Human hepatitis viruses-associated cutaneous and systemic vasculitis.

Human hepatitis viruses (HHVs) include hepatitis A virus, hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis delta virus, and hepatitis E virus and can cause liver inflammation in their common human host. Usually, HHV is rapidly cleared by the immune system, following acute HHV invasion. The morbidities associated with hepatitis A virus and hepatitis E virus infection occur shortly after their intrusion, in the acute stage. Nevertheless, the viral infectious process can persist for a long period of time, especially in HBV and HCV infection, leading to chronic hepatitis and further progressing to hepatic cirrhosis and liver cancer. HHV infection brings about complications in other organs, and both acute and chronic hepatitis have been associated with clinical presentations outside the liver. Vascular involvement with cutaneous and systemic vasculitis is a well-known extrahepatic presentation; moreover, there is growing evidence for a possible causal relationship between viral pathogens and vasculitis. Except for hepatitis delta virus, other HHVs have participated in the etiopathogenesis of cutaneous and systemic vasculitis via different mechanisms, including direct viral invasion of vascular endothelial cells, immune complex-mediated vessel wall damage, and autoimmune responses with stimulation of autoreactive B-cells and impaired regulatory T-cells. Cryoglobulinemic vasculitis and polyarteritis nodosa are recognized for their association with chronic HHV infection. Although therapeutic guidelines for HHV-associated vasculitis have not yet been established, antiviral therapy should be initiated in HBV and HCV-related systemic vasculitis in addition to the use of corticosteroids. Plasma exchange and/or combined cyclophosphamide and corticosteroid therapy can be considered in patients with severe life-threatening vasculitis manifestations. ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.

Core Tip: The human hepatitis viruses (HHVs) hepatitis A virus, hepatitis B virus, hepatitis C virus, hepatitis delta virus, and hepatitis E virus can cause liver inflammation in their common human host. With the exception of hepatitis delta virus, all other HHVs can participate in the pathogenesis of cutaneous and systemic vasculitis via different mechanisms like direct viral invasion of vascular endothelial cells and immune complex-mediated vessel wall damage. Cryoglobulinemic vasculitis and polyarteritis nodosa are recognized for their association with chronic HHV infection. Antiviral therapy should be initiated in hepatitis B virus and hepatitis C virus-related systemic vasculitis.

INTRODUCTION

Hepatocellular injury caused by acute or chronic inflammation of the liver is derived from adverse factors, including alcohol consumption, autoimmune response, drug use, steatosis, and viruses[1]. Hepatotropic viruses are known for their role in the etiology of viral hepatitis, and, from the public health perspective, the disease is associated with heavy health burden and higher annual mortality[2]. In addition to uncommon herpes viruses-related hepatitis due to Epstein-Barr virus, cytomegalovirus, and herpes simplex virus infection[3], human hepatitis viruses (HHVs) are the most common causes of acute and chronic hepatitis in their human host[4]. The discovery of HHV starts with clinical description of disease, antigen/antibody reaction establishment, virus-like particles visualization, and finally viral genomes sequencing[5]. Early experiments illustrated two types, infectious hepatitis and serum hepatitis[6]. Australia antigens in serum hepatitis yielded the detection of 42-nm Dane particles[7,8]. Subsequently, deoxyribonucleic acid (DNA) sequencing was performed and hepatitis B virus (HBV) was found[9]. Later, virus-like particles were observed in infectious hepatitis, and complementary DNA (cDNA) from hepatitis A virus (HAV) was sequenced[10,11]. Hepatitis C virus (HCV) was identified in non-A, non-B hepatitis patients receiving multiple transfusions[12], transmission to chimpanzees[13], and cDNA library screens[14]. Hepatitis delta virus (HDV), a HBV-associated virus[15], is a separate defective virus requiring the help of HBV for its infection[16]. After elucidating the hepatitis E virus (HEV) cDNA[17], an endemic non-A, non-B hepatitis[18], there are five members of HHVs[5].

Typically following HHV invasion into humans, there is rapid clearance of viruses by the host defense system, with a self-limiting disease course[4]. The morbidities associated with HAV and HEV infection, commonly transmitted via the fecal-oral route, occur shortly after their intrusion in the acute stage[19-21]. The infectious processes can persist for a long period of time in HBV, HCV, and HDV infection, progressing to chronic hepatitis and leading to liver fibrosis, irreversible cirrhosis, and hepatocellular carcinoma[22-24]. Table 1 summarizes and compares the common characteristics of the five HHV members[4,5,19-29].

