I'm sorry and can imagine your concern as a mother.

Typically CSS presents in confusing ways making diagnosis difficult, as I'm sure your son found out. Luckily, Mayo, Rochester provided a diagnosis. Hopefully, it helped bring closure for your son.

From my experience of living with CSS, and learning a great deal about it while attending Mayo Clinic's Pain Rehabilitation Program, its my understanding that aging may add to aches, pains, pyschosicial change and the ebbs and flows of CSS. What I learned in class was that symptom-management of CSS stems from an all inclusive approach of mind and body. The importance of physical activity, emotional support, cognitive behavioral therapies, and chemical management all remain just as important no matter the age.

I found these government articles that might be helpful in exploring CSS -

The Effects of Age on Pain Sensitivity:

- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565621/

Psychosocial Factors and Central Sensitivity Syndromes:

- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728142/

Although I am not a medical professional, I don't think organs can be harmed by CSS as the disorder is a central nervous system malfunction.
False signals travel via the spinal cord to the brain. The brain receives louder messages as the body feels hypersensitivity without there being actual damage. The tricky part with CSS, however. is deciphering when there are false signals versus acute harm. I can understand that becoming a challenge as one ages.

Here is a video from Mayo Clinic's Dr. Sletten addressing CSS. He runs the Florida Pain Rehab program. I hope it may help bring clarification.

Given that CSS is a disorder not a disease it is likely best to be self managed and somewhat controlled by lifestyle choices as taught in the video. How has your son been managing his CSS over the past 5 years?