Multiple Hereditary Exostoses (MHE), also known as Hereditary Multiple Exostoses (HME) or diaphyseal aclasis, is a rare genetic disorder characterized by the development of multiple bony outgrowths or protuberances called exostoses. These exostoses usually form along the long bones, such as the arms and legs, and can also affect the pelvis, ribs, and spine.
The exostoses in MHE are benign bone tumors that manifest as irregular, cartilage-capped growths or bumps. They can vary in size and number, ranging from only a few to dozens of exostoses. These bony growths typically appear during childhood and continue to develop until skeletal maturity. Although benign, the exostoses can cause significant morbidity, leading to pain, deformities, restricted range of motion, shortened limbs, and limb-length discrepancies.
MHE is an autosomal dominant condition, which means that an affected individual has a 50% chance of passing the condition on to their children. The disorder is caused by mutations in the EXT1 or EXT2 genes, which are responsible for producing proteins involved in the regulation of bone growth. These mutations disrupt the normal signaling pathways involved in bone development, leading to the abnormal formation of exostoses.
Diagnosis of MHE is often based on clinical examination, X-rays, and genetic testing. While there is no cure for MHE, treatment primarily focuses on managing symptoms and complications. This may include regular monitoring of exostoses growth, pain management, physical therapy, orthopedic surgery for severe cases, and genetic counseling for affected individuals and their families. With proper management, individuals with MHE can maintain a good quality of life and functionality.
