Multiple hereditary exostoses and enchondromatosis.

Multiple hereditary exostoses (MHE) and enchondromatosis are rare multifocal benign disorders usually causing skeletal deformities appearing already in childhood. MHE is a dominant autosomal inherited disorder characterized by multiple osteochondromas (exostoses) growing outward from the metaphyses of long bones as well as from flat bones. They may cause reduced joint motion and pain due to tendon, muscle, and nerve compression. Enchondromatosis (or Ollier's disease) is a noninherited disorder characterized by the presence of multiple intraosseous enchondromas located asymmetrically in the skeleton and with a wide variation regarding location, size, and number ranging from the involvement of a single hand to the involvement of the entire skeleton. It can occur together with soft-tissue hemangiomas in Maffucci's syndrome. Clinical problems caused by the enchondromas are mainly related to skeletal deformities causing malalignment and restricted motion of joint. In both disorders, there is a risk of malignant transformation as well as secondary degenerative joint changes.