The evolutionary and clinical implications of the uneven distribution of the frequency of the inherited haemoglobin variants over short geographical distances

Abstract

SummaryStudies of the frequency of heterozygous carriers for common inherited diseases of haemoglobin in over 7500 adolescent children in 25 districts in Sri Lanka have disclosed a highly significant variation over very short geographical distances. A further analysis of these findings, including their relationship to the past frequency and distribution of malaria, climatic variation, altitude, ethnic origin and consanguinity rates, have provided evidence regarding the evolutionary basis for the variable distribution of these conditions over short distances. It is likely that the complex interplay between malaria and the environment, together with related ethnic and social issues, exists in many countries across the tropical belt. Hence, these observations emphasise the importance of micromapping heterozygote distributions in high-frequency countries in order to define their true burden and the facilities required for the prevention and management of the homozygous and compound heterozygous disorders that result from their interaction.

Anaemia in children: are we using the correct prevention strategies?

“…However, a recent survey showed a high (8.0%) prevalence of -thalassaemia trait [7]. Surprisingly, -thalassaemia is more prevalent than betathalassaemia and IDA in many parts of the country (Table 1) [7]. In contrast to what was previously described, this data suggests, that haemoglobinopathy rather than ID is the likely cause of anaemia in a significant proportion of children.…”

“…This is due to the rarity of clinically significant -thalassaemia (haemoglobin H disease and Barts hydrops foetalis) in Sri Lanka and to technical difficulties in confirming -thalassaemia trait which is only feasible through DNA analysis. However, a recent survey showed a high (8.0%) prevalence of -thalassaemia trait [7]. Surprisingly, -thalassaemia is more prevalent than betathalassaemia and IDA in many parts of the country (Table 1) [7].…”

“…Milder form of the disease which is due to heterozygous mutations of the -globin gene is known as -thalassaemia trait [12]. A recent island wide survey in Sri Lanka reported on the prevalence of -thalassaemia trait (2.0%), HbE trait (0.5%), sickle cell trait (0.1%) and HbD trait (0.2%) [7]. Collectively this contributes to an overall prevalence of 2.8% of heterozygous -globin mutations which accounts for approximately 19% of children with asymptomatic anaemia.…”

Re: Anaemia and iron deficiency in pregnant women attending an antenatal clinic in a Teaching Hospital in Southern Sri Lanka

“…The National prevalence of β-thalassaemia trait is reported as 2.8% and the prevalence in the Galle District where this study was conducted 1.0%. Contrarily to previous believes, a recent island wide survey by Premawardhana et al reported that the prevalence of α-thalassaemia trait is as high as 8.0% in Sri Lanka and that it is found in every district including Galle [2]. As reviewed by us previously, α-thalassaemia is commoner than β-thalassaemia and may in fact be as common as iron deficiency anaemia [3].…”

“…, DGH de Silva 2 We read with interest the article by Senadheera et al, which describe the rate of anaemia and iron deficiency in women presenting for antenatal care in a Teaching Hospital in the Galle District of Sri Lanka [1]. We agree with the content on the rate of anaemia defined as haemoglobin concentration <11g/dl however, the subsequent analysis to determine a cut-off level of serum ferritin for detection of anaemia is inaccurate.…”