Idiopathic plasmacytosis (IP) is a rare benign inflammatory condition of gingiva of unknown etiology characterized by massive infiltration of plasma cells into the sub-epithelial gingival tissue. The classical presentation of IP includes painless, diffuse, erythematous and papillary lesion of the gingiva with a sharp demarcation along the mucogingival border. It mimics clinical presentation of mucous membrane pemphigoid, pemphigus, erosive lichen planus, squamous cell carcinoma or allergic gingivostomatitis. Thus, diagnosis of idiopathic plasmacytosis depends on clinical pathological correlation. A proper diagnosis and effective treatment strategy is must for successful management of IP. This presentation highlights a rare case of an 18 yrs. old male with chief complaints of painful gums and swollen lips since two years. Clinical and histopathological examination led to the diagnosis of IP. Scaling and root planing was performed and antihistaminic (cetrizine 10 mg daily for 15 days) was prescribed. Within a period of 8 months, patient reported just once with slight swelling in upper lip and poor oral hygiene. Again scaling and root planing was done and antihistaminic (for 15 days) was prescribed to the patient. Then patient reported after 2 years with poor oral hygiene, abundant plaque and painful bright red inflammed gingiva. Oral prophylaxis was performed and systemic corticosteroids were prescribed for 1 month followed by antihistaminics for 1 month. Patient was followed up to 2 yrs. without any recurrence. The objective of this presentation is to raise awareness of idiopathic plasmacytosis as a rare differential diagnosis for oral ulceration and its macroscopic similarity to malignancy. Schlagwörter: Benign, Idiopathic, Plasma cells, Scaling, Antihistaminics, Corticosteroids