Core Dermatology Diagnoses / CategoriesInfectious

Scabies

Author: Faculty Reviewer:

Publish date: Posted on
Last updated: May 11, 2022

Keywords #

scabies
Sarcoptes scabiei
crusted scabies
bug bite
scabies mite

Diagnosis #

Scabies is caused by a skin infestation of the mite Sarcoptes scabiei. Scabies rash is very pruritic, commonly occurring in the webspaces of the fingers, as well as the wrists, axillae, areolae, and genitalia. Lesions appear as small, erythematous papules, usually with excoriation. Diagnosis can be made by clinical history and physical exam, along with visualization of scabies mites and/or eggs on microscopy.[2,3]

Key Concepts #
  • Scabies is a pruritic skin eruption from an infestation of the skin mite Sarcoptes scabiei.[2]
  • Clinical diagnosis can be confirmed by visualizing the mites microscopically in a skin scraping.[2, 3]
  • Transmission occurs through prolonged human skin-to-skin contact.[3]
  • First-line treatment for scabies includes topical permethrin or oral ivermectin.[1]
Epidemiology #

Scabies can affect anyone. Higher prevalence exists in Pacific regions and Latin America. Crowded living quarters, such as nursing facilities, prisons, dorm rooms, increase the risk for scabies transmission.[4]

Clinical Features #
  • Commonly affects webspaces of the fingers, wrists, axillae, areolae, and genitalia.[2]
  • Presents as pruritic, erythematous papules with excoriation.[2,3]
  • Characteristic burrowing appears as serpiginous lines, up to 15 mm, usually on hands and feet.[3]
  • Crusted scabies appears as erythematous patches and plaques with overlying scale and can present anywhere upon skin.[2]
Differential Diagnoses #
Diagnostic Workup #

A diagnosis of scabies should be considered if a patient has widespread itching, especially if worse at night. Another diagnostic clue is the presence of similar pruritic symptoms in other members of the same household. For diagnostic confirmation, dermoscopy can be used to visualize mites and burrows in excoriated, erythematous papules. Further, microscopic examination of skin scrapings can reveal mites, mite eggs, and/or scybala (feces).[2,3]

Treatment #

First-line treatment includes topical permethrin or oral ivermectin. Both of these agents are usually well tolerated with few side effects. Of note, the entire household needs to be treated as scabies spreads via close human contact. For crusted scabies, combination topical permethrin and oral ivermectin should be used. For pregnant or lactating women and young children, topical permethrin is the preferred therapy.[1]

References #
  1. Currie BJ, McCarthy JS. Permethrin and ivermectin for scabies. N Engl J Med. 2010;362(8):717-725. doi:10.1056/NEJMct0910329
  2. Heukelbach J, Feldmeier H. Scabies. Lancet. 2006;367(9524):1767-1774. doi:10.1016/S0140-6736(06)68772-2
  3. Johnston G, Sladden M. Scabies: diagnosis and treatment. BMJ. 2005;331(7517):619-622. doi:10.1136/bmj.331.7517.619
  4. Romani L, Steer AC, Whitfeld MJ, Kaldor JM. Prevalence of scabies and impetigo worldwide: a systematic review. Lancet Infect Dis. 2015;15(8):960-967. doi:10.1016/S1473-3099(15)00132-2
Contents