Table 1

Common characteristics and comparative features in five members of human hepatitis viruses

	HAV	HBV	HCV	HDV1	HEV
Family; Genus	Picornaviridae Hepatovirus	Hepadnavirida Orthohepadnavirus	Flaviviridae Hepacivirus	Deltaviridae Deltavirus	Hepeviridae Orthohepevirus
Discovery2; Frequency	1983 Highest in AH	1979 Highest in CH	1989 Second in CH	1986 Less in CH	1990 Less in AH
Genome3; Length; Diameter4; Envelope5; Receptor	Linear ssRNA; 7500 nt; 27-32 nm; Quasi-envelope; Unknown	Circular dsDNA; 3200 nt; 42 nm; Envelope; NTCP, HSP	Linear ssRNA; 9600 nt; 55-65 nm; Envelope; CD81, SR-BI	Circular ssRNA; 1700 nt; 36-43 nm; Envelope; NTCP, HSP	Linear ssRNA; 7200 nt; 30-34 nm; Quasi-envelope; Unknown
Incubation; Age6; Course	14-30 d; Children; Acute	30-180 d; Any; Acute/chronic	14-180 d; Any; Acute/chronic	14-160 d; Any; Acute/chronic7	14-70 d; Adults; Acute
Route of spread	Enteric, sexual	Parental, sexual, vertical	Parental, sexual	Parental, sexual, vertical	Enteric, vertical, parenteral
Hepatitis diagnosis	Anti-HAV IgM	Anti-HBc IgM, HBs antigen, DNA by PCR	Anti-HCV IgG, RNA by PCR	Anti-HDV IgM, RNA by PCR	Anti-HEV IgM, RNA by PCR
Vaccine; Post-exp; Av agent	Available; Ig/vaccine; Not available	Available; Ig/vaccine; NA, IFN-α	Not available; Not effective; DAA agent	HBV vaccine; Not available; IFN-α	Available in China; Not available; Not available
FH8; LC/HCC; Prognosis9	Very rare; Nil; Full recovery	Very rare; Yes; Chronic carrier	Extremely rare; Yes; High carrier rate	Yes; Yes; Chronic carrier	Yes; Nil; Full recovery

Co-infection/superinfection with hepatitis B virus.

By cloning and sequencing.

Partial dsRNA in hepatitis B virus.

Diameter of virion.

Quasi-envelop with internal protein rather than viral glycoprotein.

Commonly affected age.

Progress to chronicity in 80% superinfection/5% co-infection hepatitis B virus.

Up to 20% in superinfection with hepatitis B virus and pregnant women.

Poorer in hepatitis B virus superinfection with hepatitis delta virus and pregnant woman with hepatitis E virus. AH: Acute hepatitis; Av: Antiviral; CH: Chronic hepatitis; DAA: Direct-acting antiviral; DNA: Deoxyribonucleic acid; ds: Double-stranded; Post-exp: Post-exposure; FH: Fulminant hepatitis; HBc: Hepatitis B virus core antigen; HBs: Hepatitis B virus surface antigen; HCC: Hepatocellular carcinoma; HSP: Heparan sulfate proteoglycans; IFN: Interferon; Ig: Immunoglobulins; LC: Liver cirrhosis; NA: Nucleoside/nucleotide analogues; nt: Nucleotide; NTCP: Sodium taurocholate co-transporting polypeptide, PCR: Polymerase chain reaction; RNA: Ribonucleic acid; SR-BI: Scavenger receptor class B type I; ss: Single-stranded.

EXTRAHEPATIC MANIFESTATIONS OF HUMAN HEPATITIS VIRUSES INFECTION

Although HHVs primarily affect hepatocytes, they can cause extrahepatic manifestations, with damage to other organs[30-34]. Both acute and chronic forms of viral hepatitis are associated with various clinical presentations outside of the liver, which may precede or follow hepatic dysfunction. The crucial pathogenic mechanism is caused by the immune responses against viral pathogens, with the deposition of immune complexes (IC) in targeted tissues.

Extrahepatic manifestations with evanescent rash and transient arthralgia that develop in acute HAV infection are rare[35]. In the protracted clinical course with cholestasis or relapsing disease, cutaneous vasculitis and arthritis occur with a predilection for lower extremities[36-38], and usually there is spontaneous recovery after the clearance of HAV. Other infrequently observed presentations include glome-rulonephritis, myocarditis, thrombocytopenia, and neurological complications like Guillain-Barre syndrome[20,32,39-41].

