Hepatitis classification

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Classification Hepatitis A Hepatitis B Hepatitis C Hepatitis D Hepatitis E Alcoholic Hepatitis Autoimmune Hepatitis
Differential Diagnosis

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Classification

Viral

Most cases of acute hepatitis are due to viral infections:

• Hepatitis A
• Hepatitis B
• Hepatitis C
• Hepatitis B with D
• Hepatitis E
• Hepatitis F virus (existence unknown)
• Hepatitis G, or GBV-C
• In addition to the hepatitis viruses (please note that the hepatitis viruses are not all related), other viruses can also cause hepatitis, including cytomegalovirus, Epstein-Barr virus, yellow fever, etc.

Hepatitis A

Hepatitis A or infectious jaundice is caused by a picornavirus transmitted by the fecal-oral route, often associated with ingestion of contaminated food or with anal/oral sex. 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. People with hepatitis A are advised to rest, stay hydrated and avoid alcohol. A vaccine is available that will prevent infection from hepatitis A for life. Hepatitis A can be spread through personal contact, consumption of raw sea food or drinking contaminated water. This occurs primarily in third world countries. Strict personal hygiene and the avoidance of raw and unpeeled foods can help prevent an infection. Infected people excrete the hepatitis A virus with their feces two weeks before and one week after the appearance of jaundice. The time between the infection and the start of the illness averages 28 days (ranging from 15 to 50 days), and most recover fully within 2 months, although approximately 15% of sufferers may experience continuous or relapsing symptoms from six months to a year following initial diagnosis.

Hepatitis B

Hepatitis B is caused by a hepadnavirus, which can cause both acute and chronic hepatitis. Chronic hepatitis develops in the 15% of patients who are unable to eliminate the virus after an initial infection. Identified methods of transmission include blood (blood transfusion, now rare), tattoos (both amateur and professionally done), sexually (through sexual intercourse or through contact with blood or bodily fluids), or via mother to child by breast feeding (minimal evidence of transplacental crossing). 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.

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 the immune complex disease seen in these patients. A vaccine is available that will prevent infection from hepatitis B for life. 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. There are six FDA-approved treatment options available for persons with a chronic hepatitis B infection: alpha-interferon, pegylated interferon adefovir, entecavir, telbivudine and lamivudine. About 65% of persons on treatment achieve a sustained response.

Hepatitis B is the most infectious bloodborne pathogen known.

Hepatitis C

Hepatitis C (originally "non-A non-B hepatitis") is caused by a virus with an RNA genome that is a member of the Flaviviridae family. It can be transmitted through contact with blood (including through sexual contact where the two parties' blood is mixed) and can also cross the placenta. Hepatitis C may lead to a chronic form of hepatitis, culminating in cirrhosis. It can remain asymptomatic for 10-20 years. Patients with hepatitis C are susceptible to severe hepatitis if they contract either hepatitis A or B, so all hepatitis C patients should be immunized against hepatitis A and hepatitis B if they are not already immune, and avoid alcohol. The virus can cause cirrhosis of the liver. HCV viral levels can be reduced to undetectable levels by a combination of interferon and the antiviral drug ribavirin. The genotype of the virus determines the rate of response to this treatment regimen. Genotype 1 is more resistant to interferon therapy than other HCV genotypes.

Hepatitis D

Hepatitis D is caused by hepatitis delta agent, which is similar to a viroid as it can only propagate in the presence of the Hepatitis B virus.

Hepatitis E

Hepatitis E produces symptoms 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.

Hepatitis F virus

Hepatitis F virus is a hypothetical virus linked to hepatitis. Several hepatitis F virus candidates emerged in the 1990s; none of these reports have been substantiated.

Hepatitis G, or GBV-C

Another potential viral cause of hepatitis, hepatitis G virus, has been identified, and is probably spread by blood and sexual contact. There is, however, doubt about whether it causes hepatitis, or is just associated with hepatitis, as it does not appear to replicate primarily in the liver. It is now classified as GBV-C.

