D
Your appeal can only consider your conditions as they were at the time of the Decision being appealed, so you will need show that this new diagnosis affected you at that time, assuming this was the case, you also need any new evidence that you have about this diagnosis to be clear that it applied to you on the Decision date, if you can't do this then it is likely that the panel will exclude the change from it's deliberations.
If you appeal is unsuccessful, then you can make a new claim immediately.
If an award is made, but less than you believe you deserve then you can report a Change of Circumstances due to a new condition, but before you do look at the PIP Descriptors, there is no point asking to be reassessed if you can't score the extra points that you need for a higher award.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
