Evaluating the Effectiveness of Intravenous Immunoglobulin Therapy in Autoimmune Autonomic Ganglionopathy

Inclusion Criteria: 1. Participants aged 18 to 85 2. Participants have neurogenic orthostatic hypotension (fall in systolic blood pressure \> 30 mmHg). 3. Symptoms of orthostatic intolerance. 4. Antibodies to the neuronal AChR of the autonomic ganglia of \>0.2nmol/l. Results must be within 6 months of the screening visit and there may not have been any immunomodulatory interventions since the time of the antibody measurement or the sample will need to be reconfirmed at screening. 5. Participants must be willing to withdraw from medications that affect vasoactive and autonomic function for 5 half-lives during testing (with the exception of stable doses of fludrocortisone up to 0.2 mg/day) and adhere to a regular diet Exclusion Criteria: 1. Women of childbearing potential (WOCP) who are not using a medically accepted contraception 2. Pregnant or lactating females- if participants become pregnant during the trial they will no longer receive IVIG, but will be followed as part of the intention to treat protocol. 3. Severe depression and/or anxiety (score of \> 29 on the Beck Depression Inventory or score on the Beck Anxiety Inventory of ≥ 36) 4. Active psychosis is ineligible, history of psychosis will be eligible, but only after review with the patients PCP and/or treating mental health provider. 5. History of asthma 6. Other causes of autonomic failure (e.g., diabetes, amyloidosis) 7. History of allergic or anaphylactic reaction to humanized or murine antibodies. 8. History or presence of recurrent or chronic infection (recurrent infections defined as \>4 times per year). 9. History of cancer, including solid tumors and hematologic malignancies (except fully resolved and resected cutaneous basal cell and squamous cell carcinomas of the skin) 10. History or presence of vascular disease potentially affecting brain or spinal cord (e.g., stroke, transient ischemic attack, carotid stenosis (greater than 80%), aortic aneurysm, intracranial aneurysm, hemorrhage, arteriovenous malformation) 11. History of severe, clinically significant central nervous system trauma (e.g., cerebral contusion, spinal cord compression) 12. History or presence of infectious causes of encephalopathy or myelopathy (e.g., syphilis, Lyme disease, human T-cell lymphotropic virus type 1 \[HTLV-1\], herpes zoster myelopathy) 13. History of thromboembolic events or deep vein thrombosis 14. Platelet count \<100,000/mL, Hemoglobin \<8.5 g/dL, Neutrophils \<1.5 x 103/mL. 15. Serum IgA deficiency: Immunoglobulin A (IgA) level \< 7 mg/dL. 16. History of immunosuppression or HIV/AIDS 17. History of cardiac arrhythmia or angina, electrocardiogram (ECG) showing significant abnormality that the treating investigator determines may jeopardize the participant's health (i.e., acute ischemia, left bundle branch, or bifascicular block) 18. History of renal failure or creatinine \>2.0 19. History of previous allergic response to albumin. 20. Treatment with IVIG or plasma exchange within 6 weeks of study enrollment. 21. Active adjustments of other immunomodulatory treatments. Patients that are on stable doses of immunomodulatory medications (no dose changes within 4 months -including, but not limited to prednisone, mycophenolate mofetil or azathioprine) but still have elevated antibody titers and meet criteria for inclusion will be allowed to participate in the study.