Systematic literature review of published cases of reactive plasmacytosis in peripheral blood and bone marrow.

Aims: This study aims to summarise published cases of reactive plasmacytosis to provide a resource to aid haematopathologists and clinicians in the diagnostic workup of reactive plasmacytosis.

Methods: We searched published articles on reactive plasmacytosis on PubMed, Scopus and Google Scholar. Data were screened following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Cases were classified into six categories, namely: (1) infection, (2) angioimmunoblastic T-cell lymphoma (AITL), (3) other malignancies, (4) drug associated, (5) autoimmune diseases and (6) others. Plasma cell percentage in peripheral blood and/or bone marrow was tabulated. Descriptive statistics were reported as median with IQR, using JASP Team.

Results: 87 articles which reported on 146 patients were included. Infectious diseases represented most cases associated with reactive plasmacytosis (n=46, 31% of all cases), with viral infections being the most frequent (n=31, 21% of all cases). AITL was the second most frequent aetiology (n=34, 23% of all cases), followed by medications (n=28, 19% of all cases), other malignancies (n=18, 12% of all cases), miscellaneous aetiologies (n=11, 7% of all cases) and autoimmune diseases (n=9, 6% of all cases). The absolute and relative levels of plasma cells in each diagnostic category showed marked variation and ranges largely overlapped between categories.

Conclusions: In patients with an increase in the number and/or proportion of plasma cells in peripheral blood and/or bone marrow, clinical context and a broad differential diagnosis are necessary to direct further evaluation and arrive at a correct diagnosis. Our literature review suggests that evaluation for infectious causes and AITL may be of the greatest yield in many cases.