A full history and physical examination is essential for recognizing the diagnosis and determining the etiology of bullous pemphigoid. Drug-induced bullous pemphigoid is well recognized and has many causes, including diuretics, antibiotics, and angiotensin-converting enzyme inhibitors. Cessation of the drug normally prevents recurrence.
Some evidence suggests an association between bullous pemphigoid and cancer; however, bullous pemphigoid itself has not been shown to increase the incidence of cancer in age- and sex-matched controls. Of note, Gül and colleagues described breast cancer with bone metastases presenting with bullous pemphigoid in a 62-year-old woman. Bullous pemphigoid is a disease of the elderly and, of course, this population is much more prone to developing cancer as well; therefore, a thorough examination for possible associated cancer is prudent.
In patients with autoimmune subepidermal blistering disease, bullous pemphigoid is the most likely diagnosis if three of the following four criteria are present:
Age > 70 years
Absence of atrophic scars
Absence of mucosal involvement
Absence of predominant bullous lesions on the neck and head
These criteria have a sensitivity of 90%, specificity of 83%, and positive predictive value of 95% when validated using immunoelectron microscopy and a sensitivity of 86%, specificity of 90%, and positive predictive value of over 95% when validated using immunoblotting as the criterion standard.
The clinical differential diagnosis for bullous pemphigoid is broad and could include pemphigus vulgaris, linear immunoglobulin A disease, epidermolysis bullosa acquisita, bullous lupus erythematosus, and dermatitis herpetiformis. Blistering rashes can also be seen with impetigo, acute viral infections, drug eruptions, and herpes zoster. The patient's history and physical examination will help narrow down the differential diagnosis. The patient's age, vital signs, the distribution of the blisters, and the nature of the blister (ie, tense or flaccid) all provide clues; however, testing is ultimately necessary and includes immunofluorescence studies, histopathologic examination, and viral and bacterial swabs.[1,3]
In bullous pemphigoid, indirect immunofluorescence using serum demonstrates circulating antibodies to the basement membrane zone of human skin or monkey esophagus substrate in a linear pattern in 70% of cases. Skin biopsy of a blister often reveals an eosinophilic inflammatory infiltrate, whereas direct immunofluorescence of normal skin adjacent to the lesion shows linear deposits of immunoglobulin G and C3 at the basement membrane zone.
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Cite this: Tuyyab Hassan. An 84-Year-Old With a Blistering Rash That Is Spreading - Medscape - Jun 28, 2016.