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Hair: leukotrichia

ISSN 2398-2977


Synonym(s): Hair whitening, White hairs

Introduction

  • Cause: leukotrichia occurs commonly as post-inflammatory change, eg from branding in saddle areas or the legs due to ill-fitting equipment and bandaging. Other infectious or immunologic causes are also reported.
  • In horses carrying the G allele color is present at birth but increasing number of white hairs develop with age, eg Arabians, Andalusians, Lipizzaners.
  • Signs: white hairs.
  • Diagnosis: history and clinical signs.
  • Treatment: no effective treatment known.
  • Prognosis: depends on condition.

Presenting signs

  • White hairs with or without pre-existing skin lesions (either localized or generalized depending on the underlying cause).

Geographic incidence

  • Hyperesthetic leukotrichia reported only in the USA.

Age predisposition

  • In gray horses, leukotrichia is progressive and it starts around 2-3 years of age.

Breed/Species predisposition

Pathogenesis

Etiology

  • Variable from genetic to inflammatory Skin: vitiligo.
  • Skin trauma.
  • Special forms of leukotrichia include reticulated leukotrichia, spotted leukotrichia and hyperesthetic leukotrichia.

Reticulated leukotrichia

  • This is uncommon. 
  • Pathogenesis is unknown and it is hypothesized to be a variation of erythema multiforme Erythema multiforme.
  • It develops at young age and starts with crusty lesions that once shed, leads to permanent leukotrichia with cross-hatched, net-like or herringbone symmetric distribution over the back between the withers and the base of the tail.
  • It may be secondary to herpesvirus infection Equine herpesvirus or vaccinations Vaccination in some animals.
Due to the poossible hereditary cause, affected animals should not be used for breeding.

Spotted leukotrichia

  • Spots of white hair (1-3 cm), in the absence of skin lesions, on the rump area or on the sides .
  • The cause is unknown and in most cases it is a permanent change.
  • The skin is usually pigmented, but when leukoderma is present, the prognosis for repigmentation of the hair is worse.

Hyperesthetic leukotrichia

  • Affects older horses (may be a variant of reticulated leukotrichia).
  • Horses develop single or multiple extremely painful crusts (1-4 mm) over the dorsum from the withers to the base of the tail that persist for 1-3 months and then result in patchy leukotrichia.
  • The disease appears to have a cyclic behavior, but the cause is unknown.

Predisposing factors

General

Timecourse

  • Depends on underlying disease.

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.
  • Stannard A A (2000) Pigmentary disorders. Vet Derm 11 (3), 205-210 PubMed.
  • Fadok V A (1995) Update on four unusual equine dermatosesVet Clin North Am Equine Pract 11 (1), 105-110 PubMed.

Other sources of information

  • Scott D W & Miller W H (2011) Pigmentary Abnormalities. In: Equine Derm. Saunders, USA. pp 389-397.
  • Knottenbelt D C (2009) Pascoe’s Principles and Practice of Equine Dermatology. 2nd edn. Ed: Knottenbelt D C. Saunders, USA.