Alpha-thalassemias are among the most common genetic diseases in the world. They
are characterized by hypochromic and microcytic anemia and great clinical
variability, ranging from a practically asymptomatic phenotype to severe anemia,
which can lead to intrauterine or early neonatal death. Deletions affecting the
α-globin genes, located on chromosome 16p13.3, are the main causes of
α-thalassemia. Multiplex ligation-dependent probe amplification (MLPA) can be
used to detect rearrangements that cause α-thalassemia, particularly large
deletions involving the whole α cluster and/or deletions in the HS-40 region.
Here, MLPA was used to investigate the molecular basis of α-thalassemia in five
unrelated patients, three of whom had Hb H disease. In addition to the
-α3.7 deletion identified in the patients with Hb H disease, four
different α0 deletions removing 15 to 225 kb DNA segments were found:
two of them remove both the α genes, one affects only the regulatory element
(HS-40) region, and another one extends over the entire α cluster and the HS-40
region. These results illustrate the diversity of α-thalassemia deletions in the
Brazilian population and highlight the importance of molecular investigation in
cases that present with microcytosis and hypochromia without iron deficiency and
normal or reduced Hb A2 levels..