Orthostatic intolerance (OI) is in short a disorder that is characterized by the impossibility to stand up straight. It has an overlap with ME (myalgia encephalomyelitis) and POTS. Momentarily a lot of research is done in the area of ME. Especially in the area of orthostatic intolerance a lot of progression is seen.
Simply said it is impossible to stand or sit up straight (for a longer period of time). When the patient is in an upright standing/sitting position the next symptoms occur: fatigue, nausea, lightheaded, heart palpitations, sweating and sometimes fainting. An important characteristic is that the complaints start/increase if you get up and decrease again if you lie down.