Bullous diseases can pose a diagnostic challenge, but a few clinical pearls can help dermatologic providers make a quick diagnosis for patients. Jason Roddick, DMSc, MBA, PA-C, shared some of these tricks in his lecture at the Society of Dermatology Physician Assistants Annual Summer Dermatology Conference 2021 in Chicago, IL.

Blistering diseases have a variety of common causes, including genetic, immune-related, drug-related, metabolism, and dermatitis. The classification, while mostly for dermatopathology, can be split into intraepidermal and subepidermal. “Most of the subcorneal bullae are infectious in nature—they’re right at the surface,” shared Roddick. Subepidermal blistering diseases, he continued, include bullous pemphigoid, pemphigoid gestationis, linear IgA disease, epidermolysis bullous acquisita, and more.

Roddick then shifted focus to differentiating between pemphigus and pemphigoid. He first stressed taking a thorough patient history, including age of onset, initial anatomical site, distribution of lesions, and lesion characteristics, at the beginning of every appointment. These factors can be critical to determining whether the presentation truly is a bullous blistering disease and, further, what blistering disease the patient has.

In age of onset, pemphigus vulgaris typically presents at a mean age range of 40 to 60 years. Alternately, bullous pemphigoid tends to present in patients 60 years and older. Initial site also varies; pemphigus vulgaris generally starts in the oral mucosa whereas bullous pemphigoid affects the extremities at onset. From onset, pemphigus vulgaris will spread widely to the face, scalp, flexural surfaces, and trunk; bullous pemphigoid moves inward to the flexural surfaces and trunk. Lesions between the two diseases look different. Pemphigus vulgaris lesions have flaccid bullae, erosions, and flexural vegetations or growths, and bullous pemphigoid has urticated plaques, tense bullae, and some milia.

In a general practice pearl, Roddick reminded that some classic signs could help determine bullous pemphigoid vs pemphigus vulgaris. While it could be redundant in flaccid-looking lesions, Nikolsky sign can be helpful to determine if there is intraepidermal cleavage. Bullous pemphigoid typically has a negative Nikolsky sign.

Another trick is to use a bulla spread sign (also known as Lutz sign) to help identify the lateral spread of the lesion when pressed. A curved blister movement, similar to the top loop part of a “B” or “P,” would indicate bullous pemphigoid, and a more angled or “V” lateral movement would likely mean pemphigus vulgaris, shared Roddick.

Reference
Roddick J. Bullous blistering diseases. Presented at: Society of Dermatology Physician Assistants Annual Summer Dermatology Conference 2021; July 22-25, 2021; Chicago, IL.