Signs of innate immune system activation with elaboration of pro-inflammatory cytokines has also been reported in a cohort of POTS patients. Secondary POTS
If POTS is caused by another condition, it may be classified as secondary POTS. Chronic diabetes mellitus is one common cause. POTS can also be secondary to gastrointestinal disorders that are associated with low fluid intake due to nausea or fluid loss through diarrhea, leading to hypovolemia. Systemic lupus erythematosus and other autoimmune diseases have also been linked to POTS.There is a subset of patients who present with both POTS and mast cell activation syndrome (MCAS), and it is not yet clear whether MCAS is a secondary cause of POTS or simply comorbid, however, treating MCAS for these patients can significantly improve POTS symptoms.POTS can also co-occur in all types of Ehlers–Danlos syndrome (EDS), a hereditary connective tissue disorder marked by loose hypermobile joints prone to subluxations and dislocations, skin that exhibits moderate or greater laxity, easy bruising, and many other symptoms. A trifecta of POTS, EDS, and Mast Cell Activation Syndrome (MCAS) is becoming increasingly more common, with a genetic marker common among all three conditions. POTS is also often accompanied by vasovagal syncope, with a 25% overlap being reported. There are some overlaps between POTS and chronic fatigue syndrome, with evidence of POTS in 10–20% of CFS cases.
Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon standing. Symptoms may include lightheadedness, brain fog, blurred vision, weakness, fatigue, headaches, heart palpitations, exercise intolerance, nausea, diminished concentration, tremulousness (shaking), syncope (fainting), coldness or pain in the extremities, chest pain and shortness of breath. Other conditions associated with POTS include Ehlers–Danlos syndrome, mast cell activation syndrome, irritable bowel syndrome, insomnia, chronic headaches, chronic fatigue syndrome, and fibromyalgia. POTS symptoms may be treated with lifestyle changes such as increasing fluid and salt intake, wearing compression stockings, gentler and slow postural changes, avoiding prolonged bedrest, medication and physical therapy. The causes of POTS are varied. POTS may develop after a viral infection, surgery, trauma or pregnancy. It has been shown to emerge in previously healthy patients after COVID-19. Risk factors include a family history of the condition. A POTS diagnosis in adults is characterized by an increased heart rate of 30 beats per minute within ten minutes of standing up, while accompanied by symptoms. This increased heart rate should occur in the absence of orthostatic hypotension (>20 mm Hg drop in systolic blood pressure) to be considered POTS. A spinal fluid leak (called spontaneous intracranial hypotension) may have the same signs and symptoms as POTS and should be excluded. Prolonged bedrest may lead to multiple symptoms, including blood volume loss and postural tachycardia.