Inclusion Criteria:  With an age ≥ 45 and ≤ 80 yo. Man or menopausal woman. - With IBM defined by the Lloyd criteria (Lloyd et al., 2014): muscle weakness of finger flexors or quadriceps, and endomysial inflammatory infiltrates on muscle biopsy, and presence of invaded fibers or rimmed vacuoles on muscle biopsy. Who gave their written informed consent Affiliated to a social security regime (expected AME) And for: -group 1: treated by sirolimus since at least 6 months (but still disabled ) - group 2: currently (for at least 3 months) without specific treatment for inclusion myositis.  Exclusion Criteria:  Impossibility to walk 10 meters Grip evaluated by MRC5 MMT at 0 OR 1. Body mass index < 18 Not able to stop any anticoagulant, or antiaggregant drugs within the week before and the 48 hours before the liposuction Severe respiratory insufficiency (FVC < 50% and/or FEV1 < 50%) Severe chronic kidney disease (Estimated Glomerular Filtration Rate < 15 ml/min and/or proteinuria > 0.5 g/24h) Cancer non in remission (necessitating specific treatment) during the past 12 months Connective Tissue Disease non in remission (necessitating specific treatment) during the past 12 months - Bone marrow transplantation Connective Tissue disease non in remission (necessitating specific treatment) during the past 12months - Immunosuppressive drugs except sirolimus, ongoing or stopped in less than 3 months Polyvalent immunoglobulins (IV or sub-cut) ongoing or stopped in less than 3 months Any biotherapies (mAbs) such as ant-CD20, CTLA4Ig, anti-TNF, anti-IL6R, anti-IL1 etc… ongoing or stopped in less than 6 months. Seropositivity for HIV, HCV or HBV Contraindication to muscle MRI Contraindications to the liposuction: eg coagulation disorders, etc… - Contraindications to anaesthetics Documented conventional antibiotics severe allergy such as ß-lactam (cephalosporin), cyclins, macrolides (for example metronidazole), quinolones Participation in another trial (Jardé 1 or Jardé 2) Legal protection (curatorship or tutorship) or safety measure