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 Dermatitis herpetiformis B. Scabies preparation Arthropod bites C. Empiric topical steroids + antihistamine Fleas, bedbugs, mosquitoes, scabies D. Empiric topical antifungal Drug reaction
Prurigo nodularis
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