Hereditary 1,25-Dihydroxyvitamin D-Resistant Rickets in a Pomeranian Dog Caused by a Novel Mutation in the Vitamin D Receptor Gene

The study described a case of hereditary vitamin D-resistant rickets (HVDRR) in a Pomeranian dog, caused by a novel mutation in the vitamin D receptor gene. The affected dog exhibited symptoms such as hypocalcemia, secondary hyperparathyroidism, bone hypomineralization, rickets, and alopecia. Despite treatment with oral calcium and 1,25-dihydroxyvitamin D3, the dog showed persistent hypocalcemia and high circulating levels of 1,25(OH)2D3, indicating resistance to the hormone. The condition led to severe complications, including a spinal fracture and neurological issues, ultimately resulting in euthanasia. This case highlighted the challenges of managing HVDRR due to the ineffectiveness of standard treatments in overcoming the receptor defect. Interestingly, the dog's alopecia resolved by the time of death, unlike in humans where it persists, suggesting a potential compensatory mechanism in dogs.