Generalized sarcoidosis and hypertrophic osteopathy in a Standardbred with poor-performance.

Background and objective: Equine sarcoidosis (ES) is a rare but emergent disease of unknown etiology. Body of literature on ES remains limited, especially on the generalized forms associated with hypertrophic osteopathy (HO). This case report describes clinical and imaging findings in a racehorse with exercise intolerance affected by generalized ES and subsequent HO.
Material and methods: A 6-year-old Standardbred gelding was presented for sudden exercise intolerance, weight loss, pyrexia, skin lesions, facial and peripheral multifocal swelling.
Results: The horse underwent diagnostic imaging of head and limbs. Radiography and ultrasonography of the head revealed periostitis and regional soft tissue swelling of the maxillary bone. Bilateral marked periostitis with palisade-like appearance involving diaphyseal or metaphyseal region was also identified on distal radius and metatarsal bones, suggestive of HO. Computed tomography excluded dental or sinus abnormalities. Due to the appearance (scaling, crusting and exfoliating) of skin lesions on the croup and lower hindlimbs during hospitalization, biopsies were performed revealing granulomatous dermatitis. This finding was consistent with ES, thus explaining HO. Rapidly declining conditions of the horse led to the decision of euthanasia. Post-mortem examination revealed splenomegaly and several pulmonary nodules. Histopathology on different organs confirmed severe granulomatous lesions; PCR on a pool of tissues identified EHV-5.
Discussion and conclusions: ES, even in its generalized form, is an emergent disease that should be considered in case of unspecific clinical signs combining exercise intolerance, weight loss, facial/distal limb bone deformities and skin lesions; EHV-5 could play a role in the development of the disease.