Doctors discovered that an 11-month-old kitten had a rare genetic problem that prevented her body from using vitamin D properly, even though she was eating a healthy diet. The kitten’s body couldn’t absorb calcium because of a tiny change in her genes that affected how vitamin D receptors work. This caused her bones to become weak and her jaw joints to develop abnormally. Scientists found the exact genetic mutation responsible and confirmed it in laboratory tests, helping them diagnose a condition called vitamin D-dependent rickets type 2. This discovery could help veterinarians recognize similar problems in other cats.

The Quick Take

  • What they studied: Why a kitten developed weak bones and couldn’t close her mouth properly, despite eating nutritionally complete food
  • Who participated: One 11-month-old female kitten with lameness and jaw problems
  • Key finding: A single genetic mutation (p.Pro170Leu) in the vitamin D receptor gene prevented the kitten’s body from responding to vitamin D, causing calcium levels to drop dangerously low and bones to weaken
  • What it means for you: This case helps veterinarians recognize a rare genetic condition in cats. If your kitten has unexplained weakness, limping, or jaw problems despite good nutrition, genetic testing for vitamin D receptor problems may be worth discussing with your vet. This is extremely rare in pets, but now doctors know what to look for.

The Research Details

This is a case report, which means doctors documented the medical history and findings from one individual patient—in this case, a young kitten. The kitten came to the veterinary clinic showing signs of lameness (difficulty walking) and an inability to close her mouth. Doctors performed blood tests, X-rays, and genetic testing to figure out what was wrong.

The research team took cells from the kitten’s kidneys and grew them in a laboratory. They then inserted either normal or mutated versions of the vitamin D receptor gene into these cells to see how they would respond to vitamin D. This allowed them to test whether the genetic mutation they found was actually causing the problem.

The doctors used computer analysis to predict whether the genetic change would damage the vitamin D receptor protein. They combined all this information—the kitten’s symptoms, blood work, imaging, genetic testing, and laboratory experiments—to reach their diagnosis.

Case reports are important because they describe unusual or rare conditions that doctors might not otherwise recognize. By documenting this kitten’s case in detail, veterinarians around the world can now learn about this rare genetic disease and potentially diagnose it in other cats. The laboratory experiments proved that the genetic mutation actually caused the problem, making this more than just a description—it’s evidence of how a specific genetic change leads to disease.

This is a single case report, which means it describes one patient rather than comparing many patients. While case reports are valuable for identifying rare diseases, they cannot prove that something works for everyone. The strength of this report comes from the genetic testing and laboratory confirmation that the mutation actually causes the problem. The findings are specific to this one kitten, but the genetic discovery could apply to other cats with similar mutations.

What the Results Show

The kitten had dangerously low calcium levels in her blood (hypocalcemia) and very high parathyroid hormone levels, which is the body’s attempt to raise calcium. Interestingly, her vitamin D levels were actually elevated, not low—her body was making plenty of vitamin D, but couldn’t use it properly.

X-ray images showed that the kitten’s bones were weak and thin throughout her entire body (generalized osteopenia). Her jaw joints were also abnormally developed (dysplasia of temporomandibular joints), which explained why she couldn’t close her mouth.

Genetic testing found three different changes in the kitten’s vitamin D receptor gene. One specific change—called p.Pro170Leu—was identified as the likely culprit. When scientists tested this mutation in laboratory cells, the mutated vitamin D receptor didn’t respond properly to vitamin D, confirming that this genetic change was breaking the system.

Based on all this evidence, doctors diagnosed the kitten with vitamin D-dependent rickets type 2, a rare genetic condition where the body can’t use vitamin D even when it’s present.

The kitten’s inability to close her mouth was caused by abnormal development of the jaw joints, a direct result of the calcium deficiency and weak bone development. The weakness in her legs (lameness) was also explained by the overall bone weakness from poor calcium absorption. These secondary findings show how a single genetic problem can affect multiple parts of the body.

Vitamin D-dependent rickets type 2 is extremely rare in cats. This case report adds to the very limited scientific literature on genetic vitamin D receptor problems in animals. Similar conditions have been documented in humans and a few other animal species, but each case helps expand our understanding of how this disease works across different species. This kitten’s case is particularly valuable because it includes genetic confirmation of the exact mutation causing the problem.

This is a single case report, so the findings apply only to this one kitten. We cannot know how common this genetic mutation is in the cat population or whether other cats with the same mutation would show identical symptoms. The study doesn’t compare this kitten to other cats with similar symptoms, so we can’t be certain this genetic change is the only possible cause of these symptoms. Additionally, the case report doesn’t describe the kitten’s long-term outcome or response to treatment, so we don’t know if the diagnosis led to successful management of her condition.

The Bottom Line

This case report does not provide treatment recommendations because it focuses on diagnosis rather than treatment. However, if a cat is diagnosed with this condition, veterinarians would likely consider vitamin D supplementation, calcium supplementation, and dietary adjustments. The confidence level for these recommendations would be low because this is such a rare condition with limited treatment data. Any cat suspected of having this condition should work closely with a veterinary specialist.

Veterinarians should care about this case, especially those who see cats with unexplained weakness, bone problems, or jaw abnormalities. Pet owners of kittens showing these symptoms should discuss genetic testing with their vet. This condition is so rare that most cat owners will never encounter it, but knowing it exists helps ensure proper diagnosis if it does occur. Breeders of cats with a family history of bone or metabolic problems might also want to be aware of this genetic condition.

Since this is a case report rather than a treatment study, there is no timeline for improvement. However, if a cat were diagnosed with this condition, the timeline for seeing improvement would depend on the treatment approach chosen and how quickly the underlying genetic problem could be managed. This would need to be discussed with a veterinary specialist on a case-by-case basis.

Want to Apply This Research?

  • If a cat has been diagnosed with vitamin D-dependent rickets, track weekly blood calcium and phosphorus levels, along with any changes in mobility or jaw function. Record any supplements given and their timing relative to meals.
  • Work with your veterinarian to establish a consistent supplementation schedule for calcium and vitamin D (if recommended). Monitor your cat’s ability to eat and move, noting any improvements or setbacks. Keep detailed records of all medications and supplements to share with your vet.
  • Schedule regular veterinary check-ups (likely monthly initially) to retest blood calcium levels and assess bone health. Take photos or videos of your cat’s mobility and eating ability to track changes over time. Maintain a log of any dietary changes or new symptoms that develop.

This article describes a rare case of genetic disease in one kitten and is provided for educational purposes only. It is not a substitute for professional veterinary medical advice, diagnosis, or treatment. If your cat shows signs of lameness, weakness, jaw problems, or other concerning symptoms, please consult with a licensed veterinarian immediately. Do not attempt to diagnose or treat your cat based on this information. Genetic testing and specialized veterinary care may be necessary for proper diagnosis of rare conditions. Always work with your veterinarian before starting any supplements or dietary changes for your pet.