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Middle-Aged Male With Melorheostosis

      A middle-aged male presented with gross enlargement of his lower right extremity (Figure 1). There was past medical history of Histiocytosis X, Parkes-Weber syndrome, and Klippel-Trenaunay syndrome. Radiographs show extensive periosteal and endosteal thickening involving multiple bones of the right lower extremity (Figure 2). Below knee amputation was performed and gross photographs reveal dense cortical bone overgrowth, entirely obliterating the intramedullary cavity (Supplemental Figure 1, available online at http://www.mayoclinicproceedings.org). The cortical surface is bosselated, producing the characteristic “dripping candle wax” appearance on plain radiograph. The radiographic and gross findings are in keeping with melorheostosis, a rare sclerosing bone disorder that is characterized by either singular or multifocal dense, irregular hyperostosis involving the periosteal and endosteal bone surfaces. The bony overgrowth can cause pain, gross limb deformity, and reduced range of motion. Melorheostosis can affect any bone, but commonly involves the large tubular bones of the lower extremity.
      • Smith G.C.
      • Pingree M.J.
      • Freeman L.A.
      • et al.
      Melorheostosis: a retrospective clinical analysis of 24 patients at the mayo clinic.
      The pathogenesis, in sporadic cases, is associated with mutations in the MAP2K1 gene which encodes the protein kinase MEK1 leading to increased phosphorylated ERK1/2 signaling, and ultimately increased osteoblast proliferation.
      • Kang H.
      • Jha S.
      • Deng Z.
      • et al.
      Somatic activating mutations in MAP2K1 cause melorheostsosis.
      Although this patient’s symptoms were successfully managed through a below knee amputation, there has been interest in using medical and targeted therapies in patients with melorheostosis patients.
      • Kotwal A.
      • Clarke B.
      Melorheostosis: a rare sclerosing bone dysplasia.
      Figure thumbnail gr1
      Figure 1Physical exam revealed abnormal enlargement of the right lower extremity.
      Figure thumbnail gr2
      Figure 2Plain radiographs show the characteristic “dripping candle wax” appearance involving the entire tibia and fibula.

      Potential Competing Interests

      The authors report no potential competing interests.

      Supplemental Online Material

      References

        • Smith G.C.
        • Pingree M.J.
        • Freeman L.A.
        • et al.
        Melorheostosis: a retrospective clinical analysis of 24 patients at the mayo clinic.
        PM R. 2017; 9: 283-288
        • Kang H.
        • Jha S.
        • Deng Z.
        • et al.
        Somatic activating mutations in MAP2K1 cause melorheostsosis.
        Nat Commun. 2018; 9: 1390
        • Kotwal A.
        • Clarke B.
        Melorheostosis: a rare sclerosing bone dysplasia.
        Curr Osteoporos Rep. 2017; 15: 335-342