HVDRR is characterized by low calcium levels leading to secondary hyperparathyroidism. Vitamin D enhances bone mineralization and calcium is essential for hardness and strength of the bones. Vitamin D-resistance causes dysfunctional bone mineralization leading to the softening of bones and skeletal deformities. The clinical signs of HVDRR include joint pain, lameness, limb deformities, spontaneous fractures, jaw deformities, and neurological signs. HVDRR can also cause alopecia (hairlessness).

As soon as a diagnosis of HVDRR has been confirmed affected dogs should be considered for treatment. Affected dogs can be treated by oral administration of active vitamin D and calcium supplements. The bone deformities are, however, irreversible.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the HVDRR mutation can be safely bred with a clear dog with no copies of the HVDRR mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the HVDRR mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the HVDRR mutation could develop due to a different genetic or clinical cause.