Hereditary multiple exostoses [2 genes]

Hereditary multiple exostoses is an autosomal dominant disorder characterized by multiple bone projections covered by cartilage (osteochondromas) in the metaphyses of long bones, and they can also occur in the diaphyses of long bones. The flat bones, vertebrae, and ribs may also be affected, but the skull is not usually involved. Deformity of the legs, forearms, and hands is usual.

Multiple exostoses: the incidence is 1 / 50,000 newborns (ORPHA:321)

The benefits derived from a genetic diagnosis are aimed at closing the diagnosis and family genetic counseling.

Service is indicated in the presence of a personal history of multiple osteochondromas arising in proximity to the growth physis of long bones or from the surface of flat bones.

Multiple exostoses have a known genetic cause in 87-90% of cases. The responsible variants are single nucleotide variants (SNV) in approximately 90% of patients, with 10% being copy number variants (CNV). The exome allows the identification of both SNVs and CNVs, although there are limitations to the technique for identifying deep intronic variants. The diagnostic performance of this service for this pathology is greater than 85%.