IL21 and postural orthostatic tachycardia syndrome: We believe that the identification of increased levels of pro-inflammatory cytokines IL-1β, IL-21, TNFα, INFα, and TNF receptor (CD30) in POTS patients with autoantibodies against adrenergic and cholinergic muscarinic receptors is highly suggestive of a coexisting inflammatory process that contributes to the disorder and requires further study.