Acute HEV infection can be asymptomatic or manifest as fulminant hepatitis[21]. Neurological involvement is the most frequently encountered extrahepatic disorder, followed by hematological and gastrointestinal manifestations, possibly caused by autoimmune responses related to molecular mimicry[42,43]. Neuralgic amyotrophy and Guillain-Barre syndrome are two common neuromuscular disorders[44,45], and other uncommon presentations include mononeuritis multiplex, meningoradiculitis, and encephalitis[46-48]. Thrombocytopenia is a frequently identified hematological disorder[49,50], and pancreatitis is the most common gastrointestinal abnormality[51,52]. Myocarditis and glomerulonephritis are rarely observed complications[53,54]. Although there is evidence to support the treatment of HEV-related neurological manifestations with corticosteroids[42,55], the currently recommended therapy is plasma exchange and immune modulation with intravenous immunoglobulin[42,56].

Although extrahepatic manifestations exist with acute infection of all HHVs, such presentations are more commonly identified in HBV, with up to 20% occurrence[57]. Acute HBV infection is often subclinical and asymptomatic in around two-thirds of cases[58]. In the pre-icteric prodromal phase, there is serum sickness-like illness with arthritis and dermatitis due to the deposition of circulating IC composed of HBV surface (HBs) antigen and further activation of complements[59]. These manifestations are usually transient and are resolved after the onset of jaundice. Guillain-Barre syndrome has been reported to be associated with acute HBV infection, and both plasma exchange and intravenous immunoglobulin are effective treatments[60], implying that there is autoimmune-mediated damage to the myelin sheath of peripheral nerves.

Owing to the availability of viral markers and our understanding of pathogenic pathways, extrahepatic manifestations of chronic HBV infection have been well-elucidated for a while[33,57]. The etiopathogenesis outside the liver in the chronic phase involves the deposition of IC comprised of HBs and/or HBe antigens, followed by the local activation of complement cascades and the recruitment of inflammatory cells[61]. Notably, higher viral load or persistent infection can promote the production of IC, leading to deposition at small or medium-sized arteries[62]. In addition, viral replication has been demonstrated in the endothelium of targeted vessels[63]. Taken together, both mechanisms suggest that inhibition of viral replication, either spontaneously or under antiviral therapy, can reduce extrahepatic manifestations. Up to one-fifth of victims with chronic HBV infection have morbidities outside the liver[61], and these are comprised of arthritis, glomerulonephritis, uveitis, peripheral neuropathy, Raynaud phenomenon, Sjögren syndrome, cutaneous vasculitis, and systemic vasculitis, including polyarteritis nodosa and cryogobulinemic vasculitis[57,62,64,65]. Since the administration of immunosuppressive agents increases the risk of additional hepatic HBV replication with worsening liver disease[61], the treatment of HBV-associated glomerulonephritis and vasculitis is mainly based on antiviral agents, interferon (IFN)- α or nucleoside/nucleotide analogues (NAs)[66-70].

In most cases, symptomatic manifestations are uncommon during acute HCV infection[71]. Extrahepatic presentations include arthralgia, myalgia, and rash[72]. Patients with HCV infection usually progress to chronic stage without recovery[71,72]. Nevertheless, antiviral therapy is highly effective for the acute infection, resulting in the clearance of HCV with sustained virological response (SVR)[72,73].

Persistent HCV infection is a leading cause of chronic liver disease[74]. Although essentially curable with direct-acting antiviral (DAA) therapy, only a portion of patients are diagnosed. Notably, extrahepatic manifestations occur in up to three-quarter of victims with chronic HCV infection[75], and cryoglobulinemia is the most frequently encountered presentation (in 40% to 60% of infected patients)[76]. Direct viral invasion and deposits of soluble IC are two pathogenic processes involved in the development of disease outside the liver[75,76]. The clinical presentations include arthralgia, myalgia, glomerulonephritis, Raynaud phenomenon, Sjögren’s syndrome, Hashimoto’s thyroiditis, Graves’ disease, ulcerative keratitis, peripheral neuropathy, and cryoglobulinemia vasculitis[74-78]. Occasionally, extrahepatic-related autoimmune comorbidities such as cryoglobulinemia vasculitis can lead to the diagnosis of HCV infection[76]. Sustained eradication of HCV by IFN-α or DAA agents has shown to be beneficial for outcomes following these manifestations[78,79]. Notably, a prospective study with 9895 HCV-infected cases receiving DAA medications revealed that viral clearance is responsible for a significant decrease in HCV extrahepatic mortality[80].

VASCULITIS MANIFESTATION IN HUMAN HEPATITIS VIRUSES INFECTION

There is growing evidence demonstrating a causal relationship between viral pathogens and vasculitis. Except for HDV[24,25], other HHVs have been shown to participate in the etiopathogenesis of cutaneous and systemic vasculitis via different mechanisms, including direct viral invasion of vascular endothelium, IC-mediated vessel wall damage, and autoimmune responses with stimulation of autoreactive B-cells and impaired regulatory T cells[81-83].

