During rescue archeological excavation in 2018, the skeletal remains of a young male with an unusually large and rare lytic focus in the right iliac fossa, dating to the Middle Bronze Age, were found at the Mikulov site (Czech Republic). The presented communication considers various diseases that could be the cause of this pathological condition (tuberculosis, syphilis, mycosis, parasitic diseases, tumors, peritoneal abscess). The examination methods used in this case were macroscopic examination, radiological, histological, and genetic analyses. Differential diagnosis helps us to focus upon the most likely etiologies, and in our opinion, we feel this erosive lesion was probably caused by inflammation from a peritoneal abscess associated with chronic appendicitis.