A case of post-viral lymphoma-like syndrome unmasking systemic lupus erythematosus

This case describes a rare presentation of new-onset systemic lupus erythematosus (SLE) that closely mimicked malignant lymphoma following influenza A, adding to limited evidence of a temporal relationship between viral infection and subsequent autoimmune disease. A previously healthy woman in her 30s developed diffuse lymphadenopathy, severe polyarthralgias, high fevers, and night sweats shortly after recovering from influenza. PET-CT showed intensely hypermetabolic lymph nodes and splenic and marrow uptake concerning for lymphoma, but lymph node biopsy revealed acute lymphadenitis without malignancy. Rheumatologic studies showed strongly positive ANA, anti-dsDNA, anti-SSB, and anti-RNP antibodies. Although her symptoms partially improved with supportive care, she later developed a malar rash and stenosing tenosynovitis, leading to a confirmed diagnosis of SLE and initiation of hydroxychloroquine with sustained clinical response. This case highlights the diagnostic difficulty of distinguishing SLE from lymphoma when lymphadenopathy and constitutional symptoms dominate, and underscores the limited specificity of PET-CT in this setting. Clinicians should consider autoimmune disease in lymphoma-like presentations and rely on biopsy and serologic evaluation to guide diagnosis when imaging is inconclusive.