Plasma cell gingivitis (PCG) is a rare inflammatory disease of the gums, which is defined by plasma cell infiltration into subepithelial tissue. This benign condition is characterized by gingival erythema and edema. Although the etiology may be unknown, this is believed to be a hypersensitivity reaction in some cases.
The clinical picture of PCG features gingival erythema and edema, which may expand to the mucogingival junction   and even to the palate. The involved regions are the anterior maxillary and mandibular segments. The gums may be friable and hence prone to bleeding during chewing, brushing teeth or flossing.
Although rare, PCG may be accompanied by cheilitis , which is characterized by lip swelling, dryness, atrophy, and the formation of fissures. PCG may also be associated with glossitis, which is marked by tongue enlargement and erythema as well as the development of furrows and crenations.
Patients report mouth soreness and burning, which is exacerbated by consumption or usage of certain products. While the etiology has not been determined , it is strongly suggested that this condition arises from a hypersensitive reaction to allergens such as certain toothpaste ingredients, chewing gum, khat, cinnamon, or other spices  .
There is a case report describing a young adult with PCG who developed gingival enlargement and generalized aggressive periodontitis (GAP) . However, it was unclear whether PCG or GAP occurred first.
Notable findings include red colored marginal and attached gingiva with swelling and diffuse enlargement . There may be granule-like formations as well. If cheilitis is present, then the lip(s) will be dry, swollen, and fissured.
During the clinical assessment of an individual with the above manifestations, the clinician should obtain a family history and a list of known allergens. Additionally, a detailed medical history is necessary to rule out differential diagnoses, which include leukemia, myeloma, HIV infection, and connective tissue diseases such as discoid lupus erythematosus, pemphigoid, and lichen planus  . Furthermore, other diseases that should be excluded are tuberculosis, Crohn disease, and Wegener granulomatosis. The clinician must also determine whether the patient is using antiseizure medications that cause gingival hyperplasia, which includes phenytoin and phenobarbital  .
Another critical component of the evaluation is a thorough oral exam of the gums, teeth, mouth, tongue and lips. Additionally, a physical exam including inspection of the skin is important.
The workup consists of a complete blood count (CBC), a complete biochemistry panel (CMP), erythrocyte sedimentation rate (ESR), thyroid function tests, HIV screening, acid-fast bacilli (AFB) sputum smear, and peripheral blood smear . Serology is done if needed. Biopsy of the affected tissue is also useful, especially if the condition is refractory to therapy. Allergen tests should be considered as well.
When a biopsy is taken, the histopathological analysis reveals the presence of diffuse plasma cell infiltration of the connective tissue. This finding confirms the diagnosis.