Findings: AP and LAT views of the right femur, tib/fib, and foot are presented. These demonstrate multiple areas of increased bone density. The femoral neck is entirely occupied by endosteal hyperostosis. No associated bony expansion or deformity is seen. A short interval of normal bone is followed by marked thickening of the lateral femoral cortex, which has a somewhat undulating medial margin. This terminates in a very globular appearing mass of hyperostotic bone within the lateral femoral condyle. The medullary space of the proximal fibula is filled with what appears to be "flowing" cortical or compact bone. The tibia is essentially unremarkable. At the distal aspect of the fibula a second "globule" of hyperostotic bone is present within the lateral malleolus. Immediately across the lateral ankle joint a second "globule" of compact bone is seen in the lateral talus. As with all of the above described bones, the talus is otherwise morphologically normal without erosion, expansion or destruction. Multiple "whirls" of hyperostotic bone are seen in the tarsus. Further changes are seen in the 2nd through 4th rays of the foot, with a "dripping wax" appearance to the margins of the hyperostotic bone distributed along bone the exterior and interior margins of the cortices.

Diagnosis: Melorheostosis.

Discussion: Melorheostosis was first described by Leri and Joanny in 1922. It typically presents in early childhood. It is equally prevalent in males and females. It is not hereditary. Affected individuals have a normal lifespan.

Patients typically present with intermittent joint swelling and pain. Pain and limitation of motion is more typical in adults rather than children. Patients may experience muscle contractures and ligament and tendon shortening. Occasionally limb length discrepancies may be present. A variety of skin changes associated with this condition have been described. These include: tense erythematous, shiny skin; anomalous pigmentation; induration; edema; muscle atrophy; and linear scleroderma. Skin changes may precede osseous findings. This disorder can, on occasion, result in significant deformity.

Plain radiography typically demonstrates lesions which are confined to one limb. The upper extremity is more often affected than the lower extremity. Lesions can also affect the bones of the skull, face and clavicle. Within the long bones lesions are characterized as peripherally located hyperostosis. Lesions tend to have a "flowing" appearance and have been compared to a "candle dripping." Endosteal lesions may partially or completely obliterate the medullary cavity. In lesions of the carpal and tarsal bones the lesions tend to be more discrete and somewhat rounded which may appear similar to those seen in osteopoikilosis. In flat bone lesions may be localized, patchy and sclerotic. Soft tissue calcifications are not infrequent, especially in the para-articular regions. These calcifications may progress to joint ankylosis. On bone scintigraphy lesions can have an appearance similar to that seen in Paget’s disease.

The etiology of this disorder is unknown. Because it is frequently distributed along a single sclerotome many authors have suggested an abnormality of embyrogenesis of a segmental sensory nerve with associated bone and skin changes.

References:
D. Resnick and G. Niwayama.: Diagnosis of Bone and Joint Disorders. 2nd edition.
W.B. Saunders Co., Philadelpia. 1988.

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