Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired disease associated with hemolytic anemia, bone marrow failure, thrombosis, and, frequently, poor quality of life. It is caused by defects in the membrane of blood cells, where there is a lack of protein on the cell surface, which inhibits complement activation. We wanted to know the recognition of the disease in Slovenia and the incidence. We prepared the recommendations for discovering of the disease. Patients and methods: We

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... ed data of 68 patients with prospective analysis of one – year period from 1.10.2013 to 30.9.2014 whose blood was sent to the laboratory of immunology and cytology because of suspected presence of PNH clone. The analysis of peripheral blood was performed with multiparametric high specific flow cytometry in a specialized laboratory KO of Haematology University Medical Centre in Ljubljana. Results: PNH clone was positive in 13/68 (19%) patients, 55/68 (81%) patients had a negative PNH clone, most positive samples were sent from the University Medical Centre Ljubljana (7/13). 4/13 positive patients were newly discovered. In average the incidence through 10-years was 1,3 / 1,000,000 population/year. The most common cause of PNH patient referral to a specialist hematologist was unexplained cytopenia - 12/13 (92.3%), the most common symptoms were fatigue and dyspnea (100%), in 2/13 patients was present dark urine with hemoglobinuria, 2/13 patients had transient renal insufficiency. 11/13 patients with positive PNH clone had associated a bone marrow failure (aplastic anemia or myelodysplastic syndrome). The size of PNH clone varied from patient to patient. Conclusions: Early identification of PNH is a key to effective treatment and survival of patients. We recommend determining PNH clone at Coombs negative hemolytic anemia, hemoglobinuria, an unexplained cytopenia, aplastic anemia, myelodysplastic syndrome with laboratory evidence of haemolysis and unexplained thrombosis.