High prevalence of alpha-thalassemia among individuals with microcytosis and hypochromia without anemia

Abstract

In order to determine the contribution of a-thalassemia to microcytosis and hypochromia, 339 adult outpatients seen at Unicamp University Hospital (with the exception of the Clinical Hematology outpatient clinics), who showed normal hemoglobin (Hb) levels and reduced mean corpuscular volume and mean corpuscular hemoglobin, were analyzed. Ninety-eight were Blacks (28.9%) and 241 were Caucasians (71.1%). In all cases, Hb A 2 and F levels were either normal or low. The most common deletional and nondeletional forms of a-thalassemia [-a 3.7 , -a 4.2 , --MED , -(a) 20.5 , a HphI a, a NcoI a, aa NcoI and a TSAUDI ] were investigated by PCR and restriction enzyme analyses. A total of 169 individuals (49.9%) presented a-thalassemia: 145 (42.8%) were heterozygous for the -a 3.7 deletion (-a 3.7 /aa) and 18 (5.3%) homozygous (-a 3.7 /-a 3.7 ), 5 (1.5%) were heterozygous for the nondeletional form a HphI a (a HphI a/aa), and 1 (0.3%) was a --MED carrier (--MED /aa). Among the Blacks, 56 (57.1%) showed the -a 3.7 / aa genotype, whereas 12 (12.2%) were -a 3.7 /-a 3.7 and 1 (1.0%) was an a HphI a carrier; among the Caucasians, 89 (36.9%) were -a 3.7 /aa, 6 (2.5%) had the -a 3.7 /-a 3.7 genotype, 4 (1.7%) presented the nondeletional form (a HphI a/aa), and 1 (0.4%) was a --MED carrier. These results demonstrate that a-thalassemia, mainly through the -a 3.7 deletion, is an important cause of microcytosis and hypochromia in individuals without anemia. These data are of clinical relevance since these hematological alterations are often interpreted as indicators of iron deficiency.

An investigation of the protective effect of alpha+‐thalassaemia against severe Plasmodium falciparum amongst children in Kumasi, Ghana

“…A number of studies done in different parts of the country all seem to be in agreement with the 20 to 30% prevalence rate of alpha+-thalassemia in West Africa (Borges, et al, 2001), though there are some slight variations (Mockenhaupt et al, 2001;Mockenhaupt et al, 2004a;May et al, 2007). Ghana-α 3.7 gene frequency between .26-.33…”

Alfa-talassemia deve ser considerada no diagnóstico diferencial de anemia na criança

“…In a study conducted in the state of Minas Gerais, southeastern Brazil, we demonstrated coinheritance of alpha-thalassemia in 30% of children with sickle cell anemia from a random sample of newborn screening. 3 This prevalence rate was also observed in other Brazilian states 4,5 (see also references 9, 37, and 38 within our reference 3 ). Rates are also high in Caucasian populations, such as in Ontario, Canada, where the prevalence of some form of α 3.7 deletion was 24.4% in adult patients referred for microcytosis investigation, defined as mean corpuscular volume (MCV) < 80 fL, after exclusion of iron deficiency.…”

“…Among 241 Caucasian participants, the prevalence was 39.4%. 4 We may infer from those studies that the prevalence of a silent carrier state (deletion of one gene) and alpha-thalassemia trait (deletion of two genes) is high in the Brazilian population. This assumption is particularly true for individuals of African descent, represented in different studies by patients with sickle cell disease or by black or brown-skinned subjects, but it also applies to "Caucasians", who may actually be representatives of the ethnic mix characteristic of Brazil.…”

Talassemias alfa

“…1 Apesar da elevada freqüência da talassemia α no Brasil, essa é a hemoglobinopatia menos investigada em nosso meio. Assim como na maioria das populações estudadas, a expressiva maioria dos casos relatados na população brasileira refere-se à talassemia α + resultante da deleção de um gene α, especificamente a deleção -α 3,7 . Quanto à doença da Hb H, são poucos os casos relatados em nosso país.…”

“…6 Borges et al observaram freqüência de talassemia alfa (deleção -α 3,7 ) de 49,9% em indivíduos com microcitose e hipocromia sem anemia, provenientes da região Sudeste. 7 …”