Introduction: Postural Orthostatic Tachycardia Syndrome (POTS) belongs to a group of orthostatic intolerance syndromes. It is defined by the increase in heart rate ≥30 bpm or heart rate higher than 120/min during first 10 minutes after standing, without significant decrease in blood pressure. It is a rare disease, typically affecting younger females. The dysregulation of autonomic nervous system plays a key role in the pathogenesis. The autonomic dysbalance can be caused by various neurohumoral mechanisms, receptor hypersensitivity, hypovolemia, mast cell dysregulation and last but not least, autoimmunity. The presence of autoantibodies targeted against various adrenergic and muscarinic receptors, as well, as angiotensin or endothelin receptors, has been identified in some but not all patients with POTS.

Case Description: We present a case of a young patient with an overlap syndrome of POTS and vasovagal vasodepressoric syncope diagnosed with the head up tilt test, without any identified trigger. The laboratory investigation documented the presence of anti-alpha-1, beta-1 and beta-2 adrenergic receptor antibodies, antimuscarinic receptor 3 antibodies and antibodies against angiotensin II type 1 receptor. MIBG (metaiodobenzylguanidine) scan has not revealed any changes in the sympathetic inervation of the heart. The initial treatment by betablockers, as well as by ivabradine failed. On midodrine medication, the symptoms of postural tachycardia and the reflex syncope improved.

Conclusion: The role of autoimmunity in POTS is currently studied, though the role of autoantibodies against autonomic nervous system in the pathogenesis of vasovagal syncope remains unclear.