Red-flag features suggesting an alternative diagnosis
| Onset | Acute to subacute onset over days to weeks |
| Widespread autonomic involvement | Involvement of the parasympathetic, sympathetic, and enteric nervous systems, affecting multiple organ systems |
| Functional decline | Loss of functional independence and increased disability level due to progression of symptoms |
| Signs and symptoms | Pupillary dysfunction, hyperhidrosis or anhidrosis, urinary retention, sexual dysfunction, and gastrointestinal dysmotility |
| Relevant personal or family history | Personal or family history of autoimmune conditions or malignancy |
| Central nervous system dysfunction | Clinical features of cortical, brainstem, cerebellum, or spinal cord dysfunction |
| Endocrinopathy | Amenorrhea, syndrome of inappropriate antidiuretic hormone secretion, adrenal insufficiency, panhypopituitarism |
Based on information in reference 14.