Mercury ‘poisoning’ in patients with syphilis within the Ca Granda hospital (17th century Italy)

The Ospedale Maggiore, called “Ca’ Granda” or “Big Home” by the Milanese, was one of the main institutions in Milan (Italy) in the 16th century and a model during the Renaissance for similar healthcare institutions across Italy and Europe because of its innovative and avant-gardist free medical assistance to the poor and scientific activity. As part of the Ca’ Granda Project undertaken by the University of Milan and the Hospital Foundation for Cultural Heritage of the Ospedale Maggiore, campaigns of archaeological excavations of the sepulchral chambers of the Ca’ Granda crypt have revealed the presence of an estimated 2.9 million commingled bones, representing the skeletonized bodies of the deceased patients of the hospital during the 17th century. During these excavations, two crania were found with pathological bone signs of tertiary syphilis, showing clustered pits, marked cavitation, bone destruction and nodular formation, consistent with advanced stages of caries sicca. Computed tomography (CT) imaging was undertaken for a better visualization of the extent of the lesions and bone samples of both crania were submitted to inductively coupled plasma mass spectrometry (ICP-MS) to measure the levels of mercury remaining in the bones. As a result, high levels of mercury were detected. By the 17th century, syphilis was a widespread and common condition in Italy. The finding of two cases of tertiary syphilis with high bone levels of mercury confirms the historical use of the heavy metal as a treatment for the infectious disease in the 17th century Italy, and in particular Milan.