PIP - Current Claim - what happens if have a new unrelated medical diagnosis

Hiya, my PIP was recently reinstated and back dated to last August but only after mandatory reconsideration was denied and my claim was registered with the tribunal service. Original claim has been ongoing since 1998 which used to be DLA and is for brain damage and a myriad of neurological fallout after a car accident in 1997. However there is now a big twist since last August when my pip was stopped. I was diagnosed with cervical cancer in December and have been through some heavy chemoradiation which finished in early March .. got 'the big scan' in 2 weeks to (fingers crossed) be told all is going to plan and its not detectable ... ive battled with horrible side effects most of this year but havent even mentioned it to PIP as their rules state 'only if it affects you day to day' and ive definately been far too poorly to even think about it.... this however is not the biggest twist in the tale. I had about 4 days once all treatment side effects had really started to subside maybe early April but then my body just failed ... now looking back to before diagnosis there were a few clues as to what could happen next but there was so much more going on that like cancer symptoms put down to perimenopause. Anyway long story so I apologise ... I woke up just over a month ago with giant swollen eyes and couldn't open them and my body would hardly move and it hurt so much .. fast forward after so many blood tests and no improvement its looking I may have a rare autoimmune condition triggered by my own immune system inotially attacking cancer cells but then for some reason it attacks muscles and skin ...ive been referred for an urgent skin biopsy to confirm or to point to a different diagnosis either way my blood is positive for autoimmune antibodies. Honestly im an absolute mess I can hardly walk, im having to hoist my legs up steps and can barely hold my phone and thats my limit everything else is out of the question The specific condition they are testing for is called Dermatomyositis which ive had a look (i camt remember where) this diagnosis has a 70% acceptance rate for PIP obviously its according to how symptoms / treatment may affect me down the road. So my question is this please - If in the near future this becomes my existence can I / is it frowned upon to add further diagnosis to a claim ? Can you only use one condition per claim ? Would i have to start all over again ? I already get LCWRA for UC would I have to go through that again ? I currently only get low rate daily care for PIP. The Macmillan advisor at CAB did my appeal for me during treatment and 3 weeks later PIP decided they had made a mistake and instead of the total 2 points they originally gave me they gave me 11.. im very thankful for her for doing that. Since then though all of this other stuff has snowballed so I was wondering where / how I stood with claims going forward. Thankyou I know its long wimded