Probable Coxsackievirus Infection in an Immunocompetent Adult With Genital and Oral Ulcerations Mimicking Herpes Simplex Virus Infection and Behçet's Disease.

Disseminated viral infections in immunocompetent adults are uncommon and may mimic autoimmune or bacterial conditions, including Behçet's disease and disseminated herpes simplex virus (HSV) infection. We report a case of a 33-year-old immunocompetent woman who developed severe, painful vulvar ulcerations, oral ulcers, and a painful maculopapular rash involving both lower extremities that evolved into pustules. She was afebrile and hemodynamically stable but demonstrated a marked systemic inflammatory response, including leukocytosis (white blood cell count: 21.3×10⁹/L; 85% neutrophils) and elevated inflammatory markers (erythrocyte sedimentation rate: 42 mm/h; C-reactive protein: 15.4 mg/dL). Extensive infectious and autoimmune evaluation was unrevealing, and imaging showed no drainable pelvic fluid collection. She received empiric broad-spectrum antibiotics and was transitioned to valacyclovir for suspected disseminated HSV infection; leukocytosis improved rapidly with persistently sterile cultures. Subsequent serologic testing demonstrated elevated Coxsackievirus A and B titers (≥1:100), supporting an enteroviral etiology in the appropriate clinical context; however, the limitations of serologic testing preclude definitive confirmation of acute infection in the absence of paired titers or lesion-based polymerase chain reaction testing. She was transferred to a tertiary center for dermatologic evaluation due to the absence of local specialty services, where skin biopsy demonstrated nonspecific inflammatory changes with negative direct immunofluorescence, arguing against immune complex-mediated vasculitis. This case highlights a rare adult presentation of Coxsackievirus infection with prominent genital and oral ulcerations mimicking HSV and Behçet's disease, underscoring the importance of considering viral etiologies in sterile inflammatory mucocutaneous eruptions to avoid unnecessary antimicrobial exposure.