Demonstration of melorheostosis on bone scan

Melorheostosis has been discussed infrequently in the nuclear medicine literature. A 25-year-old female patient presented with a one-year history of b:union: pain, sclerotic change and skin pigmentation on the left big toe interphalangeal joint. Ulceration, poor healing and hyperkeratoses of the wound were noted post debridement. The plain film of the left foot incidentally showed melorheostosis. Radiographs revealed cortical hyperostosis of big toe. After further evaluation by X-ray and bone scan of the left foot, the radiologic findings still indicated melorheostosis. A further Tc-99m MDP bone scan revealed extensive bone involvement in the left side of the pelvis and entire left lower extremity. Moreover, plain film whole body bone scan and MRI also revealed melorheostosis. The clinical symptoms of her left big toe included interphalangeal joint callus formation, debridement, ulcer and hyperkeratoses. X-rays often reveal a pattern of thickened bone that resembles dripping candle wax, with periosteal cortical thickening, confined to sclerotomes; and can be seen apparently flowing across joints to the next bone. In the nuclear medicine image, an increase in radiotracer uptake is usually present on late phase bone scans. There was excellent correlation between the scintigraphic and radiographic distribution of these lesions in the following radiographs of pelvis, left femur, lower leg and MRI of the left foot. This study reported a rare case of melorheostosis affecting the big toe and reviewed the role of various imaging diagnosis of this rare bone dysplasia.