Alopecia is a common disorder in dogs that is characterized by partial or complete hair loss from areas which normally are covered by hair. Some breeds of dogs have been shown to be more prone to alopecia. Among these are the alopecic breeds which include the Mexican hairless, Chinese crested, Inca hairless, American hairless terrier which is mostly associated with furunculosis, comedones and folliculitis; and Peruvian Inca Orchid. Cocker spaniel, poodle, Belgian shepherd, French bulldog, whippet, beagle, Yorkshire terrier, and Labrador retriever commonly are prone to congenital hypotrichosis. Others like the Doberman pinscher, cream chow chow, silver Labrador, blond Irish setter, and blue pit bull terrier; appear to have color dilution alopecia. Even more interesting a feature, some breeds of dogs have what is referred to as seasonal or cyclic (canine lank) alopecia. These are the English bulldog and the boxer.
Alopecia in dogs is due to a multiplicity of causes. However, this disorder is as a sequel of removal of hair or the disruption in hair growth from infection, hypersensitivity , trauma, autoimmune attack, endocrine abnormalities, neoplasia, drug reaction and/or blockage of the receptor sites for stimulation of the hair growth cycle and mechanical removal of hair.
A wide range of signs are seen in alopecic dogs and vary from acute at onset to those considered as slowly progressive. Multifocal patches of circular alopecia my be seen and often associated with folliculitis from bacterial infection and multifocal areas of demodicosis. Large and more diffuse areas of alopecia indicate a follicular dysplasia or metabolic component. The pattern and degree of hair loss are important for establishing a differential diagnosis.
Causes Of Alopecia In Dogs
Multifocal alopecia may be due to one of the following causes: Localized demodicosis, staphylococcal folliculitis, injection reactions, dermatophytosis, rabies vaccine vasculitis, localized scleroderma, Sebaceous adenitis of short-coated breeds, and alopecia areata.
The form of alopecia that is described as patchy to diffuse may be as a result of many various causes which include: demodicosis, epitheliotropic lymphoma, anagen deluxion and telogen deluxion, sebaceous adenitis, color mutant/dilution alopecia, bacterial folliculitis, dermatophytosis, hypothyroidism, hyperadrenocorticism, Keratinization disorders and due to pemphigus foliaceus.
Symmetrical alopecia is hormone responsive and is described as one which is present on both symmetrical sides of the dog’s body. Causes of this disorder are numerous and include: hyperadrenocorticism, non-inlammatory alopecia (alopecia X), hyperestrogenism (females), hypothyroidism, testosterone-responsive dermatosis in castrated males, hypogonadism in intact females, male feminization from Sertoli cell tumor, etrogen-responsive dermatosis in spayed female dogs, seasonal/cyclic/canine lank alopecia, and castration-responsive dermatosis.
Diagnosis And Treatment
The pattern and extent of the hair loss are important features for formulating a differential. Inflammation, scale, crust, are important samples for determining diagnosis.
It is of importance to rule out metabolic causes such as hyperadrenocorticism by carrying out biochemical tests such as urinalysis. Other Lab tests may be done include the thyroid test to diagnose hypothyroidism. These tests are the ACTH-response test, LDDST, and HDDST. Ultrasonography my be done to evaluate adrenal glands for evidence of hyperadrenocorticism.
Treatment varies with specific cause, hence the pet should be taken to a veterinarian for specific testing, diagnostics and treatment as needed.