The Characteristics of Compound Heterozygosity for Hemoglobin G-Makassar with Hb E in Malaysia

Human hemoglobin of G-Makassar and hemoglobin E (Hb E) are hemoglobin variants that affect Beta (β) globin. Hb G-Makassar is a very rare variant while Hb E is estimated to affect at least one million people worldwide. Both Hb G-Makassar and Hb E can be inherited in the heterozygous, homozygous or compound heterozygous state. This case series describes the characteristics of four individuals with compound heterozygosity for Hb G-Makassar/Hb E cases in Malaysia. To the best of our knowledge, these are the only four individuals with this genotype reported in the literature.

We present four cases of compound heterozygosity for Hb G-Makassar/Hb E identified from October 2014 to January 2021. All the cases were incidental findings whereby the screening Hb analysis showed the presence of peaks in both Hb S and Hb E zones on capillary electrophoresis (CE) and cation-exchange high-performance liquid chromatography (HPLC). Molecular analysis confirmed the findings of compound heterozygous Hb G-Makassar/Hb E. Two cases had a history of anemia secondary to unrelated conditions that resolved with treatment of the underlying cause. The other two cases were asymptomatic individuals who were detected through Malaysia's National Thalassemia Screening program. On the last follow-up, all the individuals were well, non-transfusion dependent, and had no reported history of chronic anemia, bleeding, hemolysis or thromboembolism complications.

The cases reported here highlight the possibilities for rare compound heterozygous states in multi-ethnicity populations such as Malaysia. Compound heterozygous Hb G-Makassar/Hb E individuals are clinically silent with laboratory values suggesting microcytic and hypochromic red blood cells. Further local epidemiology or population studies with genotyping tests are required for a better understanding of the diversity of its clinical phenotype.