Disease versus disease: Paolo Zacchia on syphilis and epilepsy

The lawyer and physician Paolo Zacchia (1584–1659) was the chief physician at the Vatican and an important advisor to the papal court. He is considered a founder of the field of forensic pathology, and the influence of his masterwork, Quaestiones medico-legales, spread throughout Europe. In this essay, we focus on one of Zacchia's consultations, first published posthumously in 1661. Emerging from a cause for beatification, the case features the intriguing medical notion of one disease curing another. Zacchia was to determine if a young man's recovery from epilepsy was miraculous or not. We will briefly review Zacchia's career, examine his argument and the sources on which he based his reasoning in this case, trace the status of the disease-versus-disease notion to the present, and demonstrate that this consultation represents a rare, if not the only example of syphilis being the curative agent – rather than the disease cured.