Fig. 2

Representative images of histological muscle changes at time of intravitam diagnosis and 2 years later. a At initial presentation muscle biopsies showed proliferative inflammatory changes (black arrows) within expanded interstitial tissue, sparse myofiber (MF) density and adipose replacement tissue (AT; “fatty” replacement). b At higher magnification of the framed area in a, intramuscular nerve branches (blue lined) are severely enlarged and their fascicular architecture is effaced by granulomatous changes with macrophages and multiple multinucleated giant cells (white arrow). Further mixed leukocytic infiltrates with lymphocytes, plasma cells and scattered neutrophils are also evident in the epineurial perimysium (black arrow). c The changes extend along most intramuscular nerve twigs (asterisk) even if perifascicular changes are sparse. d In other areas, as seen in this cryosection, inflammatory infiltrates affect the endomysial branches (asterisk) and from there invade deeply in between the myofibres. e No such granulomatous lesions are seen at post mortem examination 2 years later while the adipose tissue (AT) has grown. Some nerve branches show myelinated fibre loss and endoneurial fibrosis (black arrow), while others present with normal histological appearance (white arrows). f Many fascicles however show necrofibrinopurulent interstitial changes (black arrows) as well as scattered necrotic myofibres infiltrated by hypersegmented polymorphonuclear neutrophils (inlet). Both phenomena are compatible with sepsis. Slide technique and stains: a–c, e Formalin fixation/paraffin embedding, haematoxylin–eosin; d cryosection, haematoxylin–eosin; f Formalin fixation/paraffin embedding, periodic acid Schiff.