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

Domestic U.S. Ectoparasites

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

See also travel-related skin conditions

Evaluation

• Clinical diagnosis, based on history and physical exam

Management

Adults

• Permethrin 5% cream neck down leave 8-12hrs repeat 1-2wks 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 200mcg/kg PO repeat in 2wks
  • 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

Pediatric

• Permethrin 5% cream, apply head to toe (avoid mucous membranes), leave 8-12hrs, wash off; repeat in 1-2 weeks
  • FDA approved for >2 months of age; also recommended for neonatal scabies
• Ivermectin 200mcg/kg PO, repeat in 2 weeks; only for children >15kg

Disposition

• Discharge