Derm Dx: A persistent pruritic rash on the buttocks - Clinical Advisor

Derm Dx: A persistent pruritic rash on the buttocks

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A 22-year-old man presents for evaluation of a papular eruption on his buttocks. The condition began several weeks earlier and is somewhat pruritic. Three weeks previously at another clinic, he was diagnosed with scabies and was treated with a course of oral ivermectin. Examination reveals multiple flesh-colored to slightly erythematous papules of the affected area. A biopsy is obtained.

Scabies is an intensely pruritic skin infestation caused by the host-specific mite Sarcoptes scabiei var hominis. Millions of cases are reported worldwide each year. The term "7-year itch" was first used to describe persistent undiagnosed infestations with scabies1; indeed, diagnosis...

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Scabies is an intensely pruritic skin infestation caused by the host-specific mite Sarcoptes scabiei var hominis. Millions of cases are reported worldwide each year. The term “7-year itch” was first used to describe persistent undiagnosed infestations with scabies1; indeed, diagnosis is still often delayed because of the broad spectrum of cutaneous manifestations.

Scabies epidemics occur primarily in institutional settings such as prisons, long-term care facilities, hospitals, and nursing homes.2-4 Scabies occurs more commonly in the fall and winter months and prevalence rates are higher in developing nations. A 2009 study conducted in an impoverished community in Brazil identified the following major risk factors: young age, presence of many children in the household, illiteracy, low family income, poor housing, shared clothes and towels, and irregular bathing.5

First-line treatment of scabies is the topical application of scabicidal agents, and a 2007 Cochrane review suggested that topical permethrin is the most effective agent for scabies.6 The use of ivermectin has increased because oral dosing enhances compliance and facilitates treatment of contacts. Treatment failure is well documented, however, as a result of the emergence of resistant strains.7

Michael Stas, DPM, is a podiatry-dermatology fellow at St. Luke’s University Hospital in Bethlehem, Pennsylvania, and at the DermDox Dermatology Center in Hazleton, Pennsylvania. Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College in Scranton, Pennsylvania, and an adjunct assistant professor of dermatology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. He practices dermatology in Hazleton, Pennsylvania.

References

  1. Barry M. Scabies. Medscape emedicine. http://emedicine.medscape.com/article/1109204-overview. Updated June 30, 2016. Accessed November 17, 2016.
  2. Makigami K, Ohtaki N, Ishii N, Yasumura S. Risk factors of scabies in psychiatric and long-term care hospitals: a nationwide mail-in survey in Japan. J Dermatol. 2009;36:491-498.
  3. Jack AR, Spence AA, Nichols BJ, et al. Cutaneous conditions leading to dermatology consultations in the emergency department. West J Emerg Med. 2011;12:551-555.
  4. Makigami K, Ohtaki N, Yasumura S. A 35-month prospective study on onset of scabies in a psychiatric hospital: discussion on patient transfer and incubation period. J Dermatol. 2012;39:160-163.
  5. Feldmeier H, Jackson A, Ariza L, et al. The epidemiology of scabies in an impoverished community in rural Brazil: presence and severity of disease are associated with poor living conditions and illiteracy. J Am Acad Dermatol. 2009;60:436-443.
  6. Strong M, Johnstone P. Interventions for treating scabies. Cochrane Database Syst Rev. 2007;(3):CD000320.
  7. Mounsey KE, Holt DC, McCarthy JS, Currie BJ, Walton SF. Longitudinal evidence of increasing in vitro tolerance of scabies mites to ivermectin in scabies-endemic communities. Arch Dermatol. 2009;145:840-841.
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