My father and I were just dna tested for cmt (the Dr's tested for the 4 main types). We both got negative results, but I know that a negative doesn't always rule out cmt. My father's neurologist diagnosed him purely on seeing him, as he does look like he has it, and has the symptoms. So my question is... I can only find that CMT1 accounts for 70-80% of cases, but what percentages account for the other types? (i.e. like, does cmt2 account for 10%, and cmtx for 5%, etc?). Bottom line I'm trying to figure out... if I got a negative test for the main 4, then what percent chance is it that I could still have it? Thank you so much to anyone who can help with any info at all! Sincerely, Amy
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HI Ilsesmi! Thank you very much for taking the time to reply to me I literally cried when I read your reply. Everywhere I turn I get different answers about my chances, so I've been (and kind of still am) so confused and concerned. But every time I hear possible good news (like I did from you), I feel more hope. Thanks again so much! I really appreciate it I pray for you and everyone suffering with CMT. Have a wonderful week, Sincerely, Amy
The tests you have had will have ruled out CMT 1A which accounts for the majority of patients and is the easiest to test, but a negative test only means that you don't have one of the four mutations being tested. There are many mutations known and more discovered all the time. Have you had nerve conduction test to find out whether you have demyelinating CMT or Axonal CMT? This will eliminate a section and refine the field. If you have Axonal CMT you may never know your exact mutation. My family have this type but all tests have been negative and we have been told that it is possible that the particular mutation exists only in our family. My sister has children and grandchilden so is entered into UCHL 's whole genome and exome project so that they can be tested before they show symptoms. But in the end it is the symptoms which matter, not the cause as the symptoms can be ameliorated, but the cause cannot be altered.
If your father shows symptoms and the diagnosis is confirmed by nerve conduction tests then he needs care ranging from orthotics and exercise to surgery and you need monitoring to deal with symptoms as they arise and slow down the progress of the disease.
HI REGreen Wow thank you so much for your detailed answer! You know so much about this... you sound like a doctor (and so far you are giving me more info than my own doctors). Doctors never take the time to go into detail and explain things. My dad and I have only had EMG's, so I will for sure be asking for a nerve conduction study now. Thanks again! Have a great 4th of July! Sincerely, Amy
Glad to be able help. The nerve conduction tests give immediate results so the neurologist should be able to tell you at the time whether you have a demyelinating for or an axonal form of CMT. The tests are a bit uncomfortable. I found they got to the point where I felt I would have to ask to stop just as they did stop, but it was no worse than a trip to the dentist and did't last too long. There are things which can be done to reduce and delay the progress of the disease so don't hold back in asking about treatment and aids.
I have just been given some wise advice by a specialist physiotherapist,- Concentrate on doing what you can do as well as possible and stop fretting about the things you can no longer do. This was not what I wanted to hear but was better advice than my desperate striving to still do what I could do at 25 (many years ago).
I love that advice And thank you for the heads up on the nerve test. It's great to know it gives instant answers, as opposed to that long 3 months waiting for the dna. Thanks again for everything! Have a great summer
Hi again, I wanted to ask your thoughts on this. I sent this to the two other people who replied as well. But I really want to know your thoughts too (if you have time, as its a long email).... My Dr said that my genetic test checked for all of the following within this link:
So based on everything listed in that link, my test came back negative. My father's did as well. But then his neurologist told him "well I guess you have the unknown cmt which accounts for 30%". Then I asked my Dr, and he said that only 10% of people with cmt have the 'unknown/un-named' version. So my question to you is... in your opinion, do you think that I don't have CMT, since my father and I were both negative for all of the main 4 cmt versions? My Dad's doctors are diagnosing him based on his legs and drop foot and neuropathy. I mainly just have neuropathy (but it started at age 36). But my Dr said it's pretty unlikely that I have cmt, but every doctor is telling me something different. I think that since cmt is 1 in 2500, and I'm negative for the main 90%, that would make my chances something like 1 in 25,000? Ugh, it's all just so confusing. I just need opinions on if I should worry that I have this 'unknown' version of CMT, because my son is 23 and getting married and having children in the next few years, so I need to find out. I'm going to get the nerve conduction test for sure. But I still would love to you know opinion based on the genetic testing being negative for us. Thank you so much again... I really appreciate it! ~ Amy (ps. basically I just want to know if it were your friend asking "do you think I have it based on this"... what would you say... yes or no (most likely, as nothing is for sure).
