Hello. New here. My daughter (14 y/o) has MCAD & OI at the least but it's looking more & more like POTS (actually, can someone explain the difference between POTS & OI?). After 2 yrs, we finally found an autoimmune specialist who will see her. Saw him Thursday & he ordered a whole array of tests. Anyway, we've battled tachycardia mostly. Her blood pressure typically drops some but not hugely (until yesterday). She doesn't really have much tingling in her hands & feet. There have been some scary heart rates but yesterday was the worst: 92hr…90/62bp lying 143hr…78/57bp sitting !!!! 240hr…54/27bp standing 2 minutes!!!!! This scared the crap out of me! Got her stabilized enough to go to ER and she had labs drawn (slightly askew) & an MRI (normal). Has anyone ever had this happen? We're still in the hospital, hoping to catch the tachycardia on an EKG (wants to rule out an electrical conduction issue). Obviously, I'm trying to figure out why this happened. Towards the end of last week she had a little bug (sore throat, etc) and her tachycardia (and overall feeling) has progressively worsened. She rarely ever catches viruses but when she does, they hit her hard. I would appreciate any advice or info y'all can share. Things have been pretty manageable up to this point but now, who knows? She needs to just be a kid and I'm afraid to let her out of my sight. Oh! Meds: Allegra D - 1 tab BID Florinef - 0.1 mg - 2 tabs BID Midodrine - 5mg - 1 tab TID Zantac - 150 mg - 2 tabs BID, I just restarted her on this the night before the 240 hr, thinking maybe it's a Mast Cell issue. We have so many unanswered questions. What type of POTS? Did the MCAD cause her POTS? Why have her overall symptoms gradually worsened over the past 2 yrs, even with the meds? Is this episode what's referred to as a POTS "flare"? Or a MCAD flare that culminated in this event (seems to me more POTS than MCAD because no hives or anaphylaxis)? What testing should be done while we're in the hospital? Please, Please, please help! Thank you in advance. God bless you all Hugs, Tonya