Distinct subgroups of paroxysmal nocturnal hemoglobinuria (PNH) with cytopenia: results from South Korean National PNH Registry

We retrospectively assessed the clinical characteristics of patients with paroxysmal nocturnal hemoglobinuria (PNH) according to severity of cytopenia. A total of 282 patients with hematological parameters assessed at the time of diagnosis of PNH were included. There were 24 patients with PNH/severe aplastic anemia (SAA) (at least two of the three criteria; hemoglobin ≤8 g/dL; absolute neutrophil count (ANC) <0.5 × 10⁹/L; platelet count <20 × 10⁹/L), 96 patients with PNH/aplastic anemia (AA) (at least two of the three criteria; hemoglobin ≤10 g/dL; ANC 0.5–1.5 × 10⁹/L; platelet count 20–100 × 10⁹/L), and 162 classic PNH patients. Compared with the classic PNH subgroup, the PNH/SAA subgroup had a significantly lower median granulocyte PNH clone size (26.7 vs. 51.0 %, P = 0.021) and lower incidence of lactate dehydrogenase ≥1.5 times the upper limit of normal (52.9 vs. 80.0 %, P = 0.049). The incidence of thromboembolism was similar in both subgroups. Overall survival was significantly lower in the PNH/SAA subgroup than in the classic PNH subgroup (P = 0.033). Our findings suggest that identification of patients with PNH/SAA at the time of diagnosis is important because of different clinical manifestations and poorer outcome compared with patients with classic PNH (clinicaltrials.gov identifier: #NCT01224483).