Cutaneous leukocytoclastic vasculitis (CLV) rarely occurs during acute HAV infection, and it may resolve after the regression of hepatitis[36-38,84]. In chronic HBV infection, CLV is rarely observed, with an 1% incidence[62]. HBs antigen has been identified in affected skin lesions[85]. Notably, IFN-α therapy is effective against HBV-associated CLV[86]. The histopathological picture of HHV-triggered CLV shows relatively less eosinophils and lymphocytes compared with those in drug-induced CLV[81].

Acute HAV or HEV infection can induce Henoch-Schönlein purpura (referred to as HSP)[87-89], a systemic vasculitis caused by the widespread deposition of circulating immunoglobulin (Ig)A IC in small-sized blood vessels of skin, joint, lung, kidney, testis, gastrointestinal tract, and nervous system[90]. HAV- and HEV-related HSP usually have a spontaneous recovery. Owing to the defective liver catabolism of IgA IC with further tissue deposits, HSP occurs in HBV or HCV chronic liver diseases, usually requiring antiviral and corticosteroid therapy[91-94].

Vascular involvement with systemic vasculitis in HHV infection is a recognized extrahepatic morbidity with potential life-threatening organ dysfunction[31,95]. Among them, cryoglobulinemic vasculitis and polyarteritis nodosa are well-known vascular comorbidities in HHV infection[96,97].

HUMAN HEPATITIS VIRUSES-ASSOCIATED CRYOGLOBULINEMIC VASCULITIS

Cryoglobulinemic vasculitis is caused by IC-mediated inflammation of small-sized blood vessels and is accompanied by the activation of complements[96]. Cryoglobulins are circulating antibodies that precipitate in vitro at temperatures less than 37 °C and dissolve after rewarming, and these are either Ig or a mixture of Ig and complement components[98]. Individuals with cryoglobulinemia may remain asymptomatic without clinical abnormalities[96,98]. A typical triad of purpura, arthralgia, and weakness associated with organic dysfunction and elevated levels of rheumatoid factor (RF) was defined as cryoglobulinemic disease in 1966 by Meltzer et al[99]. Based on the composition of Ig, cryoglobulinemia can be classified into type I with monoclonal Ig (usually IgM), type II with polyclonal IgG and monoclonal IgM RF, and type III with polyclonal IgG and polyclonal IgM RF[100]. Type I is an infrequently encountered subgroup and is only found in hematological malignancies[101], whereas mixed types II and III can be associated with viral hepatitis caused by HBV, most commonly observed with HCV, and rarely identified with HAV infection[96,102-104]. Despite the presence of cryoglobulins in up to 60% of chronic HCV patients, cryoglobulinemic vasculitis only appears in around 10% of cases[76]. In chronic HHV infection, envelope glycoproteins can help the virus enter intrahepatic and circulating B lymphocytes to produce Ig with RF activity, resulting in the generation of cryoglobulins and formation of IC with vascular wall deposition[105,106].

Recurrent palpable purpura with the characteristic histopathological finding of leukocytoclastic vasculitis is the most common clinical manifestation[107]. Other cutaneous presentations are ischemic ulcers, digital gangrene, and Raynaud’s phenomenon. In Figure 1, the presence of leukocytoclastic vasculitis in biopsied skin lesions from a HCV-infected patient with cryoglobulinemia-associated purpura is shown. In addition, the presence of Meltzer triad was identified in most patients at the onset of disease[108], and skin, joint, kidney, and peripheral nerve are frequently affected organs in cryoglobulinemic vasculitis[96,108]. Renal involvement with membranoproliferative glomerulonephritis as the most common finding is associated with significant morbidity and even mortality[109]. HCV core protein and Ig are major components of IC and are distributed along the capillary walls of glomeruli[110]. Peripheral neuropathy with mononeuritis multiplex is commonly observed, which can be the first clinical manifestation[111]. Other rarely involved organs include the central nervous system, gastrointestinal tract, myocardium, and lung, and their involvement leads to the clinical presentations of impaired cognitive function, intestinal ischemia, hypertrophic cardiomyopathy, and diffuse alveolar hemorrhage[96,108,112-115].

Figure 1

Cryoglobulinemic vasculitis. The small vessels show neutrophilic inflammation, with fibrinoid necrosis and fragmented neutrophil nuclei (black arrows). Hematoxylin and eosin staining, 400 ×.

Sporadic cases with cryoglobulinemic vasculitis, either in adults or children, have been observed during acute HAV infection[36,84,104,116,117]. These patients had biopsy-proven CLV plus arthritis or glomerulonephritis, and the use of corticosteroids were required to control these complications.

