This patient was given a diagnosis of bullous pemphigoid. Although there were a number of clues that pointed to this diagnosis, confirming that this was the case required 2 biopsies and a blood draw. (More on this in a bit.)
Although rare and potentially lethal, bullous pemphigoid is the most common autoimmune blistering disease in the elderly. Patients present with tense bullae over limited or widespread areas of the skin. The pathogenesis includes development of autoimmune antibodies that target important proteins (BP180 and BP230) that bind basal epidermal keratinocytes to the dermis. When weakened by inflammation at these sites, the skin delaminates at the dermal-epidermal junction, while the cells of the epidermis continue to bind to each other. This leads to itching, hive-like wheals, and tense fluid-filled bullae.
The differential diagnosis of an acute or semi-acute bullous disease includes bullous pemphigoid, IgA pemphigoid, linear IgA bullous dermatosis, epidermolysis bullosa acquisita, and Senear-Usher syndrome. In this case, the large tense bullae suggested bullous pemphigoid over the other diagnoses.
Initial diagnosis requires 2 biopsies be performed: One at the edge of a bulla for a standard pathologic exam to identify the skin level at which the bulla is forming, and another biopsy of skin near the site of inflammation (5-10 mm away) to be sent for direct immunofluorescence (DIF) in Michel’s medium or Zeus medium. In bullous pemphigoid, the separation is at the dermal-epidermal junction, and IgG and C3 are found in the DIF in the same location. There are a couple ways to differentiate this disorder from epidermolysis bullosa acquisita—a similar blistering disorder in which autoantibodies attack collagen at the dermal-epidermal junction. A common approach is to send a patient’s serum for indirect immunofluorescence. This is done because it is impossible to distinguish between the 2 clinically.
While bullous pemphigoid has historically been treated with high-dose prednisone, it is more common now to treat with whole-body topical clobetasol and oral doxycycline 100 mg twice a day to avoid the adverse effects of the prednisone. Other immunosuppressive options, such as mycophenolate mofetil and cyclosporine, can provide the potency of prednisone with a more favorable long-term safety profile. Rituximab infusions are another very powerful and durable option in refractory or severe cases.1
This patient was treated with topical clobetasol and doxycycline 100 mg twice a day, but he had incomplete clearance after 2 to 3 weeks. At that point, mycophenolate mofetil was added to the regimen and was titrated up to 1000 mg twice daily. When clearance occurred, the clobetasol was discontinued and the mycophenolate mofetil was titrated down to 250 mg/d; the patient continues to maintain clearance at this dose. He continues on doxycycline 100 mg bid.
Photos and text for Photo Rounds Friday courtesy of Jonathan Karnes, MD (copyright retained). Dr. Karnes is the medical director of MDFMR Dermatology Services, Augusta, ME.