pin point diagnosis

[Pistol]

I have a question regarding classification of dysautonomia symptoms. Here is the story: my sisters, mother and several nieces all have a dysautonomia diagnosis ( mine is definitely HPOTS ). Everyone else shares the same symptoms as me ( high BP, tachycardia, syncope, fatigue, brain fog, cold hands and feet etc ) , except one sister. She shares all of the symptoms EXCEPT syncope and tachycardia. She sees the same autonomic specialist as me ( he diagnosed me with HPOTS by drawing neurotransmitters and based on symptoms ), but since she does not have tachycardia she does not have a diagnosis of HPOTS. She had 2 TTT's which both were considered normal ( her BP went up but HR stayed normal ). She had no further autonomic testing so far. Her current diagnosis is autonomic disorder and autonomic neuropathy. 

I have researched both of these conditions and find that they are pretty much a catch-all diagnosis for everyone with dysautonomia. My sister lives in Europe and has problems getting approved for some medications b/c of the non-specific diagnosis. She will be undergoing extensive testing soon to try and find the actual condition that causes her symptoms ( she is disabled from it ). 

Does anyone have an idea what could be the reason she is different from the rest of us? And why would she not have tachycardia? (She did always have a slower HR, even in childhood. )