Long MT, Foreman JH, Wallig MA, et al.
A five year old American Saddlebred gelding was admitted to the University of Illinois Veterinary Medical Teaching Hospital with a history of multiple leg lameness, depression and intermittent fever for a duration of six months. Physical examination revealed the horse to be underweight, depressed and afebrile. No abnormalities were detected during auscultation of the heart and lungs. All limbs possessed multiple hard swellings of the distal long bones and digits. The horse walked with a stiff gait and was reluctant to trot. Nuclear scintigraphy of the distal limbs revealed multiple areas of focally increased uptake in all limbs. Radiographs of several sites on the distal limbs showed evidence of periosteal new bone production corresponding to the areas of abnormal uptake. The horse was euthanized and at necropsy chronic, multifocal, fibrous pericarditis and epicarditis were observed grossly. The left atrial myocardium contained areas of osseous metaplasia. Histological evaluation of the distal long bones revealed proliferative periosteal new bone formation consistent with a diagnosis of hypertrophic osteopathy.