Pemphigus foliaceus in a racing Standardbred

Abstract

Pemphigus foliaceus (PF) is the most common autoimmune skin disease in the horse. PF results in severe crusting and matting of the hair coat. There is no age, sex or breed predilection, but seasonality and drug induced PF have been observed. The most common clinical presentation is severe matting and crusting of the coat with oozing of serum from the skin. The definitive diagnosis is made by routine histologic examination of a skin biopsy specimen. An autoantibody against the desmosome of keratinocytes results in the release and activation of keratinocyte proteolytic enzymes into the intercellular space. The desmosome is hydrolyzed and intercellular cohesion is lost, leading to acantholysis. Treatment recommendations vary depending on the age of onset of PF, usually self-limiting in horses less 1 year in age, and difficult and often unrewarding in adults. Adults are typically treated with an immunosuppressive dose of glucocorticoids but survival rate have been documented to be 46%, so a guarded prognosis should be given to owners who have horses diagnosed with PF.