16 October 2009 – Case of the Week #160
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Thanks to Dr. Daniel Ostler, Baylor College of Medicine, Texas (USA), for contributing this week’s case.
Case of the Week #160
A 52-year-old white woman presented with chronic, diffuse, lichenified eruptions on her leg. A biopsy was obtained:
4x 10x 40x
What is your diagnosis?
Histology revealed mites in the epidermis (Figures 1 and 2). Figure 3 shows a mite and scybala (hardened masses of feces).
Scabies, the first human disease recognized as caused by a specific pathogen (eMedicine), is caused by the mite Sarcoptes scabiei, which burrows into the skin and causes intense itching. It is highly contagious and difficult to diagnose early; symptoms may not occur for up to 6 weeks after infection (Clin Microbiol Rev 2007;20:268). Diagnosis requires examining the skin for burrows, then confirming the presence of mites, ova or scybala by microscopy (Dermatol Ther 2009;22:279).
Scabies is spread by prolonged (15 to 20 minutes) skin-to-skin contact with an infected individual, often as a sexually transmitted disease or between members of a household. Overcrowding in hospitals or nursing homes may also encourage its spread. Although animals can get scabies, they do not spread human scabies. Bedding or clothing of infected individuals should be machine washed and dried with hot water or sealed in a plastic bag for at least 3 days (Centers for Disease Control and Prevention).
Mite Burrow Norwegian scabies in AIDS patient
Excessive scratching may lead to sores, bacterial infections and even glomerulonephritis (Postgrad Med J 2004;80:382). Patients with immunocompromise are at risk for developing “crusted scabies”, also called “Norwegian scabies”, characterized by scaly rashes, a thickening of the skin, and an overwhelming number of mites (J Am Podiatr Med Assoc 2004;94:583).
Clinically, scabies can mimic eczema, mycosis fungoides, syphilis and bullous pemphigoid (Dermatol Online J 2006;12:19). Scratch marks often obscure signs of burrows. Microscopic examination is required for definitive diagnosis.
Treatment consists of topical permethrin (drug of choice), topical lindane or oral ivermectin (Am J Clin Dermatol 2002;3:9). Topical treatments must coat the body to be effective. Household members and close personal contacts should be treated at the same time.
Additional references: Wikipedia
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