Clinical and haematological evaluation of beta thalassaemia intermedia characterised by unusually low Hb F and increased Hb A2: beta thalassaemia intermedia II.

A total of 15 patients from different families with thalassaemia intermedia was studied. Haematological studies showed that the fetal haemoglobin was only slightly raised, being between 2 and 11.5% of the total haemoglobin. Haemoglobin A2 was high in all cases. The family study indicated that homozygosity or compound heterozygosity for beta thalassaemia was present in five patients, while dominant inheritance was observed in three. In seven patients family studies were not sufficient to predict the genotype. Haematological findings in the parents of the homozygous patients were as severe as those seen in common Hb A2 beta thalassaemia traits. The decrease in MCH and MCV was more severe and the Hb A2 higher in homozygous patients than in cases of common beta thalassaemia major (p less than 0.01, p less than 0.01, and p less than 0.001 respectively). The imbalance in in vitro globin synthesis was more severe in classical beta thalassaemia major than in homozygous patients in this study (p less than 0.01). However, the imbalance in alpha/non-alpha synthetic ratios showed variation among the homozygous and heterozygous patients in this study (2.1 to 4.0). Haematological severity and Hb F value showed some slight variation among affected persons of the same family in the case of patients with severe beta thalassaemia heterozygosity. The G gamma/A gamma ratio of haemoglobin F was found to be close to that of the adult level. Haematological studies suggested that clinical and haematological findings were more severe in patients with homozygous beta thalassaemia than in patients with heterozygosity for beta thalassaemia. The prevalence of thalassaemia intermedia with low Hb F and increased Hb A2 was found to account for 3% of the Turkish beta thalassaemic patients diagnosed before the age of 8 years.