Page 227 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

Polyarteritis Nodosa 203

Etiology and Precipitating Factors

Relation to HBV Infection

Trepo and colleagues [16, 26] described the close relation between PAN and HBs
antigenemia. In 1987 Guillevin and colleagues [3] reported one of the first addict patients
who were proven to be contaminated by intravenous drugs [3]. Intravenous drug abuse and
sexual transmission of HBV to at risk, non-vaccinated individuals are the major causes of
HBV-related PAN. The development and distribution of anti-HBV vaccines to at-risk
individuals explains the dramatic decrease in the number of new cases since 1989. Over the
past few years, the frequency of HBV-related PAN has progressively declined and almost
disappeared. Indeed, for the last 5 years, fewer than five cases have been identified annually
throughout France.

Other Etiologies

In spite of occasional anecdotal cases [27], neither hepatitis C (HCV) nor GB virus, the
latter phylogenetically related to the former were considered etiologically important in the
development of PAN. Although there were several reported patients with parvovirus B19-
infection (28), systematic testing of PAN patients did not find their occurrence to be
statistically significant compared to controls [29]. Calabrese (30), and Gisselbrecht and
colleagues [31] suggested a role for human immunodeficiency virus type 1 (HIV1) in the
development of vasculitis. A close relation between hairy-cell leukemia and PAN was
suggested by Elkon and colleagues [32, 33], but the relation to other malignancies has not
been apparent. A Cleveland Clinic Foundation retrospective study by Hutson and coworkers
[34] reported 69 patients with systemic vasculitis and malignancy, twelve of whom had both
diseases occurring in same twelve month period, including two with PAN.

Pathology

PAN lesions can occur in any artery, but involvement of the aorta, other large elastic
arteries and the pulmonary vasculature have rarely been described. The acute phase of arterial
wall inflammation is characterized by fibrinoid necrosis of the media and intense pleomorphic
cell infiltration, with predominant neutrophil and variable lymphocytic and eosinophilic
inflammatory cells. The normal architecture of the vessel wall, including the elastic lamina, is
completely destroyed and replaced by a band of amorphous eosinophilic material that
resembles fibrin when appropriately stained. Arterial aneurysms and thromboses can occur at
lesion sites. Arterial healing is characterized by fibrotic endarteritis that can lead to aneurysm
regression or when too abundant, vascular occlusion. A characteristic histological feature of
PAN is the coexistence of necrotizing vasculitis and healed lesions or normal arteries in
different tissues or in portions of the same tissue sample.

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