Background: Osteogenesis imperfecta is a severe genetic disease rarely described in veterinary medicine. This multisystemic condition is caused by a defect in the production and metabolization of collagen, which implicates in bone fragility. This disease has been described in cattle, sheep, domestic felines, mouse and dogs of different breeds, including collie, golden retriever, beagle, dachshund and chow chow. Animals affected by this condition present multiple fractures without previous occurrence of trauma. Therefore, this report aimed to describe a case of osteogenesis imperfecta type III in a miniature pinscher dog.Case: A 1-year-old male miniature pinscher dog, was admitted for clinical evaluation in Fortaleza, Brazil, with a history of spontaneous fractures without known causes. This animal was maintained indoors, fed on dry feed and presented recurrent events of claudication and pain. In the physical examination, the individual walked solely with the forelimbs, avoiding the use of the hind limbs and presented pain behavior. Bulging of the skull was observed laterally, which promoted a triangular appearance of head and face. Fontanelles were soft, and the eyes presented blueish sclera and corneal opacity. Teeth were small, translucid, fragile and deformed. Radiography images revealed bulging of the calvaria and persistent fontanelles with open cranial sutures. In addition, cranial convolutions were less clear, which was compatible with hydrocephalus. Dental roots were narrow, short and presented partial pulp obliteration. The radiographic contrast of the dentin was low with a reduction of periapical radiolucency. Bone radiopacity was low in the bones of the abdomen and pelvis, in addition to femur. Metaphysis of the right tibia was enlarged and angular. Multiple fractures were identified in the pelvis with the formation of opaque bony calluses and bone marrow sclerosis. Physiological parameters and blood test results were unaltered. After the diagnosis of osteogenesis imperfecta type III, treatment was performed with meloxicam 0.1 mg/kg, SID, VO) and tramadol (2 mg/kg, TID, VO) until pain was controlled. When the patient was stable, the treatment was halted until the next event of fractures followed by pain.Discussion: Type I collagen is considered the most abundant protein in connective tissue, accounting for 95% of the various types of collagen found in bone tissue. In osteogenesis imperfecta, there is a shortage in coding of type I collagen, which prevents this protein from exerting its structural functions properly. In addition, it is subjected to intra and extracellular degradation, affecting cell migration and differentiation and, concomitantly, cell-matrix interaction. Hence, these changes are considered the main pathophysiological factors of osteogenesis imperfecta. There is a wide range of phenotypic presentations in individuals with osteogenesis imperfecta. However, there is a pattern of fractures and features that aid clinically and radiologically in the characterization of the disease and form the basis for case identification and diagnosis. In this case, the diagnosis was concluded primarily considering significant clinical signs, such as: repetitive fractures, triangular face, bulging of the skull, bluish sclera and corneal opacity. Radiographic examinations were used to confirm the diagnosis and to aid in treating the fractures. Although the genetic test provides a better understanding of the disease, it was not performed in this case, as it is routinely unavailable in many treatment centers. In conclusion, we described a case of osteogenesis imperfecta in a miniature pinscher dog.
Osteogenesis imperfecta type III: mutations in the type I collagen structural genes, COL1A1 and COL1A2, are not necessarily responsible.