Common Case 1  50 year-old male presents with “a very itchy Dermatologic rash” on his hands, wrists, axilla, periumbilical Infections region, and groin

Laura B. Pincus, MD Assistant Clinical Professor Dermatology and Pathology University of California, San Francisco

DDx: Pruritic papules What would you do next?

 Papular eczema A. Skin biopsy  herpetiformis B. Scabies preparation  Arthropod bites C. Empiric topical steroids + antihistamine Fleas, bedbugs, mosquitoes, scabies D. Empiric topical antifungal  Drug reaction

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1 What would you do next? Scabies prep

A. Skin biopsy

B. Scabies preparation

C. Empiric topical steroids + antihistamine

D. Empiric topical antifungal

Image courtesy of Dr. Luis Requena

Clinical course of scabies infection

Burrowing of mite into skin Hypersensitivity reaction

2-4 weeks

•Small round erythematous •Tortuous linear papule, 1-10mm papules •Finger webs, feet, breasts, groin •Hands, wrists, periumbilical •Asymptomatic at time of infection region, groin •“Itchiest rash ever” •Typical burden: 10-15 mites Currie B, McCarthy J. N Engl J Med 2010;362:717-725

Clinical course of scabies infection Crusted (Hyperkeratotic) Scabies Burrowing of mite into skin Hypersensitivity reaction  Clinical findings

 Thick white plaques with fine scale (“white sand stuck on the skin”) 2-4 weeks  Risk factors •Small round erythematous  Immunosuppression •Tortuous linear papule, 1-10mm papules  Elderly •Finger webs, feet, breasts, groin •Hands, wrists, periumbilical •Asymptomatic at time of infection region, groin (spares face)  Heavy-mite burden •Typical burden: 10-15 mites •“Itchiest rash ever” •Typical burden: 10-15 mites

2 Transmission Methods to confirm diagnosis

 Close personal contact and fomites  Skin scraping (Scabies prep)  How easy is it to transmit scabies via fomites?  Skin biopsy  4/272 non-infected people developed scabies after getting into beds vacated by infected people  Scabies can be spread via fomites, but infrequently  Crusted scabies exception: easily spread by fomites

Prins C et al. Dermatology 2004;208:241. Arenziano G et al. Arch Dermatol 1997;133:751.

Mellanby K. Br Med J. 1944;20:689. Bezold G et al. BJD 2001;144:614.

Role of skin scraping Skin scraping

 Method:  Examine slide under low  Identify burrows power for mites, eggs, and fecal pellets  Apply a 1-2 drop of mineral oil to burrows and slide  Scrape burrows with scalpel  Rub contents from scalpel onto glass slide  Apply cover slip Hengge UR, et al. Lancet Infect Dis 2006;6:769. Uptodate.com

How to make the diagnosis if tests Skin scraping negative

 Frequently, testing is negative since  Burrows can be difficult to identify Epidemiology  Mite burden usually low (household contacts with similar  Skin biopsy - similar limitations to skin scraping symptoms)

Morphology and History of distribution of severe pruritus clinical lesions

Treat empirically if high index of clinical suspicion

3 Treatment Permethrin  Antiscabetic therapy  FDA approved for scabies (> 2 mo age)  Permethrin  Formulation: 5% topical cream (Elimite)  Ivermectin (systemic)  Pregnancy category B  Precipitated sulfur 5-10%  Treatment regimen  Lindane  Apply neck down, leave overnight; repeat in 1-2 wks  Crotamiton  Advantages: Very effective  Benzyl benzoate  Side effects: Burning upon application, dermatitis  Symptomatic treatment  Topical steroids and antihistamines Currie BJ et al. NEJM 2010362:717.

Ivermectin Precipitated sulfur 5-10%

 Advantages: oral and effective  Safe for infants and pregnant women  Side effects:  Advantages:  Neurotoxicity, data mixed (caution with elderly)  Saf