A 21-year-old man comes to the office due to several days of intense pruritus of the inguinal-genital area. He has had no fever, dysuria, or skin rash. He is not using any new soaps, detergents, or lotions. The patient has had 3 sexual partners in the past year. He was treated for chlamydial urethritis 6 months ago and since then has been using condoms consistently. Vital signs are within normal limits. Genitourinary examination shows no urethral discharge, penile lesions, or inguinal lymphadenopathy. There are skin excoriation marks in the pubic area and other findings as shown in the exhibit.
Which of the following is the most appropriate pharmacotherapy for this patient's condition?

Question

A 21-year-old man comes to the office due to several days of intense pruritus of the inguinal-genital area.  He has had no fever, dysuria, or skin rash.  He is not using any new soaps, detergents, or lotions.  The patient has had 3 sexual partners in the past year.  He was treated for chlamydial urethritis 6 months ago and since then has been using condoms consistently.  Vital signs are within normal limits.  Genitourinary examination shows no urethral discharge, penile lesions, or inguinal lymphadenopathy.  There are skin excoriation marks in the pubic area and other findings as shown in the exhibit.
  Which of the following is the most appropriate pharmacotherapy for this patient's condition?

Quizplus · Accepted Answer

Phthirus pubis, the human pubic louse, is a translucent parasite approximately 1 mm long with crab-like claws that allow it to grip pubic hair. Transmission usually occurs during sexual contact whereby an infected individual transmits the louse to an uninfected individual by skin-to-skin contact. Therefore, condoms are unable to prevent transmission (it is not transmitted by fluids). Teenagers and young adults are affected most commonly due to higher numbers of sexual partners. Manifestations typically include intense pruritus in the pubic area with excoriations due to scratching. Other hairy areas such as the axillae may be affected, but the scalp is typically spared. Visualization of the louse or nits (oval, white, louse eggs on the hair shaft) confirms the diagnosis. First-line treatment includes a topical permethrin cream to the affected area. Permethrin blocks parasite sodium ion conduction in nerve cell membrane channels and results in louse paralysis and death. (Choice A) Oral acyclovir is used for genital herpes simplex virus infection, which usually causes painful vesicular genital lesions on an erythematous base. (Choice B) Oral doxycycline is first-line treatment for hidradenitis suppurativa, a chronic follicular occlusive disease that manifests in the intertriginous skin areas (eg, groin, axilla, inframammary). Manifestations usually include recurrent inflammatory nodules and abscesses with pain and malodorous discharge. (Choice C) Oral fluconazole can be used to treat mucocutaneous Candida infections. Candida balanitis can cause severe pruritus but would be associated with white patches on an erythematous base. (Choice D) Topical imiquimod increases the immune-response to anogenital warts due to human papilloma virus infection. It stimulates interferon-alpha, tumor necrosis factor, and interleukin-1/6/8. Anogenital warts can have many presentations (eg, flat, dome-shaped, filiform, pedunculated, verrucous) and may occasionally be pruritic. (Choice F) Topical corticosteroids can be used to treat inflammatory cutaneous conditions such as psoriasis and contact dermatitis. Although these conditions can cause erythema and pruritus, they would not be associated with a translucent louse on examination. Educational objective: Phthirus pubis is the human pubic louse. It is transmitted sexually via skin-to-skin contact and causes intense pruritus. Louse and nits can often be visualized on examination, which is diagnostic. Treatment with topical permethrin is generally curative. __________ References: Scabies and pediculosis pubis: an update of treatment regimens and general review. (http://www.ncbi.nlm.nih.gov/pubmed/17342668)

A 21-Year-Old Man Comes to the Office Due to Several