Pomeranians: Demystification of Colour Dilution Alopecia (CDA)
I wrote this article following some misinformation circulating on the internet on Colour Dilution Alopecia (CDA), with the aim to provide some information, which I hope will help to clarify certain points.
The purpose is not to create controversies, but instead, constructive debates supported by scientific information and/or real-life experiences.
Having several Poms, of which a few with diluted coats, I am of course interested in this fascinating subject of genetics and more specifically that of CDA. I got them all genetically tested at all possible Loci for the German Spitz breed.
I have read many erroneous information, with very biased and too categorical positions about CDA. In many instances, Poms with diluted coats are presented as carrying a serious flaw and CDA…
To me, these alarming beliefs are not sufficiently scientifically founded.
1
A lot of scientific researches have been and continue to be done on CDA, especially in the United States, and scientific reports have been published on the findings. All the reports I have read so far agree that the origins of CDA are still largely unknown. However, hypotheses have been made that it is a genetic recessive inherited disease, possibly related to the D Dilution Locus.
There is also a general consensus that many other factors, unrelated to the D Locus, influence the onset of CDA. Otherwise, it would have meant that all dogs with diluted coats, of all breeds, would have CDA, which is far from being the case.
The very frequently cited breeds, subject to CDA, are: Doberman pinschers, Miniature pinschers, Labrador retrievers, Schnauzers, Chow chows, Dachshunds, Great danes, Irish setters, Italian greyhounds, Standard poodles, Salukis, Whippets, Yorkshire terriers , Bernese mountain dogs, Chihuahuas, Shetland sheep dogs, Boston terriers, Newfoundlands, Schipperkes.
Blue Doberman Pinschers tend to develop the most severe symptoms. This is why CDA is very often associated with that breed.
Note that the German Spitz breed is not mentioned in the list. Of course, it does not mean that the breed is not subject to it. It may just mean that there have not been enough proven cases to be cited, or that the breed may not be as well-known as the other ones.
2
I have seen a couple of articles mentioning dogs “carrying the d/d1 genotype”… This statement is clearly wrong, if we have some scientific knowledge here.
The D dilution Locus has 4 known alleles:
➖ D (undiluted, dominant)
➖ d1 (dilution variant 1, common, recessive)
➖ d2 (dilution variant 2, recessive)
➖ d3 (dilution variant 3, rare, recessive).
Each parent gives an allele to their offspring. The combination of the 2 alleles received is called a genotype.
✔️ A dog carrying the D/D genotype will not have a diluted coat.
✔️ A dog carrying D/d1 or D/d2 or D/d3 will not have a diluted coat either but carries the dilution allele and can of course pass it on to his offspring.
✔️ A dog carrying d1/d1, or d1/d2, or d1/d3, or d2/d2, or d2/d3, or d3/d3 will have a diluted coat. These genotypes dilute the black coat into blue, the brown coat into lavender (also called lilac or beaver or isabella) and the cream coat into very pale cream.
In the past, before the discovery of the d1, d2 and d3 variants, we used to talk about the d allele. The nomenclature changed when the d2 and d3 variants were discovered. There is therefore no difference between d and d1.
So, differentiating between d and d1 and talking about d/d1 is completely incorrect. It is as if we classified the d allele as a separate variant, in addition to the 3 known ones.
FYI regarding the German Spitz breed: only the d1 variant has been found so far.
3
I often read that we should not breed 2 Poms of diluted coats together, so to reduce the risk of CDA. It seems logical at first, but not scientifically founded because a dog carrying the dilution genotype does not necessarily have or carry CDA. We would have known it otherwise.
The risk level of CDA is the same as that of Alopecia X to which dogs of all coats can be prone.
Just as with Alopecia X, since there is currently no way to screen dogs that will declare, or transmit the disease (this is only detectable once declared), it is better to avoid reproducing:
🔻 affected dogs,
🔻 dogs that have already produced affected dogs,
🔻 brothers and sisters of affected dogs,
🔻 dogs from an affected parent.
These measures will limit the spread of the disease within the breed, until a genetic test becomes available one day.
4
I have also read that CDA causes “serious skin lesions”. This statement is rather scaring me…
According to scientific researches but also according to dog owners, a dog with CDA (as well as Alopecia X), very often, does not have any other health problems, apart from the purely cosmetic consequences.
The aesthetics are indeed very strongly affected because the coat becomes sparse. It usually begins to be thin and takes on a dull or dry appearance. The fur may fall out in patches or clumps, also creating an uneven appearance.
Yes, for some dogs, the hair follicles develop bacterial infections around them, which results in papules or small bumps on the skin as well as inflammation, itching and even peeling.
On these dogs, they will be seen to have endocrine disorders, or skin infections, or allergic skin diseases, or immune system dysfunction and other conditions that could be a factor in the presence or the severity of their alopecic conditions..
5
I have heard people say that “there is a good reason as to why diluted colours are not accepted by the FCI”. The FCI is the Fédération Cynologique Internationale, a canine Club to which many countries belong.
My answer to this is that while there is always a story behind the fact that a colour is not part of the standards of the FCI, diluted colours are an integral part of the standards of other large Clubs, like the AKC in the US, the CKC in Canada or the KC in the UK.
Conclusion
I do not wish to deny the facts and the observations, nor to prevent creating awareness on CDA, but I think that we must do it in an objective and correct way, and with sufficient input of information and without being alarming.
As said above, the risk level of CDA is not higher than that of Alopecia X, and other congenital diseases, and even less than other known problems of the German Spitz breed, like the problems of patella or trachea, which affect Poms of all colours.
With the appropriate information in hand, we can create better awareness and better advise accordingly.
