Relationship between hepatitis C virus infection and pulmonary disorders: potential mechanisms of interaction

HCV Extrahepatic Manifestations

Hepatitis C virus (HCV) has been shown to affect many tissues other than liver. However, of the many extrahepatic manifestations (EMs) that have been associated with HCV, including cryoglobulinemia, lymphoma, insulin resistance, type 2 diabetes and neurological disorders, only a few have been shown to be directly related to HCV infection of extrahepatic tissues. HCV-triggered immune-mediated mechanisms account for most of the EMs. It is estimated that up to 74% of patients with chronic hepatitis C can develop at least one EM. All HCV patients with EMs should be considered for antiviral therapy, although not all will resolve with sustained virological response.

Uncommon immune-mediated extrahepatic manifestations of HCV infection

INTRODUCTION

Chronic hepatitis C virus (HCV) infection has been associated with myriad extrahepatic manifestations, often resulting from aberrant immune responses. Among the most common immune-mediated manifestations of HCV infection, mixed cryoglobulinemia is the best known extra-hepatic complication. Areas covered: Here we review less common extrahepatic manifestations of HCV infection, with ascertained or presumed immune pathogenesis and the role of the new all oral direct-acting antiviral agents. Rheumatologic, dermatologic, ophthalmologic, renal, pulmonary, hematologic, cardiovascular, and neuropsychiatric manifestations of HCV infection have been considered. Expert commentary: Pathogenesis of HCV-induced aberrant immune responses resulting in peculiar clinical manifestations is not restricted to a single mechanism. A sound approach would therefore consider implementation of an etiologic treatment, through use of antiviral medications, to stop upstream in the pathogenic process all the immune mechanisms leading to hepatic and extrahepatic abnormalities. With the recent introduction of interferon-free, direct antiviral agents, capable of warranting cure for nearly all HCV-infected patients subjected to therapy, both common and uncommon extrahepatic manifestations of chronic hepatitis C are expected to no longer constitute a matter of comorbidity in the course of HCV infection.

Other Extrahepatic Manifestations of Hepatitis C Virus Infection (Pulmonary, Idiopathic Thrombocytopenic Purpura, Nondiabetes Endocrine Disorders)

Extrahepatic manifestations of hepatitis C virus (HCV) infection are a rare but serious condition. This article summarizes the current literature on the association between HCV and endocrine and pulmonary manifestations, as well as idiopathic thrombocytopenic purpura (ITP). HCV may directly infect extrahepatic tissues and interact with the immune system predisposing for obstructive and interstitial lung disease, ITP, autoimmune thyroiditis, infertility, growth hormone and adrenal deficiencies, osteoporosis, and potentially lung and thyroid cancers. However, in many cases, the current evidence is divergent and cannot sufficiently confirm a true association, which emphasizes the need for future targeted projects in this field.

A Study of the Interaction between Hepatitis C Virus Infection and Pulmonary Disorders: Assessment of Interferon Gamma and Alpha-1-Antitrypsin

Objectives: To study lung diseases in chronic HCV infection and vice versa and to find immunological and/or hereditary interrelating factors.Material and Methods: Study included 134 individuals, all were subjected to screening for anti-HCV antibodies by ELISA, HCV-RNA by real time PCR, pulmonary function tests, quantitative assay of interferon gamma and alpha-1- antitrypsin in serum by ELISA and genotyping of alpha-1- antitrypsin gene by Light Cycler PCR.Results: 76.5% of chronic HCV patients had abnormal PFT (P = 0.03), mainly reduced DLCO and reversible airway obstruction, and 41.6% of chest diseased patients were HCV-positive with a significant decrease in large and small airways functions. Interferon therapy improved PFT parameters. Only 33% of chronic HCV infection affected by chest abnormality responded to interferon therapy while 50% of chest free patients did. Serum IFN-γ was higher in HCV and chest patients than in control (P=0.02). All serum α1AT deficient patients had M/null genotype.Conclusions: A pathogenic role of chronic HCV infection in lung diseases is evident. Interferon treatment may reduce chest complications and improve pulmonary functions. However, chest affection may reduce the response to interferon treatment. M/null genotype of α1AT gene might play a role in chronic HCV infection and chest co-affection.