Clinical communication — Kliniese mededeling Steroid-sparing effect of mycophenolate mofetil in the treatment of a subepidermal blistering autoimmune disease in a dog

INTRODUCTION Bullous skin diseases are characterised by the formation of clefts, leading to vesicles or bullae. Separation most commonly occurs between the dermis and epidermis and results from loss of structural integrity of the basement membrane zone. Subepidermal bullous diseases (SEBD) have been described mostly in the dog. Although their clinical presentation is variable, it is not possible histopathologically to identify a specific disease beyond the term ‘subepidermal blistering or bullous’. Immunological studies for detection of in situ and circulating autoantibodies directed against basement membrane specific antigens are required for a definitive diagnosis. Bullous pemphigoid (BP), mucous membrane pemphigoid (MMP), epidermolysis bullosa acquisita (EBA), linear IgA disease and bullous drug eruptions are SEBD described in the dog. However, because of the lack of appropriate immunologic techniques, SEBD in dogs were all diagnosed as BP until 1998, when the 1st case of canine EBA was reported. Soon, linear IgA disease was described in 2 dogs, and MMP was established as the most common autoimmune disease of the basement membrane zone in the dog and cat. Conventional therapy of SEBD in humans and dogs is troublesome. Corticosteroids are combined with immunosuppressants such as azathioprine and cyclophosphamide but treatments may be unsuccessful and side effects associated with high corticosteroid doses are common. In humans, there are no randomized, controlled, double-blind studies comparing the use of various therapeutic agents. Treatment decision still relies heavily on the experience of individual clinicians. Mycophenolate mofetil (MMF) is an immunosuppressive drug that selectively inhibits purine synthesis primarily in lymphocytes (T and B-cells) and has been used for human MMP and other autoimmune diseases. A retrospective study evaluated the effectiveness and toxicity of immunosuppressive therapies in the treatment of 338 human ocular MMP cases. The therapies based on MMF were the second-most successful after those based on cyclophosphamide and the best tolerated with the least side effects of all therapies used. In this case report the use of MMF as steroid sparing agent in a dog diagnosed with SEBD is described. The combined use of MMF and prednisone allowed good control of the cutaneous lesions for more than 1 year follow-up with a minimal dose of oral prednisone (0.25 mg/kg e.o.d.) and MMF (10 mg/kg b.i.d.).