Scabies

Background

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

Diagnosis

Scabies

Scabies burrow at high resolution

Must elicit history of symptomatic close contacts (human or animal)

• Older children / adults
  • Generalized eruption w/ 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
• Infants
  • Hyperpigmented nodules, vesiculopustules, papules may be found in axilla and diaper areas
  • May be generalized

Differential Diagnosis

• Impetigo
• Atopic Dermatitis
• Insect bites
• Drug Rash
• Dermititis Herpetiformis

Domestic U.S. Ectoparasites

• Bed bugs
• Lice
• Scabies (Mites)
• Ticks
• Fleas
• Pseudoparasites
• Delusional parasitosis (Ekbom syndrome)

See also travel-related skin conditions

Treatment

Adults

• Permethrin 5% cream for all family members
  • Apply from neck down
  • Infants may require applicatio nto scalp/face (avoid mucus membranes)
  • Leave on for 8-12hr before washing off
  • Has 95-98% success rate, may reapply in 1-2wks if incomplete effect
• Ivermectin 200mcg/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
• Wash linens/clothes in hot water or bag bulky items and keep sealed for 2wks
• Pruritus may continue for weeks despite successful elimination of infestation

Infants

• Permethrin 5% is FDA approved for > 2 months of age although still recommended for neonatal scabies