Handwritten lecture about Hepatitis B Virus pathophysiology, diagnosis and treatment for medical students studying for the USMLE boards.
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BONUS QUESTION- What kind of vaccine is Hepatitis B?
Vaccine is a subunit against sAg
0:00 Structure
2:33 Pathophysiology
5:50 Transmission
8:24 Epidemiology
10:26 Diagnosis and Serology
18:35 Acute Hepatitis
24:30 Chronic Hepatitis
30:04 Prevention
The hepatitis B virus is a common cause of liver disease, cirrhosis and cancer. So it's important to be able to diagnose and treat this illness.
VIROLOGY OF HEPATITIS B
Hepatitis B virus is unique because it is a partially dsDNA. It has a nucleocapsid core which is made up of core antigen and envelope antigen. Around the envelope there is a surface antigen. PATHOPHYSIOLOGY OF
HEPATITIS B VIRUS
There is a receptor for the hepatitis B virus on the cell. Once attached the nucleocapsid goes into the cells and uncoats. The partially dsDNA hepatitis B virus goes into the nucleus where the remainder of the DNA is completed where it is covalently completed circular DNA cccDNA. Now it is a double stranded DNA. The cccDNA is used by the hepatitis B virus for transcription of the nucleocapsid. The hepatitis B Virus can then go back into the nucleus or go into the Golgi apparatus to get a new envelope. The virus than exits the cell using exocytosis.
TRANSMISSION OF HEPATITIS B
It can transfer from mother to child during delivery. Hepatitis B can be transferred via sexual contact. It can also be transmitted through blood transmission, which is rare.
EPIDEMIOLOGY
Hepatitis B virus is highly prevalent in Subsaharan Africa. Moderately present in Northern Africa, Asia and South America. Hepatitis B has a low prevalence in US, Europe and Australia with the primary mode of transmission being sexual contact and IV Drug use. Over 2 Billion people have been exposed to hepatitis B and 887 thousand individuals have died from Hepatitis B-related liver disease such as cirrhosis and hepatocellular carcinoma.
DIAGNOSIS OF HEPATITIS B
The surface antigen of the HBV represents infection while the antibody to the hepatitis B surface antigen represents immunity. The window period is between the hepatitis B surface antigen and the Hepatitis B surface antibody. The core antibody helps diagnose during the window period and determine if the patient has an acute hepatitis B infection or chronic infection. The envelope antigen helps determine the replication of the hepatitis B virus during chronic infection.
ACUTE HEPATITIS
Majority of the time acute hepatitis B infection doesn't have symptoms, however, 30 percent of the time they present with icteric symptoms. Less than 1 percent of the time they present with fulminant infection. Liver function tests such as AST and ALT can be in the thousands with variable bilirubin. INR is prognostic. For neonate, 95 percent of the time hepatitis B can progression from acute to chronic and in adults the progression only occurs 5 percent of the time. Hepatitis C virus, Hepatitis A virus, and Hepatitis D virus increase risk of fulminant liver disease. There are some extra hepatic manifestations of hepatitis B virus such as polyarteritis nodosa, GN and aplastic anemia. Treatment of acute hepatitis B virus infection is primarily to vaccinate contacts. However, some individuals with certain risk factors should be treated such as severe protracted course, high INR or bilirubin, immunodeficiency, hepatitis C or hepatitis D virus.
CHRONIC HEPATITIS
Chronic hepatitis occurs when the surface antigen is present for longer than 6 months. Symptoms are typically related to chronic liver disease. It is important to test for HBV DNA viral load as this suggest increased risk of cirrhosis and hepatocellular carcinoma. It also predicts low response of the hepatitis B virus to interferon treatment. Also check for envelope antigen to monitor for replication and transmission. Patient with hepatitis B infection should be routinely screening for hepatocellular cancer with ultrasound with and without AFP. They should also have fibrosis testing with elastography and liver biopsy to rule out hepatitis b associated liver disease. Treatment of hepatitis B depends on whether they have cirrhosis or not. If they have cirrhosis, they should be treatment. If compensated cirrhosis should start on interferon for 48 weeks and if decompensated cirrhosis than start on nucleostide treatment. If no cirrhosis it depends on whether the Hepatitis B envelope antigen is present or not.
PREVENTION
Hepatitis B immunoglobulins can provide protection for 3-6 months. Vaccine can also prevent, it is a 3 dose vaccine and for some a booster is necessary. For needlestick injuries treatment depends on whether the patient is vaccinated vs unvaccinated.