PGY3 George Samaan presented a very interesting case of a 22 year old M who presented with 2 months of polyarthralgias and a full body rash. Physical exam was significant for multiple violaceous plaques and nodules over the face, chest and back, with tenderness to palpation over multiple joints but no evidence of erythema, swelling or synovitis.
The differential for polyarthralgias is broad and includes infectious, reactive arthritis, rheumatoid arthritis, systemic rheumatic disorders (lupus, vasculitides, Still’s disease, sarcoidosis).
Work up for infections and rheumatologic disorders were negative, including ANA, RF/anti-CCP, anti-streptolysin, ANCA, HIV, Hepatitis B/C. The patient eventually received a skin biopsy which showed Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN), and patient’s diffuse joint pain was thought to be due to paraneoplastic arthritis. BPDCN is a rare hematologic malignancy that commonly manifests as cutaneous lesions. Malignant cells can be detected in peripheral blood in ~60% of case, however the number of circulating cells is variable and may not be detected. Similarly although bone marrow involvement occurs in ~80% of cases, it may be difficult to identify the malignant cells. Diagnosis should be suspected in those presenting with brown/violaceous bruise-like lesions, and skin biopsy is necessary.
Thank you George for presenting this interesting and rare case, and for reminding us that unusual skin lesions without clear etiology may be the presenting sign of an occult malignancy!