We established a database of hereditary multiple exostoses for the state of Washington, on the basis of a retrospective review of the medical records and a clinical evaluation of family members, to determine the prevalence, clinical range of expression, and rate of malignant degeneration. The database comprised forty-six kindreds with 113 affected members; all kindreds had at least one member living in the state of Washington. The over-all prevalence was at least one in 50,000. Approximately 10 per cent of the subjects had no family history of multiple exostoses. With the use of twenty-three pedigrees that demonstrated an adequate multigenerational history for determination of penetrance of the gene, we identified one unaffected individual among twenty-six obligate heterozygotes, a rate of penetrance of 96 per cent. There was no evidence for a substantial reduction of penetrance in female subjects. The median age at the time of the diagnosis in the 113 affected individuals was three years (range, birth to twelve years). In a cohort of eighty-four subjects for whom we had complete information, the clinical range of expression was wide: thirty-three (39 per cent) had an obvious deformity of the forearm, eight (10 per cent) had an inequality in the lengths of the limbs, seven (8 per cent) had an angular deformity of the knee, and two (2 per cent) had a deformity of the ankle. The average number of operations for the patients for whom the operative history was known was two.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Orthopaedics, University of Washington Medical Center, Seattle 98195.