human papillomavirus
Summary
Human papillomavirus (HPV) is a non-enveloped, double-stranded DNA virus that infects epithelial cells, causing lesions ranging from benign warts to malignant cancers. High-risk types (16, 18) are the primary cause of cervical cancer, while low-risk types (6, 11) cause genital warts (condyloma acuminata). It is the most common sexually transmitted infection worldwide.
Detail
HPV is a member of the Papillomaviridae family with a circular dsDNA genome. It infects basal keratinocytes of skin and mucosa, replicating in differentiating epithelial cells. Over 150 types exist, classified as low-risk or high-risk based on oncogenic potential.
Pathophysiology: High-risk types (especially 16 and 18, responsible for ~70% of cervical cancers) express oncoproteins E6 and E7. E6 promotes degradation of p53 (tumor suppressor), while E7 inactivates retinoblastoma protein (Rb), leading to unchecked cell cycle progression, genomic instability, and malignant transformation. Persistent infection with high-risk HPV is necessary for cervical cancer development, progressing through cervical intraepithelial neoplasia (CIN I-III) stages.
Low-risk types (6, 11) cause condyloma acuminata (genital warts) and laryngeal papillomatosis, typically without malignant potential, presenting as cauliflower-like verrucous lesions.
Clinical associations: HPV is linked to cervical, vulvar, vaginal, penile, anal, and oropharyngeal squamous cell carcinomas. Pap smear screening detects cytologic changes (koilocytes - cells with perinuclear halos and nuclear atypia) indicative of HPV infection. HPV DNA co-testing enhances screening sensitivity.
Transmission: Primarily sexual contact (vaginal, anal, oral) and skin-to-skin contact; vertical transmission can cause juvenile laryngeal papillomatosis.
Prevention: Prophylactic vaccines (Gardasil 9) cover types 6, 11, 16, 18, and additional oncogenic types, recommended for adolescents before sexual debut. Vaccination significantly reduces incidence of cervical dysplasia and cancer.
Diagnosis: Clinical inspection, Pap smear cytology, HPV DNA testing, colposcopy with biopsy for confirmed dysplasia, and histopathology showing koilocytic atypia.
Management: Genital warts treated with topical agents (imiquimod, podophyllin), cryotherapy, or surgical removal. High-grade dysplasia managed with excisional procedures (LEEP, cone biopsy). No specific antiviral therapy exists; management focuses on treating lesions and monitoring for progression.
Sources
- First Aid for the USMLE Step 1
- Robbins and Cotran Pathologic Basis of Disease
- CDC HPV Clinical Guidance
- UpToDate: Human papillomavirus infections
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.