Generalized sarcoidosis associated with hypertrophic osteopathy in a Standardbred racehorse

A Standardbred racehorse was presented for exercise intolerance, weight loss, pyrexia and facial deformity. Radiography and ultrasonography revealed periostitis and regional soft tissue swelling of maxillary bones. Computed tomography excluded any dental or sinus origin of these abnormalities. Further deformities on distal limbs and skin lesions appeared during hospitalization. Radiography identified bilateral periostitis and soft tissue swelling in the distal radius and metatarsal bones, as observed in the head, suggestive of hypertrophic osteopathy (HO). Skin biopsies revealed granulomatous dermatitis, indicating equine sarcoidosis (ES). The horse was euthanized due to rapid deterioration of his condition. Post-mortem examination and histopathology revealed splenomegaly, several pulmonary nodules and disseminated granulomatous lesions. These findings confirmed the diagnosis of generalized ES, or equine idiopathic systemic granulomatous disease. The concurrent with HO was probably associated with the intrathoracic pathology. Polymerase chain reaction (PCR) on pooled tissues identified equine herpesvirus 5 (EHV-5) DNA.