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Color Dilution Alopecia
Color-dilution alopecia is a relatively uncommon hereditary skin disease seen in dogs with blue or fawn coats, which are dilutions of black and brown, respectively. Dilution is caused by irregularities in melanin transfer and storage. This syndrome is associated with a color-dilution gene. The initial clinical signs are the gradual onset of a dry, dull and poor hair coat quality. Hair shafts and hair regrowth are poor, and follicular papules may develop and progress to frank comedones. Hair loss and comedo formation are usually most severe on the trunk, especially color-diluted area on the skin. The disease is found in several breeds of dogs that have blue- or fawn-colored mutations.
The highest incidence is in the blue Doberman Pinscher (93%) and fawn Irish Setter (73%). Other breeds in which color dilution alopecia has been observed include Miniature Schnauzer, Dachshund, Chow Chow, Poodle, Great Dane, Whippet, Yorkshire Terrier, Chihuahua, Italian Greyhound, Saluki and Newfoundland.
Signs of Alopecia
Clinical signs are first noticed between 6 months and 3 years of age. Patchy hair loss on the ears, head and along the spinal column seems to be the most common symptom. Dermatitis, wrinkled skin, allergic skin reactions, etc. all occur. Some dogs are free of symptoms early in life and then develop them later. Recurrent superficial bacterial skin inflammation (pyoderma) is common. Intense itch (pruritus) occurs if secondary pyoderma is present. The alopecia is irreversible. Dry scaling is common and usually severe. Papules and pustules (cystic hair follicles with secondary bacterial infection) are also commonly seen. The trunk is most severely affected, and the head and extremities least affected. Tan points remain normal.
Diagnosis of Alopecia
The early age of onset of progressive alopecia in one of the predisposed breeds is compatible with a clinical diagnosis of color dilution alopecia. A preliminary diagnosis is made from direct examination of the hair shafts (trichogram). Biopsies show characteristic epidermal, follicular, and pigmentary changes.
Treatment of Alopecia
This disease is chronic and poorly responsive to treatment.
Hair will not regrow. The goal is to keep the follicles open and free of keratinous debris, and therefore less likely to become secondarily infected.
Benzoyl peroxide shampoo (oxyDex, SulfOxyDex, Pyoben) is especially effective because of its follicular flushing and antibacterial activity. To prevent worsening of the dry scale, baths with benzoyl peroxide should be followed by a moisturizing rinse. For dogs with very dry skin the rinses can be diluted and sprayed on daily. Systemic antibiotics are indicated when secondary pyoderma develops. Coexisting diseases, such as hypothyroidism should also be treated since this may improve the dry skin and decrease the incidence of recurrent pyoderma. These dogs should not be used for breeding.
- Kim JH, Kang KI, Sohn HJ, Woo GH, Jean YH, Hwang EK. Color-dilution alopecia in dogs.
- Scott, Miller, Griffin. Small Animal Dermatology, 5th ed.
- Nesbitt & Ackerman. Canine & Feline Dermatology, 1st ed., New Jersey, Veterinary Learning Systems.
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