You say you were tested for CMT1 - did this include testing for CMT1b MPZ Mutation as this is a rarer sub type of the CMT1 group only affecting smaller percentage I think something like 6% of the population. CMT1A is the most common type of Charcot Marie Tooth disease and the percentages you quote I think may apply to this type. It might be worth asking if they checked this as well?
Thank you so much for taking the time to write such a nice informative email. If you wouldn't mind... my Dr said that my genetic test checked for all of the following within this link: genedx.com/wp-content/uploa...
So based on everything listed in that link, my test came back negative. My father's did as well. But then his neurologist told him "well I guess you have the unknown cmt which accounts for 30%". Then I asked my Dr, and he said that only 10% of people with cmt have the 'unknown/un-named' version. So my question to you is... in your opinion, do you think that I don't have CMT, since my father and I were both negative for all of the main 4 cmt versions? My Dad's doctors are diagnosing him based on his legs and drop foot and neuropathy. I mainly just have neuropathy (but it started at age 36). But my Dr said it's pretty unlikely that I have cmt, but every doctor is telling me something different. I think that since cmt is 1 in 2500, and I'm negative for the main 90%, that would make my chances something like 1 in 25,000? Ugh, it's all just so confusing. I just need opinions on if I should worry that I have this 'unknown' version of CMT, because my son is 23 and getting married and having children in the next few years, so I need to find out. I'm going to get the nerve conduction test for sure. But I still would love to you know opinion based on the genetic testing being negative for us. Thank you so much again... I really appreciate it! (I'm going to send this to the other person who replied as well, as I'm looking for as many opinions on my results as possible). Have a great day! Thank you, Amy
CMT is a Neurological Disease in which your "peripheral" nerves (near to, and sited just below your skin) are faulty: The myelin a (waxlike) insulation which wraps around these nerves to insulate them and contain a "strong-sinal"are defective: Therefore the electrical signals "to and from" the brain to your various muscle groups are weak, and "leak" resulting in over a very long time, these normally lower limbs will start to waste away (Atrophy):
A neurologist is the only medical professional who can diagnose CMT:
This is normally done by sending phials of blood to a specialist university laboratory: The results will take 6 weeks to return, and will identify the exact type of CMT gene mutation that you have:
The last time I checked the cost(s) to your local NHS Medical Trust is around £10,000: A Nerve Conduction Study (very uncomfortable) is also used to support your diagnosis:
Sorry at this time there is no known cure for CMT: You can only adopt, accept
this disease by your own personal 'MANAGEMENT' attitude, including accepting each downward change and saying "CMT get lost, as you aint' gonna beat me" : ! ! !
Thank you so much for your message John I did get the lab test done which was negative for all of the main ones. Luckily here in the US it's very inexpensive (but you are correct in that it took 6 weeks). So now I just need to get the nerve conduction test done. Thank you again for the information! Sincerely, Amy
Remember a "Nerve Conduction Study" may no be suitable as it can be most painful:
Warning ? It is definately NOT suitable for children:
A round metal frame is placed on your head, and conections are attached to your scalp: Then the technician, or sometimes a doctor then proceeds to probe the bodies "long-nerves" endings with an electrical probe (ouch) !which then records the speed (velocity/strength) of the signal(s) from the brain to the particular nerve ending point:
This test is not a definate diagnosis of CMT, it only used to assist, and support your Neurologist reach a confirmed diagnosis:
Your description bears almost no resemblance to the one I had in 2012 ! The tester only worked with my forearms and wrists and lower legs and ankles. There certainly wasn't a metal frame on my head - or anywhere else. I didn't feel a thing, but maybe that was because of the nerve impulses being almost non existent and mostly unmeasurable. She concluded that it probably showed slow speeds suggesting faulty myelin sheaths ( as in CMT 1A, later proved by a genetic test) but that the axons were also damaged.
