Sickle cell–haemoglobin E (HbSE) compound heterozygosity: a clinical and haematological study

Abstract

The paucity of clinical reports in the world literature suggests that, as a disease entity, haemoglobin SE compound heterozygosity is of negligible importance. In view of the significant community prevalence of this haemoglobinopathy in the Sultanate of Oman where it is the second most prevalent sickling disorder, a hospital study of 12 SE compound heterozygotes from six unrelated Arab families was undertaken to determine their clinico-haematological features. Our findings were compared with those reviewed in the literature. Clinical and haematological evaluation was carried out by conventional methods including chromatographic haemoglobin analysis. At least 50% of those studied were asymptomatic throughout the study period but sickling-related complications occurred in the rest and included the acute chest syndrome (1/12), severe vaso-occlusive skeletal pain (2/12), frontal bossing (1/12) possibly indicative of significant chronic haemolysis and recurrent infections of the urinary tract (1/12). Steady-state haemoglobin levels fell within the reference range while MCV and MCH values were, as expected, reduced in most cases; nevertheless, concomitant inheritance of alpha-thalassaemia trait was also likely. Red cell morphology was striking by the absence or rarity of pseudo-sickled cells in the blood films of many patients during the steady state and in crises. Bearing in mind the prevalence of 0.05% of SE compound heterozygosity in Oman, the findings in this single study of the largest number of SE patients and their relatives confirm the predominantly asymptomatic nature of this sickling disorder in individuals in the community at large. HbF levels do not appear to explain the heterogeneous nature of this haemoglobinopathy. Correlation of the variable clinical and haematological features of SE cases with their alpha-globin gene status and beta-cluster haplotypes (linked to the beta(s)- and beta(e)-genes) merits a separate investigation, which is being currently organized.