Color Dilution Alopecia, CDA

N E B K C

Color Dilution Alopecia (CDA)

Other Names:Alopecia, Black hair follicular dysplasia, Blue Doberman syndrome.

Dilution BHFD, CDA

Affected Genes:MLPH

Mutation: Point Mutation

As no test is available at the time and due to the inherited nature of this disease, dogs with CDA, their parents, and their siblings should not be used in breeding programs.

This pathology may be difficult to contain since the first symptoms of the disease may appear only around 2 years of age and the affected dog will already have a progeny that has unintentionally spread the disease.

The major problem is also the taboo around this disease. No breeder will admit to you that he has had cases of CDA in his breeding stock and some will use descendants of affected dogs and sell puppies, knowing that the disease often appears late enough, sometimes only around 2 years when any health guarantee has expired.

Diluted dogs over 3 years old are not likely to develop CDA, however they could theoretically be CDA carriers.

The cause of CDA is not clearly understood. Microscopic examination of hairs of dilute individuals reveals that the pigment (melanin) forms large granules (macromelanosomes) which are rarely found in deeply pigmented hairs. In dilute individuals with normal appearing coats, these macromelanosomes are not grouped or clumped and cause no distortion of the cuticle (outer covering) of the hair. Dogs with CDA have many large groups or clumps of macromelanosomes which tend to distort the cuticle of the hair. It is hypothesized that this distortion of the cuticle causes the hairs to break easily, resulting in the short stubby hairs commonly found in affected individuals. (See Drawing). It is further hypothesized that the rupture of the hair releases by-products of pigment formation, which are toxic to the hair follicles. Re-growth of broken hairs is reduced because of damage to the follicles caused by
these toxins.

Why in some dilute dogs the macromelanosomes are clumped and in others they are not, is an interesting question at this time. The relationship between dilute pigment and hair loss is clear, but why are some dilute individuals unaffected? Weimeraners as a breed are dd, all individuals are dilute, yet the disease is unreported in this breed. In Dobermans, the dilute individuals comprise only 8-9% of the breed, yet 50-80%6 of the dilute dogs have CDA. In Italian Greyhounds, many individuals are dilutes, yet the IGCA health survey reported only 71 affected individuals among the approximately 2200 dogs included in the survey. If half the dogs included in the survey were dilutes, the incidence of CDA in IG’s would be around 7% of the dilute population, as opposed to the 50-80% affected dilute Dobermans.

A third allele (dl) which is associated with CDA has been proposed. While this is a long way from being proven, it could help explain why some dilute animals are unaffected. Dogs with a genotype dd would be normal coated dilutes, ddl would be intermediates (mildly affected?) and dldl would be CDA affected. A genotype of Ddl should represent deeply pigmented dogs which were carriers of CDA.

If you are a owner of a dog diagnosed with CDA or of a diluted dog over 3 years with no symptoms, you can help science to develop a test, sending a biopsy to the University of Bern, Switzerland. Link below.

Research for a CDA test in dogs

Since the collection and sending of a biopsy is not free, participate by making a donation. We will pay the veterinarian directly for the biopsy and the shipment of the sample to the University of Bern.

Attention, the dog must have been diagnosed with CDA and all other possible causes must have been ruled out. See the conditions on the documents provided by the University of Bern by clicking on the above link.

Transmission or Cause: This is a genetic defect affecting the way pigment is distributed in the hairs of affected dogs. Dogs with unusual haircoat coloration such as blue or fawn are affected. Abnormal pigment (melanin) clumping in the hairshafts and subsequent changes in light refraction are responsible for the unusual coloration, and in severely affected animals, excessive pigment clumping causes breakage of the hairshafts and abnormal or stunted hairgrowth.

Affected Animals: Dogs with blue or fawn haircoats. Doberman pinschers are often most severely affected, but it can occur in any breed. Color dilution alopecia does not occur in all dogs with blue or fawn coats, and the frequency varies within affected breeds.

Clinical signs: Hair breakage and hairloss in color dilute areas usually begins in late puppyhood or young adulthood and may progress to total hairloss over several years. The underlying skin is normal, but the hair follicles often become occluded with skin cells and fragments of broken hairs, leading to secondary bacterial skin infection/folliculitis. There is usually no itching unless secondary skin infection occurs, and there are no systemic signs of illness.

Diagnosis: It is necessary to rule out other causes of hairloss such as hormonal disorders or skin infections. Consideration of dog breed and coloration, demonstration of hairloss only in color dilute areas, and visualization of pigment clumping and hairshaft abnormalities when the hair is viewed under the microscope (trichogram) are all supportive of color dilution alopecia. Skin biopsy shows abnormal hairshafts and distorted hair follicles full of keratin and melanin.

Treatment: There is no cure for color dilution alopecia. Treatment is aimed at controlling secondary skin infections and avoidance of harsh grooming products and abrasive brushes which can worsen hair breakage. Mild shampoos containing sulfur and salicylic acid may be helpful in reducing follicular plugging. In some dogs, supplementation with oral melatonin or retinoids can be helpful to stimulate partial hairgrowth.

Prognosis: Although the prognosis for normal hairgrowth is poor, this is only a cosmetic disorder which does not interfere with an affected pet’s quality of life.

Prevention: Since this is a genetic disorder, prevention involves avoidance of breeding affected or carrier dogs.