Pathophysiology of Dysautonomia and Postural Tachycardia Syndrome (POTS) in Post-viral Syndromes and COVID-19

Inclusion Criteria: * Female participants aged ≥18 years * Diagnosis of idiopathic POTS (neuropathic form with evidence of neurodegeneration on skin biopsy) or Long COVID with or without POTS * Age-matched healthy controls with normal autonomic testing * Symptoms consistent with POTS: orthostatic intolerance ≥3 months with a clearly defined antecedent event (infection, travel, surgery) * Orthostatic tachycardia \>30 BPM without orthostatic hypotension, associated with reduced cerebral orthostatic blood flow and hypocapnia * Availability of electronic health record Exclusion Criteria: * Known causes of small fiber neuropathy, including: diabetes, amyloidosis, lupus, Sjogren syndrome, cancer, Ehlers-Danlos syndrome * Other medical explanations for POTS symptoms