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| {{Hepatitis}} | | {{Hepatitis}} |
| {{CMG}} | | {{CMG}} |
| | | ==Overview== |
| == Types of hepatitis == | |
| :''Please see the respective articles for more detailed information''.
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| {{Seealso|Infectious canine hepatitis}}
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| === Viral ===<!-- This section is linked from [[Hepatitis B]] -->
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| Most cases of acute hepatitis are due to viral infections:
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| * [[Hepatitis A]]
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| * [[Hepatitis B]]
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| * [[Hepatitis C]]
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| * [[Hepatitis D|Hepatitis B with D]]
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| * [[Hepatitis E]]
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| * [[Hepatitis F virus]] (existence unknown)
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| * [[Hepatitis G]], or GBV-C
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| * 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.
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| ====Hepatitis A====
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| [[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|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),<ref>{{cite web | title = CDC Hepatitis A FAQ | url=http://www.cdc.gov/ncidod/diseases/hepatitis/a/faqa.htm#general | accessdate = 2008-03-03}}</ref> 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]].<ref>{{cite web | title = CDC Hepatitis A Fact Sheet | url=http://www.cdc.gov/ncidod/diseases/hepatitis/a/fact.htm | accessdate = 2008-03-03}}</ref>
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| ====Hepatitis B====
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| [[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), [[tattoo]]s (both amateur and professionally done), [[sexually transmitted disease|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 [[syringe]]s in [[intravenous drug]] use, shaving accessories such as razor blades, or touching [[wounds]] on infected persons. [[Needle-exchange programme]]s have been created in many countries as a form of [[prevention]].
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| 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 (epidemiology)|endemic]] in a number of (mainly South-East Asian) countries, making [[cirrhosis]] and [[hepatocellular carcinoma]] [[big killer]]s. 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.
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| Hepatitis B is the most infectious bloodborne pathogen known.
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| ====Hepatitis C====
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| [[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.
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| ====Hepatitis D====
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| [[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.
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| ====Hepatitis E====
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| [[Hepatitis E]] produces symptoms similar to [[hepatitis A]], although it can take a fulminant course in some patients, particularly [[pregnancy|pregnant]] [[women]]; it is more prevalent in the Indian subcontinent.
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| ====Hepatitis F virus ====
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| [[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.
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| ====Hepatitis G, or GBV-C====
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| Another potential viral cause of hepatitis, [[hepatitis G]] virus, has been identified,<ref>{{cite journal
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| | author = Jeff Linnen ''et al''
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| | date = 26 January 1996
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| | title = Molecular Cloning and Disease Association of Hepatitis G Virus: A Transfusion-Transmissible Agent
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| | journal = Science
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| | volume = 271
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| | issue = 5248
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| | pages = 505 - 508
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| | doi = 10.1126/science.271.5248.505
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| | accessdate = 6.11.2006
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| }}</ref> and is probably spread by blood and sexual contact.<ref>{{cite journal
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| | author = K Stark ''et al''
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| | date = December 1996
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| | title = Detection of the hepatitis G virus genome among injecting drug users, homosexual and bisexual men, and blood donors
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| | journal = The Journal of Infectious Diseases
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| | volume = 174
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| | issue = 6
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| | pages = 1320-1323
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| | id = PMID 8940225
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| | accessdate = 6 November 2006
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| }}</ref> 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.<ref>{{cite journal
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| | author = Mario G. Pessoa ''et al.''
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| | date = 30 December 2003
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| | title = Quantitation of hepatitis G and C viruses in the liver: evidence that hepatitis G virus is not hepatotropic
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| | journal = Hepatology
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| | volume = 27
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| | issue = 3
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| | pages = 877 - 880
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| | doi = 10.1002/hep.510270335
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| | accessdate = 6 November 2006
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| }}</ref> It is now classified as GBV-C[http://phene.cpmc.columbia.edu/Ictv/fs_flavi.htm#Genus00].
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| === Other viral causes of hepatitis ===
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| Other viral infections can cause hepatitis (inflammation of the liver):
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| * [[Mumps virus]]
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| * [[Rubella virus]]
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| * [[Cytomegalovirus]]
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| * [[Epstein-Barr virus]]
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| * Other [[taxonomic family herpesviridae|herpes virus]]es
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| === Alcoholic hepatitis===
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| {{main|Alcoholic hepatitis}}
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| [[Ethanol]], mostly in [[alcoholic beverage]]s, 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.
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| 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<ref>requested</ref>. The combination of hepatitis C and [[alcohol consumption]] accelerates the development of cirrhosis in Western countries.
