Clinical Expression and Progression
Two patterns of HDV infection have been described: co-infection and superinfection.
Co-infection involves simultaneous infection with both HDV and HBV resulting in the occurrence of both acute hepatitis D and B. This type of infection is usually acute, self-limiting and clinically indistinguishable from classical acute hepatitis B. Like patients with HBV mono-infection, less than 5 % of patients progress to chronic HBV and HDV infection. Coinfection, however, may cause severe hepatitis with a high risk for developing fulminant hepatitis. This is of special concern in intravenous drug users.
Superinfection involves the HDV infection of a chronically infected HBV carrier. In contrast to co-infection, the HDV is cleared spontaneously only in a minority of patients. Generally, there is severe acute hepatitis with a short incubation time that leads to chronic hepatitis delta in up to 80% of cases. Superinfection may cause acute on chronic liver failure or severe chronic active hepatitis rapidly progressing to cirrhosis. HDV suppresses the replication of HBV in most individuals with superinfection.
Chronic HDV infection causes an accelerated progression to fibrosis and early decompensation in the presence of cirrhosis. About 60 to 70% of patients with chronic hepatitis D develop cirrhosis, which usually takes 5 to 10 years to develop but can occur as quickly as 2 years after the initial infection. However, indolent courses and asymptomatic patients have also been reported.
Hepatic decompensation (decreased liver function), rather than the development of HCC, is the first usual clinical endpoint during the course of HDV infection. Nonetheless, HDV infection increases the risk of liver cancer. HDV patients have lower platelets, larger varices on endoscopy and smaller liver sizes. Data analyzed from the HDIN registry showed that poor liver function, indicated by low platelet counts of <100,000/μL occurred in approximately one-fourth of all HDV infected patients, while liver cancer developed in 2.5% of HDV patients. Factors associated with poor long-term outcomes include age above 40, male sex, low platelet counts, high bilirubin and INR values and Southeast Mediterranean origin.
Author: Minaam Abbas