A Rare Case of Limited Muscle Involvement in Polyarteritis Nodosa

Abstract

Polyarteritis nodosa (PAN) is a systemic vasculitis that can affect multiple organs in its diffuse form and is associated with high rates of morbidity and mortality. From the standpoint of pathology, PAN is necrotizing arteritis predominantly involving medium and small muscular arteries, without glomerulonephritis or vasculitis in the arterioles, capillaries, or venules (1, 2). PAN has protean manifestations, and it may present as a systemic disease or in its limited form, be confined to a single organ (2). The limited form of PAN is rare and may pose a diagnostic challenge; it can mimic other common diseases, and its nonspecific presentation may lead to confusion or delays in diagnosis. Musculoskeletal system involvement in PAN is known to present as myalgia, arthralgia, polymyositis-like syndrome, asymmetric nondeforming polyarthritis, or rarely, as intermittent claudication, acute leg ischemia, or myopathy (2). Muscular involvement in PAN may occur as a component of systemic PAN or as a limited form. Patients with the limited form of PAN are known to present with pain, swelling, and tenderness of the lower leg (3). Magnetic resonance imaging (MRI) findings of muscular involvement in PAN have been reported in other studies, all in cases with the limited form of PAN (4). Most of the previous studies have reported nonspecific edematous signal changes in the affected muscles with hyper-signal intensities on T2-weighted or fat-saturated sequences (5), which may be found in all clinical mimics such as inflammatory or infectious myositis. Ultrasound is particularly useful in the diagnosis of largeand medium-sized vessel vasculitis, as the characteristic wall thickening of the affected arteries allows for the confirmation of a suspected diagnosis. However, only a few studies have reported ultrasonography findings for the limited form of PAN. Herein, we describe a rare case of PAN involving skeletal muscle as indicated on This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Received: January 16, 2021 Revised: February 22, 2021 Accepted: February 23, 2021