Pediatric Clinics of North America - CIPERJ

THALASSEMIA UPDATE
451
Fig. 1. Changing demographics of patients who have thalassemia in the North American Thalassemia
Clinical Research Network. Patients of Asian descent predominate in the younger population.
(From Vichinsky EP, Macklin EA, Waye JS, et al. Changes in the epidemiology of
thalassemia in North America: a new minority disease. Pediatrics 2005;116(6):e818–25; with
permission.)
of 6.9 million in the census count in 1990. Coupled with other changes that
have occurred over the past few decades, it is estimated that up to 100 million
people of African, Hispanic, Southern and Eastern European, Middle
Eastern, and Asian ethnic backgrounds reside in the United States. Similarly,
it is estimated that approximately one sixth of the Canadian population
is foreign born. This includes a considerable influx of Asians: in the
1990s more than 2 million people immigrated to Canada, approximately
half from Asia. Many of the ethnic immigrants who relocated to North
America are carriers of globin gene mutations, which have important implications
for carrier screening. Recent reports reveal births of children who
have severe a- orb-thalassemia in which appropriate screening and counseling
was not offered to the parents [18].
Screening is inexpensive and simple but requires clinicians to be astutely
attentive and aware of potential carriers. A complete blood cell count identifies
microcytosis and hypochromia, which are present in nearly all thalassemia
carriers at risk for having babies who have a severe thalassemia
syndrome. In an adult, a mean corpuscular volume of less than 80 fL and
mean corpuscular hemoglobin of less than 27 pg should alert a clinician
to perform further screening, specifically hemoglobin electrophoresis and,
in some cases, globin genotype testing. In addition, b-thalassemia carriers
have elevated hemoglobin A 2 on adult electrophoresis unless there is
concomitant iron deficiency, which may falsely normalize the hemoglobin