Anti-LRP4 antibody-positive myasthenia gravis: a complex case

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Introduction: Myasthenia gravis (MG) is an autoimmune disorder marked by fluctuating muscle weakness due to autoantibodies targeting the neuromuscular junction. While most patients present antibodies against acetylcholine receptor or muscle-specific kinase, about 10–15% are double-seronegative (DNMG). However, anti-LRP4 antibodies emerged as another marker, corresponding to 0.5%. Based on previous studies, anti-LRP4 has a mild and manageable course. Case report: A 41-year-old woman followed the neuromuscular clinic in Santo André–SP, being diagnosed with anti-LRP4 MG in 2011. Treatment started with corticosteroid and pyridostigmine. Since she was a carrier of the hepatitis C virus, immunosuppressants were delayed. Patient developed cataracts due to steroid use, demanding exchange in therapy and starting azathioprine, once the hepatitis C infection was suppressed. During this medication transition, the patient developed a myasthenic crisis, and she was hospitalized for 7 days, when she received immunoglobulin, with little response. After this, the patient was hospitalized again for 15 days with a new crisis, being submitted to plasmapheresis, also with little response. Her clinical condition worsened, and her Osserman classification, which at the beginning was IIB, now progressed to IV, and she remained dependent on her routine activities. Then started on rituximab, progressing without new crisis, but maintaining functional dependence. Discussion: This case highlights a severe refractory disease. Only one series has been reported presenting the clinical features in the last 10 years, which demonstrates the importance of further studies to get conclusions about the severity of the clinical presentation and complexity of treatment. Based on this, we propose testing for anti-LRP4 antibodies in this group of patients (DNMG) with refractory symptoms.

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