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Case Note

Case Note: Rash on a 6-year-old

History

6-year-old male. Attends elementary school; develops intensely pruritic rash on wrists, umbilicus, hands and feet. No sick contacts.

Initial evaluation

  • Excoriated scaly papules clustered on the wrists/hands, umbilicus and scattered across the trunk; genitalia, face and scalp are spared
  • A skin scraping taken from the feet reveals mites and eggs 

Possible considerations

  • Scabies due to animal sarcoptes
  • Human scabies
  • Acropustulosis of infancy
  • Onchocerciasis in patients coming from endemic areas

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Enter your diagnosis

Diagnosis

  • A diagnosis of scabies is rendered 

No further initial evaluation details from the case are available; however, consider the following for the general initial evaluation for scabies.

Clinical variants

  • Scabies incognito: Minimal clinical signs. Superinfection is rare
  • Scabies in the infant: Infants may present with typical features seen in adults but also with a vesiculo-pustular eruption of the palms and soles in association with linear burrows
  • Generalized or crusted scabies: Mainly in HIV-positive and immunocompromised individuals. May not be pruritic, and the scalp can be affected. Very frequently due to systemic immunosuppression
  • Bullous form: Rare, may mimic immunobullous disease such as bullous pemphigoid. Direct immunofluorescence (DIF) is negative

Erythematous, crusted, excoriated papules, pustules and vesicles. Linear burrows representing the path of the mite through the skin may also be seen. Wrists, interdigital web spaces, axilla and genitalia are typically affected sites.

Initial Treatment

  • The patient is prescribed:
    • Permethrin 5% cream, to be applied overnight to the whole body except face/scalp and repeated in 1 week
    • Triamcinolone 0.1% ointment b.i.d. (started 24 hours after first anti-parasitic treatment)
    • Hydroxyzine for nocturnal pruritus
  • Simultaneous treatment of entire family and babysitter is mandatory
  • Instructions for decontamination protocol are given
  • Report infection to school
  • Follow-up in 2 weeks
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Follow-up evaluation strategy

  • Patient's eruption has resolved, but pruritus persists
  • Patient has several follicular-based pustules with surrounding erythema on the legs; a bacterial culture is taken, oral cephalexin is empirically started for presumed staphylococcal pyoderma, the culture reveals methicillin-sensitive Staphylococcus aureus
  • No additional sick contacts
  • Continue oral antihistamines and topical steroids for 1-2 more weeks
  • Follow-up in 1 month (lesions, pruritus resolved)

General discussion

Scabies is associated with an infestation of the skin by an epidermal-dwelling mite, Sarcoptes scabiei. It is a highly contagious condition that is primarily transmitted through close contact and rarely through exposure to infested clothing, bedding or other household items. Patients typically present with symptoms 7 days after the first exposure, but may develop skin lesions as early as 3-4 days after subsequent exposures. Skin lesions are usually intensely pruritic, with the exception of infants, elderly and other individuals who have neurologic disease or immunocompromised status. A rare form, crusted scabies, can be generalized. Risk factors for scabetic infestation include crowded living conditions, healthcare facilities and institutions.

Further reading

Currie BJ and McCarthy JS. Permethrin and Ivermectin for scabies. N Engl J Med 2010;362:717-25.

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