Table 2.

2011 European Neuromuscular Centre Inclusion Body Myositis research diagnostic criteria 2011 (adapted from Ref. [71•])

Category	Clinical features	Pathological features
Clinico-pathologically defined IBM	○ Duration of weakness >12 months ○ Creatine kinase ≤15 × ULN ○ Age at onset >45 years ○ FF weakness > SA weakness and/or KE weakness ≥ HF weakness	All of the following: ○ Endomysial inflammatory infiltrate ○ Rimmed vacuoles ○ Protein accumulationa or 15–18 nm filaments
Clinically defined IBM	○ Duration of weakness >12 months ○ Creatine kinase ≤15 × ULN ○ Age at onset >45 years ○ FF weakness > SA weakness and KE weakness ≥ HF weakness	One or more, but not all, of: ○ Endomysial inflammatory infiltrate ○ Up-regulation of MHC class I ○ Rimmed vacuoles ○ Protein accumulationa or 15–18 nm filaments
Probable IBM	○ Duration of weakness >12 months ○ Creatine kinase ≤15 × ULN ○ Age at onset >45 years ○ FF weakness > SA weakness or KE weakness ≥ HF weakness	One or more, but not all, of: ○ Endomysial inflammatory infiltrate ○ Up-regulation of MHC class I ○ Rimmed vacuoles ○ Protein accumulationa or 15–18 nm filaments

^aEvidence of amyloid or other protein accumulation by established methods (e.g. for amyloid Congo red, crystal violet, thioflavin T/S, for other proteins p62, SMI-31, TDP-43)

FF, finger flexion; HF, hip flexion; KE, knee extension; SA, shoulder abduction; MHC class I, major histocompatibility complex class I; ULN, upper limit of normal