CMT blood result negative, now what?

[KayJayTee]

Hi all,

Following our initial shock that our son may have CMT, the blood tests came back negative.

Everything points to CMT:

Nerve damage arms and legs

Scoliosis

High arch feet

Foot drop

Muscle atrophy

Age of onset: 15

After being on here and getting lots of support. We started to look at CMT differently.

Now this has thrown a spanner in the works and we are fearing it may be something more sinister.

Can you have a negative test and still have CMT?

Thank you for reading.

[HorshamMalc]

I'm not medically trained but, having done a fair bit of background study on CMT, I'm not aware of any form that doesn't result from a genetic abnormality. It's also familial so very likely there would be others in your family with symptoms, if it were CMT, though they may be very mild. Another possibility is a faulty blood test? I've no idea how likely, or otherwise, that might be.

Good luck with getting a conclusive diagnosis and suitable therapy. Malcolm

[KayJayTee in reply to HorshamMalc]

Thank you Malcolm 🙏

I just spoke with a lovely lady at CMT UK and given the timescale (less than 2 months) it is likely they only looked for CMT1A & X. Like you said, it could also possibly be a faulty blood test.

Another point is my sons foot drop has completely reversed after a week of physio. This is not normal with CMT.

I think I may have some symptoms of CMT (muscle twitching, burning/freezing cold hands and feet , high arch numbness in fingers etc) but nothing that bothers me or noticed until this year. My sister and dad both suffer with severe cramps. My sister has high arched feet and can’t walk far.

It is all a mystery and I am a year into this already and still no diagnosis. My next neurology appointment is not until late December.

I will post my updates here.

Thank you for responding 🙏

[Amanita in reply to KayJayTee]

Hi, KayJayTee,

As I understand it, there are about 100 genes involved, any one of which can cause the symptoms of CMT by being faulty - and new ones are being discovered.

I believe that with the blood test they probably only look at the more common CMT-causing genes, so that could be why a test comes back negative.

CMT can begin to make itself apparent at various ages. With some people it is in early childhood and with others it doesn't appear until ones fifties. I think during ones teens is fairly typical. With some individuals the symptoms are apparently virtually un-noticeable, and with others they can be very severe indeed.

With CMT it is really more important to treat the symptoms - with exercises, walking aids, etc., etc., whatever is appropriate and helps one to lead a more "normal" life. Knowing (if possible) which gene is responsible becomes relevant when thinking of starting a family.

Of course I hope you will get some meaningful answers in December. At least meanwhile you'll have time compile a list of really good questions.

All the best...

[KayJayTee in reply to Amanita]

Thank you for responding Amanita,

It is great to hear other people’s input on this. Like you said, the speed in which the blood test came back (7 weeks) does suggest they only looked at the more common genetic mutations. If that is the case I will not be happy. These things take time and with Covid delaying things too it could be a long time before we get a diagnosis at this rate. In the meantime my son remains muscle thin and who knows what further damage is going on in his body and if it is another neuromuscular disorder. 😭Very frustrating and worrying.

CMT UK have been really helpful and have given me details of experts in this field. I am going to have to push through to get answers.

The fact my sons foot drop has disappeared; suggests it may not be CMT and possibly HNPP? Both have very similar symptoms.

Thank you I will compile a list of questions, that’s a great idea!

KJT

[cmt_exercise]

They likely didn't look for all the types of CMT. CMT-1A is the main suspect, but CMT 2 makes up a large percentage of CMT patients. If you're in the UK, get the consultant to run more thorough genetic blood tests. Here's a complete list of all that are currently known, but more keep being found on a regular basis: cmtcentral.com/cmt-types

Also, have you spoken about doing blood work in general? It'd be worth checking to see if everything else is okay, such as GH and IGF levels as these can be impacted by neuropathies.

[KayJayTee in reply to cmt_exercise]

Thanks for the advice. 👍

I don’t think we had GF and IGF bloods. What are they measuring?

DS had full blood count plus EPK and C-Pep; all came back normal.

🙏

[cmt_exercise in reply to KayJayTee]

GH: Growth Hormone and IGF-1: Insulin-like growth factor 1. They tend to only be tested in children who are showing issues early on in their childhood, but while it's not traditional to test for, it's worth checking these levels are normal as neuropathy can impact them, which could have life-long consequences such as increased muscle atrophy, or the inability to build new muscle through exercise.

[KayJayTee in reply to cmt_exercise]

Ok, very interesting thank you for this information. I will contact my GP tomorrow. 👍

[KayJayTee]

Hey there thank you for your message.

My son tested negative for 86 genes relating to CMT. Also his latest nerve conduction tests said he no longer had nerve damage. It’s a complete mystery, even tests looking at possible connective tissue issues are negative.

It’s amazing news but does not explain the foot drop, quadruple nerve damage (last year) curved spine and deviated septum.

I think this will be a long road and even then may not come to a conclusion.