I am so sorry to hear you are going through this at such a young age. It sounds like you are doing everything to find the diagnosis and I know this is difficult.
Dementia is a mysterious disease and not all is Alzheimers. It would be helpful for more people to do what you are doing even though it is so hard.

My husband is older-now 77 with MCI but I am wondering if it would do us any good to pursue more diagnostic testing. All he has had is an MRI and meetings with the neuropsychologist and geriatrician. I asked his PCP to order a PET scan. He was no help when I asked about looking at APOE-the PCP ordered a lipoprotein A test instead.

I have thought of further eval at a Mayo Clinic, but at our age what will we accomplish?

Thank you for sharing. I hope you find support here.