Cutaneous Markers of Disorders Affecting Adult Horses

In adult horses, skin lesions and changes in the haircoat may serve as primary owner complaints for underlying systemic diseases. Cutaneous markers of systemic disorders of adult horses may include crusting or nodular dermatopathies (eg, photosensitization consequent to liver disease, purpura hemorrhagica, idiopathic granulomatous disease, multisystemic eosinophilic epitheliotropic disease, or lymphoma) or haircoat changes (eg, alopecia or hirsutism) that should alert equine practitioners and dermatologists alike to search for underlying primary disease processes. Diseases with skin manifestations range from those in which the skin is one of the primary organs affected (eg, idiopathic granulomatous disease or multisystemic eosinophilic epitheliotropic disease) to those for which dermatological lesions are secondary and resolve with treatment of the underlying disease (eg, photosensitization consequent to liver disease). This review focuses on disorders for which skin lesions or haircoat changes are markers for systemic diseases in adult horses.