- Bullous Pemphigoid is a autoimmune disease caused by direct antibody-mediated disruption of proteins which connect the epidermis to the underlying basement membrane, thus yielding subepidermal blisters. Onset is typically in the later decades and is thus a disease of elderly.
- Bullous Pemphigoid is essentially a Type II Hypersensitivity process caused by inappropriate development of IgG auto-antibodies to two hemidesmosomal proteins which connect basal cells to the underlying basement membrane. Binding of these antibodies disrupts these connections, yielding separation of the epidermis from the basement membrane.
- Separation of an otherwise intact epidermis from the underlying dermis is the prototypical finding of bullous pemphigoid. Direct immunoflourescence studies reveal IgG and complement deposited in a linear band along the basement membrane. Additionally, a perivascular infiltrate of eosinophils and lymphocytes can be seen in the dermis and likely plays some role in the pathogenesis of the disease.
- Because separation occurs beneath an otherwise intact epidermis, the bullae of bullous pemphigoid retain structural integrity, remain intact, and are thus termed "tense" bullae. Placing pressure on the bullae do not lead to their extension into underlying skin, and thus the bullae are negative for "Nikolsky Sign". The retained integrity of the skin means that prognosis is typically excellent for most patients and blisters usually heal without scarring.
- In severe cases systemic corticosteroids are often used.