Science Fair Project Encyclopedia
Signs and symptoms
Hepatitis is characterised by abdominal pain, fever, hepatomegaly (enlarged liver) and jaundice (icterus). Some chronic forms of hepatitis show very few of these signs and only present when the longstanding inflammation has led to the replacement of liver cells by connective tissue; the result is cirrhosis.
Types of hepatitis
Most cases of acute hepatitis are due to viral infections:
- Hepatitis A
- Hepatitis B
- Hepatitis C
- D-agent (requires presence of the hepatitis B virus)
- Hepatitis E
- Hepatitis G
- Please see the respective articles for more detailed information
Hepatitis A is an enterovirus transmitted by the orofecal route , such as contaminated food. It causes an acute form of hepatitis and does not have a chronic stage. The patient's immune system makes antibodies against Hepatitis A that confer immunity against future infection. A vaccine is available that will prevent infection from hepatitis A.
Hepatitis B causes both acute and chronic hepatitis in some patients who are unable to eliminate the virus. Identified methods of trasmission include blood (blood transfusion, now rare), tattoos (both amateur and professionally done), sexually or vertically (from mother to her unborn child). However, in about half of cases the source of infection cannot be determined. Blood contact can occur by sharing syringes in intravenous drug use , shaving accessories such as razor blades, or touching wounds on infected persons. Needle-exchange programmes have been created in many countries as a form of prevention. In the United States, 95% of patients clear their infection and develop antibodies against Hepatitis B virus. However, 5% of patients do not clear the infection and develop chronic infection. Only these people are at risk of long term complications of Hepatitis B. Patients with chronic hepatitis B have antibodies against Hepatitis B, but these antibodies are not enough to clear the infection that establishes itself in the DNA of the affected liver cells. The continued production of virus combined with antibodies is a likely cause of immune complex disease seen in these patients. A vaccine is available that will prevent infection from hepatitis B. Hepatitis B infections result in 500,000 to 1,200,000 deaths per year worldwide due to the complications of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Hepatitis B is endemic in a number of (mainly South-East Asian) countries, making cirrhosis and hepatocellular carcinoma big killers.
Hepatitis C (originally "non-A non-B hepatitis") is probably not transmitted sexually but only by blood contact. It leads to a chronic form of hepatitis, culminating in cirrhosis. It can remain asymptomatic for 10-20 years. No vaccine is available for hepatitis C. However, patients with hepatitis C are prone to severe hepatitis if they contract either hepatitis A or B. Therefore all hepatitis C patients should be immunized against Hepatitis A and Hepatitis B if they are not already immune.
Two other hepatitis viruses are known, hepatitis D and E. The D agent, an RNA passenger virus, cannot proliferate without the presence of hepatitis B virus, because its genome lacks certain essential genes. Hepatitis E produces a picture quite similar to hepatitis A, although it can take a fulminant course in some patients, particularly pregnant women; it is more prevalent in the Indian subcontinent.
Another kind of hepatitis, hepatitis G, has been identified.
Other viruses can cause infectious hepatitis:
Ethanol, mostly in alcoholic beverages, is an important cause of hepatitis. Usually alcoholic hepatitis comes on after a period of increased alcohol consumption. Alcoholic hepatitis is characterized by a variable constellation of symptoms, which may include feeling unwell, enlargement of the liver, development of fluid in the abdomen ascites, and modest elevation of liver blood tests. Alcoholic hepatitis can vary from mild with only liver test elevation to severe liver inflammation with development of jaundice, prolonged prothrombin time, and liver failure. Severe cases are characterized by either obtundation or the combination of elevated bilirubin levels and prolonged prothrombin time; the mortality rate in both categories is 50% within 30 days of onset.
Alcoholic hepatitis is distinct from cirrhosis caused by long term alcohol consumption. Alcoholic hepatitis can occur in patients with chronic alcoholic liver disease and alcoholic cirrhosis. Alcoholic hepatitis by itself does not lead to cirrhosis, but cirrhosis is more common in patients with long term alcohol consumption. Patients who drink alcohol to excess are also more often than others found to have hepatitis C. The combination of hepatitis C and alcohol consumption accelerates the development cirrhosis in Western countries.
