Bullous pemphigoid (BP) and dermatitis herpetiformis (DH) are autoimmune bullous skin diseases. DH has been described to evolve into BP and the two diseases can have overlapping clinical appearances and diagnostic findings, but the association between DH and BP has not previously been studied in a large population. To evaluate DH and celiac disease as risk factors for BP, we conducted a retrospective case-control study of patients with BP and matched controls with basal cell carcinoma diagnosed in Finland between 1997 and 2013. A total of 3,397 patients with BP and 12,941 controls were included in the study. Forty-one (1.2%) BP patients and 7 (0.1%) controls had preceding DH. Diagnosed DH increased the risk of BP 22-fold (odds ratio = 22.30; 95% confidence interval = 9.99-49.70) and celiac disease 2-fold (odds ratio = 2.54; 95% confidence interval = 1.64-3.92) compared to controls. Eighteen (43.9%) of the patients who had DH and subsequent BP had bought dapsone during the 2 years prior to their BP diagnosis. Mean time between diagnosed DH and BP was 3 years. We conclude that diagnosis of DH is associated with a striking increase in the risk for BP.
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