Melorheostosis

Melorheostosis (also known as Léri disease, Léri melorheostosis, or flowing hyperostosis) is a rare sclerosing bone dysplasia characterized by the progressive thickening and densification of cortical bone, typically affecting one limb or one side of the body. The hallmark radiographic finding is a pattern of dense, irregular cortical hyperostosis that flows along the length of a bone, resembling dripping candle wax on X-ray imaging. The condition most commonly affects the long bones of the upper and lower extremities, though it can also involve the pelvis, spine, ribs, and small bones of the hands and feet. Soft tissue abnormalities, including fibrosis, joint contractures, and overlying skin changes such as scleroderma-like thickening, may accompany the bony changes. Clinical manifestations vary widely in severity. Key symptoms include pain, stiffness, and limited range of motion in affected joints, limb-length discrepancy, muscle weakness or atrophy, and deformity of the affected limb. Some patients may be asymptomatic and diagnosed incidentally on imaging, while others experience significant functional impairment. The condition typically follows a slowly progressive course. Somatic (postzygotic) mosaic mutations in the MAP2K1 gene have been identified as a major cause in many cases, explaining the segmental distribution of the disease. There is no cure for melorheostosis, and treatment is primarily symptomatic and supportive. Pain management with analgesics and anti-inflammatory medications is a mainstay of therapy. Physical therapy and occupational therapy are important for maintaining joint mobility and function. Surgical intervention, including osteotomy, excision of excess bone, joint release, or fasciotomy, may be necessary in cases of severe contracture, nerve compression, or significant functional limitation. Bisphosphonates have been tried in some patients with variable results. Management is best coordinated by a multidisciplinary team including orthopedic surgeons, rheumatologists, and rehabilitation specialists.

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