Hematology of beta-thalassemia trait--age-related developmental aspects and intrafamilial correlations.

Beta-thalassemia trait is a frequent cause of microcytic anemia in Mediterranean children. Because striking age-related changes occur in hemoglobin and mean corpuscular volume during childhood, we assessed developmental hematologic characteristics of 132 patients less than or equal to 18 years of age with beta-thalassemia trait. Thirty-nine kindred were studied to examine intrafamilial correlations of hematologic abnormalities. Patients with beta-thalassemia trait demonstrated Hgb values about 2 gm/dl below normal standards, with a progressive rise with age paralleling normal trends. Thalassemic MCV values showed a far greater deviation from normal than Hgb levels. In contrast to normal developmental trends which show a sharp increase in the first five years of life, the MCV in thalassemia trait showed no age-related increase prior to adolescence. No age-related changes in hemoglobin A2 levels were noted. Kindred studies demonstrate a correlation of the degree of anemia, microcytosis, and elevated hemoglobin A2 levels in affected family members (r = 0.318 P < 0.004, r = 0.525 P < 0.001, r = 0.416 P < 0.0015, respectively). Our findings support the use of electronically determined MCV values as an initial screening procedure for children with beta-thalassemia trait. Values of < 70 fl prior to adolescence and < 75 fl during adolescence were present in nearly all thalassemic subjects. Intrafamilial correlations of Hgb, MCV, and hemoglobin A2 levels suggest that these characteristics are genetically determined.