Osteoporosis in an Asian small-clawed otter (Aonyx cinereus Illiger, 1815).

Osteoporosis is a skeletal disease that occurs in many mammals. Our report describes osteoporosis in an Asian small-clawed otter (Aonyx cinereus). Gross, histological, and radiographic observations showed that all of the bones had numerous pockmarks on their surfaces. Histologically, the pockmarks were filled with fibrous tissue without inflammation. However, the spongy bone was normal according to the histological and radiographic results. Overall, the results showed that this was a case of osteoporosis that mainly involved external rather than internal surfaces.