Acute Hepatitis B Associated Polyarteritis Nodosa Presenting as Mononeuritis Multiplex

Abstract

Purpose: A 39 year old male presented with a two month history of progressive weakness and neuropathic pain resulting in difficulty walking or griping objects. Physical exam was unremarkable except for bilateral weakness, decreased vibratory sense, and hypoactive but symmetric reflexes. Laboratory studies revealed elevated inflammatory markers. CT of his abdomen showed multiorgan wedge-shaped hypodensities likely representing infarction. EMG demonstrated a severe asymmetric sensory, motor polyneuropathy characterized as a mononeuritis multiplex consistent with a neurovasculitic process. Nerve biopsy revealed a massive mononuclear cell infiltration of surrounding epineural connective tissue with a marked perivascular distribution. Further studies were positive for an acute hepatitis B infection. Given the high likelihood of an acute hepatitis B associated polyarteritis nodosa (PAN), treatment with prednisone and entecavir was initiated with rapid improvement in his strength and ability to ambulate. Extrahepatic manifestations of acute HBV infection occur in approximately 20% of patients. They can involve any body system and are important to recognize as they may occur without clinically apparent liver disease and can be mistaken for an independent disease process. One of the most severe extrahepatic manifestations is PAN, which occurs in less than 1% of patients with HBV infection. However, as many as 30% of patients with PAN are infected with HBV. Pathogenesis of the peripheral neuropathy is likely from direct cytotoxicity of the virus itself on the nerve fibers, or via deposits of immune complexes on the vasa nervorum of the nerves leading to a vasculitis and subsequent ischemia of the nerve fibers. There is no apparent relationship between severity of the vasculitis and severity of the hepatic disease. Interestingly, our patient did not have an obvious hepatic response to his acute infection given his normal liver function tests despite relatively severe vasculitis. In fact, the hepatic disease is often relatively mild despite high levels of viral replication. The prognosis for PAN is usually favorable if appropriate treatment is started early. The treatment of HBV-associated PAN includes plasma exchange to clear immune complexes, antiviral treatment, and a short course of corticosteroids. Cytoxan®, used in primary PAN, promotes persistence and replication of the virus leaving the antigen-triggering factor of the disease intact. This case illustrates the importance of recognizing the extrahepatic manifestations of acute HBV infection as it significantly impacts management with a goal of halting viral replication and achieving HBe seroconversion to accomplish complete remission without relapse.