Bullous pemphigoid can masquerade as psoriasis

May 1, 2008

Dermatologist Jean-Claude Bystryn, M.D., is used to seeing cases that most dermatologists consider rare, such as pemphigus, pemphigoid and superficial pemphigoid. But even Dr. Bystryn, professor of dermatology at New York University School of Medicine, was reminded recently that not everything is as it appears.

Key Points

A woman had flown to New York University from the Middle East for evaluation of what seemed to be bullous pemphigoid. Indeed, she had a history consistent with bullous pemphigoid, according to Dr. Bystryn. Although her biopsy had been nondiagnostic, she had a positive direct immunofluorescent stain.

Dr. Bystryn did indirect immunofluorescent studies, which helped to give credibility to the previous diagnosis.

A second biopsy came back indicating psoriasis.

He had prepared his recommendation based on her managing bullous pemphigoid for her final visit before returning overseas, but the new diagnosis called for a new approach. He questioned the patient, again, and found that she and her father had histories of psoriasis.

"All of (a) sudden, this straightforward case turned out to be a patient with two separate diseases, which can look like each other - as it turns out," Dr. Bystryn says.

How much is pemphigoid, psoriasis?

"She clearly had bullous pemphigoid, because in the past she had blisters and had positive direct and indirect fluorescent studies," Dr. Bystryn tells Dermatology Times.

"But the problem that she had at the time was really psoriasis, which looked like resolving bullous pemphigoid lesions," he says.

The case proved unusual and interesting because of the coexistence of two separate diseases.

"You do not typically think of psoriasis being mistaken for bullous pemphigoid, but, if you have a patient with resolving lesions of bullous pemphigoid, it can actually be mistaken for resolving lesions of psoriasis," Dr. Bystryn says.

Dr. Bystryn, who wrote a report about bullous pemphigus for the National Organization of Rare Disorders, says he had a similar experience with a patient who appeared to have recalcitrant pemphigus, based on the patient's presentation of crusted, oozing, weeping lesions on her face and torso, which were increasing in number. The patient, however, was not responding to prolonged use of high doses of steroids.

"Here is a patient who has a biopsy consistent with pemphigus, but immunofluorescent studies were negative. No test is positive 100 percent of the time, so it is not unusual to see patients who have a disease, although confirmatory tests are negative. But it makes you think," he says.

Cultures of the lesions showed that the patient, in fact, had the bacterial infection impetigo. The common disease mimicked pemphigus clinically and under the microscope.

"Treating impetigo patients with steroids is going to make the disease worse - not better - which is what happened. The patient was thought to have a difficult, unresponsive case of pemphigus, but, in fact, had a different disease," he says.

"When you evaluate patients with potentially severe diseases, you want to go through the whole diagnostic panel of tests to be absolutely sure that you are treating the patient appropriately," Dr. Bystryn says.