Haemoglobin CO-Arab Mimicking HbSS and HbSC: A Case Report

Introduction: Haemoglobin C-O Arab is an infrequent condition with limited literature documentation. The underlying mutations in HbC and HbO-Arab affect positions 6Glu → Lys and 121Glu → Lys of the Beta-globin gene, respectively. Interestingly, when both HbC and HbO-Arab are inherited, the individual has the same mutations (Glu → Lys) at different positions (6 and 121) of the same globin chain. The consequences of these interactions make this a unique and enigmatic condition. Aim: To report a case of HbCO-Arab mimicking HbSS in a patient. Method: A case report of the patient’s clinical note. Results: A 26-year-old Fulani lady presented to the Haematology Day Care (HDC) due to varying Hb electrophoresis results. She gave a history of recurrent headaches, occasional bone pains and easy fatiguability. However, no history of jaundice or blood transfusions. Hb electrophoresis done at 6 years was suggestive of HbSS. No history suggestive of sickle cell complications except for a history of parapneumonic effusions at the age of 21 years. Two of her siblings are said to be patients living with sickle cell disease. There was no jaundice, pallor, cyanosis or sickle cell habitus. Four previous Hb electrophoreses using alkaline media revealed a single band in the S position except for one, which showed two bands in the S and C regions. A repeat upon presenting to the unit showed a single band at the S region on alkaline electrophoresis. Haematocrit over three years ranged from 32.7% to 40.8% Given the atypical presentation (history and physical examination) and discrepancies in electrophoresis results, HPLC was done. The presence of an unknown band further added to the diagnostic dilemma. The sample was then sent to the Synnovis Special Haematology Laboratory at Guys and St Thomas Hospital, London, for further testing. Sanger sequencing was performed on the beta-globin genes. This demonstrated compound heterozygous mutations for Hb C due to the HBB;c.19G>A and Hb O-Arab due to the HBB;c.364G>A mutations. Conclusion: A high index of suspicion and domesticated diagnostic algorithms are needed, especially in resource-constrained settings.