KYOTO, JAPAN — The annual incidence of both bullous pemphigoid and pemphigus vulgaris has climbed steadily over the past decade in the United Kingdom for reasons unknown, according to a study of more than 1,000 patients.
The mortality associated with these autoimmune diseases may have been underestimated in the past, based upon the results of Dr. Sinéad Langan's large, population-based study presented at an international investigative dermatology meeting.
"People with bullous pemphigoid are twice as likely to die and those with pemphigus vulgaris are three times as likely to die as [are] matched controls," said Dr. Langan of the University of Nottingham (England).
Her study of The Health Improvement Network (THIN)—a large, population-based database of computerized primary care medical records—identified 868 patients diagnosed with bullous pemphigoid (BP) and 139 diagnosed with pemphigus vulgaris (PV) during 1996-2006. Each patient was matched by age and gender with four controls from the same general practice.
She undertook the study because, despite the substantial morbidity and mortality associated with these autoimmune diseases, little is known about their epidemiology. For example, there are only two published studies addressing PV mortality; one, from the Middle East, reported a 1-year mortality of 5%, while a 1975 U.S. study found a 50% 1-year mortality, she said. The reported BP mortality has cut a similarly wide swath.
The incidence of BP in the new U.K. study climbed with advancing age, peaking in a group aged 80-84 years. The median age at presentation was 80 years, and 62% of affected patients were women.
PV incidence showed a bimodal distribution, with a peak at ages 45-49 years and a second, larger one at 80-84 years. Median age at presentation was 71 years, and two-thirds of patients were women.
The incidence of BP was 4.3 cases/100,000 person-years; for PV it was 0.7/100,000 person-years. The incidence of BP showed a "dramatic" average yearly increase of 17% during the study period, while PV incidence increased by 11% each year, according to Dr. Langan. The 1-year mortality rate among patients with BP was 19%, resulting in an estimated 70 excess deaths/1,000 person-years. After adjustment for age and gender as potential confounders, BP patients had a 2.3-fold greater risk of mortality than did controls. The adjusted mortality risk in PV patients was 3.4-fold greater than in controls; PV resulted in 62 excess deaths/100,000 person-years.
Dr. Joel M. Gelfand commented that he doesn't believe the rising annual incidence rates of BP and PV observed in the U.K. study are real, and suspects that more sophisticated statistical analyses would show as much.
"If you look at these kinds of data sets across almost all diseases, the incidence seems to increase over time. It's probably an issue of chronic diseases being picked up over time," according to Dr. Gelfand, who has led several landmark studies carefully documenting increased cardiovascular and cerebrovascular risks in psoriasis patients using the U.K. General Practice Research Database. He is medical director of the clinical studies unit in the department of dermatology at the University of Pennsylvania, Philadelphia.
Dr. John R. Stanley, professor and chair of dermatology at the University of Pennsylvania, said Dr. Langan's study left him uncertain about how to apply the findings in clinical practice. "We don't know [from the U.K. study] whether to treat more aggressively or less," Dr. Stanley observed at a meeting of the European Society for Dermatological Research, the Japanese Society for Investigative Dermatology, and the Society for Investigative Dermatology.
Dr. Langan agreed these data are not illuminating on that score. However, the database also contains information on medications, and she is planning a study she hopes will help guide treatment decisions.
'People with bullous pemphigoid are twice as likely to die and those with pemphigus vulgaris are three times as likely.' DR. LANGAN