RESUMO
OBJECTIVE: To determine the clinical, haematological and genetic factors responsible for variable phenotypes of sickle haemoglobin, sickle haemoglobin-beta, and beta-thalassemia patients. METHODS: The study was conducted in Bannu, Lakki, Tank and Dera Ismail Khan districts of Khyber Pakhtunkhwa province of Pakistan from September 2016 to November 2017, and comprised sickle haemoglobin, sickle haemoglobin-beta, and beta-thalassemia patients. Clinical, haematological and genetic determinants were evaluated using haemoglobin electrophoresis and allele-specific primers through polymerase chain reaction to determine alpha and beta thalassemia, and CgT substitution at position -158 (referred to as Xmn-I polymorphism) in gamma-globin gene. Data was analysed using SPSS 20. RESULTS: Eight b-thalassemia mutations were identified that included IVS I-5(G C), codon 8/9 (+G), codon 30 (G C), -88 (C T), Cap+1(A G), codon 41/42 (-TCTT), IVS I-1(G T) and codon 16(-C). Codon 30 (G C) and -88 (C T) were found only in Pashtoon subjects, Cap+1(A G) and IVS I-1(G T) in Balochi subjects, while 75% of IVS I-5(G C) mutation cases were found in Punjabi ethnic group. In the Pashtoon group, 13 sickle haemoglobin homozygous patients were identified for the first time. Both alpha thalassemia and Xmn-I polymorphism in homozygous condition were common among those with mild phenotype. CONCLUSION: Phenotypic expression of sickle haemoglobin beta thalassemia was found to be extremely variable and alpha thalassemia and Xmn-I polymorphism in homozygous condition were found to be additional genetic modifiers of the disease.