Patients with thalassemia in the United States

Thalassemia is one of the most common monogenic diseases of man, prevalent in tropical and subtropical regions of the world. Population migration during the past decades has led to increasing numbers of these patients being encountered in all parts of the world, including in the United States. A clinical research network, supported by National Institutes of Health (NIH), was established to study β-thalassemia major/intermedia. A report on disease complications was published in July 2004, based on 342 patients (222 in the United States and 120 in Toronto).¹ 

Our laboratory was established in 2003 to provide molecular diagnosis of hemoglobinopathies and thalassemias. In the past 18 months, we have genotyped 40 β-thalassemia major/intermedia patients of all ethnic backgrounds (Table 1). Only 4 cases are of Mediterranean ancestry, hitherto the source of most β-thalassemia patients in our country. Seventy percent of the cases are 15 years of age or younger. They reside in Massachusetts (18), Rhode Island (3), West Virginia (4), New York (1), Maryland (3), and Georgia (11). Surprisingly, only one patient in this recently diagnosed cohort has the β-thalassemia mutation genotype [IVS1-6 (T>C)/IVS1-110 (G>A)] that corresponds to 1 of the 5 genotypes reported to be most commonly found in the United States.¹ 

These findings highlight the fact that β-thalassemia is more common and diverse than generally thought of in the United States; many of the recently diagnosed patients are not of the Mediterranean ancestry any more. They also suggest that carrier screening and genetic counseling may not be used optimally for this disease (12 of our patients are 5 years of age or younger). Additionally, our laboratory has diagnosed 11 cases of clinically significant hemoglobin (Hb) H disease³  from Massachusetts, New York, and Georgia: 1 (- -^MED/-α^3.7); 5 (- -^SEA/-α^3.7), including 1 Hb E heterozygote; and 5 (- -^SEA/α^{Constant Spring} α), including 2 Hb E heterozygotes. Efforts devoted to community public education appropriately adapted to different cultures and languages, continuous education for health care providers, and research in disease pathophysiology and treatment for α- and β-thalassemias are needed.