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melorheostosis

Thursday 25 March 2010

Melorheostosis is a rare, nonfamilial condition related to osteopoikilosis and Buschke-Ollendorff syndrome in having an LEMD3 functional loss mutation.

The affected bones display an irregular cortical hyperostosis, similar in appearance to melting wax dripping down the sides of a candle.

The lesions occur on both the periosteal and the endosteal surface and may be monostotic, monomelic, or polymelic. Radioisotope bone scans usually show increased uptake in the lesional tissue.

Melorheostosis or periarticular fibrosis was first described in 1922.

In melorheostosis, hyperostosis is associated with fibrosis of adjacent soft tissues leading to stiffness and loss of function.

Melorheostosis is a condition of mixed clinical and histologic diagnosis. Surgery does not improve function and has little role other than that of diagnostic biopsy.

While melorheostosis is classified with the sclerosing bone dysplasias, it warrants inclusion in the clinical differentiation of the fibromatoses.

The swelling and periarticular fibrosis may precede the classical bony sclerosis and “dripping candle wax” appearance of radiographs.

The fibrosis may involve all layers of soft tissue, extending to the dermis and giving a linear scleroderma-like clinical picture.

Associated cutaneous lesions, including vascular malformations and focal subcutaneous and para-articular fibrosis, are common, and in children prominent soft tissue fibrosis may predate osseous abnormalities.

With an onset in childhood, the skeleton is characterized by hyperostoses of the bones of the extremities and pelvic girdle, inequality in the length of the extremities, and by contractures resulting in joint deformity.

On radiographs, the lesions may be found to involve the epiphysis, and the dense osseous tissue may be seen to cross the growth plate. (Attempts at surgical management of the contractures have been unrewarding.)

With adult onset, the patients most often present with pain, deformity, or limitation of joint motion.

The lesion may involve one or many bones. Ectopic bone may be present in para-articular locations.

The involvement of one side of a bone (or row of bones, in some cases) has suggested a sclerotome distribution.

Macroscopy

On gross examination of the affected bones, the periosteal and endosteal surfaces are irregular, and the bones display thickened cortices.

The marrow cavity is narrowed.

Microscopy

Histologic examination reveals that the new bone may be either woven or lamellar.

However, even when the new bone tissue is lamellar, its cancellous architecture is irregular, and there is a distinct differentiation between the normal and melorheostotic bone.

Synopsis

- thickened endosteal and periosteal bone
- characteristic appearance of candle wax dripping
- large juxta-articular swellings formed of dense osseous tissue.
- markedly irregular bone with relatively little cellular activity on the endosteal surfaces.
- The marrow may show mild fibrosis.

See also

- bone-forming tumors

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  • From Bullough's Orthopaedic Pathology
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