OBJECTIVE: To evaluate erosive pathological lesions on a skeleton from medieval Transylvania. MATERIALS: A skeleton from a Székely archaeological site in Transylvania was examined and radiocarbon dated to Cal 1300 CE - 1415 CE. METHODS: The skeletal remains were examined macroscopically and with radiographic imaging. A differential diagnosis was conducted following established protocols. RESULTS: The individual was estimated to be a probable adult female. Periarticular erosive lesions involving multiple synovial joints, particularly on the small joints of the hands and feet, were observed. CONCLUSIONS: A differential diagnosis identifies lesions characteristic of rheumatoid arthritis dating prior to the mid-15th century. SIGNIFICANCE: The significance of this diagnosis is great since researchers debate the antiquity and spread of rheumatoid arthritis. Some researchers hypothesize that RA originated in the Americas and spread to Europe after the mid-15th century. However, this study asserts that RA existed in Europe prior to European colonization of the Americas. LIMITATIONS: Only 30-40 % of the skeletal material was excavated, potentially impacting the differential diagnosis. SUGGESTIONS FOR FURTHER RESEARCH: This case encourages researchers to explore the presence of RA in other medieval groups within and beyond Transylvania as a means to reconstruct the antiquity and geographical distribution of the condition.