Association of Bullous Pemphigoid and Malignant Neoplasms

Methods | Our study cohort comprised all newly diagnosed patients with BP who were seen at the National Skin Centre in Singapore from April 1, 2004, to December 31, 2009. A diagnosis of BP was based on the presence of at least 3 of 4 criteria: (1) clinical findings consistent with BP; (2) histopathological findings of subepidermal blister; (3) a direct immunofluorescence finding of IgG and/or complement proteins along the dermo-epidermal junction; and (4) indirect immunofluorescence findings of a roof or roof-and-floor pattern or positive anti–BP180-NC16A IgG antibodies.2 Patients with BP were matched with persons in the Singapore Cancer Registry and Death Registry to identify those who had cancer and/or had died. Person-years were accrued from BP diagnosis until death, cancer diagnosis, or December 31, 2011, whichever was earliest. The expected number of cancer cases was calculated as the exposure multiplied by the incidence within each ageand sex-specific category and then summed across all categories for the period 2004-2008 in Singapore. The standardized incidence ratio was calculated as the ratio of observed to expected cancers, and 95% CIs were calculated for the standard incidence ratio based on Poisson distribution. The study was approved by the ethics committee of the National Healthcare Group, Singapore. Patient consent was waived.