Acquired neuromyotonia or Isaacs' syndrome is an immune mediated inflammatory disorder characterized by involuntary continuous muscle fiber activity manifesting as twitching and stiffness along with autonomic dysfunctions like hyperhidrosis and/or tachycardia. Here we report a young male who developed acquired neuromyotonia following COVID-19 vaccination.

A 20-year-old male presented in our clinic with gradually progressive pain and numbness in bilateral lower limbs, tremors in both hands, shivering while walking, excessive sweating and difficulty in micturition for last 15 days. He also noticed twitching of muscles in calf and thigh muscles along with these symptoms. According to patient, these symptoms started after he took his first dose of COVID-19 vaccination (Covishield- Oxford-AstraZeneca viral vector vaccine) 10 days back. There was no history of fever or backache. He had no chronic illness and was not on any medications.

Examination revealed hyperhidrosis, mild proximal muscle weakness in both lower limbs with twitching in muscles suggestive of myokymia. There were quivering and rippling movements of intrinsic muscles of both hands resembling polyminimyoclonus. In view of the above findings, possibility of acquired neuromyotonia possibly following COVID-19 vaccination was kept and further evaluation was done.

Routine blood investigations, thyroid function test, anti-thyroid peroxidase antibodies and anti-nuclear antibodies were normal. Cerebrospinal fluid analysis was normal. Anti-VGKC antibodies were detected in serum with strongly positive anti-CASPR and weakly positive anti-LGI1 antibodies confirming diagnosis of acquired neuromyotonia.  

Pulse dose of intravenous methylprednisolone for 5 days was given which resulted in visible improvement in pain, twitching, hyperhidrosis and urinary symptoms. He was continued on oral steroids and complete resolution of his symptoms was noted over a period of 2 months.

COVID-19 vector vaccine associated acquired neuromyotonia is a rare condition, but its early recognition and treatment is the key for a favorable prognosis.