Increasing incidence of bullous pemphigoid in Northern Finland: a retrospective database study in Oulu University Hospital

• Published in: British journal of dermatology (1951) Vol. 171; no. 5; pp. 1223 - 1226
• Main Authors: Försti, A.-K., Jokelainen, J., Timonen, M., Tasanen, K.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.11.2014; Wiley-Blackwell; Oxford University Press
• Subjects: Adult; Age; Age Distribution; Age of Onset; Aged; Aged, 80 and over; Biological and medical sciences; Biopsy; Bullous diseases of the skin; Bullous pemphigoid; Dermatology; Epidemiology; Female; Finland - epidemiology; General aspects; Geriatrics; Humans; Immunofluorescence; Incidence; Male; Medical sciences; Middle Aged; Miscellaneous; Pemphigoid, Bullous - epidemiology; Public health. Hygiene; Public health. Hygiene-occupational medicine; Retrospective Studies; Sex Distribution; Skin diseases; Standardization; Europe; Finland; Bullous dermatosis; Immunopathology; Skin disease; Dermatology; Autoimmune disease; Hospitalization; Retrospective study; Epidemiology; Incidence; University; Bullous pemphigoid; Database; North; Hospital; Public health
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1111/bjd.13189

Summary Background Bullous pemphigoid (BP) is an autoimmune blistering skin disease of elderly people. Some studies have suggested that the incidence of BP has increased, but the diagnostic accuracy and methodology of studies have varied considerably. Objectives To examine the incidence of BP in Northern Finland, and whether the incidence has changed over time. Methods This was a retrospective database study of all BP cases diagnosed in the Oulu University Hospital, Finland between 1985 and 2009. The diagnostic criteria were clinical features characteristic of BP (all patients) and positive direct or indirect immunofluorescence in the skin biopsy. The age‐standardized incidences were calculated by the direct standardization method. Incidence rate ratios (IRR) were estimated by the Poisson regression model. To derive adjusted IRRs, age and sex were used as potential confounding factors. Results The crude incidence of BP was 17 per 1 million person‐years [95% confidence interval (CI) 15–20] between 1985 and 2009. Using the general European population as a reference, the age‐standardized incidence was 14 per 1 million person‐years (95% CI 12–17). The incidence of BP increased 1·8‐fold (IRR 1·8, 95% CI 1·3–2·6; P < 0·001) in 2005–09 compared with the mean incidence of BP between 1985 and 2004, but after the adjustment for age and sex the increase was 1·4‐fold (IRR 1·4, 95% CI 1·0–2·0; P = 0·043). Conclusions This is the first study with immunohistologically verified BP diagnoses that reports the increase in the incidence of BP in age‐ and sex‐adjusted populations. What's already known about this topic? Bullous pemphigoid (BP) is an autoimmune blistering skin disease caused by IgG autoantibodies against BP antigen 180 (collagen XVII), a structural protein of hemidesmosomes. Some studies have suggested that the incidence of BP has increased, but the diagnostic accuracy and methodology of studies have varied considerably. What does this study add? We investigated the incidence of BP in Northern Finland between 1985 and 2009. The crude incidence was 17 per 1 million person‐years between 1985 and 2009, and the incidence had increased 1·4‐fold by 2009 compared with the mean incidence level between 1985 and 2004. The reasons for BP becoming more common are unknown.