I am wondering whether yours was some time ago and maybe the test has been streamlined or modified since...?
I am certainly not denying that other people may find it hurts, or that it may be unsuitable for children.
Thank you so much for taking the time to write such a nice informative email. If you wouldn't mind... my Dr said that my genetic test checked for all of the following within this link: genedx.com/wp-content/uploa...
So based on everything listed in that link, my test came back negative. My father's did as well. But then his neurologist told him "well I guess you have the unknown cmt which accounts for 30%". Then I asked my Dr, and he said that only 10% of people with cmt have the 'unknown/un-named' version. So my question to you is... in your opinion, do you think that I don't have CMT, since my father and I were both negative for all of the main 4 cmt versions? My Dad's doctors are diagnosing him based on his legs and drop foot and neuropathy. I mainly just have neuropathy (but it started at age 36). But my Dr said it's pretty unlikely that I have cmt, but every doctor is telling me something different. I think that since cmt is 1 in 2500, and I'm negative for the main 90%, that would make my chances something like 1 in 25,000? Ugh, it's all just so confusing. I just need opinions on if I should worry that I have this 'unknown' version of CMT, because my son is 23 and getting married and having children in the next few years, so I need to find out. I'm going to get the nerve conduction test for sure. But I still would love to you know opinion based on the genetic testing being negative for us. Thank you so much again... I really appreciate it! (I'm going to send this to the other person who replied as well, as I'm looking for as many opinions on my results as possible). Have a great day! Thank you, Amy
Thanks for your email. Your doctors seem to have tested you for quite a range of possible CMT causing mutations, but there are at least as many more known mutations which could be causing your symptoms, if you have CMT. More are being discovered regularly. The biochemical processes which control the production and maintenance of either the myelin sheath or the axons in your nerves are many and require a large number of genes to control them. Any one of the genes in the pathway could mutate and compromise function. It is quite possible that your family have a mutation which has not yet been identified, as in my family. Genetic testing sounds so scientific and cut and dried but it can only give answers within the known body of knowledge at the time of testing.
The question of percentages and probability is to some extent a red herring as there is not enough known to give precise figures and, as you have already found out, doctors do not all know all there is to know. It is difficult to say how many cases are of unknown mutations if patients are tested for a handful and told that their tests are negative and they are therefore not recorded as having CMT symptoms.
To carry forward your search you need to know whether you have a demyelinating (Type 1) form or an axonal (Type 2) form of distal neuropathy. Nerve conduction tests will give you the answer to this query. There are two factors in the passage of a nerve impulse; the speed and the strength, or velocity and amplitude. As John has told you if you have a defective myelin sheath the electrical current of the impulse will "leak" through the faulty insulation so that the velocity is reduced. If yours axons (nerve cell processes which conduct nerve impulses) are dying off, so you have very much smaller number of fibres to carry the impulse, the speed will remain normal but the amplitude will be reduced.
You may not get a precise genetic diagnosis yet, but things are moving fast and this may come before your son starts a family. However from a practical point of view the reason for your symptoms is less important than getting all the available treatment and monitoring of the condition within the family. If you have CMT you have it and it cannot be cured Remember that even with the same mutation different people have very different expressions of the same gene. My sister has more severe sensory symptoms while my motor function is affected. There are other causes of distal neuropathy as well as CMT. I have a friend with symptoms similar to mine who has autoimmune problems. He is helped by regular treatment with immunoglobulin.
You should also bear in mind that being diagnosed, or not, can have implications with regard to insurance, driving licences, employment, welfare benefits and financial transactions.
