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

Scabies

Scabies burrow at high resolution

Clinical Features

Must elicit 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

• Insect bites
• Impetigo
• Atopic dermatitis
• Drug rash
• Dermatitis herpetiformis

Ectoparasites

• Bed bugs
• Lice
• Myiasis
• Scabies
• Ticks

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
  • 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
  • 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

Authors

Daniel Ostermayer, Jordan Swartz, Manuel Celedon, Aaron Snyder, Ross Donaldson, Michael Holtz, Kevin Lu, Neil Young, Claire