Updated: 5/21/2015

Pediculosis Pubis (Crabs)

Review Topic
Snap Shot
  • A 21-year-old female presents to her primary care physician after recently having unprotected sexual intercourse at a college party "a few weeks ago". She complains of intense genital pruritis that has been going on for the past 3 days. Nothing she has tried has alleviated the intense itching. 
  • Parasitic infection of human pubic hair and skin by lice
    • caused by Pthirus pubis 
    • the lice do not transmit disease
  • Epidemiology
    • incidence
      • approximately 2% of the population
    • risk factors
      • poor hygiene
      • unprotected sexual intercourse
    • transmission
      • sexual contact
      • fomites
        • clothing
        • towels
  • Mechanism & Pathophysiology
    • female louse lays eggs (nits) at the base of the hair
    • lice can be visible to the naked eye
      • 3-4 mm in size
    • the lice are obligate parasites that feed on human blood
  • Associated conditions
    • other STDs
  • History 
    • pubic pruritis
    • sexual contact with someone diagnosed with pediculosis pubis
  • Symptoms
    • intense itching of the pubic area
      • due to parasitic saliva
      • becomes stronger over 2 or more weeks after initial infestation
      • other hairy areas of the body can be involved
    • pyoderma may develop from scratching
    • some patients are asymptomatic
  • Diagnosis
    • examination of hair under microscope
      • identification of adult lice or nits
  • General
    • proper cleaning of clothing and bedding is necessary
  • Pharmacologic
    • permethrin 1% shampoo
      • apply to all hairy regions from the neck down
      • sexual partners should be treated as well
    • lindane
      • indications
        • 2nd line treatment due to toxicities
      • side effects
        • contraindicated in pregnancy
        • headaches
        • seizures
        • dizziness
        • convulsions

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