Melorheostosis Beyond the Bone: Mixed-Pattern Presentation in the Pelvis

Melorheostosis is a rare benign sclerosing bone dysplasia classically characterized by flowing cortical hyperostosis described as dripping candle wax. Although melorheostosis typically involves the appendicular skeleton and has a characteristic radiographic appearance of flowing cortical hyperostosis along the shaft of a long bone, uncommon and mixed radiologic patterns occur and may involve adjacent soft tissues. Axial skeletal involvement is uncommon and may mimic more aggressive processes. We present the case of a 20-year-old man with buttock discomfort whose imaging illustrates a mixed-pattern melorheostosis of the pelvis and emphasizes recognition of atypical presentations to avoid misdiagnosis as parosteal neoplasm or myositis ossificans.