[Clinical and pathophysiological features of acquired pure red cell aplasia: based on the concept of T-cell dysregulations].

Acquired pure red cell aplasia (PRCA) develops in a variety of contexts and thus, should be regarded as a syndrome. The three major subtypes of acquired PRCA are idiopathic PRCA, T cell large granular lymphocytic leukemia (T-LGLL)-associated PRCA, and thymoma-associated PRCA. Although the Japanese National Research Group on Idiopathic Bone Marrow Failure Syndromes of the Ministry of Health, Labor and Welfare of Japan has made significant contributions to our understanding of PRCA, details of its clinical characteristics, and pathophysiological mechanisms remain largely unknown. A recent epidemiological analysis using the JSH Hematologic Disease Registry revealed that approximately 100 new cases with acquired PRCA were diagnosed annually in Japan, which was higher than previously thought to be. The median age of the patients was 73 years. A prospective observational study on chronic PRCA (PRCA2016) is currently ongoing, and it may provide new clinical insights into acquired PRCA. Dysregulation of T cells has been shown to play a central role in PRCA. We studied T cell clonalities and STAT3 mutations in 90 PRCA patients and discovered that clonal T cell expansions were frequently recognized and closely associated with STAT3 mutations in the three major types of PRCA.