Multiple Hereditary Exostoses/Multiple Osteochondromas (MHE-MO) is an affliction of the skeleton, which affects the long bones (e.g. arms and legs), pelvis, ribs and the shoulder belt. It is characterized by a large number of benign bone tumours (exostoses/osteochondromas) which have a cartillage top and sometimes a slime bursa. The osteochondromas develop often at a very young age and grow very much particularly during the growth time of the organism. The MHE-MO is a hereditary syndrome which is autosomal dominant. This mean that an MHE-MO patient has a 50% chance to transmit the syndrome to his / her child. In some 38% of the cases there is a situation of a so-called spontaneous mutation and a child can therefore develop MHE-MO while none of the parents have it themselves. MHE-MO is caused by one of 2 known genes, namely EXT1 or EXT2 on chromosome 8 and 11, respectively. MHE-MO is a rarely forthcoming condition which occurs at a rate of about 1 case by every 50.000 people according scienes literature. However there is estimated that there are about 600 individuals in the Netherlands who have MHE-MO.
The World Health Organization (WHO) changed the name of the MHE as syndrome to Multiple Osteochondromas (MO), because the term "exostoses", bone outgrowth is confusing and unspecific. According to WHO the diagnosis of MO is applicable when at least two osteochondromas have been found at a patient. Besides there must be one of more family members with MO known or a mutation in one of the EXT- genes. In Dutch we use the name "Multiple Osteochondromen". Within the HME-MO Association we use both names for the time being, "Hereditaire Multiple Exostosen" and "Multiple Osteochondromen" (HME-MO) The diagnosis of MHE-MO is relatively easy to make for a specialist, based on X-ray pictures. Sometimes additional examination is required with the help of MRI scans. An orthopaedic surgeon may ask a genetic examination in order to confirm the diagnosis. The specialist may ask the Bone Tumour Committee of the Netherlands for advice without any costs involved.