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What is MHE?
Multiple Hereditary Exostosis (MHE) is a genetic condition that causes people to develop growths called exostoses or osteochondromas on their bones.
How Does MHE Affect the Body?
People with MHE often have growths on long bones, like the arms and legs, but they can appear anywhere on the skeleton. Osteochondromas very rarely grow on the face or skull. The growths can vary in size and shape. For some people they do not cause problems, while for others they can lead to pain, reduced movement, or challenges with alignment and how bones grow.
The severity of MHE can vary widely, with some individuals having only a few osteochondromas and mild symptoms, while others may develop numerous growths that can cause significant challenges and physical limitations.
What Causes MHE?
MHE is primarily caused by mutations in the EXT1 or EXT2 genes. These genes disrupt the normal growth of bones leading to the formation of benign bone tumors. They genes play an important role in the production of heparan sulfate, a molecule that regulates cell growth and differentiation, particularly in cartilage. Mutations in either of EXT 1 or EXT2 genes disrupt the normal functioning of cartilage cells, leading to abnormal bone growth and the development of multiple osteochondromas.
MHE is autosomal dominant, which means it only requires one copy of the mutated gene to inherit MHE. This is why some families have many people with MHE.
Sometimes MHE is caused by a random genetic mutation and only one person in the family has MHE. This person can pass MHE onto their children.
Types of Osteochondromas
Osteochondromas are classified based on their shape into two types: pedunculated and sessile.
Pedunculated Osteochondroma are connected to the bone by a narrow, stalk-like structure, resembling a mushroom.
Sessile Osteochondroma have a broad, flat base that merges more directly into the bone, without a distinct stalk. Sessile osteochondromas tend to appear as wide-based elevations of the bone surface and, while less protrusive than pedunculated osteochondromas, they can still cause discomfort or deformities as they grow.
How is MHE Diagnosed?
Doctors, most often Orthopedic Surgeons, diagnose MHE through a combination of medical history, physical exams, genetic testing, and imaging tests like X-rays. These tests help doctors see the growths and check how they might be affecting bones and joints.
Receiving a MHE diagnosis, whether inherited or a random mutation, can be overwhelming. Often people with MHE are diagnosed at a very young age before they are symptomatic, when parents notice a bump.
When someone is diagnosed with MHE at a young age it can be difficult to understand what the diagnosis means. Every MHE journey is unique, and it is impossible to forecast the road the patient and family will encounter through childhood and beyond.
Information provided on MHELS.org is for educational and informational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment. Always consult your healthcare team for decisions regarding your care.
The MHE Learning System (MHELS) is committed to improving the lives of people with MHE through collaboration and shared learning.
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