Another cause of varied mystery symptoms is chronic Lyme, and other tick borne infections. That includes Lyme arthritis.
I am separating posts to try and make sure you answer everything. I am being very deliberate, not just saying random things. Everything is important.
Is she hyper flexible? There is Ehlers Danlos Syndrome which gives many mystery symptoms in mainly women.
"works in a children's hospital"
As a shot in the dark, she can ask around if there were any mystery cases there before she got sick.
"Her eGFR is 74 and since she works in the healthcare field she knows it should be around 116. The doctor told her it was normal."
That's an odd thing to say. 116 is average, minimum is 90 as far as I remember. Unless there is a valid reason for her creatinine to be high. The eGFR uses creatinine level in the calculation. Is she very muscular? High protein diet? Does she take the creatine supplement? Probably the answer to all those is "no".
Hopefully now you have more of a handle on how her doctors think. They went through all the usual steps and haven't found the answer. So we know that she's not a usual case. That doesn't mean we give up.
Here is what I would do for now.
1) a person can have lupus even though they have normal ANA
2) lupus can create many symptoms, it's called the disease of a thousand faces
3) one of the worst and more common results of lupus is destruction of the kidneys
4) I'd push for lupus specific antibody tests, such as dsDNA and Smith
"She had a rash on her feet the other day that itched"
What did she walk on? If it was like nettle or poison ivy, then that's not significant. But if there is no usual explanation then that can point to an immune dysfunction. Especially if it is recurring and mysterious, which would be very very significant.
It is not unusual at all for young, healthy, exercising women to get immune dysfunction. More so than men.
ESR is a blood test for acute (short term) inflammation. But it won't show chronic (long term) inflammation which would be more likely in her case. Still, ESR is going out of favor so it's not slacking if docs didn't do that test.
There are various other blood tests for chronic inflammation such as IL-6 and TNF and IL-1. Did she have those? She should. This is like a fishing expedition, and if any are high then that is a big clue.
The immune system is not well understood. Ten years from now, docs will look back at 2023 as being in the Flintstone Age of understanding the immune system.
"She traveled to Greece"
Foreign travel means a person might have gotten a bacteria or parasite that isn't well known to doctors back home. Or toxin. Was she there not long before she got sick?
"No family history of those things"
Family history would have made autoimmunity more likely.
"not sudden onset.."
That makes a post viral syndrome less likely. I take it she didn't have a "bad cold" before she got sick.
"just has progressively gotten worse over time"
Since what age? Think very deliberately about what changed before she got sick. Use logic. E.g., moving to a new home. Was there a divorce? Friend died? Got a new pet? Worked a summer on a farm or around chemicals? Started an extreme diet? Started extreme exercise?
"She got blood work which said she didn't have rheumatoid arthritis."
Right, that's why I'd mentioned docs who only go by the book. RA is not the only inflammatory condition to be considered. Not by far.
In modern medicine, docs pretty much have to go by the book (the "standard of care"), evaluate a patient quickly and don't have time for mysteries. We can't really blame them. Mostly.
Prbly because of kidney inflammation, which also causes the low eGFR. Or less likely, it could be that her system is trying hard to get rid of something bad. She should not restrict water, to try to prevent frequent urination.
Over time, she might end up low on electrolytes.
"constantly aches-non stop"
That's too general to go by, but look up fibromyalgia so you can compare, knowing her complaints better.
Be wary of docs who will suspect her of "drug seeking behavior".
Is there a family histopry of immune conditions, like Sjogren's, Raynaud's, severe allergies? What's her ANA test result? CRP and ESR?
Did she have sudden onset of her symptoms? Did she have a bad cold beforehand? Severe stress? Travel?
If not sudden onset, what changed in the year or two beforehand?
To a rheumatologist. Not just an average one who just goes by the book, but one who handles unusual cases.
Or an Internist that practices Functional Medicine.
She most likely has immune dysfunction, and it's not unusual at all for such patients to be wrongly referred to a shrink.
You can tell her to look into lupus nephritis and spondyloarthropathies -- which is NOT because she has either of those, but that DOES tell her what damage the immune system can do.