Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal hematopoietic disorder. It is a disease classified as one of the bone marrow failure syndromes (BMFs), but had a better prognosis due to a low rate of clone evolution or progression to acute myeloid leukemia (AML) compared with aplastic anemia (AA) or hypoplastic myelodysplastic syndromes(1-3). PNH and AA are closely correlated diseases. Nearly 30% of patients with AA can be detected a PNH clone larger than 1% (4, 5). Mutations in myeloid cancer candidate genes and its clinical correlations in AA had already been well studied(6). However, the mutational landscape and its clinical significance in PNH are still unknown.
Therefore, we performed whole-exome sequencing in peripheral blood samples from 41 patients with PNH. The 10 most frequently mutated genes included PIGA, BCORL1, RUNX1T1, MAP3K4, CSMD1, NOTCH1, FANCD2, PEG3, DIS3, and SETBP1. RUNX1T1 mutation correlated with a larger PNH clone size (p<0.001), a lower hemoglobin level (p=0.020), and a higher level of unconjugated bilirubin (p=0.008). Uncommon mutations indicating an unfavorable outcome in aplastic anemia as one group were associated with a smaller PNH clone size (p=0.017), a lower level of LDH (p=0.008), and a lower level of unconjugated bilirubin (p=0.022).
To further explore the potential role of mutations in PNH clone expansion, we compared the mutational scale of sorted CD59- and CD59+ cell fractions from 6 patients. CD59- fraction tended to have more mutations in the genes related to cell proliferation compared with CD59+ fraction (p=0.062). We also tried to explore genes correlated with thrombosis events in PNH. We found that SRRD mutation was higher in patients with visceral thrombosis (p=0.032), whereas EGR4 mutation was more common in patients with myocardial infarction (p=0.007). The number of mutations was negatively correlated with PNH clone size (p=0.036, R2=0.341).
In summary, our data verified the existence of myeloid cancer-related mutations in patients with PNH, their correlations with clinical manifestations and the potential protection effects of PNH clone in the clone evolution in BMFs. Cell expansion-related gene mutations are more common in CD59- counterparts, suggesting expansion activities dominant in the PIGA mutated clones. Apart from PNH clone size, some thrombotic related genes may also contribute to the occur of thrombosis, especially for those with small PNH clone size.
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- Bat T, Abdelhamid ON, Balasubramanian SK, Mai A, Radivoyevitch T, Clemente M, et al. The evolution of paroxysmal nocturnal haemoglobinuria depends on intensity of immunosuppressive therapy. Br J Haematol. 2018;182(5):730-3.
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- Okamoto M, Shichishima T, Noji H, Ikeda K, Nakamura A, Akutsu K, et al. High frequency of several PIG-A mutations in patients with aplastic anemia and myelodysplastic syndrome. Leukemia. 2006;20(4):627-34.
- Ogawa S. Clonal hematopoiesis in acquired aplastic anemia. Blood. 2016;128(3):337-47.
- Yoshizato T, Dumitriu B, Hosokawa K, Makishima H, Yoshida K, Townsley D, et al. Somatic Mutations and Clonal Hematopoiesis in Aplastic Anemia. New England Journal of Medicine. 2015;373(1):35-47.
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