Hi Unique1
If you already have an enhanced award for daily care and or mobility - you are right - it cannot increase with a possible new diagnosis. If you have a standard award for mobility - it cannot increase after you reach state pension age - but if you have standard rate for care - it could do.
So if your award can't change, you can always wait until your next review to tell them of any new diagnosis or you can drop them a line - asking them to keep the information on file.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems