Polyarteritis nodosa.

Polyarteritis nodosa, as a diagnosis, has been progressively narrowed from a collection of ill-defined vasculitides to its current definition as a systemic transmural necrotizing vasculitis that usually affects medium-sized muscular arteries and sometimes small muscular arteries, commonly within the kidneys, gastrointestinal tract, skin, nerves, joints, and muscles. In this review, we will highlight the clinical features and classification of this disease and emphasize that more accurate diagnosis of subtypes leads to more effective treatment.