Colour dilution alopecia
This condition develops in some, but not all dogs that have been bred for unusual coat colour, especially "fawn" (a dilution of a normally red or brown coat) or "blue" ( a dilution of the normal black and tan coat colour). Alopecia means hairlessness - affected dogs have a poor, patchy haircoat progressing to widespread permanent hair loss. At the cellular level, there are abnormalities of the hair follicles and uneven clumping of pigment (melanin) granules in the hair shafts in affected areas
The inheritance is unclear. The condition is thought to be due to the interaction of different factors at the gene position for colour. It is not simply determined by the genes at that locus, because not all dogs with colour dilution develop coat problems.
Dogs with this condition are born with a normal haircoat. Those with lighter blue or fawn hair coats usually start to show changes by 6 months while in dogs with darker steel blue coats, the changes may not be evident until 2 or 3 years of age. Your dog will experience hair loss and dry skin. Sometimes the earliest sign is a recurring bacterial infection (folliculitis), generally on the back, where you will see small bumps which are infected hair follicles. This clears up temporarily with antibiotics, but the affected area is very slow to regrow hair, or remains hairless.
Hair loss is usually first apparent on the back and by 2 or 3 years has spread over all the light coloured areas of the body. The exposed skin is often scaly and is susceptible to sunburn or extreme cold. Your dog's health is not otherwise affected by this condition.
Your veterinarian may suspect this disorder if your dog has typical haircoat changes and is an unusual colour for the breed. The diagnosis is confirmed through microscopic examination of plucked hairs or a skin biopsy. The latter is a simple procedure, done with local anesthetic, in which your veterinarian removes a small sample of your dog's skin for examination by a veterinary pathologist. The biopsy will show changes characteristic of this condition.
Your dog can lead a normal healthy life with periodic symptomatic treatment as needed - moisturizing rinses for dry scaly skin or antibiotics for bacterial infections.
Since early hair loss occurs due to breakage, you may be able to slow the rate of loss by avoiding harsh shampoos and vigorous grooming.
For the veterinarian: There have been some early reports of hair regrowth using etretinate treatment . (See resource below.)
Careful microscopic examination of plucked hairs will show large clumps of melanin distributed unevenly along the hair shaft.
In young dogs, demodicosis or other inherited hair defects should be considered while in dogs with a later onset (2 to 3 years of age), endocrine disorders (particularly hypothyroidism) should be ruled out.
Affected dogs, their parents and siblings should not be used for breeding. The condition can be entirely avoided by the use of non-colour-diluted dogs in breeding programmes.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Muller and Kirk's Small Animal Dermatology. p. 777. W.B. Saunders Co., Toronto.
Power, H.T., Ihrke, P.J. 1995. The use of synthetic retinoids in veterinary medicine. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine. p 585-590. W.B. Saunders Co., Toronto