We defined the molecular basis and analyzed hematological phenotype associated with an unusual form of
thalassemia intermedia caused by interaction of the
hemoglobin Constant Spring (
Hb CS), homozygous Hb E and alpha degrees -
thalassemia found in two unrelated pregnant Thai women. Both patients had moderate
anemia and characteristic of
thalassemia intermedia. Hb-HPLC analysis demonstrated in both cases, Hb E and
Hb Constant Spring with 3-4%
Hb Bart's. Hb F was marginally elevated (3-5%). Both of them were diagnosed hematologically as the
Hb CS EE Bart's disease.
DNA analysis revealed the homozygosity for Hb E in both cases and identified the
Hb CS mutation in trans to the alpha degrees -
thalassemia allele with the SEA deletion in one case and with the Thai deletion in another. The appearance of Hb-HPLC peak resembling the
Hb CS in peripheral blood of the two cases indicated the ability to form a tetrameric Hb molecule between alpha(CS) and beta(E) chains leading to a hybrid Hb namely the Hb E-CS (alpha2(CS)beta2(E)) with similar characteristics to
Hb CS (alpha2(CS)beta2(A)). Hematological data of the patients were presented comparatively with other forms of related disorders in our series including 2 Hb H/Hb EE diseases, 16 homozygous
Hb CS with and without Hb E, 14 Hb H diseases and 35 Hb H-CS diseases. Different genotype-phenotype correlations observed in these Thai patients with these disorders are illustrated.