The incidence of internal malignancies in autoimmune blistering diseases: pemphigus and bullous pemphigoid in Japan.

To evaluate the significance of the association of malignancy with autoimmune blistering diseases, we studied the incidence of internal malignancies in 496 pemphigus and 1,113 bullous pemphigoid (BP) patients in Japan. Statistical analysis showed that an association ratio of internal malignancies with pemphigus was 5.0% and that with BP was 5.8%. These ratios were significantly higher than that of the controls aged over 70 years (0.61%). Our results indicate that detailed examination for internal malignancy is essential for patients with pemphigus or BP.