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A. Propertiesnavigator

  1. Highly contagious, pruritic Dermatosis
  2. Caused by the mite Sarcoptes scabei (variety hominus)
  3. An obligate human parasite; only females burrow into the skin
  4. Mites cannot fly or jump; they crawl ~2.5cm/minute on warm skin
  5. Common in children, long-term elderly and chronic care facility, homeless persons
  6. Norwegian Scabies is a subtype and occurs in institutionalized adults
  7. Increased incidence and severity in HTLV-1 and HIV infection
  8. Usually begins on hands, interdiginous regions
  9. About 300 million cases worldwide per year

B. Appearance navigator

  1. Intensely pruritic eruption, usually generized
    1. Usually found in interdigital spaces of the hand
    2. Also found in skin folds, buttocks, breasts in women, and genital areas
    3. Usually worse at night
    4. Due to inflammatory reaction to mite
  2. Classic Lesions is "Burrow"
    1. Burrow is a thread-like, wavy, gray-white fissure
    2. Length is several millimeters
  3. May have small vesicle at the end of the burrow (presence of mite)

C. Diagnosisnavigator

  1. History and physical exam are most helpful
  2. Definitive diagnosis reqiures demonstration of either
    1. Mites
    2. Mite eggs or eggshell fragments
    3. Mite pellets
  3. Obtain multiple skin scrapings from characteristic lesions
    1. Scrape carefully across lesions to avoid bleeding
    2. Examine under microscope
    3. Do not use potassium hydroxide, which can dissolve mite pellets
    4. Failure to find mites is common and does not rule out scabies
  4. Nonspecific inflammatory reactions in skin biopsy sample can be found
  5. Empirical treatment of patients with generalized itching is not recommended
    1. Treatment for definitive diagnosis
    2. Treatment for clear exposure and symptoms
    3. Treatment for very typical eruptions even without definitive diagnosis

D. Differential Diagnosis navigator

  1. Atopic dermatitis
  2. Dermatitis herpetiformis
  3. Insect bite dermatitis
  4. Senile pruritus
  5. Many others

E. Treatment [2] navigator

  1. Overview
    1. Multiple topical agents are available
    2. Lindane and permethrin are best studied topical agents
    3. Permethrin is superior to lindane and is the preferred topical agent in the USA
    4. Ivermectin, an oral antiparasitic, has been shown to have excellent activity
    5. Ivermectin should be considered a first-line alternative therapy
    6. All contacts of infected persons MUST be treated (regardless of symptoms)
    7. Clothes and bed linens must be decontaminated by machine washing at 60°C
    8. Itching may persist up to 1-2 weeks after initiation of effective therapy
  2. Permethrin (Elimite®)
    1. 5% topical cream applied once to all affected surfaces
    2. May be combined with ivermectin therapy in difficult cases
    3. Permethrin is washed off 8-12 hours after application
    4. Overall well tolerated, much moreso than lindane
  3. Lindane (Kwell®)
    1. 1% lindane (hexachlorocyclohexane) cream, lotion or shampoo
    2. Systemic absorption of agent occurs
    3. Great care must be taken when used on children due to this absorption
    4. Contraindicated in persons with seizure disorders
    5. In general, total body application of agent is made from neck down
    6. Leave cream or lotion on for 6 to 12 hours
  4. Other Topical Agents
    1. Benzyl benzoate - 10% and 25% lotions, often causes skin irritation and eczema
    2. Malathion - 0.5% lotion
    3. Sulfiram - 25% lotion
    4. Crotamiton - 10% cream
  5. Ivermectin (Stromectol®) [3]
    1. Single dose 200µg/kg given to Norwegian scabies patients (HIV + and - were included)
    2. Most patients had impressive improvement within 2 weeks of dosage, regardless of HIV
    3. Some patients received a second dose 2 weeks after first
    4. No adverse effects were noted (22 patients total; 21 complete responses)
    5. Also available as a 0.8% lotion, though not as effective
  6. Pregnancy, Lactating Women, and Infants
    1. Lindane and ivermectin should not be used
    2. Precipitated sulfur 2-10% in petrolatum recommended
    3. Infants can be treated with esdepallethrine or benyl benzoate with caution
    4. Permethrin approved for use only in babies >2 months, though may be safe in <2 months

References navigator

  1. Chosidow O. 2006. NEJM. 354(16):1718 abstract
  2. Heukelbach J and Feldmeier H. 2006. Lancet. 367(9524):1767 abstract
  3. Meinking TL, Taplin D, Hermida JL, et al. 1995. NEJM. 333(1):26 abstract