Physiology of GCA and PMR

I am curious about how this all happens e.g. why do the giant cells gather in only some arteries, how come when they worry about the giant cells interrupting the blood flow to the optic nerve why do they cut the temporal artery...

None of this is very important but I wondered if anyone can point me to any physiology for non medics that might satisfy my curiosity?

I 'Dr googled' temporal artery biopsy but the you tube video of the op was NOT the sort of thing I had in mind!

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  • As far as I know the giant cells in GCA only form in arteries that have a specific structure - an elastic component to their walls. There are various sorts of giant cells and they are probably formed by the fusion of cells which have a single nucleus to form cells with multiple nucleus. However - no-one knows why it happens or the details of how.

    The temporal artery is used because historically it was the one they saw becoming enlarged due to inflammation. That is why the other (less accurate) name for GCA is temporal arteritis. It is also a superficial artery that can be got at easily and isn't essential - they can just tie it off cut out the bit to look at. What is called collateral blood flow eventually replaces the supply to the areas the other side - new arteries grow to provide bypasses. Almost all other arteries lie too deep to be biopsied without proper surgery - although they do sometimes take biopsies of the aorta if they happen to be doing open heart surgery.

    If they do PET scans (using a radioactive tracer) you can see inflamed tissue in many arteries - but the only time you can do the histology to demonstrate the giant cells is on cadavers. The case of GCA often quoted for young victims is one of those - the pathologist found giant cells in arteries of a 37 year old who had died of a stroke which was probably caused by the GCA.

    As the well known black joke says - pathologists know it all, but it's too late.

  • Hi Pmrpro,

    Very informative reply thanks. Taking into account of what you have posted, is it therefore possible to do a PET scan to see if GCA is still present?

  • Not if you are still on any pred - even 5mg is felt to interfere a LOT with the result although if you can reduce that far they may do one. Though I don't think you could really take it as "it's gone" - it is more use to say "it is still active".

  • Thanks a lot for your reply. I take your point about the pred interference. A I am on 5mg at present , it appears that symptoms are the best measure.

  • Thanks PMRpro for taking the time to give answers to my 'musings'. I so like things to make sense. 😖

  • I like musings - it's what really makes all the forums fun (I know, I should get out more!). Sorry I can't give a better answer!

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