Epidemiologic sequential analysis of pure red blood cell aplasia and T-cell large granular lymphocyte leukemia in Korea.

Pure red cell aplasia (PRCA) is a rare hematologic syndrome characterized by anemia with marked reticulocytopenia and, in Asia, is often accompanied by T-cell large granular lymphocyte leukemia (T-LGL). Minimal research has been done on the epidemiology and sequential events of PRCA combined with T-LGL. This study identified 2801 PRCA and 840 T-LGL patients by using big data of the National Health Insurance Service between 2003 and 2022. The average annual crude incidence of PRCA was 2.77 per million and remained stable over 20 years, while T-LGL incidence was 0.82 per million with an increasing trend, possibly reflecting improved diagnostic accessibility. The average age for PRCA and T-LGL onset increased over the study period, consistent with aged society. Associated PRCA conditions are rheumatic diseases (10.5%), thymoma (4.7%), parvovirus infection (1.0%), inflammatory bowel diseases (0.8%), T-LGL (0.6%) and no specific cause (82.4%). Among 18 patients with both PRCA and T-LGL, PRCA preceded T-LGL (50%) or diagnosed concurrently (44%), suggesting that autoreactive T cells in PRCA which suppress erythropoiesis and sequentially evolve into clonal T cell proliferation and, eventually, T-LGL occurrence. This observation supports the hypothesis that both conditions might share a common pathogenic pathway. Further study should identify the causal relationship of PRCA diagnosis followed by T-LGL diagnosis.