Based on clinical observations, the Meltzer triad had been regarded as an IC-mediated disease secondary to the HBV infection[118]. Since then, HBs antigen in biopsied vessel wall and HBs antigen/anti-HBs in circulating cryoprecipitates have been identified in cryoglobulinemic vasculitis[119]. A retrospective study from 913 cases with cryoglobulinemia demonstrated a HBs antigen positivity of 5.8%[120], whereas analyzed data from 231 patients with mixed cryoglobulinemia only revealed an HBV infection rate of 1.8%[107]. Nevertheless, HBV is among three common infectious etiologies in patients with cryoglobulinemia[108]. This virus is predominantly associated with type II cryoglobulinemia, and its common extrahepatic manifestations are purpura, arthralgia, and neuropathy[121]. Furthermore, compared to adults, children with symptomatic cryogobulinemia have a lower occurrence of HBV infection but higher frequencies of articular and cutaneous involvement[122]. Notably, the presence of HBs antigen represents one of the main independent predictors of mortality in cryogobulinemic vasculitis[70].

Accumulated evidence indicates that the use of NAs for viral suppression in HBV-related cryogobulinemic vasculitis can cause the disappearance of cryoglobulins, normalize liver function, and significantly clinically improve most patients with mild disease, indicating a role for HBV replication in the pathogenesis[70,123]. Antiviral therapy with NAs should be a life-long prescription, and discontinuation is considered only after persistent HBs antigen loss with the seroconversion and undetectable HBV DNA[70,124]. Despite an observation with ineffective responses[70], IFN-α can be an alternative therapeutic modality[123]. The use of corticosteroids without NA therapy is ineffective for suppression of HBV viremia, resulting in refractory or relapsing disease[121]. Nevertheless, only a portion of patients with severe disease, including peripheral neuropathy and renal involvement, can achieve clinical regression under NA therapy[70,123,125]. CD20-positive B-cells are expanded and activated in mixed cryogobulinemia, and they participate in the production of cryoglobulins[126]. Clinical remission has been reported in patients with glomerulonephritis treated with NA in combination with rituximab, a monoclonal antibody against CD20 on the surface of B-cells[127,128]. Considering the risk of viral reactivation in patients with positive HBs or an occult infection with negative HBs and positive anti-HBc, prophylaxis with NAs should be initiated before the rituximab treatment[70,124,129]. Because of a potentially fatal complication, its use should be avoided during an active flare of HBV infection[70,130]. Prescription of this biologic as a second-line agent can be considered in patients with severe disease refractory to NA therapy[70,123].

Among the underlying diseases in cryoglobulinemia, HCV infection is the most common cause, with a 73% positive frequency of anti-HCV and a 86% occurrence of HCV ribonucleic acid[102,108,131]. Nevertheless, only a small portion of cryoglobulinemia with HCV infection develops significant vasculitis manifestations[96]. Similar to HBV infection, HCV is mainly associated with type II cryoglobulinemia[108]. The interaction of HCV envelope proteins with CD81 surface receptor can stimulate B-cells to expand clonally and produce monoclonal IgM RF that binds polyclonal anti-HCV core antigen, which suggests that cryoglobulinemia is due to host immune responses against HCV infection[132-134]. Although the HCV-related mixed cryoglobulinemia is a benign B-cell lymphoproliferative condition, chronic viral stimulation on the immune system leads to the selection of abnormal clones[135]. An epidemiological survey elucidated a link between HCV infection and B-cell non-Hodgkin’s lymphoma (NHL)[135]. A large-scale cohort with 146394 HCV-infected patients demonstrated a more than 20% increased risk of this malignancy[136]. Furthermore, the overall risk of B-cell NHL in mixed cryoglobulinemia patients was estimated to be 35 times higher than that in the general population[137]. Collectively, these observations have indicated a pathogenic role of HCV in B-cell NHL.

Since HCV-related cryoglobulinemic vasculitis is an antigen-driven process and its activity usually correlates with viremia, the most effective treatment is the eradication of underlying viral infection[96]. Anti-HCV therapy can follow the existing guideline as cryoglobulinemia does not specifically influence the choice of antiviral drug[138]. DAA agents alone induce SVR with less adverse events and are more effective than the combined IFN-α and ribavirin regimen in cryoglobulinemic vasculitis[79]. In a prospective multicenter study carried out in these patients, all achieved SVR with a 90% complete clinical response after DAA therapy for 12 wk or more[139]. Altogether, patients with HCV-associated cryoglobulinemic vasculitis had higher SVR (74%-100%) and clinical remission (61%-100%) rates after receiving DAA medications[79]. Higher complete response rates (75%-100%) were observed in cutaneous and musculoskeletal presentations, while lower responses (30%-70%) were identified in peripheral nerve and renal involvement[139]. In addition, DAA therapy is beneficial for HCV-associated B-cell malignancy, resulting in higher SVR and lymphoproliferative disease response rates in indolent NHL patients[140].

