D017085:alpha-Thalassemia / Q000453:epidemiology / Q000208:ethnology / Q000235:genetics*
chemical_list: D005914:Globins