Table 1:

Comorbid conditions associated with postural orthostatic tachycardia syndrome^*

Comorbid condition	Common clinical features	Prevalence, %
Migraine headaches	Frequent headache, often throbbing and unilateral May be associated with a prodrome	40
Hypermobile Ehlers–Danlos syndrome and hypermobile spectrum disorder	Hyperextensible joints with frequent subluxation Substantial peri-joint pain	25
Myalgic encephalomyelitis/chronic fatigue syndrome	Profound fatigue with regular activities Postexertional malaise	21
Fibromyalgia	Serious and diffuse myofascial pain	20
Autoimmune disorders	Often previously diagnosed Chronic dry eyes or mouth	16
Mast cell activation disorder	Strong allergic tendencies Dermatographism Frequent severe flushing	9
Celiac disease	Abdominal cramping and diarrhea Gluten sensitivity	3

^*Data adapted from Shaw and colleagues⁴ using Creative Commons Attribution (CC BY-NC-ND 4.0) licence.