Plasma Cell Mucositis: A Differential Diagnosis–Oriented Case Report

We present the case of an 80-year-old woman who reported painful gingival swelling and bleeding gums persisting for 6 months. She had hypertension (treated with amlodipine and losartan), arrhythmia (digoxin), and hypothyroidism (levothyroxine). Examination revealed diffuse erythematous, fissured swelling with a cobblestone surface on the gingiva, extending to the vestibule, labial, and buccal mucosa. Laboratory tests were normal. Differential diagnoses included plasma cell mucositis, orofacial granulomatosis, lichenoid and granulomatous stomatitis, and allergic contact stomatitis. Biopsy from gingiva and mucobuccal fold showed dense plasma cell infiltrate, epithelial hyperplasia, and spongiosis. Immunohistochemistry revealed both kappa and lambda light chains. The final diagnosis was plasma cell mucositis. Treatment began with discontinuation of mouth rinses and switching to sulfate-free toothpaste. Partial relief occurred, but full resolution required systemic and topical corticosteroids. Because several inflammatory diseases share similar clinical patterns, histopathology is essential for correct diagnosis. Plasma cell gingivitis shows dense plasma cell infiltrate; the main histologic differentials are plaque-related gingivitis and plasmacytoma. Immunohistochemistry confirming polyclonally helps rule out plasma cell neoplasms. Management focuses on allergen elimination, with corticosteroid therapy as needed. Some cases persist despite treatment, and the allergen may remain unidentified.