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RESEARCH: S M Langan, L Smeeth, R Hubbard, K M Fleming, C J P Smith, and J West Bullous pemphigoid and pemphigus vulgaris—incidence and mortality in the UK: population based cohort study BMJ 2008; 337: a180 [Abstract] [Full text]

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Is the incidence of pemphigoid really increasing?

Richard W Groves, Balbir Bhogal, Kathy Taghipour, Paola Caposciutti, and Monika Saha   (29 July 2008)

Is the incidence of pemphigoid really increasing? 29 July 2008
Richard W Groves, Head, Clinical Immunodermatology St. John's Institute of Dermatology, St. Thomas' Hospital, London SE1 7EH, Balbir Bhogal, Kathy Taghipour, Paola Caposciutti, and Monika Saha Send response to journal: Re: Is the incidence of pemphigoid really increasing?	Sir: We read with interest the work of Langan & colleagues (Br Med J 2008; 337:a180) regarding the epidemiology of pemphigoid and pemphigus. In particular, we found their data on the apparent increasing incidence of pemphigoid to be striking. It might reasonably be expected that a five-fold increase in incidence of pemphigoid would be apparent to physicians caring for patients with the disorder. Blistering disorders are perhaps unusual amongst skin conditions in that they are nearly always reported to dermatologists and specialised testing is required to establish the diagnosis. A straw poll amongst dermatological colleagues last week did not support the view that pemphigoid had been seen more frequently and to examine this further we reviewed the incidence of positive tissue diagnoses of pemphigoid in our laboratory over the period 1994-2004. Such diagnostic biopsies tend only to be taken once, and generally at the onset of the disease. Thus they represent a surrogate marker of incidence of the condition. Currently we receive over 2,000 samples annually and in the period 1994-2003 (for which we have easily accessible data) made 1656 new diagnoses of pemphigoid using direct immunofluorescence on skin biopsy material. Whilst the number of pemphigoid diagnoses increased significantly over the period (from 71 in 1994 to 245 in 2003), when we normalised these crude data to the number of tissue specimens received (Figure 1), or to the frequency of unconnected diagnoses (mean frequency of diagnosis of discoid lupus erythematosus and dermatitis herpetiformis, Figure 2) we found no increase in incidence of pemphigoid using either technique. Reconciling our experience and diagnostic data with that of Langan & colleagues is difficult. Whilst our samples are received predominantly from London and the South East, Langan reported no association between pemphigoid incidence and geographical area; thus this ought not to play a role. Whilst it is possible that dermatologists are preferentially avoiding our laboratory for the diagnosis of pemphigoid this seems unlikely. Epidemiological surveys are important tools in developing hypotheses for further testing, and this is the strength of Langan & colleagues report. Moreover, we welcome focus on these severe and disabling dermatological diseases. For now however we urge caution in interpretation of these findings and trust that they will provide an important stimulus to further research. Sincerely yours, Monika Saha, Balbir Bhogal, Kathy Taghipour, Paola Caposciutti and Richard Groves Competing interests: None declared