The Great Mimickers: Navigating Diagnostic Pitfalls in Modern Rheumatology

Background Rheumatological mimics frequently cause diagnostic errors and unnecessary immunosuppression due to overreliance on positive serology or non-specific imaging. This review evaluates eight illustrative cases where initial objective findings heavily conflicted with the final, etiology-driven diagnosis. Methods A retrospective chart review of eight patients from a tertiary rheumatology practice was performed. Cases were selected based on significant incongruence between initial laboratory or high-sensitivity imaging profiles and the final clinical etiology. A literature search across PubMed and Google Scholar up to June 2026 contextualized these pitfalls. Results The cohort highlighted critical diagnostic traps: crystal arthropathy misdiagnosed as systemic vasculitis, lupus phenocopies, and structural/functional disorders (e.g., temporomandibular joint dysfunction) misattributed to fibromyalgia. Comprehensive clinical re-evaluation led to the cessation of inappropriate immunomodulatory treatments and the initiation of targeted, etiology-specific therapies. Comprehensive re-evaluation led to the cessation of inappropriate immunomodulatory treatments in all eight patients, with six receiving targeted etiology-specific therapies and two benefiting from lifestyle or occupational modifications. Conclusions Isolated laboratory titers and imaging findings must never supersede strict clinical correlation. Recognizing these common mimics is essential to halt diagnostic momentum and prevent treatment-related morbidity.