Melorheostosis

Tumor biology and incidence

Melorheostosis is a rare, noninheritable, progressive bone dysplasia characterized by irregular cortical hyperostosis that follows the long axis of a bone. The disease usually affects multiple bones in the same extremity, possibly due to somatic mosaicism. Ossification may occur in skin and soft tissures overlying the affected bones. The overlying skin is often tight and shiny, and joint contractures result from soft tissue fibrosis. The genetic defect in the majority of sporadic and isolated melorheostosis remains unknown. A neuropathic etiology has been hypothesized due to the dermatomal pattern of hyperostosis.(McCarthy & Frassica. Pathology of Bone and Joint Disorders. Philadelphia: W.B. Saunders company, 1998.) The underlying cause may be due to altered expression of several adhesion proteins, including betaIG-H3.

Age

Typically presents as a painless contracture before age 6

Gender

Presentation

Flexion contracures are common. Flexion contracture of knee is most common, followed by the ankle, hip, and fingers. Pain typically develops in late adolescence and may be the only complaint. May also present as a leg length discrepance due to premature closure of physis or deformity of the limb, hand or foot. Skin overlying affected area may be tight and shiny.

Physical findings

See presentation

Plain films

Dense cortical hyperostosis appearing as "dripping candle wax".

Site

Rarely affects axial skeleton.

Size

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Tumor effect on bone

Bone response to tumor

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Matrix

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Cortex

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Soft tissue mass

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Bone scan

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CT Scan

MRI

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Differential Diagnosis

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Natural history

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Pathology

Corical hyperostosis is the product of new periosteal bone deposition. This bone eventurally matures into lamellar bone. Endosteal hyperostosis may also be seen. Diseases associated with melorheostosis include osteopoikilosis, osteopathia striata, scleroderma and Buschke-Ollendorff syndrome.

Diagnosis

"Dripping canle wax" pattern of cortical hyperostosis on plain x-rays is diagnostic.

Treatment

Treatment is supportive. NSAIDS may be used for analgesia. Surgery performed for the sole purpose of pain relief is rarely effective, unless the pain is secondary to nerve impingement. Surgical realease of flexion contractures is more successful in skeletally mature patients as they are not as affected by the formation of aggressive scar tissue. Surgery is effecective, however, for the treatment of boney impingement secondary to bone overgrowth.

Complications

Soft tissue releases alone in skeletally immature patients have a 100% failure rate in the literature. This does not mean that they should not be done, however families should be counseled that these procedures may need to be repeated.

Recommended Reading

Melorhesostosis Association - http://www.melorheostosis.com/

References

McCarthy & Frassica. Pathology of Bone and Joint Disorders. Philadelphia: W.B. Saunders company, 1998.