Scabies
Gonzalo De Toro, MD
Key Facts
Etiology/Pathogenesis
Caused in humans by scabies mite Sarcoptes scabiei variety hominis
Clinical Issues
Predilection for interdigital areas and flexures, waist, ankles, and intergluteal fold
3 different clinical forms
Microscopic Pathology
Diagnostic finding is presence of mite, feces, or eggs in stratum corneum
Many levels may be necessary
Superficial and deep infiltrate of lymphocytes, histiocytes, mast cells, and eosinophils
Top Differential Diagnoses
Dermal hypersensitivity reactions
Lymphomatoid papulosis
 Scabies presented in this patient as multiple, excoriated papules  and burrows  on the hand. |
 Positive KOH scraping from a patient with Norwegian (crusted or keratotic) scabies shows a large scabietic mite  with an oval egg casing to the left  . |
TERMINOLOGY
Synonyms
Itch mite infestation, “7-year itch”
Definitions
Ectoparasitic infestation with about 300,000,000 cases worldwide each year
Common predisposing factors are overcrowding, immigration, poor hygiene, poor nutritional status, homelessness, dementia, and sexual contact
Direct skin-to-skin contact for 15-20 minutes is needed to transfer mites from 1 person to another
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