Page 230 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

Polyarteritis Nodosa 205

Specific Organ System Manifestations

Clinical Features

Table 3 shows the main clinical manifestations of PAN. This disorder occurs in patients
of all ages, including children and the elderly, albeit most often between the ages of 40 and 60
years, without sexual predominance. A poor general condition is common, with two-thirds of
patients experiencing weight loss and fever. Non-specific symptoms which occur early in the
course of disease may be present at onset or even the singular manifestation. Although PAN
is most often diagnosed after systemic manifestations appear, it is important to consider the
diagnosis among individuals with unexplained or prolonged poor general health.

Figure 1. Peroneus muscle hyperintense signals on T2-weighted MRI in a PAN patient with skeletal
muscle involvement.

Myalgia and Arthralgia

Up to one-half of patients have variably intense, diffuse and spontaneous myalgia, with
normal or slightly elevated muscle enzyme levels. Amyotrophy may be marked reflecting
weight loss sometimes exceeding 20 kilograms (kg), or underlying peripheral neuropathy.
Affected patients may be bedridden due to pain severity and amyotrophy. Magnetic resonance
imaging (MRI) of painful muscles can show hyperintense signal intensities on T2-weighted
enhanced images after administration of gadolinium (Figure 1) due to inflammatory lesions.
Skeletal muscle MRI, which correlates poorly with the presence of vasculitis, is not
recommended in the selection of the site for muscle biopsy. Rather, the biopsy should be
performed distally in an affected limb especially in painful areas to maximize pathogenic
vasculitic lesions which may be in differing stages of evolution. Arthralgia occurs in the

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