It is a condition resulting in hair loss and skin irritation that only affects the dilutes of the Doberman breed, so blues (which are a dilute of black) and fawns (which are a dilute of red). I think Nola from Thursday's post is a blue, if that gives you some color perspective (I'm not saying she has CDA, just pointing out her color):
Now, CDA is not something guaranteed to affect all dilute Dobermans. Some fawns and blues live their whole lives without ever having their coat thin or their skin be affected. Some are pretty much bald once they're five. I'm not really sure what decides it, and I'm not sure science is either. Dilute Dobermans make up less than 10% of the breed, but up to 60% of them have CDA. Isn't genetics fun? The cause is, in fact, unknown. It is thought to perhaps be caused by an autosomal recessive gene transmission (which is, to me, a peculiar similarity to Dilated Cardio Myopathy, which also may not present in a young dog, but make itself very apparent as the dog gets older).
This is Hercules. He's with Doberman Rescue Unlimited, and is a Fawn Doberman. His blurb says his is deaf, and has been fostered by DRU's trainer, so his obedience is very good. They make no mention of thinning coat, and from his picture, it looks all right. Who's to say?
It is important to note that Color Dilution Alopecia is a mostly cosmetic disorder; the dog is not in constant discomfort. If the skin is itchy and otherwise affected, than it is possible a secondary infection is present, and needs to be treated. Gentle shampoos may also help with the existing fur, to help prevent breakage. Thin coats can be caused by thyroid issues, but not all dogs with thin coats have thyroid problems. As the writer of Storm's Regimen (a course of management for CDA he or she as a blue Doberman owner has devised, involving diet and supplements) says, "a blue Doberman with a thin coat should be thyroid tested" and really, any Doberman suddenly presenting with a thin coat should. But, thyroid is a post for another day.