Myasthenia gravis, myositis, myocarditis and anti-titin antibodies after Nivolumab/Ipilimumab: response with plasmapheresis

Context: Severe neurological manifestations following use of immune checkpoint inhibitors (ICIs) occur in 0.93% of patients, and together with cardiac toxicity have the higher lethality. Myasthenia gravis (MG) and polymyositis (PM) are rare, and treatment includes discontinuation of the immunotherapy, corticosteroids, and intravenous immunoglobulin (IVIG), with occasional use of plasmapheresis (PLEX). Biomarkers are not consistently reported. We report the case of a patient with MG, PM and myocarditis after ICI, with positive anti-titin antibodies and response to plasmapheresis. Case report: 81-year-old male developed ascending, subacute, progressive tetraparesis, dysphagia, ophthalmoparesis, and respiratory failure 2 weeks after second cycle of nivolumab/ipilimumab for metastatic melanoma. Physical examination showed: globally reduced strength, hypoactive reflexes, bilateral sixth nerve palsy and bilateral semi-ptosis. Prostigmine test was positive and electroneuromyography was compatible with myopathy. Labs revealed CPK 4000 U/L, troponin 9000U/L, autoimmune myositis panel negative, anti-titin antibodies (described in paraneoplastic MG and associated with severity) positive and cardiac MRI without fibrosis. Clinical picture was compatible with MG and PM with cardiac involvement. He received methylprednisolone and six PLEX sessions, with complete recovery. Four months after treatment, he developed cognitive impairment and large B-cell lymphoma (ICI complication). Conclusions: PM and MG may occur after ICI, especially in the first cycles, and anti-titin may be a biomarker of severity in these patients. Although guidelines recommend adding IVIG or PLEX in refractory or severe cases, PLEX may be first choice, especially if multiple ICI are present.