An unusual case - appears intolerant to B12

We get lots of letters requesting advice, and most of them are too personal to post; but I thought this was a particularly interesting one.

The patient was due to have her two-monthly injection of cyanocobalamin, however she's been told that cyanocobalamin is no longer available and she'll have to take hydroxocobalamin.  The last time she had hydroxocobalamin it caused a terrible itchy rash.

OUR ADVICE

The patient is under the care of an understanding doctor, though she is clearly exhibiting symptoms consistent with B12 deficiency.  I'm responding to an email so I don't have a complete list of symptoms and blood test results, nor do I have the patient in front of me to recognise symptoms that might indicate something else, which the patient doesn't mention in her email.  So we aren't going to diagnose her, but we can offer the following:

1. some people do get symptoms when they first receive B12 treatment.  Symptoms typically include rashes, itching, acne on the face,neck and shoulders, and even some other lumps and bumps in the skin.  These are fairly rare (1-3%) and seem to go away within a few days.  We think they are the body's successful efforts to get rid of any accummulated toxins, through the largest organ in the body which is the skin.  if you stop taking B12 before the toxins have been removed, then you will just make up for it next time you take B12 as the body will have another go at getting rid of the toxins - far better to work through it but of course that's fine for me to say as I'm not the one suffering
2. cyanocobalamin may be practically ineffective in some people (the main reason that it is no longer available on prescription), which is why it wasn't triggering the same reaction.  Incidentally, the patient's other symptoms didn't go away whilst she was on treatment with cyanocobalamin
3. in a very few people (it may be as few as 1 in 4000), taking methylcobalamin or substances that turn into methylcobalamin (eg hydroxocobalamin) may develop an imbalance between methylcobalamin and adenosylcobalamin.  Usually the body uses these two in different places (methylcobalamin in the cell and adenosylcobalamin in the organelles I think) and they change from one to the other with no problems, but it is just possible that in some people, high levels of one upsets the reaction that changes one into the other, so the body kicks up a stink.  These people have found that taking adenosylcobalamin seems to restore their energy and enthusiasm (and everything else) - adenosylcobalamin can be bought as dibencozide which is an oral preparation
4. the most important thing, as always, is to talk about this with your GP.  They are there to discuss your needs and they can see you and take further tests, and refer you as appropriate, and of course if anything goes wrong, they are there so they need to know what you've been doing.

the patient is still corresponding so we'll see what develops - a very unusual case!