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Integumentary system ORGAN SYSTEMS

Orf

Orf disease, also known as contagious pustular dermatitis or ecthyma contagiosum, is a zoonotic infection caused by the parapoxvirus, Orfviridae.

Orf disease, also known as contagious pustular dermatitis or ecthyma contagiosum, is a zoonotic infection caused by the parapoxvirus, Orfviridae.

Orfvirida (poxvirus):

Zoonotic infection transmitted to humans via contact with infected goat and sheep
Sore/scabby mouth disease with the typical mucosal eschar. | Meier, R., Sommacal, A., Stahel, A., Grünert, J., & Hoffmann, M. (2015). Orf – an orphan disease?. JRSM open, 6(6), 2054270415593718. https://doi.org/10.1177/2054270415593718

Clinical features

After a 3-5 day incubation period, well-described cutaneous lesions develop, progressing through 6 stages, about a week in duration.

  1. Maculopapular – erythematous
  2. Target lesion – target shaped with a necrotic center and surrounding red halo
  3. Acute nodular/weepy – draining papule
  4. Regenerative/dry – firm crusted papule
  5. Papilloma – papillomatous surface
  6. Regressive stage – resolution with little if any scarring
(a) Clinical presentation with papulo-bullous lesion on the digit and (b) histological examination showing vacuolisation of squamous epidermal cells and intracytoplasmatic eosinophilic inclusion bodies (H&E × 200). | Meier, R., Sommacal, A., Stahel, A., Grünert, J., & Hoffmann, M. (2015). Orf – an orphan disease?. JRSM open, 6(6), 2054270415593718. https://doi.org/10.1177/2054270415593718
  • Hand and digital involvement comprise > 90% of affected site
  • Constitutional symptoms (uncommon): Fever, malaise and lymphadenopathy
  • Immunocompromised state: Giant orf (large size)

Complications:

  • Superinfection
  • Lymphangitis

Differential diagnosis:

Disorders that share zoonotic-exposure history to farm animals and exhibit cutaneous lesions.
  • Paravaccinia (Milker’s nodules): Very similar parapoxvirus infection arising from cows rather than goats/sheep as in orf disease. Clinically they are indistinguishable and resolve spontaneously within six weeks or so.
  • Cutaneous anthrax
  • Other differentials: Pyoderma, herpetic whitlow, cowpox, cat-scratch disease, tularemia, tuberculosis, other mycobacteria, syphilis, sportrichosis, keratoacanthoma, and pyogenic granuloma
Milkers’ nodule: A typical lesion A) 13 days, B) 24 days (granulation of the border after biopsy), C) 32 days, and D) 41 days after appearance. | Adriano AR, Quiroz CD, Acosta ML, Jeunon T, Bonini F. Milker’s nodule—case report. An Bras Dermatol. 2015;90(3):407–10.

Management

The lesions are self-limiting, and in immunocompetent patients – symptoms would spontaneously resolve in a 4- to 6-week window.

  • Reassurance and expectant care

Immunocompromised hosts:

  • Topical cidofovir (blocker of DNA dependent RNA polymerase enzyme) + mechanical eradication (cyotherapy, surgical excision, imiquimod)

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