Abstract
RATIONALE: This case of Erythroplasia of Queyrat (EQ) in a 52-year-old male, driven by high-risk human papillomavirus (HPV)-18, is notable for progressing to carcinoma in situ despite photodynamic therapy (PDT). It highlights PDT's limitations in HPV-positive EQ, emphasizing HPV genotyping and aggressive initial therapies to prevent malignancy. PATIENT CONCERNS: The patient had a persistent, erythematous, velvety plaque on the glans penis with mild pruritus. Examination showed a well-demarcated lesion. DIAGNOSES: Biopsy confirmed dysplastic squamous epithelium. Molecular testing identified HPV-18, indicating high malignant potential, leading to a diagnosis of EQ. INTERVENTIONS: The patient received PDT, followed by conservative treatments including topical therapies upon recurrence. OUTCOMES: PDT achieved partial lesion regression, but recurrence as carcinoma in situ was confirmed histologically. Conservative treatments failed to stop progression, with HPV-18 driving the aggressive course, necessitating escalated interventions. LESSONS: HPV genotyping is vital to identify high-risk subtypes like HPV-18; PDT may be inadequate for HPV-positive EQ, requiring aggressive therapies; rigorous long-term surveillance is essential to prevent squamous cell carcinoma progression.