Haemoglobin Olympia {β Codon 20 (B2) G→A, Val→Met}: A Silent Haemoglobin Variant

Abstract

High oxygen affinity haemoglobin variants are rare and often underdiagnosed in persistent erythrocytosis with no apparent aetiology. Here the author present a 29-year-old Indian male patient with a long-standing history of erythrocytosis which was incidentally detected. The proband had a prothrombotic family history of cerebral vessel stroke in his paternal grandfather at a young age and unexplained erythrocytosis in his father and brother. A review of his haemograms showed persistent high haemoglobin values. Routine tests did not reveal any specific aetiology and haemoglobin electrophoresis by High-Performance Liquid Chromatography (HPLC) showed absence of any abnormal peak or unstable haemoglobin. DNA sequencing of the β globin gene revealed heterozygosity for codon 20 {GTG→ATG, Valine (Val)→ Methionine (Met)} mutation confirming the presence of an electrophoretically silent Hb variant - Haemoglobin Olympia in him and his extended family members. This case study emphasises importance of this rare entity of high oxygen affinity haemoglobin variant as a differential diagnosis while screening for erythrocytosis. This is the first case report of Haemoglobin Olympia from India reported in the literature.

Keywords

• : electrophoresis
• haematocrit
• mutation
• oxygen affinity
• polycythemia