This was posted on the lupus forum a couple of days ago. It explains as a cartoon film how the immune system goes wrong to cause autoimmune disease.
If you do decide to watch it, remember that this is adapted for lupus patients - for us with PMR and GCA the damage being done is to blood vessels, we do not get damage to other organs such as the kidneys or skin although sometimes there might be the brain aspect of brain fog. Also, there are not yet any autoantibodies that have been identified as being closely enough associated with PMR and GCA to be used for confirmation of that being what you have. They would also offer a handle to be able to develop targeted treatments. But it does explain the immune system going wrong quite well and might be useful to get through to partners and family why you feel so unwell despite being on "pills" - because this is still all going on in the background despite the pred.
The "music" is not my cup of tea - I can only assume that they wanted to make it all sound mysterious and threatening. Irritating would be my description!
PS However - if you look to the right of the download bar under the image, you will see 5 blue vertical bars. Click on that and you can reduce the volume dramatically and at 2 bars I found it wasn't too bad, at one bar they guy was almost whispering and I couldn't hear the plonking and wizzes.