In addition to optimized DAA agents, corticosteroids in combination with cyclophosphamide are also considered as first-line therapy in severe fulminant manifestations, such as intestinal necrotizing vasculitis, rapid progressive glomerulonephritis, and diffuse alveolar hemorrhage[108,141]. Plasma exchange with warm apheresis solution to avoid cryoglobulin precipitation is an adjunct treatment that is useful in life-threatening disease by removing circulating cryoglobulins to interrupt the IC-mediated pathogenesis[141]. An earlier investigation showed that the addition of rituximab to the combined IFN-α and ribavirin regimen can enhance the clearance of cryoglobulins and shorten the time to clinical remission[142]. A subsequent randomized controlled trial in patients with severe disease revealed that rituximab monotherapy is as effective as conventional immunosuppressive treatment[143]. Despite the promise of rituximab as a therapeutic agent[144], there is a substantial risk for IC formation between this biologic and RF-positive IgM to exacerbate the vasculitis activity in HCV-associated type II cryoglobulinemic vasculitis[145].

HUMAN HEPATITIS VIRUSES-ASSOCIATED POLYARTERITIS NODOSA

Polyarteritis nodosa is a rare disease, with an annual incidence ranging from 0 to 2 cases per million population[97]. It is a necrotizing vasculitis affecting small- and medium-sized arteries, with systemic involvement but usually sparing the lungs. A skin-restricted form involving the area below the knees can progress to the systemic form, suggesting the same entity for both forms[146,147]. Most patients with polyarteritis nodosa belong to the idiopathic type with autoimmune-mediated mechanisms[97,148]. The secondary type is often observed in viral diseases, like cytomegalovirus, human immunodeficiency virus, and HHV infections. The association between HBV and polyarteritis nodosa was first recognized in 1970[149,150], and since then a substantial portion of cases have been identified after HBV infection. Later on, owing to the introduction of the vaccination protocol, the occurrence of HBV-related polyarteritis nodosa has gradually disappeared from clinical practice[151]. Although HCV positivity has been observed in this disorder, it is not a dominant etiological factor[152]. The occlusion and rupture of inflamed arteries can produce ischemia and hemorrhage in various organs and tissues, including skin, joint, kidney, testis, gastrointestinal tract, and peripheral nerve[97,148]. The most frequently involved organ system is the skin, presenting manifestations of palpable purpura, livedoid lesions, subcutaneous nodules, and necrotic ulcers[153]. Figure 2 demonstrates the histopathological findings of transmural necrotizing arteritis with neutrophilic infiltration and fibrinoid necrosis in a cutaneous biopsy specimen from a patient with polyarteritis nodosa-associated nodules (Case No. 2 in Table 2). Mononeuritis multiplex and symmetrical polyneuropathy are common neurological complications[154]. Gastrointestinal manifestations are usually associated with significant morbidity and can manifest as an acute surgical abdomen[155]. Renal involvement without glomerulonephritis is related to infarction or hemorrhage caused by the rupture of renal micro-aneurysms[97]. Although rare as an initial presentation, orchitis due to testicular ischemia is a characteristic finding of polyarteritis nodosa[156].

Figure 2

Polyarteritis nodosa. The vascular wall shows transmural necrotizing inflammation, with intense neutrophilic infiltration and fibrinoid necrosis (black arrow). There is residual muscular wall of the vessel (orange arrow). Hematoxylin and eosin staining, 100 ×.

Table 2

Clinical and medication profiles in five polyarteritis nodosa patients naïve to human hepatitis virus infection1

No	Age/sex	Initial symptom	Diagnosisperiod2	BVAS/FFS3	HHV status4	Follow-up manifestation	Therapy	Outcome
1	23/F	Arthralgia, rash5	2 mo	6/0	Negative	Joint, PN, skin	Az, Cs	Survival, remission
2	29/F	Arthralgia, fever, rash5	1 yr	11/0	Negative	FN, GI, joint, PN, skin	Az, Cs	Survival, remission
3	38/F	Fever, rash5	1 yr 5 mo	14/0	Negative	Joint, PN, skin	Az, Cs, Cy	Survival, remission
4	39/M	Rash	3 yr 10 mo	18/1	Negative	Kidney, skin	Az, Cs, RTX	Survival, chronic renal insufficiency
5	42/M	Arthralgia, rash	6 mo	7/0	Negative	Joint, PN, skin, kidney, testis	ADA, Az, Cs, Cy	Survival, remission

Enrollment from 2012 to 2019.

