Polyostotic cortical hyperostosis in an 8-week-old cat with a 3-year follow-up.

A 2 month-old female cat, mixed breed, was referred for difficulty moving and severe enlargement of the mandible and limbs. Polyostotic cortical hyperostosis was diagnosed based on diagnostic imaging and histopathological changes of the mandible and limbs. Marked cortical bone thickening was detected on radiographs and CT scan images. The diaphyses of both radii and ulnae, together with the mandibular rami and bodies, were most severely affected. The many similarities shared with the human condition, Caffey's disease, are discussed.

A case of congenital hyperostosis in a newborn piglet.

One female newborn piglet showed prominent thickening of both forelimbs and died soon after birth. Histopathologically, thin and woven trabeculae of bone was extending out from the edge of cortical bone in the affected forelimbs, and diagnosed as congenital hyperostosis. The extent of radially proliferated trabeculae was most prominent in radioulna. Many round- to spindle-shaped cells were observed in periosteum, which were considered to be osteoblasts. Around the periosteum, the mesenchymal proliferation was extensive with abundant mucus, and cartilaginous metaplastic changes were observed mainly around the radioulna and humerus. Dilatation of vessels with fibrin deposition in vessel walls was often observed, which were considered to reflect the localized circulatory disturbance.