I'm just a laymen but I really think the boundaries can get pretty stretched with orthostatic intolerance and all sorts of combinations can show up.....That's my gut feeling.
might have some ideas on this....she has an different form of OI.
There are so many subset forms of POTS. We can't all be treated the same either. What works for me, may not work for someone else.
I have more high blood pressure than not. It will go up with standing. There are drops, but mostly back down to normal - but that causes symptoms.
However, POTS isn't DXd on what your blood pressure does. It's based on what your pulse rate does. It is supposed to go up at least 30 points from lying. Or to 120. At my worst, mine was about 170 (that we measured) from lying to standing - no exercise required.
The different subsets have similiar but different things going on with their body.
I have abdominal and leg vein pooling. But do better with an abdominal binder and not so good with leg compression. Not only will it hike my blood pressure higher it makes my neuropathy in my legs worse.
Many POTS people do better with vasoconstriction, I don't. I use vasodilators. (That's where you have to be careful with the meds.)
Since I have more high bp I don't need extra salt. I also have very low aldosterone - again not much salt. (Usually docs would use diuretics with that. Not with POTS. We have issues getting water into our cells properly. We feel dehydrated a good bit of the time.)
With the Hyperadrenic subset of POTS, most of us have high NE levels with standing. Some so high they will check for adrenal tumors. That gives a very unsettling surge with tachycardia and anxiety feelings. But, our body is trying to get blood to our head and heart and is trying to compensate for our bodies inadequate function.
(Hope that helps.)