HIV-Associated Norwegian Scabies

“Norwegian” scabies is an infestation with Sarcoptes scabiei var. hominis in an immunocompromised host.
Immunocompetent hosts are able to limit the number of mites (10 to 12) that remain in the epidermis.
The rash and itching are the result of a delayed hypersensitivity response to the mite, its eggs, and its fecal products.
Immunocompromised hosts are not able to contain the population of mites and may be infested with millions of mites. These patients may not itch because of their defective cell-mediated immunity.
HIV-infected patients with Norwegian scabies infestation pose a significant risk for transmission of scabies to household contacts and medical personnel.

Mineral oil preparation is done by scraping the epidermal surface of a burrow with a scalpel that has been dipped in mineral oil. The scraping is examined with a low-power microscope. Mites, ova, or fecal pellets are seen (Fig. 33.15).

Differential Diagnosis

Psoriasis

Psoriatic lesions tend to be located on extensor aspects of the extremities.
Predominance of scale in the finger webs should lead to suspicion of Norwegian scabies.

Solar Keratoses

Norwegian scabies on sun-exposed areas in elderly patients can mimic solar keratoses (seeFig. 33.14).

Management

Scabicides

Permethrin 5% (Elimite) cream is applied, after a warm bath, to all skin surfaces from head to toe, including the palms and soles and scalp in small children; it is left on for 8 to 12 hours, usually overnight, and is washed off the next morning, or
Lindane 1% (kwell) lotion is applied from head to toe after bathing. Treatment should be continued once weekly until there is no evidence of residual lesions. Lindane is not as effective as permethrin and may cause neurologic toxicity, particularly in children and in elderly patients.
- Ivermectin, 0.2 mg/kg by mouth, has been shown to be effective in eradicating infection. It is not approved by the United States Food and Drug Administration for this use.

Keratolytic Agents

Keratolytic agents, such as 10% to 40% salicylic acid, remove crusts and allow penetration of the scabicides.

Points to Remember

Norwegian scabies is an infestation with millions of scabies mites and is highly contagious. Failure to treat patients promptly has led to epidemics affecting dozens of people.
Because of the immunodeficiency in patients with Norwegian scabies, prolonged treatment may be necessary.
Household contacts and medical staff who come into contact with the patient or the patient's bedclothes should undergo treatment as for scabies in an immunocompetent host, regardless of symptoms.