diaphyseal aclasis /dī′əfiz″ē·əl ak″ləsis/ [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. Also called hereditary deforming chondroplasia, multiple cartilaginous exostoses, multiple exostoses. ▪ OBSERVATIONS: 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. The major signs of the disease are the noticeable protrusions in the areas of the exostoses. Pain is not usually associated with the exostoses, but if present, it 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. One form of the disorder, dyschondroplasia, results in dwarfism. ▪ INTERVENTIONS: 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 physical therapy and 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. ▪ PATIENT CARE CONSIDERATIONS: 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.
