Widespread Osteolysis as an Uncommon Manifestation of Equine Sarcoidosis

Equine sarcoidosis is an uncommon disease characterized by granulomatous inflammation presenting in a spectrum of body system involvement and severity. Musculoskeletal manifestations are sporadically reported but without correlation between imaging and pathologic findings. In a mature Quarter Horse mare eventually diagnosed with a progressive form of sarcoidosis, phalangeal osteolysis discovered on radiography prompted further evaluation, revealing diffuse, discrete osteolysis throughout the axial skeleton. Due to disease progression, humane euthanasia was elected, and computed tomography and histopathology were performed. Regions of osteolysis correlated to sites of granulomatous inflammation, providing a novel and possibly underestimated feature of equine sarcoidosis.