1. General Considerations

   1. There is no specific treatment for follicular dysplasias. Owners have to be made aware of the genetic influence in the development of this condition and advised to not breed their affected pets.
   2. Pattern baldness is a relatively common canine disorder that affects dogs of either sex independent of their reproductive status
   3. The hair loss typically starts before 1 year of age.
   4. It is recognized predominantly in short-coated breeds.
   5. The distribution of the hair loss is typically related to the breed. To simplify for clinicians the various clinical presentations can be grouped as follows: (i) pinnal alopecia of dachshunds, (ii) pattern baldness of American water spaniels, (iii) pattern baldness of greyhounds, and (iv) predominantly ventral alopecia of short-coated breeds.

2. Pathogenesis

   1. The pathogenesis is currently unknown; however, the strong breed predisposition suggests that genetics play a role.

3. Clinical Signs

   1. Pinnal alopecia of dachshunds – The hair loss typically starts between 6 to 9 months of age and progresses slowly to involve both pinna entirely by 8 to 9 years of age. The skin becomes hyperpigmented at affected sites.

1. 2. Pattern baldness of American water spaniels – The hair loss develops at the ventral and lateral neck, trunk, rump, and posterior thighs by 6 months of age. Follicular dysplasia has been described histologically in about half of the cases prompting a discussion whether or not this condition should be classified under follicular dysplasias.
   3. Pattern baldness of greyhounds – The hair loss develops solely at the caudal aspect of both thighs. This condition has to be differentiated from the “bald thigh” syndrome where the alopecia involves the lateral thighs and likely has an endocrine cause.
   4. Predominantly ventral alopecia of short-coated dogs – This condition is recognized more frequently in dachshunds but has also been described in Boston terriers, whippets, Chihuahuas, Manchester terriers, greyhounds, and Italian greyhounds. According to anecdotal reports from colleagues and the authors’ experience other breeds such as boxers and American Staffordshire terriers can also develop pattern baldness. The alopecia starts around 6 months of age and progresses gradually over the period of 1 year to involve the pre- and post-auricular areas, ventral neck, entire ventrum, and caudomedial thighs. Fine and small hairs may be noted at areas of alopecia.

1. 4. Diagnosis:

      1. The development of non-inflammatory alopecia before 1 year of age in predisposed breeds suggests pattern baldness alopecia.
      2. Histopathology shows miniaturization of hair follicles characterized by shorter and thinner follicles with smaller bulbs.

   5. Treatment:

      1. Melatonin at the dosage of 3 to 6 mg/dog every 8 to 12 hours has resulted in significant hair regrowth in some cases after 3 to 4 months of therapy.
      2. Owners need to be advised to not breed affected dogs.

References

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Gross TL, Ihrke PJ, Walder EJ, et al. Atrophic diseases of the adnexa. In: Gross TL, Ihrke PJ, Walder EJ,  Affolter VK, eds. Skin Diseases of the Dog and Cat, Clinical and Histopathologic Diagnosis. 2nd ed. Oxford: Blackwell Publishing; 2005:480–513.

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Muntener T, Schuepbach-Regula G, Frank L, et al. Canine noninflammatory alopecia: a comprehensive evaluation of common and distinguishing histological characteristics. Vet Dermatol  2012; 23: 206-e44. DOI: 10.1111/j.1365-3164.2012.01049.x

Paradis M. Canine pattern alopecia. In: Mecklenburg L, Linek M, Tobin DJ, eds. Hair Loss Disorders in Domestic Animals. Ames, IA: John Wiley & Sons, 2009; 164–168.

Welle MaL K. Adnexal disorders. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:1196–1200.

Welle MM. Canine noninflammatory alopecia:  An approach to its classification and a diagnostic aid. Vet Pathol 2023; 60: 748-769.