A narrative literature review of equine sarcoidosis

Equine sarcoidosis (ES) is a rare disease characterised by granulomatous inflammation of one or multiple organs. The skin is most frequently affected in horses and the clinical presentation can range from scaling and crusting lesions to nodular or tumour-like masses. ES has been divided into three subtypes depending on the distribution of lesions in the body: the localised, partially generalised and generalised form. Overall, no breed or sex predilections have been consistently observed so far. Most affected horses are older than 3 years although the disease may occur at any age. While aetiology and pathogenesis of ES have not yet been fully determined, a chronic exaggerated immune response to one specific or multiple antigens is frequently hypothesised. Diagnosis is based upon history, clinical presentation, histopathology and exclusion of likely differential diagnoses. The treatment of choice in ES is initial anti-inflammatory to immunosuppressive doses of corticosteroids with subsequent tapering doses. Reported treatment success seems to be highly variable and prospective studies on the efficacy of corticosteroids or other agents are currently lacking in ES. Prognosis for survival is good for the localised form and poor for the other forms of ES. Complete remission of lesions in the localised form following treatment is less frequent and response to treatment is typically characterised by a slowdown or cessation of disease progression. There are scarce reports of spontaneous remission of this disease.