Osteogenesis Imperfecta in Two Finnish Lapphund Puppies.

Two 8-week-old Finnish Lapphund dogs presented with pain on manipulation, abnormal long bone conformation, retrognathism, and stunted growth compared to their litter mates. Multiple long bone fractures were evident on radiographs. Clinical pathology showed an atypically normal serum alkaline phosphatase activity for dogs this age. Due to poor quality of life, the dogs were humanely euthanized and subjected to a complete necropsy. On necropsy, all bones were soft and easily broken. Histologic examination revealed that the secondary spongiosa was diminished with abnormal bony trabeculae embedded in abundant loose vascular stroma. No Haversian canals were observed and the cortices contained abundant woven bone separated by fibrovascular tissue consistent with the diagnosis of osteogenesis imperfecta (OI). Inbreeding of the sire and female offspring led to a suspicion of recessive inheritance and the particular genetic collagen disorder remains to be identified in this breed.