WHAT IS CHRONIC HEPATITIS C?
Chronic hepatitis C is defined as the persistence of HCV RNA in the blood for six months or more. In people with chronic hepatitis C, the immune system has failed to clear the virus from the body. Therefore, all individuals with chronic hepatitis C will always have an elevated HCV RNA. Once a person is chronically infected with HCV, the potential exists for liver damage and cirrhosis along with its complications, including liver failure and liver cancer. (The treatment of chronic hepatitis C will be discussed in Chapter 13.)
The Reason So Many Cases of Acute Hepatitis C Become Chronic
HCV is a virus that is very difficult to clear from the body. Thus, most people who become infected with HCV (acute hepatitis C), develop chronic disease (chronic hepatitis C). In fact, approximately 60-85 percent of infected people develop chronic hepatitis C. This is in stark contrast to the incidence of progression from acute to chronic in other forms of viral hepatitis. For example, hepatitis B progresses to chronic disease only about 5 percent of the time when the infection is acquired as an adult. And, hepatitis A never leads to chronic disease. It appears that the immune system is not very efficient in clearing HCV. So, what makes HCV so formidable?
The genes that make up HCV can vary slightly from one strain to another. These different genetic variations of HCV are known as hepatitis C mutants, or quasispecies. The entire hepatitis C viral population that is present in a person infected with HCV is made up of a conglomerate of related, yet slightly different, HCV species. This virus population usually consists of one HCV mutant group that is strongest and dominant and numerous other HCV mutants that are weaker. These mutants are all similar in structure but differ slightly from one another. These slight variations in structure account for the fact that some HCV mutants are stronger and thus better equipped to fight the immune system than other HCV mutants. This is analogous to Darwin’s theory of evolution: the survival of the fittest.
The fact that HCV is such a resourceful and cunning virus probably accounts for why most people progress to chronic disease. When HCV is being attacked by the immune system during the acute infection, it can mutate into a stronger quasispecies variant. In this manner, HCV is able to outwit the body’s immune system and thwart its attempts to fail eradicate it. Thus, HCV tricks the body’s immune surveillance and escapes eradication, allowing for progression to chronic disease. This partly explains why long-term response rates to therapy with interferon (see Chapter 13) although getting much better, are still not 100 percent. It also may explain why it is so difficult to create a vaccination against HCV (see Chapter 24).
Certain factors have been identified as being predictive of which people are most likely to progress to chronic disease (that is -least likely to clear acute HCV). These are listed in Table 10.1
TABLE 10.1 Risk Factors Predictive of Progression From Acute to Chronic HCV
1. Men
2. Older Age (greater than 40 years old) at the time of infection ( children have a chronicity rate of 50-60 percent/ adults have a chronicity rate of 60-85 percent)
3. African- American men
4. Transfusion – Acquired HCV
5. Immunosuppressed State ( such as HIV infection or chronic dialysis)
6. Asymptomatic Acute HCV ( lack of jaundice, fatigue, joints aches etc. during acute infection)
7. Genetic Predisposition (Certain histocompatibility genes code for disease progression)
All contents of this article are Copyright © Melissa Palmer, MD
Melissa Palmer, MD is the author of " Dr. Melissa Palmer's Guide of Hepatitis and Liver Disease". (Published 2004. Penguin Putnam).
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