Role of IgE in bullous pemphigoid: a review and rationale for IgE directed therapies.

Bullous pemphigoid (BP) is an autoimmune blistering disorder that is characterized by elevated total serum IgE and both IgG and IgE class autoantibodies directed against the hemidesmosomal proteins BP180 and BP230. In BP, IgE is found at the basement membrane zone and coating mast cells in lesional skin. IgE binding to immune cells is mediated through its high affinity receptor, FcεRI on the surface of mast cells, basophils and eosinophils. In BP lesions, IgE binding is thought to be a critical step in the activation of these cells. Models of the disease have demonstrated that BP IgE can replicate the early stages of BP lesion formation. These findings suggest that IgE inhibition may be a therapeutic approach for BP. Omalizumab is a humanized monoclonal antibody that inhibits IgE binding to FcεRI and is currently FDA-approved for the treatment of severe allergic asthma. To date, two case reports have each described the efficacy of omalizumab in a patient with severe recalcitrant BP. These studies are the first to provide clear evidence of the contribution of IgE autoantibodies in the pathogenesis of human BP and suggest that omalizumab may provide an additional therapeutic tool for treatment.