The Bone Finding Few People Know About: Metaphyseal Sclerosis and Distemper in Puppies
3 min read
Sometimes distemper leaves a mark in a place nobody looks: a puppy's long bones. A 2022 report published in the Journal of Veterinary Internal Medicine, authored by a team from the Universities of Tennessee and California-Davis, described for the first time in the literature what this finding looks like on an X-ray.
Four cases, one repeated pattern
The study documented four puppies, between 2.5 and 4 months old, seen at two different veterinary hospitals for respiratory, neurological, or gastrointestinal signs typical of distemper. In all four, the X-rays taken to check the lungs (not the bones) incidentally showed something unexpected: symmetrical bands of denser-than-normal bone, just below the growth plate, in the upper part of the humerus and other long bones.
The distemper diagnosis was confirmed in all four cases, by necropsy or PCR. In the case where tissue was studied, immunohistochemistry confirmed that the virus itself was present in the cells of the affected bone, which supports the idea that the bone lesion is not a coincidence but a direct effect of the infection.
Why it is not the same as the "bone disease" you may already know
If you have searched for bone problems in large-breed puppies, you probably came across metaphyseal osteopathy (formerly called hypertrophic osteodystrophy), a different and better-known condition, typical of fast-growing large breeds, which usually does cause pain and limping. The sclerosis from distemper described in this study is something else: it showed no signs of bone destruction or active inflammation on the X-ray, and in most cases it did not cause obvious pain. It is a silent finding that appears alongside the rest of the clinical picture, not a separate bone disease.
The real value of this finding
The authors themselves are honest about the scope of the study: it is a series of just 4 cases, not a large sample. What they propose is not that owners look for this sign on their own, but that veterinarians keep it in mind: if an unvaccinated puppy, or one with an incomplete schedule, arrives with respiratory or neurological signs and, incidentally, a chest X-ray shows these density bands in the bones included in the image, that adds evidence in favor of suspecting distemper, even before a PCR confirms the diagnosis.
It is also worth being honest about the outcome of these four cases: three of the four puppies were euthanized because of the severity of the disease, and the fourth was lost to follow-up. This is not meant to scare you, it is the usual reminder: distemper in young, unvaccinated puppies can be severe, and any warning sign merits a prompt veterinary visit, not waiting to see whether it improves on its own.
Source: Johnson KL, Craig LE, Wilson S, McLarty E, Hespel AM. "Radiographic evidence of metaphyseal sclerosis secondary to canine distemper virus: 4 cases in juvenile dogs." J Vet Intern Med. 2022;36(4):1303-1311. DOI: 10.1111/jvim.16453. Published under a CC BY 4.0 license.