Time period from initial symptoms to the established diagnosis.

Calculation at the disease diagnosis.

Human hepatitis virus status, including examinations for hepatitis A virus, hepatitis B virus, hepatitis C virus, and hepatitis delta virus.

Erythematous nodosum-like skin lesions. ADA: Adalimumab; Az: Azathioprine; BVAS: Birmingham vasculitis activity score; Cs: Corticosteroids, Cy: Cyclophosphamide; F: Female; FFS: Four-factor score, including age above 65 years, cardiac symptoms, gastrointestinal involvement, and renal insufficiency; FN: Foot necrosis; GI: Gastrointestinal; HHV: Human hepatitis virus; M: Male; PAN: Polyarteritis nodosa; PN: Peripheral neuropathy; RTX: Rituximab.

As supported by clinical evidence, the idiopathic type benefits from combined corticosteroids and cyclophosphamide therapy, which induce remission in severe disease with organ dysfunction; whereas, mild manifestations can be treated with corticosteroids alone[97,148]. After the completion of cyclophosphamide therapy, azathioprine or methotrexate can be prescribed as a remission-maintenance agent[97]. Currently, small-molecule targeted drugs and biologics have been used in refractory patients naïve to HBV infection with successful outcomes, including Janus kinase inhibitor, B-cell targeted agent, tumor necrosis factor blocker, and interleukin-6 blockade[157-161]. The clinical data and medication profiles with biologics in polyarteritis nodosa patients recently diagnosed by authors are shown in Table 2. Although poor prognosis in earlier years is due to a delayed diagnosis[97], the overall outcome has improved to a 5-year survival rate of 80%. Outcomes are significantly worsened in association with HBV infection, age above 65 years, new-onset hypertension, renal impairment with high creatinine levels, gastrointestinal involvement requiring surgery, and peripheral nerve involvement[153].

There are no available reports related to the association of polyarteritis nodosa with HAV. Nevertheless, published cases with cutaneous or renal manifestations have shown histopathological evidence of medium-sized blood vessels’ involvement compatible with the diagnosis of polyarteritis nodosa[162,163].

Simultaneous development of mixed cryoglobulinemia and polyarteritis nodosa has been documented in patients with coinfection of HCV and HBV[164,165]. In a clinical survey on polyarteritis nodosa, the positive frequency of anti-HCV was 20% (5% with detectable HCV ribonucleic acid and they were more likely to have cutaneous manifestation)[166]. In a large cohort with 161 cases of HCV-related vasculitis (19% polyarteritis nodosa and 81% cryoglobulinemic vasculitis), there were more acute and severe clinical presentations in the former group, including constitutional symptoms, new-onset hypertension, gastrointestinal tract involvement, and mononeuritis multiplex[167]. Despite no differences in the 5-year survival rates, there was a higher complete remission rate for polyarteritis nodosa than for cryoglobulinemic vasculitis. The therapeutic guidelines for HCV-related polyarteritis nodosa have not been established yet. Reported cases have received various combinations of corticosteroids, cyclophosphamide, and antiviral agents. B-cell targeted therapy has been applied to patients with HCV-related polyarteritis nodosa[167,168]. A higher clinical relapse rate was observed for rituximab treatment than for a combined regimen with IFN-α and ribavirin in this disease[167].

During the 1970s to 1980s, HBV was a major cause of polyarteritis nodosa, with nearly half of cases having this infection, but the frequency has decreased due to improved blood safety and a viral vaccine campaign since early the 1990s, indicating HBV as a causal etiology[169]. Although histopathological studies have rarely confirmed the presence of HBV antigens in the vessel wall[151], the pathogenesis of HBV-related type is related to the deposits of IC, different from the idiopathic disease[169]. When comparing HBV- with HCV-associated polyarteritis nodosa[167,169], the former group has more general symptoms and orchitis, less cutaneous manifestation and new-onset hypertension, a lower survival rate, and a much shorter average period from viral infection to vasculitis development, 7 mo vs 20 years. In the HBV-related type, most cases have higher viral replication and HBV DNA levels, leading to the persistent presence of circulating IC[169].

