Treatment with complement inhibitors may significantly reduce the risk of thrombosis and increase survival in patients with paroxysmal nocturnal hemoglobinuria (PNH), according to an abstract published in HemaSphere.

The study results were presented during The European Hematology Association (EHA) Hybrid Congress 2023, held in Frankfurt, Germany, this June.

For this retrospective analysis, the researchers assessed thrombotic episodes in 38 patients with PNH from 13 hematology centers in Greece. There were 17 female patients and 21 male patients, with a median age at diagnosis of 38 years. Twenty (52.6%) patients had the classic form of PNH while 16 (42.1%) patients developed PNH in the setting of another bone marrow disorder. The most common symptoms included weakness, abdominal pain, hemoglobinuria, back pain, headache, dysphagia, and erectile dysfunction.

According to the results, 92.10% of patients with PNH had anemia at diagnosis and 60.52% required red blood cell transfusion, whereas 25 patients (65.79%) had thrombocytopenia and 15.7% received platelet transfusion.

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Most commonly, patients developed thrombosis at the following sites: hepatic arteries (Budd-Chiari syndrome; n=6 patients), portal vein (n=2), mesenteric veins (n=4), and ocular arteries (n=2). Thrombosis at multiple sites was observed in 5 patients.

Of the 15 (39.47%) patients who experienced at least one episode of thrombosis, 8 (21.05%) suffered the complication at diagnosis, and the rest during the course of the disease.

Of the 8 patients who developed thrombosis at diagnosis, 6 received eculizumab and remained thrombosis-free to date (median time of follow-up was 22 months). Among 15 patients who had not suffered thrombosis but received eculizumab due to hemolytic anemia, 2 developed thrombosis during the course of the disease.

The patients received acenocoumarol as well as low molecular weight heparin as antithrombotic therapy. None of the thrombotic events was fatal.

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“Thrombosis is the most common cause of death in PNH with 29%-44% of patients experiencing at least one thromboembolic event during the course of the disease. Although thrombosis can affect any anatomical site, the most frequent sites include intra-abdominal and cerebral veins. The mechanism of thrombosis in PNH is complex and continues to be of great research interest,” Chatzileontiadou and colleagues noted.

PNH is a rare, acquired clonal hematopoietic stem cell disorder, often associated with hemolytic anemia, thrombosis, and various degrees of bone marrow failure.


Chatzileontiadou S, Loutsidi NE, Asimakopoulos I, et al. Paroxysmal nocturnal hemoglobinuria and thrombosis: a multicentric retrospective study. HemaSphere. Published online June 23, 2022. doi:10.1097/01.HS9.0000850584.11471.65.