Question
Papilloma virus
Answer
Human Papillomavirus (HPV) is a small, non-enveloped, double-stranded DNA virus (family Papillomaviridae) that infects squamous epithelium (skin and mucous membranes), with over 200 identified genotypes, broadly classified by their association with malignancy.
Classification by oncogenic risk:
- Low-risk types (e.g., HPV 6, 11) — associated with benign lesions: common skin/plantar warts (verruca vulgaris/plantaris), and genital/anogenital warts (condyloma acuminata) — a sexually transmitted infection.
- High-risk (oncogenic) types (e.g., HPV 16, 18, and others) — strongly associated with malignancy, most importantly cervical carcinoma (HPV is the necessary/causal factor in virtually all cases of cervical cancer, established through persistent infection with a high-risk type), and also implicated in a proportion of other anogenital cancers (vulvar, vaginal, penile, anal) and oropharyngeal carcinoma.
Pathogenesis: high-risk HPV types encode the oncoproteins E6 and E7, which respectively inactivate the host tumour suppressor proteins p53 and retinoblastoma (Rb) protein, disrupting normal cell cycle control and apoptosis, and driving progressive dysplastic change from cervical intraepithelial neoplasia (CIN) through to invasive carcinoma over years in persistently infected individuals.
Laboratory diagnosis: Pap smear (cervical cytology) — screening test detecting dysplastic/koilocytic changes in exfoliated cervical cells; HPV DNA testing (PCR/hybrid capture) — direct detection and genotyping of high-risk HPV, increasingly used alongside or as an alternative primary screening method to cytology; colposcopy and biopsy for definitive histological diagnosis of dysplasia/malignancy in screen-positive women.
Prevention: HPV vaccination (quadrivalent, 9-valent, or bivalent vaccines targeting the most important oncogenic and/or wart-causing genotypes), ideally given before the onset of sexual activity for maximal effectiveness; regular cervical cancer screening (Pap smear/HPV testing) for early detection of precancerous changes; safe sexual practices to reduce transmission.