Crusted or Norwegian scabies is a rare form of scabies seen in immunosuppressed individuals. The crusted lesions represent the actions of hundreds to thousands of scabies mites. Patients are often covered from head to toe and are extremely pruritic. A scraping shows the presence of numerous mites. Individuals with crusted scabies should be treated with a multimodal approach.
Scabies can cause outbreaks in long-term care facilities. These outbreaks can affect many individuals within the facility and are difficult to eradicate.
Histology: Skin biopsies are rarely performed. If a biopsy were to be done, one would see a mixed inflammatory infiltrate in the dermis with many eosinophils. This is a nonspecific finding and can be the result of any bug bite reaction. If the actual mite is biopsied, scabies parts will be present within the epidermis.
Pathogenesis: S. scabiei is spread from one human to another by close physical contact. The mite burrows into the epidermis but is unable to penetrate the basement membrane zone. Its presence sets off a massive inflammatory response. The female mites lay eggs as they burrow through the skin. Each egg hatches within 2 to 3 days and releases a larva. The larvae quickly grow and form nymphs and then mature adult mites. This process occurs within 1 week’s time. The mites have a life span of 2 months. The female mite can lay 3 eggs per day.
Treatment: Permethrin is currently the drug of choice to treat scabies. It should be applied overnight and repeated in 1 week, because it is pediculicidal but not ovacidal. The second application makes sure that any recently hatched mites are killed before they can reach reproductive age. Colloidal sulfur may be used on pregnant women. It is efficacious and safe but has a terrible odor. Outbreaks in long-term care facilities are often treated with oral ivermectin, which has shown good efficacy. Lindane has fallen out of favor because of its potential neurotoxicity. The use of malathion is advocated if permethrin fails.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
