Differing pathologies in myositis subtypes. The distribution of immune system cells differs among myositis subtypes. (a) In dermatomyositis, immune system cells are predominantly in the regions of connective tissue that lie between muscle fascicles and include medium-sized and large blood vessels. In (b) inclusion body myositis and (c) polymyositis, immune cells surround myofibers. (d) Especially in inclusion body myositis, these may sometimes invade myofibers.
Greenberg Arthritis Research & Therapy 2010 12(Suppl 1):S4 doi:10.1186/ar2885