Clinical, laboratory and electrophysiological features of Morvan's fibrillary chorea

Morvan's Fibrillary Chorea (MFC) is a rare autoimmune disorder causally associated with auto-antibodies directed at the voltage-gated potassium channel (VGKC-Abs). It classically presents with sleep disturbances, neuromyotonia and dysautonomia. We aimed to systematically characterise the features of MFC by describing a patient and reviewing published literature. Case notes of 27 patients with MFC (one from our clinic and 26 from the literature) were reviewed and clinical data were extracted and analysed. We found that MFC mainly affects men (96%) and runs a subacute course over months. Neoplasia (56%), VGKC-Abs positivity (79%) and autoimmunity (41%) are frequent associations. Myokymia, insomnia and hyperhidrosis were almost universally described. Other autonomic features were present in 63% with the most common being cardiovascular and bowel disturbances. Clinical, radiological or electroencephalographical features of limbic encephalitis were present in 19% of patients. Outcome was fair with an overall recovery rate of 78%. All patients with malignancies underwent surgery. Immunotherapies including corticosteroids, intravenous immunoglobulins and plasma exchange were instituted in 22 patients and 19 (86%) responded. Of all symptomatic treatments tried, carbamazepine, phenytoin, sodium valproate, levetiracetam and niaprazine were found to be effective. The broad clinical spectrum of VGKC-Abs diseases can make early recognition of MFC difficult. Myokymia, insomnia and hyperhidrosis are invariably present. There may be abnormalities on cerebrospinal fluid testing and VGKC-Abs can occasionally be absent. Early initiation of immunotherapies and malignancy screening are important to prevent adverse outcomes in a condition that generally responds favourably to treatment.