Introduction : Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired stem cell disorder that manifests by hemolytic anemia, thrombosis and cytopenia. There are no data on PNH among Omani patients. Methods : We performed a retrospective review of all patients tested for PNH by flow cytometry at the Sultan Qaboos University Hospital between 2012 and 2019. Manifestations, treatment modalities and outcomes were assessed. Results : Total of 10 patients were diagnosed or were on follow up for PNH (median age 22.5 years). Clinical manifestations included fatigue (80%) and anemia (70%). There were six patients who had classical PNH with evidence of hemolysis, three patient had PNH in the context of aplastic anemia, and one patient with subclinical PNH. The median reported total type II+III clone size was 95.5 (range 1.54-97) in neutrophils (FLAER/CD24) and 91.6 (range 0.036-99) in monocytes (FLAER/CD14). There were four patients who were found to have a clone size > 50% at time of diagnosis. The median follow up of the patients were 62 months (range: 8-204). One patient suffered thrombosis. Three patients were on immunosuppressant agents, five were initiated on eculizumab and four had bone marrow transplant. No deaths were reported in the cohort. Estimated average incidence rate was 1.5 per 5,000,000. Conclusion PNH is rare in the Omani population with predominance presentation with hemolytic anemia. Keywords: Flow cytometry, granulocytes, Quantification, Aplastic anemia, Paroxysmal Nocturnal Hemoglobinuria

Introduction : Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired stem cell disorder that manifests by hemolytic anemia, thrombosis and cytopenia. There are no data on PNH among Omani patients. Methods : We performed a retrospective review of all patients tested for PNH by flow cytometr...