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

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 Az and F levels were either normal or low. The most common deletional and nondeletional forms of cl-thalassemia [-alpha (3.7), -alpha (4.2), --(MED), -(alpha)(20.5), alpha (HphI)alpha, alpha (NcoI)alpha, alpha alpha (NcoI) and alpha (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 -alpha (3.7) deletion (-alpha (3.7)/alpha alpha) and 18 (5.3%) homozygous (-alpha (3.7)/-alpha (3.7)), 5 (1.5%) were heterozygous for the nondeletional form alpha (HphI)alpha (alpha (HphI)alpha/alpha alpha), and 1 (0.3%) was a --(MED) carrier (--(MED)/alpha alpha). Among the Blacks, 56 (57.1%) showed the -alpha (3.7)/ alpha alpha genotype, whereas 12 (12.2%) were -alpha (3.7)/-alpha (3.7) and 1 (1.0%) was an alpha (HphI)alpha carrier; among the Caucasians, 89 (36.9%) were -alpha (3.7)/alpha alpha, 6 (2.5%) had the -alpha (3.7)/-alpha (3.7) genotype, 4 (1.7%)presented the nondeletional form (alpha (HphI)alpha/alpha alpha), and 1 (0.4%) was a --(MED) carrier. These results demonstrate that a-thalassemia, mainly through the -alpha (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.