Features of repeated muscle biopsies and phenotypes of monocytes in paired blood samples and clinical long-term response to treatment in patients with idiopathic inflammatory myopathy: a pilot study

Clin Exp Rheumatol. 2020 Jan-Feb;38(1):42-49. Epub 2019 May 22.


Objectives: In a pilot study we aimed to identify biomarkers in repeated muscle biopsies and paired blood samples, taken before and after conventional immunosuppressive therapy, in order to predict long-term therapeutic response in patients with idiopathic inflammatory myopathies (IIM).

Methods: Muscle biopsies were selected from 13 new onset patients, six responders and seven non-responders. Repeated muscle biopsies after a median of 11 months follow-up were available from 9 patients and paired peripheral blood mononuclear cells (PBMCs) from 5 patients. Treatment response after 3 years was defined by MMT-8 measuring muscle strength and the ACR/EULAR 2016 improvement criteria. Frozen biopsy sections were immunohistochemically stained for expression of CD3, CD66b, IL-15, CD68, CD163 and myosin heavy chain neonatal (MHCn). PBMCs were analysed by flow cytometry for monocyte phenotypes (CD14, CD16, CD68, CX3CR1, and CCR2).

Results: Before treatment there were no significant differences in any clinical or muscle biopsy variables or monocyte subsets between responders and non-responders. MMT-8 was significantly higher compared to baseline in the responders at 3-year follow-up. In responders the expression of CD68 in the repeated biopsies was significantly lower compared to non-responders (p<0.05).

Conclusions: Baseline biopsy, monocyte profile or clinical data did not predict long-term treatment response, but in the repeated biopsy within 1 year of immunosuppressive treatment, the lower number of macrophages (CD68+) seemed to predict a more favourable long-term clinical response with regard to improved muscle strength.

MeSH terms

  • Biomarkers / analysis
  • Biopsy
  • Follow-Up Studies
  • Humans
  • Leukocytes, Mononuclear / cytology
  • Monocytes / classification
  • Monocytes / cytology*
  • Muscle, Skeletal / pathology*
  • Myositis / therapy*
  • Phenotype
  • Pilot Projects


  • Biomarkers