Melanoma is associated with an increased risk of bullous pemphigoid: a large population-based longitudinal study.

The association between bullous pemphigoid (BP) and melanoma is yet to be investigated. We aimed to assess assess the bidirectional association between BP and melanoma and to delineate the epidemiological features of patients with both diagnoses. A population-based cohort study was performed comparing BP patients (n = 3924) with age-, sex- and ethnicity-matched control subjects (n = 19,280) with regard to incident cases of melanoma. A case-control design was additionally adopted to estimate the risk of BP in individuals with a preexisting diagnosis of melanoma. The prevalence of preexisting melanoma was higher in patients with BP than in control subjects (1.5% vs. 1.0%, respectively; P = 0.004). A history of melanoma confers a 50% increase in the risk of subsequent BP (OR 1.53; 95% CI 1.14-2.06). This risk was higher among males (OR 1.66; 95% CI 1.09-2.54) and individuals older than 80 years (OR 1.63; 95% CI 1.11-2.38), and persisted after adjustment for multiple putative confounders including PD-1/PDL-1 antagonists (adjusted OR 1.53; 95% CI 1.14-2.06). Conversely, the risk of melanoma among patients with BP was slightly elevated, but did not reach the level of statistical significance (adjusted HR 1.13; 95% CI 0.73-1.74). Patients with a dual diagnosis of BP and melanoma were older at the onset of BP and had lower body mass index. A history of melanoma is associated with a 50% increase in the incidence of subsequent BP. Physicians managing patients with both conditions should be aware of this association. Further research is warranted to reveal the underlying mechanism of these findings.