Zoon's Vulvitis and Coexisting Lichen Planus: A Rare Vulval Dermatosis

This case report describes Zoon's vulvitis or plasma cell vulvitis (PCV) with coexisting lichen planus (LP) treated with methotrexate. PCV is a rare, chronic, benign idiopathic inflammatory condition of the vulvar mucosa, characterized by a bright-red, chronic lesion of mucosa. Typically, it presents as atrophic, shiny, red plaques that can affect any part of the vulva and can spread symmetrically and bilaterally with the propensity of chronicity and gradual coalescence. LP is an uncommon inflammatory dermatosis that can affect skin, nails, and mucosa. There is a strong association between vulvovaginal and oral LP. Clinical presentation is similar to PCV, however, LP has the potential for malignant transformation between 0 % and 5.6%. Our patient was a 60-year-old diabetic female who had a nine-month history of progressive vulvar irritation and itch associated with dyspareunia, urinary stream disturbance, and occasional mouth soreness. Pelvic examination revealed well-demarcated red-orange areas of erythema covering the clitoral hood with effacement, obvious peri-urethral scarring, and fusion of the labia. Oral buccal mucosa revealed bilateral buccal mucosal lichenoid changes with erosive gums in addition to white stria or Wickham stria classic of LP. The potent topical steroid, Clobetasol propionate, provided relief initially, but the patient became intolerant following long-term use and stayed non-respondent, which prompted the vulval mucosal skin biopsy. Histology showed erosion of the surface epithelium with a dense band-like infiltrate of plasma cells in the underlying sub-epithelium with lymphocytes and neutrophils. The presence of 90% plasma cell-rich lichenoid inflammatory infiltrates with less than 1% of lymphocytes and neutrophils. The clinicopathological diagnosis was suggestive of PCV with coexisting LP. There is convincing evidence from studies that early and accurate diagnosis is important, as, unlike Zoon's balanitis, PCV is benign. However, the coexisting LP makes it necessary for regular dermatology follow-up.