diaphyseal aclasis

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Related to diaphyseal aclasis: neurofibromatosis


pathologic continuity of structure, as in dyschondroplasia.
diaphyseal aclasis hereditary multiple exostoses.

diaphyseal aclasis

[dī′əfiz′ē·əl ak′ləsis]
Etymology: Gk, dia + phyein, to grow, a, klasis, not breaking
a relatively rare abnormal condition that affects the skeletal system. Characterized by multiple exostoses or bony protrusions, it is inherited as a dominant trait. Approximately half of the children of an individual with diaphyseal aclasis display varying degrees of its symptoms. The characteristic exostoses are radiographically and microscopically similar to osteochondromas. Evident involvement is diffuse, with the long bones usually affected more severely and more frequently than the short bones. Depending on the specific area involved, various angular or rotational deformities may result. Diaphyseal aclasis is usually bilateral and occurs more frequently in boys than in girls. Although this disease is hereditary, its signs and symptoms are not usually evident until the affected individual is 2 years of age or older. Children of a parent who has the disease are often routinely examined for symptoms. The major signs of the disease are the noticeable protrusions in the areas of the exostoses. Pain is not usually associated with the exostoses and, if present, is usually minimal. Deformities of the extremities may be evident, depending on the severity and location of the exostoses. Radiographic examination reveals a broadened metaphyseal area, and the specific lesion is identified by abnormal continuity and decreased density. Asymptomatic lesions characteristic of diaphyseal aclasis usually require little or no treatment other than continued observation. The lesions located near the joints that interfere with joint motion or impair neurovascular function may be surgically excised. Angular and rotational deformities caused by the lesions may require surgical correction to facilitate function. Inequalities in the length of lower extremities resulting from unilateral involvement may require epiphysiodesis. A relatively small number of these lesions may become malignant. One form of the disorder, dyschondroplasia, results in dwarfism. Also called hereditary deforming chondroplasia, multiple cartilaginous exostoses, multiple exostoses.
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Diaphyseal aclasis: massive exostoses at muscle attachments of both knee joints

exostoses, multiple, type 1

An autosomal dominant skeletal disorder (OMIM:133700) that primarily affects endochondral bone during growth, characterised by formation of numerous cartilage-capped, benign bone tumors (osteochondromas) and often accompanied by skeletal deformities and short stature. Rare cases undergo malignant transformation of osteochondromas to osteosarcoma or chondrosarcoma.

Molecular pathology
Caused by defects of EXT1, which encodes exostosin 1, a glycosyltransferase required for heparan sulfate synthesis.


pertaining to or affecting the shaft of a long bone (diaphysis).

diaphyseal aclasis
see multiple cartilaginous exostosis, inherited multiple exostosis.
diaphyseal dysplasia
see juvenile hyperostosis.