Melorheostosis

DISCUSSION: The radiographs, CT scan, bone scan, and histology slide are consistent with a diagnosis of melorheostosis, a rare, developmental dysplasia of cortical bone characterized by a "flowing hyperostosis" (Illustration A & B). While melorheostosis is most common in the long bones, its occurrence in the foot has been documented in the literature.

The radiographs show a non-aggressive sclerosis of the second metatarsal with complete obliteration of the intramedullary canal on CT scan. While the bone scan is "hot" this isn't a marker for malignancy in this case given the generalized increased osteoblastic activity seen with melorheostosis. The histology slide shows a sheet of bland osteoid without any malignant cellular features in the stroma.

Jain et al review the clinical features, diagnosis, and management of patients with melorheostosis. They describe that while this is a benign condition, the hyperactive osteoid formation can often lead to limb malalignment or joint contracture requiring surgical intervention.

Gagliardi and Mahan review the literature and diagnosis of melorheostosis and describe their management of two patients with this diagnosis. One patient, a 10-year-old with metatarsus adductus secondary to melorheostosis required multiple bi-planar metatarsal osteotomies to correct his deformity (Illustrations C and D).

Incorrect answers:
1,2,3) The histology slide does not show carcinoma, malignant osteoid, nor malignant spindle cells.
5) The radiographs do not show a fracture.