ISSN 2398-2977      

Skin: vitiligo

pequis

Synonym(s): Snowflakes, Arabian fading syndrome, pinky syndrome, juvenile Arabian leukoderma


Introduction

  • Cause: an acquired melanin pigmentary disorder. 
  • Signs: focal reduction of pigment in the skin (leukoderma) and/or the hair (leukotrichia).
  • Diagnosis: history, clinical presentation, histopathology to rule out other causes.
  • Treatment: observation only, topical steroids, tacrolimus?
  • Prognosis: good.

Pathogenesis

Etiology

  • The cause of vitiligo, leukoderma/leukotrichia and Arabian fading syndrome is not known.

Predisposing factors

General
  • Arabian fading syndrome: a genetic predisposition is suspected.

Pathophysiology

  • To the authors knowledge the pathophysiology of vitiligo/leukoderma/leukotrichia in horses remains unknown.
  • Three hypotheses for pigment loss in human vitiligo have been advanced:
  • Autotoxicity hypothesis: reactive melanin precursor molecules are thought to predispose melanocytes to destruction, possibly due to inhibition of thioredoxin reductase, a free-radical scavenger associated with the melanocyte cell membrane.
  • Neural hypothesis: melanocytes originate from the neural crest and have characteristics of nerve cells; thus, neural injury has been advanced to explain dermatomally distributed vitiligo.
  • Auto-immune hypothesis: melanocytes can be destroyed by humoral or cellular immune mechanisms; in humans and horses with vitiligo auto-antibodies against melanocytes have been found but it is unclear whether these antibodies are the cause or a result of the disease.
  • Multiple mechanisms may contribute to development of vitiligo in individual horses.

Epidemiology

  • The incidence of equine vitiligo has not been reported. 
  • One university clinic diagnosed vitiligo in 0.67% of their equine dermatological caseload. 
  • In humans approximately 2% of the population is affected and it is likely that the condition is also more common in horses as many clients may not seek veterinary attention for the problem.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kanwar A J et al (2004) Topical tacrolimus for treatment of childhood vitiligo in AsiansClin Exp Derm 29 (6), 589-592 PubMed.
  • Montes L F et al (2003) Value of histopathology in vitiligoInt J Derm 42 (1), 57-61 PubMed.
  • Halder R M & Brooks H L (2001) Medical therapies for vitiligoDerm Ther 14, 1-6 Wiley Online Library.
  • Stannard A A (2000) Pigmentary disordersVet Derm 11, 205-210 Wiley Online Library.
  • Le Poole I C et al (1993) Review of the etiopathomechanism of vitiligo: A convergence theoryExp Derm (4), 145-153 PubMed.

Other sources of information

  • Scott D W & Miller W H Jr (2003) Equine Dermatology. W B Saunders, USA.
  • Yu A A (1997) Dermatologic Conditions Associated With Abnormal Pigment. In: Current Therapy in Equine Medicine. pp 391-393. Eds: Robinson N E. W B Saunders, USA.

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