Chondrodystrophy and CDDY in Bichon Frises: What a DNA Panel Is Actually Telling You

The variant works by inserting an extra copy of a growth factor gene into the genome. That extra copy is active during development, and it does two distinct things.

The first is the visible one. It shortens and curves the long bones of the limbs, which is why the affected breeds all look the way they do. Legs finish growing earlier and shorter while the spine and skull develop normally, giving that characteristic long-low silhouette.

The second effect is invisible and more consequential. The soft gel-like centre of each spinal disc undergoes premature change, mineralising much earlier in life than it should. A disc with a hardened centre behaves like a stone rather than a cushion, and under load it can burst upward into the spinal canal and press on the cord.

That is why breeds carrying this variant have such a high rate of dramatic, sudden spinal injuries in young and middle-aged dogs, while other breeds develop spinal problems slowly and much later.

The Bichon Frise does not have the long-low body plan. It stands 9 to 12 inches with legs in normal proportion, and disc disease does not appear on its documented health list, which covers skin allergies, patellar luxation, bladder stones, cataracts and dental disease.

Consumer panels test the same large set of variants for every dog regardless of breed. That design produces a long report, most of which is irrelevant to your particular animal. These principles keep the exercise useful.

If you think your Bichon has chondrodystrophy, the plan is three steps: write down what you have seen and when it started, book a veterinary appointment rather than waiting for the next flare, and take video of the behaviour or symptom before you go — the thing you are worried about rarely happens in the consulting room. Screening in the parents covers skin allergies, patellar luxation, bladder stones.

What the vet visit should produce is a diagnosis and a written plan, not just reassurance: what is being ruled out, what the monitoring interval is, and which signs mean you come back sooner. Ask what the treatment costs across a year rather than per visit, because that is the number that decides whether you are managing this condition or reacting to it.

Between appointments, keep a short log — dates, what you saw, what changed. It is the single most useful thing an owner brings to a follow-up, and for chondrodystrophy it is often what separates a clear pattern from a guess.