Scabies

Background
  • Infestation with the Sarcoptes scabiei mite
  • 4-6 week incubation period after initial exposure
    • Those previously infected, symptoms begin in 1-3 days (sensitization)
    • Type IV hypersensitivity
  • Not a reflection of poor hygiene

Clinical Features
Traditional infantile scabies.
10-X magnification showing numerous scabies heads (arrows).
Scabies
Scabies burrow at high resolution

Seek history of symptomatic close contacts (human or animal)

Infants
  • Hyperpigmented nodules, vesiculopustules, papules may be found in axilla and diaper areas
  • May be generalized

Older children / adults
  • Generalized eruption with linear burrows, papules, pustules
  • Predominance in web spaces of the fingers, flexor aspect of the wrists, axillae, groin, nipples, and the periumbilical region
  • Pruritus is classically worse at night

Norwegian Scabies
  • In immunocompromised
  • Severe disease with diffuse scabies
  • Requires multiple treatments

Differential Diagnosis

Domestic U.S. Ectoparasites

See also travel-related skin conditions

Evaluation
  • Clinical diagnosis, based on history and physical exam

Management

General Care
  • Wash all linens/clothes in hot water or bag bulky items and keep sealed for 2wks
  • Pruritus may continue for weeks despite successful elimination of infestation
    • Consider steroids for symptom relief

Adults
  • Permethrin 5% cream for all family members[1]
    • Apply from neck down
    • Leave on for 8-12hr before washing off
    • Has 95-98% success rate, may reapply in 1-2wks if incomplete effect
  • Ivermectin 200 mcg/kg may be necessary for severe infection
    • Also viable option in adolescent or adult with insecure social situation
    • Success rate 70%, increases if give repeat dose 2wks after
    • Contraindicated in lactating women and children < 15kg

Infants
  • Permethrin 5% is FDA approved for > 2 months of age although still recommended for neonatal scabies[2]
    • May require application head to toe (avoid mucus membranes)
    • Leave on for 8-12 hours, then wash off

Avoid
  • Lindane - effective treatment but associated with potential for toxic manifestations (seizures, neurotoxicity)
    • Reserved for refractory cases

Disposition
  • Discharge

References
  1. Strong M. Johnstone P. Interventions for treating scabies. Cochrane Database Syst Rev. 2007;(3):CD000320
  2. Subramaniam S. Rutman MS. Wnger JK. A papulopustular, vesicular, crusted rash in a 4-week old neonate. Pediatric Emergency Care. 2013;29:1210-1212
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