scabies
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Etiology
- infestion with Sarcoptes scabiei
Epidemiology
- transmitted through personal contact
- skin-to-skin contact
- sexual contact
- the parasite can live up to 48 hours without a host
- outbreaks occur in nursing homes, mental institutions & hospitals
Pathology
- the parasites burrow serpinginous tunnels through the upper layers of the epidermis leaving behind eggs & excrement
- inflammation & intense pruritus results from sensitization to the mite excreta
- the initial infestation remains asymptomatic for 4-6 weeks
- scratching generally eliminates the burrowing mite, but symptoms remain in its absence
- eosinophils, lymphocytes & histiocytes infiltrate burrows generally limiting infections to < 15 mites/individual
- a generalized dermatitis may occur in the elderly, immunocompromised, or patients taking glucocorticoids secondary to infestation with thousands of mites, known as crusted scabies or Norwegian scabies
- lesions often become secondarily infected
Clinical manifestations
- rash & intense pruritus (worse at night)
- small papules & vesicles, eczematous plaques, pustules, nodules & diffuse scaling may occur
- found primarily in the interdigital spaces (web spaces) & flexor surfaces of the wrists, forearms, elbows, axillae
- less commonly found on the breasts, buttocks, umbilicus, nipples, & external genitalia of men
- burrows appear as dark wavy lines in the epidermis 3-15 mm & end in a pearly bleb that contains the female mites
- burrows are generally obscured by excoriations
- AIDS patients & institutionalized patients may develop crusted scabies (Norwegian scabies), widespread scabies with extensive scaling that may not itch
- pruritus may persist for weeks after eradication of scabies[6]
* images of crusted scabies[17]
Laboratory
- diagnosis is made by microscopic examination of skin scraping in mineral oil
- eggs, 6-legged larvae, eight-legged nymphs or adults may be seen
- gravid females measure 0.3-0.4 mm in length
- it may be necessary to scrape several lesions to find a live mite[6]
- skin biopsy may also establish diagnosis
* images of mite [12,13, 17]
Complications
- impetigo from excoriations due to scratching
Differential diagnosis
- differentiate eczema from crusted scabies (Norwegian scabies)
Management
- anti-scabies agent applied to all areas of the skin, sparing the eyes, nose & mouth
- permethrin 5% (Elimite)
- lindane 1% (gamma benzene hexachloride, Kwell)
- mainstay of treatment before introduction of permethrin
- for used with refractory scabies[4]
- do not use in pregnant or nursing mothers, infants or small children because of reports of neurotoxicity
- 2 treatments 7-10 days apart[6]
- crotamiton (Eurax)
- preferred treatment for pregnant women & infants before introduction of permethrin
- high failure rate
- applied on 2 to 3 successive nights
- may be repeated 1 week later
- persistent itching may continue for 2 weeks after successful treatment
- oral ivermectin, single dose (kills scabies, but not eggs)
- treatment of contacts
- all symptomatic family members must be treated concurrently
- sexual contacts must be treated
- in institutional settings
- roommates must be treated
- symptomatic caregivers should be treated
- environmental factors
- clothing, towels used in the 24 hours prior to treatment must be laundered
- wash in hot water
- dry at high heat
- furniture not a concern, except in Norwegian scabies
- clothing, towels used in the 24 hours prior to treatment must be laundered
- symptomatic treatment for persistent pruritus
- midpotency topical steroids
- triamcinolone 0.1%
- hydrocortisone 2.5%
- tapering dose of prednisone
- antihistamines
- skin moisturizers may be useful in winter months
- Eucerin
- Moisturel
- Nutraderm
- midpotency topical steroids
- secondary infection
- Staphylococcus & Streptococcus pyogenes common
- oral antibiotics
- consider post-streptococcal glomerulonephritis in children
- secondary infection in immunocompromised hosts may lead to septicemia
- patient education
- persistence of symptoms for weeks after treatment suggest treatment failure
- discuss proper use of scabecides
- do not over use scabecides
- notify close contacts
- discuss proper handling of clothing & linens
- follow-up
- routine follow-up 2 weeks after treatment
- follow-up severe or refractory cases until clear
More general terms
Additional terms
References
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 1305
- ↑ Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 991-993
- ↑ Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 2548
- ↑ 4.0 4.1 Prescriber's Letter 10(5):28 2003
- ↑ Takahashi S. In: Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 29-Oct 2, 2004
- ↑ 6.0 6.1 6.2 6.3 6.4 Medical Knowledge Self Assessment Program (MKSAP) 14, 15, 16, 17, 18, 19. American College of Physicians, Philadelphia 2006, 2009, 2012, 2015, 2018, 2022.
Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022 - ↑ Geriatrics at your Fingertips, 13th edition, 2011 Reuben DB et al (eds) American Geriatric Society
- ↑ Wolf R, Davidovici B. Treatment of scabies and pediculosis: facts and controversies. Clin Dermatol. 2010 Sep-Oct;28(5):511-8. PMID: https://www.ncbi.nlm.nih.gov/pubmed/20797511
- ↑ Currie BJ and McCarthy JS Permethrin and ivermectin for scabies.. N Engl J Med. 2010 Feb 25;362(8):717-25 PMID: https://www.ncbi.nlm.nih.gov/pubmed/20181973
- ↑ 10.0 10.1 Geriatric Review Syllabus, 8th edition (GRS8) Durso SC and Sullivan GN (eds) American Geriatrics Society, 2013
- ↑ Hicks MI, Elston DM. Scabies. Dermatol Ther. 2009 Jul-Aug;22(4):279-92 PMID: https://www.ncbi.nlm.nih.gov/pubmed/19580575
- ↑ Scabies (image of mite) American Academy of Dermatology https://www.aad.org/public/diseases/contagious-skin-diseases/scabies
- ↑ Centers for Disease Control and Prevention (image of mite) Parasites - Scabies http://www.cdc.gov/parasites/scabies/
- ↑ Heukelbach J, Feldmeier H. Scabies. Lancet. 2006 May 27;367(9524):1767-74. PMID: https://www.ncbi.nlm.nih.gov/pubmed/16731272
- ↑ Shimose L, Munoz-Price LS. Diagnosis, prevention, and treatment of scabies. Curr Infect Dis Rep. 2013 Oct;15(5):426-31 PMID: https://www.ncbi.nlm.nih.gov/pubmed/23904181
- ↑ Strong M, Johnstone P. Interventions for treating scabies. Cochrane Database Syst Rev. 2007 Jul 18;(3):CD000320. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/17636630
- ↑ 17.0 17.1 Elosua-Gonzalez M, Garcia-Zamora E. (images) Crusted Scabies N Engl J Med 2017; 377:476. August 3, 2017 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/28767353 <Internet> http://www.nejm.org/doi/full/10.1056/NEJMicm1616169
- ↑ Rosamilia LL. Scabies. Semin Cutan Med Surg. 2014 Sep;33(3):106-9. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/25577847
- ↑ Thomas C, Coates SJ, Engelman D, et al. Ectoparasites: scabies. J Am Acad Dermatol. 2020;82:533-48. PMID: https://www.ncbi.nlm.nih.gov/pubmed/31310840
- ↑ Engelman D, Yoshizumi J, Hay RJ et al The 2020 International Alliance for the Control of Scabies Consensus Criteria for the Diagnosis of Scabies. Br J Dermatol. 2020 Nov;183(5):808-820. PMID: https://www.ncbi.nlm.nih.gov/pubmed/32034956 PMCID: PMC7687112 Free PMC article. Review.