Color dilution is a normal occurrence in many dog breeds. The colors blue (from black) and fawn (from red) are considered color-diluted. Color dilution occurs during the breeding process and is determined by the type of color genes that the parents pass to their offspring. Color dilution alopecia is a skin condition that affects a large number of color-diluted dogs and is considered a hereditary condition.
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Color Dilution
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To understand how color dilution occurs, we will look at the Doberman pinscher. The genes that determine the color of the dog's hair coat consist of a (B) gene for black and a (b) gene for red. Genes represented by a capital letter are dominant genes, and those represented by a lower-case letter are recessive genes; therefore, a dog with (BB) will be black, (Bb) will be black and (bb) will be red. Every dog has two color genes and passes one to his or her offspring.
Dogs also carry a pair of genes that determine the intensity of the coat color; these are the color dilution genes. One of these genes from each parent is also passed to the dog's offspring. Color dilution genes are (d) dilute, or (D) non-dilute. During breeding, a dog with (dd) can pass only a (d) gene to the offspring, a (DD) dog can pass only a (D) gene, and a (Dd) can pass either. If both parents pass a dilute (d) gene, then the pup's color will be diluted.
For example: If a (BB) dog has (dd) dilution genes he will be a blue color. A (Bb) dog with (dd) dilution genes will also be a blue color, and a (bb) dog with (dd) will produce a fawn color. If only one color dilution gene is dilute, then the dog's color will be normal (BB) and (Dd); however, dogs can pass the dilute gene to their offspring.
Color Dilution Alopecia
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Color dilution alopecia is a condition that affects some color-diluted dogs. Alopecia means hairlessness. Dogs with this condition have an unhealthy, patchy hair coat, which progresses to widespread hair loss and secondary infections.
Not all color-diluted dogs are affected; however, it is more common in some breeds. As many as 90 percent of blue and 75 percent of fawn Doberman pinschers are affected by alopecia. Other breeds commonly affected are chow-chows, dachshunds, poodles, Great Danes and Irish setters; however, any color-diluted dog could be affected.
Symptoms
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Most of these dogs will have a dry, dull hair coat that appears unhealthy. In addition, comeodones, which are acne-like pustules, will appear on the skin at the base of the hair follicles. Hair loss is also associated with color-dilution alopecia and is usually most noticeable on the trunk, ears and head. Recurrent skin infections are common, resulting in dry, very itchy skin.
Diagnosis
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Diagnosis is based on breed as well as coat color and the dog's age at time of clinical signs. This is usually enough to consider color-dilution alopecia as the diagnosis. However, your veterinarian may also perform a microscopic examination of the hair follicles, called a trichogram. Skin biopsy will also show characteristic changes in the epidermal cells.
Treatment
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This is an incurable, chronic disease that is difficult to treat. The alopecia is permanent, and the goal of treatment is to keep the hair follicles open and control secondary bacterial infections. Weekly bathing in a benzyl peroxide shampoo such as OxyDex, SulfOxyDex or Pyoben along with a moisturizing rinse such as Avoderm or Perfect Coat will help make your dog more comfortable. If your dog has extremely dry skin, you can make a spray by diluting the rinse and spraying your dog daily. A fatty acid supplement may also be beneficial. Antibiotics will be prescribed to treat outbreaks of bacterial infections.
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