Leprosy Misdiagnosed as Rheumatoid Arthritis: A Case Report

Abstract

A 53-year-old woman presented with an eight-year history of progressively worsening lower limb and facial edema, accompanied by a three-year history of a generalized erythematous rash that had significantly exacerbated over the preceding six months, with associated pruritus and occasional desquamation. Prior to our evaluation, she had been repeatedly diagnosed with rheumatoid arthritis at several other institutions and had received long-term corticosteroid therapy, which provided only transient symptomatic relief without halting disease progression. Skin biopsy revealed that the vacuolated cells in the dermis were negative for AB-PAS staining but positive for acid-fast bacilli, while immunohistochemical profiling demonstrated CKpan (AE1/AE3) (-), CK (-), CD68 (PGM1) (+), EMA (-), and AR (-), confirming these cells as histiocytic foam cells rather than epithelial or other neoplastic elements. The acid-fast positivity strongly suggested mycobacterial infection. Integrating the clinical presentation, physical examination findings, histopathological features, and microbiological staining results, the final diagnosis was established as leprosy, highlighting the importance of considering this entity in patients with chronic skin and systemic manifestations, especially when conventional therapies for presumed autoimmune disorders prove ineffective.