Wow, yet again you have been far far more informative than any doctors that my father and I have seen. You are truly an expert in this field and should be a neurologist. Thank you so much! I'm going to take all of your emails to my neurologist to ensure that I get checked for everything, and so that I know what all to ask him about. Thanks again so much to you, and everyone on this site... I'm very grateful! Have a wonderful weekend/week Sincerely, Amy
Thanks for your email. I'm far from being an expert. I'm a biologist with this annoying disease so I want to know as much as possible about it, which in our case is not a lot, as our mutation has not been isolated. My sister is in the whole genome and exome project at University College Hospital London so we may eventually get some answers. When it comes down to individual cases the pressing need is for recognition that you have a peripheral neuropathy and to get it treated as far as possible. You already know that diagnosis is not easy or clear cut. Most people with CMT find that diagnosis takes years. My family had been taking our wobbly ankles and sore, numb feet and hands to doctors for more than thirty years before my sister and I were diagnosed in 2008. My father was never diagnosed and had four knee replacements as nobody looked a few inches further than his knees and saw that his ankles were the problem
It is very hard when you finally get your suspicions that you have more than normal wear and tear confirmed. On the one hand it is a relief to know that your problems are not of your own making and that you could not have reduced them by living a different life style, but on the other hand you have to face the loss of your plans and expectations and the guilt of possibly passing on faulty genes to your offspring. It is like a bereavement when you have to face the fact that the employment, travels and plans you had for your future may have to be modified and that the person you thought you were has changed and will change more. Apart from worrying about your son and his future children being affected, knowing which mutation you have is not really going to make much difference to your treatment. Getting appropriate treatment to ameliorate symptoms and delay the deterioration as long as possible is the important thing . I hope you have a successful session with a neurologist and your father gets the treatment he needs to make life more comfortable.
I was first diagnosed with CMT 1 based on nerve conduction tests. I then saw a specialist who said it was most likely CMT 2. Nerve and muscle biopsies confirmed axonal problems. It is common to have low NCV results and still have CMT 2. A diagnosis between CMT 1 and other types can't always be determined by NCV results.
I have had a complete battery of genetic testing about 5 years ago and again this year. Close to 100 genes were evaluated including 9 very rare ones. Still no diagnosis.
Hi we are still yet to be diagnosed but i feel its Cmt2 and thats not common so as my cousins all have cmt1c my genetic neurologist sent our blood to get dna tested in dec last year as im sure we have the same un known litaf gene with poddibly a new mutation im still waiting on answers meanwhile my daughter now 7 is getting no treatment at and has toe walked her whole life her achilles tendon will probably have to be stretched due to no castings physio these rare cmt diseases might never get diagnosed they just seem to be more interested in the unknown gene ? Looking at our feet same phenotype everything points to cmt i wish i had a dr like your dad! How long did your dna test take ? I feel as though the past 3 years got us nowhere only frustrated
Hi Ally ~ My doctor used genedx (a saliva test that was mailed to me, I spit in the tube, then mailed it back). It took about 6 weeks until I received the results. It only costs $250 without insurance. It has the same accuracy as blood tests from any other companies. I wish you all the very best! God bless you and your family, Sincerely, Amy
This past February I submitted a sample of saliva to Invitae and was checked for every known type of CMT. Close to 100 genes have malformations causing the known types. No hits on any of them.My symptoms are classic CMT. Hand and and foot weakness and muscle wasting, poor balance, etc. I am 69 years old and, other th an loss of sensations in my feet, I had no other suspected neurological problems. At 64 years of age I found out what cmt is. Thankfully I can walk well, although not always in a straight line, with just foot braces to prevent drop foot.
I do sometimes worry about getting a field sobriety test. I would fail miserably, I'm sure.
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I literally cried when I read your reply. Everywhere I turn I get different answers about my chances, so I've been (and kind of still am) so confused and concerned. But every time I hear possible good news (like I did from you), I feel more hope. Thanks again so much! I really appreciate it 
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