Human Papillomavirus

Posted on February 11th, 2008 by olga

Human papillomavirus (HPV) is a member of the Papovavirus family and is a closed, circular, double-stranded DNA virus. The viral genome is enclosed in an icosahedral capsule composed of several protein capsomeres and lacks the lipid-containing envelope ordinary to many other viruses for example herpes simplex. Not like other human STD virus infections such as herpes simplex, but HPV growth in cell culture have been complicated as its replication is dependent on epithelial cell differentiation and maturation.
The general clinical presentation of HPV is the genital wart or external condyloma acuminatum. But with the advent of DNA amplification systems, it has become clear that HPV has wide clinical expression ranging from latency to condyloma to invasive cancers, mainly of the anogenital tract. Subclassification of HPV into over 100 types has been based on dissimilarities in degree of DNA homology. Common skin warts are related with types 2 and 4, whereas benign genital condyloma is usually associated with HPV type 6 or 11. In contrast, anogenital neoplasias are commonly associated with types 16, 18, 31, 33 or 35, 45, and 56.
Pathogenesis
The classic mechanisms of HPV infection are uncertain. Vulnerable human sites where basal cells not only are physically accessible to viral inoculation but as well are actively dividing include the active squamous metaplasia of the transformation zone of the female cervix and areas of wound healing in the genital area. In adolescents and young women, 70 to 90% of HPV infections are transient. Alternatively, constant infection has been closely connected to the development of anogenital cancers. Recent information has linked several viral-host protein interactions with the loss of cell cycle control, a possible step in the development of these cancers. The natural progression from infection to cancer is not well understood.
Clinical symptoms:
multicentric disease including much of the anogenital area: the vaginal introitus, vulvar labia minora and majora, clitoris, perineum, anus, and cervix in women; and the penis, including the prepuce, frenulum, corona, glans, and shaft, with the anus and scrotum in men. The common genital warts, condyloma acuminatum, which are seen on the skin surfaces, present as polypoid masses with fissured and irregular surfaces.
Diagnosis and Treatment
Screening for HPV infections in adolescents is presently limited to visual inspection for external genital warts and cytology screening for LSIL, HSIL, and invasive cancers during the pelvic examination. Diagnosis of genital warts by visual inspection is considered adequate, and HPV testing plays little to no role in confirming the diagnosis unless the diagnosis is questioned. In this case, biopsy is the best confirmation. The differential diagnosis includes bowenoid papulosis, vulvar intraepithelial neoplasia, Bowen disease, condylomata lata, skin tags, nevocellular nevus, benign tumors, sebaceous glands, seborrheic keratosis, pearly penile papules, molluscum contagiosum, squamous cell carcinoma, vulva papillomatosis, and vestibular papillae. Treatment for genital warts consists of primary ablative therapy including application of 85% trichloroacetic acid to the wart itself. Cryotherapy with liquid nitrogen is also quite effective. Treatments are usually applied weekly up to 4 to 6 weeks. Other methods consist of excisional and laser therapy. Self-applied therapies are also available and may be more cost-effective.