Color Dilution Alopecia

written by R.M. (Bug ) Russell

The dilute colors (fawn and blue) do have coat and skin problems and there is a ton of available information on them. There is one major problem called CDA (see below) that is an alopecia (hair loss) directly related to the coat color. The granules of material which provide the color of the coat are located in the hair shaft…in blacks and most reds and fawns and blue who don’t have CDA the material is evenly spread through the hair shaft. In the CDA dogs it is found in clumps…the clumping evidently makes the hair shaft fragile at that point and prone to breaking. When this happens below the skin line in the follicle itself it can “kill” the follicle so no new hair is produced. That’s the abbreviated version of the major problem.

Dobes in general are rather prone to staph infections…their immune systems are rather slow to mature…in a black and most reds this may be a problem in puppies and may result in temporary hair loss but in blues and fawns it can be a disaster coupled with CDA.

The rarity of seeing these colors in the ring is due in part to the difficulties in keeping them in good coat. Barbara Russell, who sort of specialized in dilutes, specifically blues, had blue Dobermans that generally had good coats she states that was that even with good blue coats she had problems and keeping blues in show condition as far as coats went was a full time job.

There are definitely some judges who aren’t fond of the dilutes and a few that wouldn’t put one up under any circumstances. In the ’60s it was harder for reds to win than blacks…I think that is about where the dilute situation in the ring is now…it’s harder to win with a dilute but not impossible if the dog is a good specimen of a Doberman.

The dilute colors are produced much less often than reds or blacks. Genetic statistics say that fawns comprise about 6% of all Dobermans born and blues somewhere between 12 & 15%…all the rest are black or red but I can’t remember what the stats are for them).

Thin coats on the dilute colors are not usually due to allergies and the dilutes don’t seem to have any more skin problems, with the exception of CDA, than blacks or reds do.

If the coat looks good from 2 or 3 feet away it probably is good but most puppies in dilute colors have decent enough coats the thinning due to CDA takes place over time so a dog who had a decent coat at 10 months might well be bald at 5 years.

The dermatology texts say that over 90% of all blues will at least have thinning hair and many will thin to the point of being bald over most of the body. Fawns seem to have a better chance of retaining their coats with about 75% of the fawns having extensive hair loss due to CDA.

The literature also says that the darker the coat color in a dilute dog (steel blue in blues and carmel in fawns) the better the chance they will retain most to all of their coats. This seems to be the case in the blues and fawns I’ve known over the years.

There are a few dilute dogs whose coats are fine, who don’t lose hair, don’t have CDA and never go bald but they are few and far between.


COLOR DILUTION ALOPECIA

By Teri Dickinson, DVM

Alopecia (hair loss) related to dilute coat color is a recognized condition in dogs. The currently accepted medical terminology for this condition is Color Dilution Alopecia (CDA). The condition may affect any dilutely pigmented dog, regardless of coat color. This condition was previously known as Blue Balding Syndrome, Blue Doberman Syndrome, Color Mutant Alopecia, Congenital Alopecia, etc. The term Color Mutant Alopecia arose because dilutes were at one time mutations from the deep pigment occurring in wild canines. Dilutes are now a regularly occurring form of pigmentation in many breeds and have been for hundreds of years. The term mutation is therefore not applicable to dilute individuals. References to Doberman Pinschers or blue hair coats arose because the condition is common in blue individuals of this breed, but it is not limited to either blue dogs or Dobermans. The term congenital means present at birth, but CDA affected dogs are born with normal hair coats.

The dilute (also known as Maltese) gene also appears in both mice and cats, and interestingly enough, is not associated with any abnormal coat conditions in those species.(1) Color Dilution Alopecia (CDA) has been recognized in dilute individuals of many breeds of dogs including Chow Chows, Dachshunds, Doberman Pinschers, Great Danes, Irish Setters, Italian Greyhounds, Standard Poodles, Salukis, Whippets, and Yorkshire Terriers.((2),(3),(4),(5)) Dilute individuals carry a recessive genotype of dd and are characterized by blue, bluish-grey, lavender or flesh-colored noses, lips and eye rims. The coat colors may include blue, fawn, blue-fawn, bronze, taupe or some variation of these. These dogs are usually easily distinguished from their deeply (non-dilute) pigmented counterparts. Deeply pigmented individuals carry a dominant genotype of Dd or DD and have black or liver noses, lips and eye rims. Coat colors may include black, red, red-fawn, liver or variations thereof.

CDA is characterized by loss of hair from dilutely pigmented areas. Coats are normal at birth, and onset of hair loss usually begins between six months and three years of age. Hair loss usually begins along the dorsal midline (middle of the back) and often spares the head, tail and limbs. The pattern seems to vary from breed to breed. It has been suggested(6) that darker colored (steel blue) individuals are less likely to be affected, may be less severely affected or may start to lose hair later in life than lighter colored dogs. This suggests that the severity of the disease may be related to the amount of dilution present. Deeply pigmented or white areas of coat are unaffected. In blue dogs with tan points (Yorkies and Dobermans) the tan areas retain a normal appearance. In piebald (white spotted) individuals, the white areas are unaffected by the hair loss. The hair loss may be total or partial and any remaining hairs are usually sparse, rough and easily broken or removed. The skin in the affected areas is usually scaly and may occasionally develop bacterial infections. Pruritus (itching) is usually absent, unless a bacterial infection has set in.

Diagnosis of CDA requires first ruling out other causes of hair loss. Diagnostic tests should include fungal cultures, skin scrapings to check for parasitic mites, etc. CDA often closely resembles endocrine (hormone related) hair loss and the dog should be carefully examined for any other abnormalities, and tested for normal thyroid function. Presence of dilute pigment and a characteristic course of disease also aid in making the diagnosis. Microscopic examination of hairs and\or skin biopsies can be used to confirm the diagnosis.

There is no cure for CDA. Treatment is limited to controlling the scaliness and any associated pruritus with various shampoos or topical treatments.

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
th
ese 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.(7) 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.6 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.

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