>>blood test for PFAS, ... perhaps this would be indicated as a rule-out possibility

So, dialysis? Chelation? I understand that misunderstanding the root causes of a condition risks using a treatment that does nothing, or worse makes the symptoms worse (e.g. anti-depressants for the patient you mention) but do we have any kind of treatment for this? Those two are what I first thought of, but if it's microplastics causing inflammation in the CNS I've no idea other than an anti-inflammatory that can cross the BBB.

Speaking of CNS inflammation, there is some evidence associating chronic inflammation with dementia.

Just wondering aloud...