steofibrous dysplasia is a benign bone dysplasia in which lytic lesions occur in the cortex of the tibia and/or fibula in skeletally immature patients. Campanacci proposed the term "osteofibrous dysplasia" and described the clinical and pathologic findings 1,2 . The dysplasia may be clinically silent, so the true incidence of the disease is unknown. Symptomatic children present with anterolateral bowing of the affected bones or with pathologic fractures. As a result of the site of involvement and the propensity for pathologic fractures, this condition may be confused with congenital pseudarthrosis of the tibia.Pathologic specimens from sites affected by osteofibrous dysplasia show bland fibroblastic tissue associated with immature woven bone rimmed by osteoblasts 3-5 . While there has been a questionable association with evolution into adamantinoma, the pathologic appearance of osteofibrous dysplasia does not include neoplastic features.Osteofibrous dysplasia was not thought to be an inherited condition until a recent report, by Hunter and Jarvis, on two siblings with pathologic fractures through lesions resembling osteofibrous dysplasia 6 . We describe six individu-als, in three generations of a kindred of nineteen people, who had lytic lesions of the tibia that resembled osteofibrous dysplasia radiographically and histologically. All six patients were treated for pathologic fracture of the tibia or fibula at our institution.
Materials and Methodsith institutional review board approval, a four-generation pedigree was obtained (Fig. 1). One patient presented with tibial lesions and gave a positive family history, after which medical records and radiographs were reviewed retrospectively to identify all of that patients' family members who had had lower-extremity fractures in childhood. All of the affected patients had been treated at our hospital between 1957 and the time of the study. There were twenty-two relatives from four generations; three had died before the initiation of the study.Radiographs of the tibia and fibula of the six affected patients were reviewed, and anteroposterior and lateral radiographs of the tibia and fibula of ten unaffected family members were made at the time of the study. These ten individuals O W Fig. 1 Pedigree of the family. Patients with documented tibial lesions in childhood are represented by numbers, family members with radiographic evidence of involvement are represented by shaded circles (females) or squares (males), family members with subtle radiographic findings are represented by partially shaded circles or squares, members who died before the time of the study are noted by a diagonal line. An asterisk indicates that a blood sample was obtained for DNA analysis, and a plus sign indicates that anteroposterior and lateral radiographs of the extremities were made.