Rheumatoid arthritis flare mimicry by parvovirus B19.

Parvovirus B19 infection can closely mimic flares of autoimmune diseases such as rheumatoid arthritis, posing diagnostic challenges. We report a case of a 50-year-old man with seropositive rheumatoid arthritis who presented with acute symmetrical polyarthropathy, a transient rash, and profound anaemia. Initially managed as a rheumatoid flare, further evaluation revealed severe normocytic anaemia with reticulocytopenia. Bone marrow aspiration demonstrated pure red cell aplasia with characteristic giant proerythroblasts containing intranuclear inclusions. Parvovirus B19 DNA was detected by polymerase chain reaction. The patient was treated with intravenous immunoglobulin, resulting in rapid hematologic recovery and resolution of symptoms. This case underscores the importance of considering parvovirus B19 as a differential diagnosis in immunocompromised or chronically ill patients presenting with atypical rheumatologic or hematologic features. Early recognition and appropriate therapy are essential to avoid misdiagnosis and ensure optimal patient outcomes.