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Immune-mediated necrotising myopathy (IMNM) is a myositis subset characterised by severe muscle weakness with chronic and refractory disease course.1 It has been hypothesised that long-lived plasma cells are implicated in the pathogenesis of IMNM by secreting pathogenic autoantibodies unresponsive to standard immunosuppression.1 Daratumumab has recently been successfully reported in cases of refractory lupus2 and other treatment-refractory antibody-mediated autoimmune diseases.3 We describe here the successful use of daratumumab, an anti-CD38 human monoclonal antibody depleting plasma cells, in a patient with severe refractory anti-SRP+IMNM.
A 27-year-old Caribbean man presented with subacute muscle weakness and swallowing difficulties. No skin rash, arthritis, Raynaud or other connective tissue disease features were reported. Muscle strength examination revealed severe proximal muscle weakness (MRC-5 scale deltoid and psoas 2/5) resulting in major functional incapacities. Creatine kinase (CK) and troponin I levels were elevated at 19 824 IU/L (normal range 24–184) and 196 ng/L (normal range 0–20), respectively. Antinuclear antibody, extractable nuclear antigen, antidouble-stranded DNA were negative. Myositis panel using a line-blot assay method was …
Footnotes
Handling editor Josef S Smolen
Contributors OL-C, HA-C, HC, SD, ER and JB-T contributed to the acquisition, analysis or interpretation of data, drafted the work or revised it critically for important intellectual content and approved the final version to be published.
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 OL-C reports participation to advisory boards from Abbvie, Astra-Zeneca, Janssen and Roche. HAC reports honoraria as speaker from Abbvie, Janssen, Pfizer, Mantra Pharma, Eli Lilly, Amgen, Sobi, AstraZeneca, Sandoz and Novartis; participation to advisory boards from Novartis, Amgen, Hoffmann-La Roche, Eli Lilly, Abbvie, BMS and Novartis; and participation in clinical studies sponsored by Pfizer, Neomed, Daiichi Sankyo Inc, Abbvie, Xencor, Sanofi and Novartis. HA-C, SD, ER report no disclosure. JB-T reports honoraria as speaker from GSK, Teva, Amgen and Pfizer; and participation to advisory boards from Astra-Zeneca, Abbvie, Janssen, Novartis, Teva and Pfizer.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.