Dear Doctor: What is Brittle Bone Disease?
Q. A friend recently adopted a young kitten from a local humane society, and soon after, the kitten was diagnosed with brittle bone disease. Neither of us had ever heard of this, and now it makes me worry about adopting a new kitten.
Elaine E. Caldwell
A. Dear Elaine: True brittle bone disease can only be diagnosed after excluding a nutritional deficiency. The most common cause of thin, brittle bones in kittens is the feeding of an inappropriate diet (lack of calcium, excessive phosphorus and/or lack of vitamin D). Thin bones secondary to nutritional deficiencies are completely reversible once a proper diet is being fed and I would have no hesitation of recommending adoption.
True brittle bone disease (technically called osteogenesis imperfecta) is an inherited disorder leading to bone fragility. This disorder is caused by a mutation in gene coding for a structural component of bone. Osteogenesis imperfecta is a well-characterized disorder in humans, but extremely rare in cats. All types are characterized by fragile bones that shatter spontaneously or with minimal trauma. The diagnosis in cats can be made only when radiographs reveal thin bones and blood levels of calcium, phosphorus, parathyroid hormone and vitamin D are normal.
Because brittle bone disease is rare, I am first wondering about this cat’s food source. If the dietary history is unknown, nutritional imbalances are the most likely cause of thin bones. If, however, it can be confirmed that a high-quality diet has been fed since weaning, then I have serious concerns about adoption of this pet.
Cats with brittle bone disease have recurring fractures from jumping on and off furniture, and despite multiple surgeries, fail to completely heal. There is a new group of drugs called biphosphonates, which might offer a glimmer of hope. But if this kitten truly has brittle bone disease, the long-term prognosis is extremely guarded.
Michael Stone, DVM, ACVIM
Clinical Assistant Professor
Cummings School of Veterinary
Medicine at Tufts University