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| === Drug induced hepatitis ===
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| {{main|Hepatotoxicity}}
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| A large number of drugs can cause hepatitis:<ref>{{cite web
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| | url = http://www.healthatoz.com/healthatoz/Atoz/dc/caz/infc/hepa/hepres.jsp
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| | title = Hepatitis as a result of chemicals and drugs
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| | accessdate = 2006-07-01
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| | work = HealthAtoZ
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| | language = English
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| }}</ref>
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| * [[Allopurinol]]
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| * [[Amitriptyline]] ([[antidepressant]])
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| * [[Amiodarone]] (antiarrhythmic)
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| * [[Azathioprine]]<ref>{{cite journal | author = Bastida G, Nos P, Aguas M, Beltrán B, Rubín A, Dasí F, Ponce J | title = Incidence, risk factors and clinical course of thiopurine-induced liver injury in patients with inflammatory bowel disease. | journal = Aliment Pharmacol Ther | volume = 22 | issue = 9 | pages = 775-82 | year = 2005
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| | pmid = 16225485}}</ref>
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| * [[Halothane]] (a specific type of anesthetic gas)
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| * [[Hormonal contraception|Hormonal contraceptives]]
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| * [[Ibuprofen]] and [[indomethacin]] ([[NSAID]]s)
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| * [[Isoniazid]] (INH), [[rifampicin]], and [[pyrazinamide]] ([[tuberculosis]]-specific [[antibiotic]]s)
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| * [[Ketoconazole]] ([[antifungal]])
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| * [[Methotrexate]] (immune suppressant)
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| * [[Methyldopa]] ([[antihypertensive]])
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| * [[Minocycline]] ([[tetracycline antibiotic]])
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| * [[Nifedipine]] (antihypertensive)
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| * [[Nitrofurantoin]] ([[antibiotic]])
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| * [[Phenytoin]] and [[valproic acid]] (antiepileptics)
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| * [[Troglitazone]] (antidiabetic, withdrawn in 2000 for causing hepatitis)
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| * [[Zidovudine]] (antiretroviral i.e. against [[HIV]])
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| * Some herbs and nutritional supplements<ref name="pmid11151906">{{cite journal |author=Nadir A, Reddy D, Van Thiel DH |title=Cascara sagrada-induced intrahepatic cholestasis causing portal hypertension: case report and review of herbal hepatotoxicity |journal=Am. J. Gastroenterol. |volume=95 |issue=12 |pages=3634-7 |year=2000 |pmid=11151906 |doi=}}</ref>
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| 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. [[Statin]]s 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.
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| === Other toxins that cause hepatitis ===
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| [[Toxins]] and [[drugs]] can cause hepatitis:
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| * [[Amatoxin]]-containing [[mushroom]]s, including the [[Death Cap]] (''Amanita phalloides''), the [[Destroying angel|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).
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| * White [[phosphorus]], an industrial toxin and war chemical.
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| * [[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]].
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| * [[Carbon tetrachloride]] ("tetra", a dry cleaning agent), [[chloroform]], and [[trichloroethylene]], all [[chlorinated hydrocarbon]]s, cause [[steatohepatitis]] (hepatitis with [[fatty liver]]).
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| * [[Cylindrospermopsin]], a [[toxin]] from the [[cyanobacterium]] ''Cylindrospermopsis raciborskii'' and other [[cyanobacteria]].
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| === Metabolic disorders ===
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| 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]].
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| ''See below'' for [[non-alcoholic steatohepatitis]] (NASH), effectively a consequence of [[metabolic syndrome]].
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| === Obstructive ===
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| "Obstructive jaundice" is the term used to describe jaundice due to obstruction of the [[bile duct]] (by [[gallstone]]s or external obstruction by [[cancer]]). If longstanding, it leads to destruction and inflammation of liver tissue.
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| === Autoimmune ===
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| Anomalous presentation of [[human leukocyte antigen]] (HLA) class II on the surface of [[hepatocyte]]s, possibly due to [[gene]]tic predisposition or acute liver infection; causes a cell-mediated [[immune response]] against the body's own liver, resulting in autoimmune hepatitis.
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| 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 disease]]s, it affects [[women]] much more often than [[men]] (8:1). [[Liver enzyme]]s are elevated, as is [[bilirubin]]. Autoimmune hepatitis can progress to [[cirrhosis]]. Treatment is with [[steroid]]s and [[disease-modifying antirheumatic drug]]s (DMARDs).
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| 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-[[mitochondria]]l [[antibody]] (AMA)) are of use, as is finding an increased [[IgG|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.
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| Four subtypes are recognised, but the clinical utility of distinguishing subtypes is limited.
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| # positive ANA and SMA, raised immunoglobulin G (classic form, responds well to low dose steroids);
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| # positive LKM-1 (typically female children and teenagers; disease can be severe);
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| # all antibodies negative, positive antibodies against soluble liver antigen (SLA)(now designated SLP/LP) (this group behaves like group 1), and
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| # no autoantibodies detected (~13%)
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| === Alpha 1-antitrypsin deficiency ===
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| In severe cases of [[alpha 1-antitrypsin deficiency]] (A1AD), the accumulated [[protein]] in the [[endoplasmic reticulum]] causes liver cell damage and [[inflammation]].
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| === Nonalcoholic steatohepatitis ===
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| [[Non-alcoholic steatohepatitis]] ([[NASH]]) is a type of hepatitis which resembles alcoholic hepatitis on [[liver biopsy]] ([[fat]] droplets, [[inflammatory cells]], but usually no [[Mallory body|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]].
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| The diagnosis depends on history, [[physical exam]], [[blood test]]s, [[radiology|radiological]] [[imaging]] and sometimes a [[liver biopsy]]. The initial evaluation to identify the presence of fatty infiltration of the liver is [[radiology|radiological]] [[imaging]] including [[medical ultrasonography|ultrasound]], [[CT scan|computed tomographic imaging]], or [[magnetic resonance imaging]]. However, [[radiology|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.
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| [[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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| ===Ischemic hepatitis===
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| {{Seealso|Ischemic hepatitis}}
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| 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 [[liver function tests|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]].
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| == References == | | == References == |