Fig. 1
Clinical characteristics of the post-COVID syndrome cohort. Demographics of study participants with Post-COVID Syndrome (PCS) and timeline of events are shown in (A). Black dots indicate the month in which PCR-testing for SARS-CoV-2 was positive. Black circles indicate the month from which serum samples were available. For two patients (PCS-7 and PCS-11), no serum was available for mass spectrometry and myositis-specific and –associated antibody screening. Black triangles indicate the month in which biopsy of vastus lateralis muscle was performed. Black cubes indicate the months of anti-SARS-CoV-2 vaccinations. Colored bars indicate the months in which the participants reported symptoms. Patients characteristics, summary of acute and chronic symptoms are reported in (B). Handgrip strength test (HGS) was performed in two subsequent sessions (session 1 and 2) in 9/11 patients around the time of biopsy (C). Dotted lines indicate the mean reference values based on ROC analyses showing the highest sensitivity and specifity to discriminate between healthy controls and ME/CFS patients for men and women respectively (Jakel et al. 2021). Fatigue ratio defined as the ratio of Fmax / Fmean per individual session (D). Dotted lines indicate the respective normal population mean reference values for women and men (Jakel et al. 2021). Recovery rate defined as the ratio of F mean of session 2 divided by F mean of session 1 (E). Dotted lines indicate the normal population mean reference value (Jakel et al. 2021). Duration of post-exertional malaise around the time of biopsy (F). Intensity of myalgia on the VAS (Visual analog scale), 0 = no muscle pain; 10 = highest pain imagineable) (G). Chalder`s Fatigue scale around the time of biopsy (H) Dotted lines indicate reference values for the general population. Bell disability score around the time of biopsy (I). MRI of proximal lower extremity with indication of ROI (regions of interest) and results of T2 mapping and mean diffusivity (J). Abbreviations: HDC Healthy-diseased control, PCS Post-COVID syndrome, 2BA type-2b atrophy control, BMI Body mass index, SD Standard deviation, ME/CFS Myalgic encephalomyelitis/chronic fatigue syndrome, DOI Duration of illness (at timepoint of biopsy), CK Creatine kinase, ANA Anti-nuclear antibodies, F Force