perifascicular

Perifascicular is an anatomical term used to describe structures or patterns located around a fascicle, where a fascicle is a bundle of fibers, such as muscle fibers or nerve fibers, within a larger tissue. The word combines peri- meaning around with fascicle from Latin fasciculus, a small bundle.

In anatomy and histology, perifascicular refers to regions that surround a fascicle. In skeletal muscle, the term is often used in relation to the perimysium, the connective tissue sheath that encloses a muscle fascicle, and thus perifascicular features describe tissues at or just outside the outer boundary of a fascicle.

In clinical pathology, perifascicular patterns are particularly noted in certain inflammatory myopathies. Perifascicular atrophy describes the tendency for muscle fibers at the outer portions of the fascicles to undergo atrophy, commonly with accompanying vascular changes and inflammation. This pattern is especially associated with dermatomyositis and can aid in distinguishing it from other inflammatory myopathies, though it is not exclusively diagnostic.

In neurology and neuropathology, perifascicular can describe changes surrounding nerve fascicles within a nerve, including alterations in the perineurium or surrounding connective tissue. However, such usage is less standardized than in muscle pathology.

Overall, perifascicular denotes a location around fascicles and is most prominently encountered in discussions of muscle pathology, where perifascicular atrophy is a key histological feature in dermatomyositis.