Drug induced hepatitis
- Halothane (a specific type of anesthetic gas)
- Methyldopa (antihypertensive)
- Isoniazid (INH) and rifampicin (tuberculosis-specific antibiotics)
- Phenytoin and valproic acid (antiepileptics)
- Zidovudine (antiretroviral i.e. against AIDS)
- Ketoconazole (antifungal)
- Nifedipine (antihypertensive)
- Ibuprofen and indomethacin (NSAIDs)
- Amitriptyline (antidepressant)
- Amiodarone (antiarrhythmic)
- Nitrofurantoin (antibiotic)
- Oral contraceptives
- Some herbs and nutritional supplements
The clinical course of drug-induced hepatitis is quite variable, depending on the drug and the patient's tendency to react to the drug. For example, halothane hepatitis can range from mild to fatal as can INH-induced hepatitis. Oral contraceptives can cause structural changes in the liver. Amiodarone hepatitis can be untreatable since the long half life of the drug (up to 60 days) means that there is no effective way to stop exposure to the drug. Statins can cause elevations of liver function blood tests normally without indicating an underlying hepatitis. Lastly, human variability is such that any drug can be a cause of hepatitis.
Other toxins that cause hepatitis
Toxins and drugs can cause hepatitis:
- The Amanita (death-cap) mushroom (Amanita) contains amatoxins such as alpha-amanitin. A single mushroom can be enough to be lethal (10 mg of α-amanitin).
- Yellow phosphorus (a metal) is an industrial toxin.
- Paracetamol (Acetaminophen in the USA) can cause hepatitis when taken in an overdose. The severity of liver damage can be limited by prompt administration of acetylcysteine.
- Carbon tetrachloride ("tetra", a dry cleaning agent), chloroform and trichloroethylene, all chlorine-containing carbohydrates, cause steatohepatitis (hepatitis with fatty liver).
Anomalous presentation of human leukocyte antigen (HLA) class II on the surface of hepatocytes — possibly due to genetic predisposition or acute liver infection — causes a cell-mediated immune response against the body's own liver, resulting in autoimmune hepatitis.
Autoimmune hepatitis has a prevalence of 1-2 per 1000. As with most other autoimmune diseases, it affects women much more often than men (8:1). Liver enzymes are elevated, as is bilirubin. Autoimmune Hepatitis can progress to cirrhosis. Treatment is with steroids and disease-modifying antirheumatic drugs (DMARDs).
The diagnosis of autoimmune Hepatitis is best achieved with a combination of clinical and laboratory findings. A number of specific antibodies found in the blood (antinuclear antibody (ANA), smooth muscle antibody (SMA), Liver/kidney microsomal antibody (LKM-1) and anti-mitochondrial antibody (AMA)) are of use, as is finding an increased Immunoglobulin G level. However, the diagnosis of autoimmune hepatitis always requires a liver biopsy . In complex cases a scoring system can be used to help determine if a patient has autoimmune hepatitis, which combines clinical and laboratory features of a given case.
Four subtypes are recognised, but the clinical utility of distinguishing subtypes is limited.
- Positive ANA and SMA, raised immunoglobulin G
- Positive LKM-1 (typically children and teenagers; disease can be severe)
- All antibodies negative, positive antibodies against soluble liver antigen (SLA)
- No autoantibodies detected
Alpha 1-antitrypsin deficiency
Non-alcoholic steatohepatitis (NASH) is a type of hepatitis which resembles alcoholic hepatitis on liver biopsy (fat droplets, inflammatory cells, but usually no Mallory's hyalin) but occurs in patients who have no known history of alcohol abuse. NASH is more common in women and the most common cause is obesity or the metabolic syndrome. A related but less serious condition is called "fatty liver" (steatosis hepatis). A liver biopsy for fatty liver shows fat droplets throughout the liver, but no signs of inflammation or Mallory's hyalin.
The diagnosis depends on history, physical exam, blood tests, radiological imaging and sometimes a liver biopsy. The initial evaluation to identify the presence of fatty infiltration of the liver is radiologic imaging including ultrasound, computed tomographic imaging, or magnetic resonance imaging. However, radiologic imaging cannot readily identify inflammation in the liver. Therefore, the differentiation between steatosis and NASH often requires a liver biopsy. It can also be difficult to distinguish NASH from Alcoholic Hepatitis when the patient has a history of alcohol consumption. Sometimes in such cases a trial of abstinence from alcohol along with follow up blood tests and a repeat liver biopsy are required.
NASH is becoming recognized as the most important cause of liver disease second only to Hepatitis C in numbers of patients going on to cirrhosis.
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