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Editor,—Some time ago a study by Snook and colleagues (Gut 1996;39:60–2) found cigarette smoking to be less prevalent among those with coeliac disease. This prompted Lear and colleagues (Gut1997;40:289) to evaluate smoking status in patients with dermatitis herpetiformis (DH), an autoimmune blistering skin disease that also presents with a gluten sensitive enteropathy. They found that 29 patients with DH were significantly less likely to be smokers than matched and unmatched controls.
As we also have a large population of patients with DH, we did a preliminary review of our existing database to evaluate smoking status in these patients. A review of over 200 patient charts with biopsy confirmed DH (granular IgA in papillary dermis) revealed smoking information on 105 patients. Fifteen of these patients were less than 20 years of age at disease onset and thus were eliminated from the study, leaving 90 evaluable patients. Of these patients eight (8.9%) were smokers, whereas 17.1% of the Utah population aged 20 years or older are smokers,1 thus confirming the findings of Learet al that patients with DH are less likely to be smokers than those in the general population.
The reasons for this finding are not fully clear. It is well known that cigarette smoking adversely affects the skin, although a few conditions have been reported where smoking may have a beneficial effect.2 Likewise, when it comes to the gastrointestinal tract, smoking may have adverse effects in the case of Crohn’s disease, yet beneficial effects in ulcerative colitis.3
How do we explain this apparent beneficial effect of smoking when it comes to DH? It is likely that the immunosuppressive effects of smoking play a role in this autoimmune disease, yet there are other autoimmune skin diseases, such as psoriasis, which are made worse and not better by smoking.4 One study found decreased serum IgA in smokers which may also play a role.5 Finally, the well known vasoconstrictive effects of nicotine could play a role at least in the cutaneous manifestations of DH.
As we found our DH patients more likely to be non-smokers, does this mean that if they take up the habit their DH will go away or even improve? We don’t know, but it seems unlikely. We also doubt our institutional review board would ever approve a study to find out. This study was a preliminary review and does not prove that being a non-smoker is a risk factor for DH. It may be only one variable of the equation, and other likely much more important confounding factors such as genetics and other environmental factors play a greater role. Further more complete studies are needed to confirm our finding.