The prevalence of HBs antigen in the general Taiwan population used to be near 20%, but the HBV seropositive rate in children has decreased dramatically from 11% to less than 1% after the initiation of the national vaccination program in 1984[170]. Despite a high inpatient prevalence with more than 10 cases per 100000 discharges in the United States[171], polyarteritis nodosa has been very rarely encountered by practicing physicians in Taiwan. In particular, even with more than 2 million infected patients, there is no reported association between HBV and polyarteritis nodosa[159,172-177]. Perinatal mother-to-infant HBV transmission is the most important factor responsible for a high carriage rate of HBs antigen in Taiwan[178]. Vertical transmission in infants is asymptomatic until adulthood and associated with a greater risk of chronic infection, suggesting that HBV infection causes an immunotolerant status in children who are less prone to develop full immune responses[179]. Parenteral HBV infection during adult life can induce polyarteritis nodosa within 1 year after viral infection, indicating an early post-infectious disease via this transmission route[169]. In Table 3, polyarteritis nodosa from various larger-number case series with different HBV-associated frequencies is compared[153,172-177,180-184]. Patients reported from Taiwan have no HBV infection, younger female predominance, and more cutaneous or testicular manifestation than those from other series with a HBV association.

Table 3

Comparisons of clinical and outcome profiles in polyarteritis nodosa from various case series with different hepatitis B virus-infected frequencies

Source of cases	No/age1 F%	HBV status	Fever	AM	Skin	PN	GI	Renal	TestisM%	Therapy	Death
Taiwan	12/31, 67%	0%	67%	58%	75%	42%	50%	75%	50%	Az, Cs, Cy, Bio	33%
United Kingdom	17/49, 24%	31%	76%	77%	65%	59%	65%	77%	NA	Cs, Is	38%
United States	53/54, 34%	11%	31%	55%	58%	60%	25%	66%	NA	Cs, Cy	42%
Canada	45/54, 47%	19%	63%	51%	44%	51%	53%	44%	4%	Cs, Cy	53%
South Korea	27/47, 37%	56%	52%	30%	44%	63%	48%	48%	24%	Az, Cs, Cy, Is	15%
France	348/51,37%	35%	64%	59%	50%	74%	38%	51%	17%	Av, Cs, Cy, Is	25%
India	27/38, 26%	26%	52%	37%	37%	82%	30%	59%	30%	Av, Az, Cs, Cy	11%

Mean age at disease diagnosis. AM: Articulomuscular; Az: Azathioprine; Av: Antiviral agent; Bio: Biologics; Cs: Corticosteroids; Cy: Cyclophosphamide; F: Female; GI: Gastrointestinal; Is: Immunosuppressive agent, M: Male; NA: Not available; PN: Peripheral neuropathy.

After initial therapy with corticosteroids to reduce acute vascular inflammation, the therapeutic approach in HBV-associated polyarteritis nodosa is to clear circulating IC and suppress HBV replication by plasma exchange and antiviral agents with NAs or IFN-α[169]. Since the addition of cyclophosphamide to corticosteroids has shown to benefit patients presenting with poor prognostic factors[185], this regimen can be considered in patients with severe disease. Notably, plasma exchange has not been shown to be beneficial in polyarteritis nodosa patients without HBV infection[186]. Furthermore, antiviral agents can be used concurrently with corticosteroids or combined cyclophosphamide and corticosteroids therapy[97,148]. Contradictory to the idiopathic disease, relapses have rarely been observed in HBV-related type, especially when viral replication has ceased and seroconversion from HBe antigen to antibody has been achieved after antiviral therapy[148,169].

CONCLUSION

Although HHVs primarily affect hepatocytes, they can also cause complications in other organs, and both acute and chronic viral hepatitis are associated with clinical presentations outside the liver. Vascular involvement with cutaneous and systemic vasculitis is a well-known extrahepatic morbidity. There is growing evidence suggesting a causal relationship between viral pathogens and vasculitis. Except for HDV, other HHVs have participated in the etiopathogenesis of cutaneous and systemic vasculitis via different mechanisms, including direct viral invasion of vascular endothelial cells, IC-mediated vessel wall damage, and autoimmune responses with stimulation of autoreactive B-cells and impaired regulatory T cells. Cryoglobulinemic vasculitis and polyarteritis nodosa are recognized for their association with chronic HHV infection. Therapeutic guidelines for HHV-associated vasculitis have not been established yet. Antiviral therapy should be initiated in HBV and HCV-related systemic vasculitis in addition to the use of corticosteroids. Plasma exchange and/or combined cyclophosphamide and corticosteroid therapy can be considered in patients with severe life-threatening vasculitis manifestations.

ACKNOWLEDGEMENTS

The authors are indebted to Dr. Wu IC, Division of Gastroenterology and Hepatology, for his valuable comments on HHV-related clinical manifestations, and to other physicians at the National Cheng Kung University Hospital involved in the diagnosis and management of reported patients. The Institutional Review Board of National Cheng Kung University Hospital approved this study (No. B-ER-105-108).