Mucopolysaccharidosis is a rare, multisystemic, progressive disease that has no cure. The objectives ofthis study were to describe the clinical, radiographic and anatomical and pathological findings of a case ofmucopolysaccharidosis in a dog. It reports the case of a male dog of the Fox Paulistinha (Brazilian Terrier)breed, four months of age, derived from cross-breeding with high degree of endogamy. The animal exhibitedapathy, walking difficulty, enlarged joints, opacity of the cornea, and inspiratory dyspnea. On X-ray, bilateralchanges were observed in the physeal lines of vertebrae, radius and ulna, as well as enlarged liver andtracheal hypoplasia. Due to the accentuated respiratory difficulty, the owner decided to euthanize thedog. Necropsy showed the absence of the larynx, cricoid and arytenoid cartilages, a distended heart, andmoderately enlarged liver and spleen. Bone changes included increased cranial perimeter, malformation ofthe sternum, and twisted ribs. Histopathology revealed dysplasia in the cartilage of the epiglottis, tracheaand joints, in which the chondrocytes presented with vacuolated cytoplasm; there was also accentuatedthickening of the aortic intima. The history of cross-breeding with a high degree of endogamy, associatedwith the clinical, radiographic and anatomical and pathological findings, converged to a diagnosis ofmucopolysaccharidosis.