Prevalence of ganglionic AChR antibodies in postural tachycardia syndrome (POTS) (P1.276)

OBJECTIVE: To determine the prevalence and relevance of ganglionic AChR antibody in patients with POTS BACKGROUND: Postural tachycardia syndrome (POTS) is a common form of autonomic dysfunction characterized by inappropriate and excessive increase in heart rate when standing. The precise pathophysiology of POTS remains unclear, and several different etiologies may produce the same clinical syndrome. Association with various autoimmune disorders has been reported. In retrospective studies from the Mayo Clinic, low levels of ganglionic AChR antibodies were found in 7-14[percnt] of POTS patients. This seropositive rate may be artificially higher (due to retrospective referral bias) than the prevalence of ganglionic AChR antibody in routine clinical autonomic practice. DESIGN/METHODS: Through a patient support and advocacy group (Dysautonomia International), patients with dysautonomia were invited to participate in a study of serological markers for POTS. Patients (and healthy family members) provided clinical information, blood samples, and orthostatic vital signs. Blinded blood samples from 103 POTS patients and 66 healthy controls were tested for ganglionic AChR antibodies using validated radioimmunopreciptation assay. RESULTS: Five POTS patients (4.8[percnt]) and two healthy controls (3[percnt]) were positive for ganglionic AChR antibodies. Three of the subjects (2 POTS and one control) had very low antibody level (0.06 nmol/L; normal < 0.05). Antibody levels (0.08 - 0.11 nmol/L) in the others were lower than those typically seen in autoimmune autonomic ganglionopathy. CONCLUSIONS: In this prospective study of unselected but well-characterized subjects, a small minority of patients with POTS (5[percnt]) were seropositive. Neither prevalence nor antibody level was significantly different from healthy controls. At these low antibody levels, clinical specificity is poor. We will report the clinical characteristics of the five seropositive cases to determine if they represent a definable phenotype. Disclosure: Dr. Vernino has received personal compensation for activities with Chelsea Therapeutics as an advisory board participant. Dr. Vernino has received personal compensation in an editorial capacity for JAMA Neurology. Dr. Vernino has receive license fee payme Dr. Hopkins has nothing to disclose. Dr. Okamoto has nothing to disclose. Dr. Black has nothing to disclose. Dr. Dorminy has nothing to disclose. Dr. Paranjape has nothing to disclose. Dr. Raj has received research support from Dysautonomia International.