Scabies

Transmitted by close skin-to-skin contact:
  • In adults, usually during sex
  • Not shaking hands, hugging with clothes on, or sitting on a couch
  • Competitive wrestling or similar activities
  • Families with young children may transmit among each other (constant contact)
Incubation period 3-6 weeks
  • Time to develop hypersensitivity to mites eggs & feces
  • If previously sensitized, reaction can start right away

 

Lesions:  Appearance is quite variable
  • Unimpressive papules, but also pustules, vesicles, nodules, or wheals
  • Commonly excoriated, sometimes with secondary impetigo or furuncles
Distribution:
  • Typically on & between fingers, volar wrists, axilla, periumbilical, waist, & buttocks
  • Almost always present near breast areola in women, on penis or scrotum in men
  • Virtually never on the back or head (except infants)
  • NOT only on exposed areas [suspect bug bites]

 

Pathognomonic burrow (mite’s current trail):
  • faint thin gray / brownish line
  • Maybe a barely-perceivable dot at an end (the mite).
  • Burrows are rarely noted (eaasily scratched away)

 

Diagnostic Technique (easiest & maybe best): sticky transparent packing tape
  • Press hard against a lesion, pull off rapidly, examine under low power microscopy
  • Look for mite eggs & feces (see Picture)
  • Need lots of specimens.  Positive clinches it, negative doesn’t rule it out
“Crusted scabies” in immunocompromised or debilitated patients
  • Diffuse scales & crusts, millions of mites, very contagious, very hard to treat
  • Often doesn’t itch (patients are too debilitated)
  • May need a KOH prep to dissolve debris on top of the mites 

Note: Treatment kills the mites immediately, but itching persists another few weeks

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