Alopecia X

From Dog
Characteristic alopecia associated with Alopecia X[1]

Alopecia X is an genetic disease of dogs characterized by a noninflammatory, progressive, bilaterally symmetrical progressive alopecia[2] caused by premature catagen (cessation phase).

A number of other terms for this condition include adult-onset growth hormone deficiency, growth hormone-responsive alopecia, castration-responsive alopecia and adrenal hyperplasia-like syndrome. No significant changes in sex hormone concentrations have been noted in these dogs[3]. Use of estrogen-receptor antagonists have been shown to be ineffective in female dogs, suggesting reproductive hormones may not be involved in the etiology of this condition[4]. However, some dogs have shown elevation in progesterone levels when injected with synthetic ACTH, suggesting a role of pituitary disease in this phenomenon or underlying borderline hyperadrenocorticism[5].

A number of breeds are predisposed to this condition, especially Toy Poodle, Miniature Poodle, Pomeranian, Alaskan Malamute, Siberian Husky and Keeshonden[6].

Alopecia X affects dogs of both sexes regardless of neuter status. The hair loss can first occur at any age and affected dogs present with gradual loss of hair over the trunk and caudal thighs, sparing the head and front limbs. Sometimes the guard hairs are lost first leaving a soft 'puppy' coat[7]. The skin may become intensely hyperpigmented. There are no systemic signs associated with this condition.

Histological examination usually reveals hyperkeratosis, follicular keratosis, excessive tricholemmal keratinization (flame follicles), thin epidermis, few small anagen bulbs, epidermal pigmentation and melanin aggregates within follicular keratin. Dogs with alopecia X also have the lowest percentage of anagen follicles and the highest percentage of telogen follicles.

A differential diagnosis would include hypothyroidism, hyperestrogenism, hyperadrenocorticism[8], Mycobacterium avium[9] and idiopathic alopecia[10].

Treatment is sometimes unwarranted, but trilostane[11] or melatonin supplementation has shown to improve hair regrowth[12].

Apart from alopecia, most dogs are generally unaffected by the condition.


  1. Dr R Hilton
  2. Mausberg EM et al (2007) Evaluation of the CTSL2 gene as a candidate gene for alopecia X in Pomeranians and Keeshonden. Anim Biotechnol 18(4):291-296
  3. Frank LA et al (2004) Adrenal steroid hormone concentrations in dogs with hair cycle arrest (Alopecia X) before and during treatment with melatonin and mitotane. Vet Dermatol 15(5):278-284
  4. Frank LA (2007) Oestrogen receptor antagonist and hair regrowth in dogs with hair cycle arrest (alopecia X). Vet Dermatol 18(1):63-66
  5. Leone F et al (2005) The use of trilostane for the treatment of alopecia X in Alaskan malamutes. J Am Anim Hosp Assoc 41(5):336-342
  6. Mausberg EM et al (2008) Exclusion of patched homolog 2 (PTCH2) as a candidate gene for alopecia X in Pomeranians and Keeshonden. Vet Rec 163(4):121-123
  7. Mausberg EM et al (2007) Inherited alopecia X in Pomeranians. Dtsch Tierarztl Wochenschr 114(4):129-134
  8. Lee YM et al (2005) A case of adrenal gland dependent hyperadrenocorticism with mitotane therapy in a Yorkshire terrier dog. J Vet Sci 6(4):363-366
  9. Campora L et al (2011) Mycobacterium avium subspecies hominissuis disseminated infection in a Basset Hound dog. J Vet Diagn Invest 23(5):1083-1087
  10. Müntener T et al (2012) Canine noninflammatory alopecia: a comprehensive evaluation of common and distinguishing histological characteristics. Vet Dermatol 23(3):206
  11. Cerundolo R et al (2004) Treatment of canine Alopecia X with trilostane. Vet Dermatol 15(5):285-293
  12. Frank LA et al (2006) Oestrogen receptor evaluation in Pomeranian dogs with hair cycle arrest (alopecia X) on melatonin supplementation. Vet Dermatol 17(4):252-258