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Myositis and myasteniform syndrome related to pembrolizumab
  1. Pablo Sanchez-Sancho1,
  2. Albert Selva-O'Callaghan2,
  3. Ernesto Trallero-Araguás3,
  4. Javier Ros4 and
  5. Bruno Montoro1
  1. 1Pharmacy Department, Hospital Vall d'Hebron, Barcelona, Spain
  2. 2Systemic Autoimmune Diseases Unit, Hospital Vall d'Hebron, Barcelona, Spain
  3. 3Rheumatology Unit, Hospital Vall d'Hebron, Barcelona, Spain
  4. 4Medical Oncology, Hospital Vall d'Hebron, Barcelona, Spain
  1. Correspondence to Dr Pablo Sanchez-Sancho; pablo.sanchez.vhebron{at}


This case report concerns a 63-year-old man affected by metastatic undifferentiated liposarcoma. After receiving pembrolizumab as a second-line treatment in a clinical trial, the patient experienced an immune-mediated myocarditis, myositis and myasteniform syndrome. The last two adverse events showed significant clinical relevance in terms of severity, duration and the required specific treatment.

Initial treatment approach consisted in pulses of 1 g of methylprednisolone, followed by 2 mg/kg/day, with clinical improvement. After 12 days, the immune-mediated myasteniform syndrome worsened, with dysphagia, dysphonia, bilateral palpebral ptosis and respiratory difficulty. Due to the refractoriness to glucocorticoid treatment, it was decided to initiate intravenous immunoglobulin at 2 g/kg, followed by 2 mg/kg every 4 weeks once discharged and mycophenolate 500 mg/12 hours, in order to reduce the dose of glucocorticoids.

After 2 months, the patient presented an optimal clinical evolution, without muscular weakness and referred to an improvement in dysphagia and speech.

  • oncology
  • neurology
  • unwanted effects / adverse reactions

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  • Contributors PS-S, BM and AS-O’C conceived of the presented idea from an original and innovative clinical report. PS-S developed the manuscript. AS-O’C, JR and ET-A verified all the data compiled in the manuscript. All authors discussed the results and contributed to the final manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.