Slowly expanding lesions are a marker of progressive MS – Yes

Abstract

About 20 years ago, John Prineas and colleagues described the neuropathology of “chronic active/ slowly expanding lesions” in secondary progressive multiple sclerosis (MS) autopsy cases pointing out their potential pathogenetic relevance to disease progression in MS. The characteristic pathological feature of these lesions is a rim of activated microglia/macrophages surrounding an inactive lesion center with only few microglia/macrophages.1 These phagocytes at the chronic active lesion edge are the prerequisite of iron accumulation and are only rarely seen around inactive and absent from remyelinated lesions.2 Large neuropathological studies1 predominantly found this type of chronic lesions in progressive MS cases highlighting the persistence of chronic inflammatory activity behind a partially repaired blood-brain-barrier in the later stage of MS.