charcot-marie tooth.o date there's no cure. >> basically what it is is it is a disorder of the peripheral nerve and that is like the wire that takes the signal from the brain and send it is out to the muscles and all the things in the preferry that you need to sense your environment and act on your environment. >> classified as a rare disease cmt affects 1-2500 people in the u.s. generally speaking a disease as rare if it afflicts fewer than 200,000 people. many of these diseases are genetic. but in truth, there's nothing rare about rare diseases. >> conditions like for instance, hearing loss or deafness, there's many genes that can -- in which mutation can lead to hearing impairment. but in one specific family an individual single gene will be responsible. so in the mixture of the phenotype of how many people can have hearing impairment it's not as rare as people think it is. the same goes for conditions like developmental delay or even birth defects. 2-3% of all children are born with a major birth defe

charcot described it way back then, it's only in the last 20 or so years that we actually have treatments that are disease-modifying. in fact, when i was training in neurology at mass general with steve hauser, we had very little we could offer our patients. but at the beginning about 20 years ago, we found a beta interferons and copaxon seemed to work in ms by decreasing the inflammation you can see in the brain. and we can actually see that in the mri scans. and they seem to work by modulating the immune system in some way. and actually there are lots of different theories about how that happens. it's not entirely clear but it is-- what is clear is that the immune system is being affected by these therapies. the problem with those therapies was that they were relatively modest in efficacy. there were inconvenient because they were injectables. some were every day injections. others were every other day or once a week. so that left a high unmet need. and using the understanding of the biology of ms, many people went after better drugs. and about six or so years ago tysabri was the next d