West nile virus infection and myasthenia gravis

Introduction: Viruses are commonly cited as triggers for autoimmune disease. It is unclear if West Nile virus (WNV) initiates autoimmunity. Methods: We describe 6 cases of myasthenia gravis (MG) that developed several months after WNV infection. All patients had serologically confirmed WNV neuroinvasive disease. None had evidence of MG before WNV. Results: All patients had stable neurological deficits when they developed new symptoms of MG 3 to 7 months after WNV infection. However, residual deficits from WNV confounded or delayed MG diagnosis. All patients had elevated acetylcholine receptor (AChR) antibodies, and 1 had thymoma. Treatment varied, but 4 patients required acetylcholinesterase inhibitors, multiple immunosuppressive drugs, and intravenous immune globulin or plasmapheresis for recurrent MG crises. Conclusions: The pathogenic mechanism of MG following WNV remains uncertain. We hypothesize that WNV‐triggered autoimmunity breaks immunological self‐tolerance to initiate MG, possibly through molecular mimicry between virus antigens and AChR subunits or other autoimmune mechanisms. Muscle Nerve 49 : 26–29, 2014