BACKGROUND: Autoimmune autonomic dysfunction is described in Myasthenia Gravis. In myasthenic crisis, the spectrum of autonomic dysfunction is hitherto uncharacterized. OBJECTIVE: The objective of this study is to describe the spectrum of autonomic dysfunction in myasthenic crises using the composite autonomic symptom scale 31 (COMPASS 31) autonomic symptom questionnaire and power spectral analysis of heart rate variability (HRV), which is a simple way of estimating general autonomic dysfunction. METHODS: Adult patients with myasthenic crisis from January 1, 2014 to March 15, 2015, were prospectively included in this study. The COMPASS 31 questionnaire for symptoms of autonomic dysfunction and power spectral analysis of HRV were assessed. These were compared with the patient\'s demographic and clinical parameters and with previous literature. IRB approval was obtained. RESULTS: Sixteen patients were included (M:F 3:1). 15/16 patents (93%) had autonomic dysfunction on COMPASS 31 questionnaire. The domains of involvement were gastrointestinal (80%), orthostatic (67.7%), pupillomotor (67.7%); sudomotor (33.3%), and vasomotor (13.3%). Parasympathetic dysfunction predominance was suggested by the symptom profile. HRV analysis showed a low frequency (LF) spectral shift suggesting slowed parasympathetic responsiveness (LF normalized unit (nu): high frequency [HF] nu mean 8.35, standard deviation +/- 5.4, 95% confidence interval 2.2-12.5), which significantly exceeded the mean LF nu: HF nu ratios of the majority of previously reported noncrises myasthenic populations. CONCLUSIONS: Myasthenic crisis has autonomic dysfunction involving multiple organ systems. Increased latency of parasympathetic reflexes is suggested. A comprehensive management protocol addressing different autonomic domains is required for holistic patient care.