Five Rare β Globin Chain Hemoglobin Variants in India.

Thalassemias as well as structural hemoglobin (Hb) variants are common monogenic inherited disorders of Hb in India. In this paper we describe 5 rare β-chain Hb variants identified in the Indian population on the basis of high performance liquid chromatography (HPLC). Of these 3 were identified during antenatal screening of β-thalassemia while the other 2 cases were referred to us for a diagnostic work up. These 5 Hb variants were Hb British Columbia (β CD 101 GAG → AAG), Hb Saint Louis (β CD28 CTG → CAG), Hb G Coushatta (β CD 22 GAA → GCA), Hb Pyrgos (β CD 83 GGC → GAC) and Hb Agenogi (β CD 90 GAG → AAG). Hb Saint Louis and Hb G Coushatta eluted in the HbA2 window, Hb British Columbia and Hb Agenogi eluted in the Hb C window while Hb Pyrgos eluted in an unknown window on HPLC. They were all identified by DNA sequencing. The child having Hb St. Louis had hepatosplenomegaly and anemia while the individuals with the other 4 variants were asymptomatic. Rare Hb variants are diagnostic curiosities that may be encountered by laboratories. Correct identification requires the application of more than one technique to avoid misdiagnosing them as more common variants (e.g. St. Louis and G Coushatta as E or D Iran on HPLC. Some, like G Coushatta may interfere with HPLC-based HbA1c estimation).