title: Haemoglobinopathies that occur with decreased HbA2 levels: a gene mutation set involving the δ gene at a Spanish centre.
abstract: OBJECTIVE
  Haemoglobin A2(HbA2) consists of two globin chains, α and β. Alterations in any of these genes influences the level of HbA2. Here, we present cases of structural Hb variants and thalassaemias which present either alone or together and reduce the level of HbA2at varying degrees. Furthermore, we present a novel structural mutation in the δ globin gene, called Hb A2-Madrid.
  
  
  METHODS
  The levels of HbA2and HbF and the different haemoglobin variants were measured and analysed by ion exchange high performance liquid chromatography (HPLC, VARIANT II), the types of haemoglobins were determined by capillary zone electrophoresis (CZE) (Sebia) and the globin chains were determined by reversed-phase HPLC. Genetic analysis was performed by automatic sequencing of the α and δ genes as well as by multiple PCRs for the α globin genes.
  
  
  RESULTS
  In α thalassaemia (n=94), the HbA2levels ranged from 1.39% to 2.43%. Among individuals with δ thalassaemia (n=5), the HbA2level of those with δ+thalassaemia was 1.77%, and that of those with δ0thalassaemia was 1.70%. Among the individuals with δβ thalassaemia (n=13), those who were homozygous lacked HbA2. All structural haemoglobinopathies (n=97) were heterozygous; the α chain variants (n=84) presented with an HbA2level of 1.76%, while the δ chain variants (n=13) presented with a level of 1.75%.
  
  
  CONCLUSIONS
  HbA2is an essential parameter in the diagnostics of haemoglobinopathies. HPLC-EC and CZE allow the quantification of HbA2. Here, we show that quantification of HbA2is critical for the identification of α, δ and βδ thalassaemias. Structural variants are discovered by HPLC. Molecular genetics is required for the proper identification of the mutations. Only with this knowledge is genetic counselling possible.
authors.affiliation: Servicio de Hematología y Hemoterapia, Hospital Clínico San Carlos, IdISS, Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Villegas
authors.affiliation: Servicio de Hematología y Hemoterapia, Hospital Clínico San Carlos, IdISS, Madrid, Spain.
authors.forename: Fernando Ataúlfo
authors.initials: FA
authors.lastname: González
authors.affiliation: Servicio de Hematología y Hemoterapia, Hospital Clínico San Carlos, IdISS, Madrid, Spain.
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Nieto
authors.affiliation: Servicio de Hematología y Hemoterapia, Hospital Clínico San Carlos, IdISS, Madrid, Spain.
authors.forename: Félix
authors.initials: F
authors.lastname: de la Fuente-Gonzalo
authors.affiliation: Servicio de Hematología y Hemoterapia, Hospital Clínico San Carlos, IdISS, Madrid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Martínez
authors.affiliation: Servicio de Análisis Clínicos, Hospital Clínico San Carlos, Madrid, Spain.
authors.forename: María Josefa
authors.initials: MJ
authors.lastname: Torrejón
authors.affiliation: Servicio de Hematología y Hemoterapia, Hospital Clínico San Carlos, IdISS, Madrid, Spain.
authors.forename: Paloma
authors.initials: P
authors.lastname: Ropero
mesh_terms: D002851:Chromatography, High Pressure Liquid; D019075:Electrophoresis, Capillary; D006443:Hemoglobin A2 / Q000235:genetics*; D006453:Hemoglobinopathies / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D009154:Mutation; D017085:alpha-Thalassemia / Q000097:blood / Q000175:diagnosis / Q000235:genetics; D017086:beta-Thalassemia / Q000097:blood / Q000175:diagnosis / Q000235:genetics; D055538:delta-Thalassemia / Q000097:blood / Q000175:diagnosis / Q000235:genetics
chemical_list: D006443:Hemoglobin A2
keywords: DNA; HAEMOGLOBINOPATHY; THALASSAEMIA