Hi there and thanks for your question. I'm sorry to hear that your cat is having these problems.
The yellow is jaundice which is either due to a liver problem or a problem with the body destroying red blood cells. However, the friable skin you have described makes me think this is most like a liver condition.
These are often treatable. I would highly advise a vet visit as soon as possible.
I hope this information helps! If you have more questions regarding this problem, just hit reply. If I am online I will respond right away. Otherwise I will respond as soon as I come online again. Or, if my answer is sufficient, then please hit accept. Thanks!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.