Primary pachydermoperiostosis associated with pigmented villonodular synovitis: An unknown association?

Primary pachydermoperiostosis is a rare genetic disease affecting the skin and musculoskeletal system. In contrast to secondary hypertrophic osteoarthropathy, primary pachydermoperiostosis is considered a benign condition. While a variety of associated abnormalities have been described in this form, any association with tumors was previously reported in the literature. We hereby describe the first case of a 20-year-old man with primary pachydermoperiostosis revealed by a knee synovial tumor.