Alcoholic Hepatitis

Ethanol, mostly in alcoholic beverages, is a significant cause of hepatitis. Usually alcoholic hepatitis comes 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 (dulled consciousness) 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 of cirrhosis in Western countries.

Drug Induced Hepatitis

A large number of drugs can cause hepatitis:

• Allopurinol
• Amitriptyline (antidepressant)
• Amiodarone (antiarrhythmic)
• Azathioprine
• Halothane (a specific type of anesthetic gas)
• Hormonal contraceptives
• Ibuprofen and indomethacin (NSAIDs)
• Isoniazid (INH), rifampicin, and pyrazinamide (tuberculosis-specific antibiotics)
• Ketoconazole (antifungal)
• Methotrexate (immune suppressant)
• Methyldopa (antihypertensive)
• Minocycline (tetracycline antibiotic)
• Nifedipine (antihypertensive)
• Nitrofurantoin (antibiotic)
• Phenytoin and valproic acid (antiepileptics)
• Troglitazone (antidiabetic, withdrawn in 2000 for causing hepatitis)
• Zidovudine (antiretroviral i.e. against HIV)
• 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. Hormonal contraception 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.

Toxin Induced Hepatitis

Toxins and drugs can cause hepatitis:

• Amatoxin-containing mushrooms, including the Death Cap (Amanita phalloides), the Destroying Angel (Amanita ocreata), and some species of Galerina. A portion of a single mushroom can be enough to be lethal (10 mg or less of α-amanitin).
• White phosphorus, an industrial toxin and war chemical.
• Paracetamol (acetaminophen in the United States) can cause hepatitis when taken in an overdose. The severity of liver damage may be limited by prompt administration of acetylcysteine.
• Carbon tetrachloride ("tetra", a dry cleaning agent), chloroform, and trichloroethylene, all chlorinated hydrocarbons, cause steatohepatitis (hepatitis with fatty liver).
• Cylindrospermopsin, a toxin from the cyanobacterium Cylindrospermopsis raciborskii and other cyanobacteria.

Metabolic Disorders

Some metabolic disorders cause different forms of hepatitis. Hemochromatosis (due to iron accumulation) and Wilson's disease (copper accumulation) can cause liver inflammation and necrosis.

Obstructive

Obstructive jaundice is the term used to describe jaundice due to obstruction of the bile duct (by gallstones or external obstruction by cancer). If longstanding, it leads to destruction and inflammation of liver tissue.

Autoimmune

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 an incidence of 1-2 per 100,000 per year, and a prevalence of 15-20/100,000. 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 recognized, but the clinical utility of distinguishing subtypes is limited.

1. Positive ANA and SMA, raised immunoglobulin G (classic form, responds well to low dose steroids)
2. Positive LKM-1 (typically female children and teenagers; disease can be severe)
3. All antibodies negative, positive antibodies against soluble liver antigen (SLA)(now designated SLP/LP) (this group behaves like group 1)
4. No autoantibodies detected (~13%)

Alpha 1-Antitrypsin Deficiency

In severe cases of alpha 1-antitrypsin deficiency (A1AD), the accumulated protein in the endoplasmic reticulum causes liver cell damage and inflammation.

Nonalcoholic Steatohepatitis

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 hyaline) 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 hepatitis), which occurs in up to 80% of all clinically obese people. 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 radiological imaging including ultrasound, computed tomographic imaging, or magnetic resonance imaging. However, radiological 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 repeated 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.

Ischemic Hepatitis

Ischemic hepatitis is caused by decreased circulation to the liver cells. Usually this is due to decreased blood pressure (or shock), leading to the equivalent term shock liver. Patients with ischemic hepatitis are usually very ill due to the underlying cause of shock. Rarely, ischemic hepatitis can be caused by local problems with the blood vessels that supply oxygen to the liver (such as thrombosis, or clotting of the hepatic artery which partially supplies blood to liver cells). Blood testing of a person with ischemic hepatitis will show very high levels of transaminase enzymes (AST and ALT), which may exceed 1000 U/L. The elevation in these blood tests is usually transient (lasting 7 to 10 days). It is rare that liver function will be affected by ischemic hepatitis.