Abstract
Background Anti-leucine-rich glioma inactivated 1 (LGI1) antibodies are most commonly associated with autoimmune encephalitis, however the clinical spectrum is evolving, and peripheral neuropathy and neuromuscular hyperexcitability syndrome have recently been recognised.1 2 We describe a case of anti-LGI1 associated hyperexcitability syndrome associated with myopathy, which has not been described previously.
Case Description A 56-year-old man presented with three months of myalgia, decreased exercise tolerance, dysaesthesias, hyperhidrosis, insomnia and diarrhoea. Examination revealed myokymia in orbicularis oris and mentalis, calf fasciculations, and absent ankle reflexes. Blood tests showed an elevated Creatine Kinase (CK). Electromyography confirmed fasciculations in right gastrocnemius and myokymia in mentalis. Magnetic Resonance Imaging (MRI) of the lower limb demonstrated hyperintensity of the mid left gastrocnemius with a biopsy of this site showing myopathic/dystrophic changes without inflammation. Further serum testing revealed positive anti-LGI1 antibodies.
He was diagnosed with anti-LGI1 associated neuromuscular hyperexcitability and myopathy. Administration of corticosteroids and azathioprine resulted in complete clinical remission and normalisation of CK.
Conclusion Myopathy with raised CK has not previously been reported as part of the anti-LGI1 clinical spectrum. Neurologists should consider CK testing in patients with anti-LGI1 antibodies and peripheral neuromuscular symptomatology, as it may assist with diagnosis of associated myopathy and provide an object marker for disease monitoring.
References
Irani SR, Alexander S, Waters P, et al. Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvan’s syndrome and acquired neuromyotonia. Brain 2010;133:2734–48
Gadoth A, Pittock SJ, Dubey D, et al. Expanded phenotypes and outcomes among 256 LGi1/CASPR2-IgG-positive patients. Ann Neurol 2017;82:79–92.
