Postural Orthostatic Tachycardia Syndrome Is Associated With Elevated G‐Protein Coupled Receptor Autoantibodies

Abstract

Background The etiology of postural orthostatic tachycardia syndrome (POTS) is yet to be established. The disorder is often misdiagnosed as chronic anxiety or a panic disorder because the autonomic failure in these patients is not severe. A growing body of evidence suggests that POTS may be an autoimmune disorder. Antinuclear antibodies and elevations of ganglionic, adrenergic, and muscarinic acetylcholine receptor antibodies have all been reported. Methods and Results We collected detailed clinical symptoms of 55 patients diagnosed with POTS. We also evaluated serum levels of autoantibodies against 4 subtypes of G‐protein coupled adrenergic receptors and 5 subtypes of G‐protein coupled muscarinic acetylcholine receptors by ELISA. Our patients had a multitude of comorbidities, were predominantly young females, and reported viral‐like symptoms preceding episodes of syncope. We detected a significant number of patients with elevated levels of autoantibodies against the adrenergic alpha 1 receptor (89%) and against the muscarinic acetylcholine M4 receptor (53%). Surprisingly, elevations of muscarinic receptor autoantibodies appeared to be dependent upon elevation of autoantibodies against the A1 adrenergic receptor! Four patients had elevations of G‐protein coupled autoantibodies against all 9 receptor subtypes measured in our study. Five POTS patients had no elevation of any autoantibody; similarly, controls were also negative for autoantibody elevations. There was a weak correlation of clinical symptom severity with G‐protein coupled autoantibodies. Conclusions Our observations provide further evidence that, in most cases, POTS patients have at least 1 elevated G‐protein coupled adrenergic autoantibody and, in some instances, both adrenergic and muscarinic autoantibodies, supporting the hypothesis that POTS may be an autoimmune disorder.

Keywords

• adrenergic receptor
• antibody
• autoimmune
• hypotension
• muscarinic receptor
• postural orthostatic tachycardia syndrome