Make the Diagnosis

Make the Diagnosis - May 2018

A 40-year-old HIV-positive male presented with a 1-month history of severely pruritic papules on his chest. The patient reported that he "removes bugs" from his skin. Microscopic examination of a hair clipping was performed.
Make the Diagnosis:

Make the Diagnosis - May 2018

A) Pediculosis corporis

B) Pediculosis pubis

C) Scabies

Pediculosis pubis, also known as pubic lice, or “crabs,” is an infestation of Phthirus pubis. Crab lice are spread sexually and through close skin contact, as well as contaminated clothes and bedding. Adult lice can live up to 36 hours away from its host. Pubic areas most commonly are affected, although other hair-bearing parts of the body often are affected, including eyelashes.

crab lice or Pediculosis pubis Courtesy Dr. Maria Hicks and Dr. Donna Bilu Martin

Pruritus can be severe. Secondary bacterial infections may occur as maculae ceruleae, or blue-colored macules, on the skin. The lice are visible to the naked eye and are approximately 1 mm in length. They have a crablike appearance, six legs, and a wide body. Nits may be present on the hair shaft. Unlike hair casts, which can be moved up and down along the hair shaft, nits firmly adhere to the hair. Diagnosis should prompt a workup for other sexually transmitted diseases, including HIV.

Treatment for patients and their sexual partners include permethrin topically; and laundering of clothing and bedding. Lice on the eyelashes can be treated with 8 days of twice-daily applications of petrolatum. Ivermectin can be used when topical therapy fails, although this is an off-label treatment (not approved by the Food and Drug Administration).

Pediculosis corporis – body lice or clothing lice – is also known as “vagabond’s disease” and is caused by Pediculus humanus var corporis. Body lice lay their eggs in clothing seams and can live in clothing for up to 1 month without feeding on human blood. Often homeless individuals and those living in overcrowded areas can be affected. The louse and nits also are visible to the naked eye. They have a longer, narrower body than Phthirus pubis and are more similar in appearance to head lice. They rarely are found on the skin.

Body lice may carry disease such as epidemic typhus, relapsing fever, and trench fever or endocarditis. Permethrin is the most widely used treatment to kill both lice and ova. Other treatments include Malathion, Lindane, and Crotamiton. Clothing and bedding should be laundered.

Scabies is a mite infestation caused by Sarcoptes scabiei. Unlike lice, scabies often affects the hands and feet. Characteristic linear burrows may be seen in the finger web spaces. The circle of Hebra describes the areas commonly infected by mites: axillae, antecubital fossa, wrists, hands, and the groin. Pruritus may be severe and worse at night. Patients may be afflicted with both lice and scabies at the same time. Mites are not visible to the naked eye but can be seen microscopically. Topical permethrin cream is used most often for treatment. All household contacts should be treated at the same time. As in louse infestations, clothing and bedding should be laundered. Ivermectin can be used for crusted scabies, although this is an off-label treatment.

This case and photo were submitted by Maria Hicks, MD, Advanced Dermatology and Cosmetic Surgery, Tampa, and Dr. Martin.

Dr. Bilu Martin is a board-certified dermatologist in private practice at Premier Dermatology, MD, in Aventura, Fla. More diagnostic cases are available at edermatologynews.com. To submit a case for possible publication, send an email to dermnews@mdedge.com.

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