The Changing Profile of Homozygous β-Thalassemia: Demography, Ethnicity, and Age Distribution of Current North American Patients and Changes in Two Decades

Abstract

Background. The age of patients with homozygous β-thalassemia is increasing because of better treatment and decreased births. A countering influence is immigration of ethnic groups with a high prevalence of thalassemia. Methods. A questionnaire sent to 48 North American centers requested information about current patients with homozygous β-thalassemia: age, clinical severity, and ethnicity. An 83% response was obtained. Twelve reference hospitals that participated in similar surveys in 1972 and 1984 were included. Results. Five hundred eighteen patients with homozygous β-thalassemia represent most North American patients. Four hundred forty-three (86%) of these had transfusion-dependent thalassemia major (TM); 75 (14%) had thalassemia intermedia (TI). Sixty-two percent were of Greek and Italian ancestry. There were approximately equal numbers of patients with TM in 5-year intervals between 0 and 25 years of age. Thereafter, the number of patients fell sharply. The mean age (±SD) of the patients with TM was 16.1 ± 9.2 years. Striking differences were seen in Italian and Greek patients compared with those of other ancestries. Sixty-six percent of the 271 Italian and Greek patients with TM were older than 16 years of age, whereas 77% of the 172 patients of other ethnic groups with TM were younger than 15 years of age. The mean age of the 75 patients with TI was greater than that of the patients with TM. Seventy-three percent of African-American patients with thalassemia had TI, compared with 0% of Southeastern Asian patients. Comparisons of patients with TM from the 12 reference hospitals for two decades show increasing mean ages of TM patients (1973, 11.4 ± 6.7 years; 1985, 14.2 ± 7.3 years; and 1993, 16.1 ± 9.2 years). Conclusions. There are probably only 750 to 1000 patients with homozygous β-thalassemia in North America. Only about 15 to 20 new cases are diagnosed each year. The increasing mean age and age distribution indicate that modern therapies are effective, but immigration of non-Mediterranean ethnic groups with thalassemia has resulted in more, younger patients. TM is increasingly becoming a disease of young adults.