Syphilis isn’t just a disease of soft tissue, it leaves lasting scars on bone. In advanced (tertiary) syphilis, the skull can develop caries sicca: irregular lesions caused by chronic inflammation and bone destruction. These changes aren’t random, their location, shape, and pattern help osteologists identify infection centuries later. By studying real human skulls like this one, we can trace the biological footprint of disease, understand how infections progressed before antibiotics, and see how