Clinical signs and diagnosis of osteogenesis imperfecta in three dogs.

When a young dog is evaluated for multiple fractures with minimal to no accompanying trauma, the primary differential diagnoses are metabolic disease, physical abuse, and osteogenesis imperfecta (OI). Of these, secondary hyperparathyroidism is most common, but if serum concentrations of ionized calcium, phosphorus, vitamin D, and parathormone are within reference ranges, OI must be considered. Osteogenesis imperfecta is a heritable disease characterized by brittle bones. Results of studies using cultured skin fibroblasts indicate that most cases of OI in human beings are caused by a mutation in a type-I collagen gene. Osteogenesis imperfecta was recently identified in 3 dogs. Radiographic findings included multiple fractures in various stages of healing and generalized osteopenia. Cultured fibroblasts from skin biopsy specimens were used to diagnose OI. Structural abnormalities were found in type-I collagen from each dog. This cell culture assay can be used to evaluate dogs with brittle bones.