Anti-Liver kidney microsomal type 1 (anti-LKM-1) antibodies are autoantibodies, proteins produced by the body's immune system that recognise and target its own enzyme called cytochrome P450 2D6 (CYP2D6), a protein found primarily in liver cells. The development of anti-LKM-1 antibodies is strongly associated with type 2 autoimmune hepatitis. This test detects the presence of anti-LKM-1 (or antibody against CYP2D6) in the blood.
Autoimmune hepatitis is an acute or chronic inflammation of the liver that can lead to liver cirrhosis and, in some cases, to liver failure. It is hepatitis that is not due to another identifiable cause, such as a viral infection, exposure to a drug or toxin, a hereditary disorder, or alcohol abuse. Anyone can develop the disorder, but the majority of those affected are women.
There are two main types of autoimmune hepatitis. Type 1 is the most common form of autoimmune hepatitis and is associated with the presence of smooth muscle antibodies (SMA) or anti-nuclear antibodies in the blood. Type 2 is less common and tends to be more severe. It is associated with anti-LKM-1 antibodies and primarily affects younger females.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
The anti- liver kidney microsomal type 1 antibody (anti-LKM-1 or CYP2D6 antibody) test is used to help diagnose autoimmune hepatitis and to differentiate between the two major types, type 1 and type 2. Anti-LKM-1, smooth muscle antibodes (SMA) and antinuclear antibodes (ANA) are all tested at the same time on the same blood sample.
These tests may be used to follow up abnormal liver test findings, such as persistently increased alanine aminotransferase (ALT), aspartate aminotransferase (AST), or bilirubin. Additional tests may be requested, such as immunoglobulins, as these may be increased with autoimmune hepatitis and/or hepatitis B and/or hepatitis C, to rule out viral hepatitis.
When is it requested?
The anti-LKM-1 test may be requested when a healthcare professional is investigating an individual's liver disease and wants to distinguish between different causes of liver injury. It is requested along with other testing, such as an SMA and ANA test. These tests are usually requested when a person presents with symptoms such as fatigue, weakness, and jaundice and has abnormal findings on routine liver tests.
Symptoms associated with autoimmune hepatitis may also include:
- An enlarged liver
- Joint aches
- Abdominal discomfort
- Abnormal blood vessels in the skin (spider angiomas)
- Nausea or vomiting
- Dark urine
- Loss of appetite
- Pale or clay-colored stools
- Muscle pain (myalgia)
- In women, lack of menstrual periods (amenorrhoea)
- Skin rashes
- Fluid buildup (oedema)
Many of these symptoms are not specific for autoimmune hepatitis; they are also seen with other causes of liver injury and with other conditions.
What does the test result mean?
A positive anti-LKM-1 antibody result indicates that it is likely that the person tested has type 2 autoimmune hepatitis, but the result is not definitive. A liver biopsy may be performed to evaluate liver tissue for damage and scarring to help confirm the diagnosis.
If both are negative, then the person's symptoms are likely due to a cause other than autoimmune hepatitis. However, the condition is not entirely ruled out. Not all people with autoimmune hepatitis will produce anti-LKM-1 or SMA antibodies; some people produce other autoantibodies that are more difficult to detect.
Is there anything else I should know?
Levels of anti-LKM-1 are not closely related to the severity of a person's symptoms or to their prognosis, most laboratories will only give a positive or negative result, but some will also give a titre or level.
People with viral hepatitis may sometimes develop an LKM antibodies. These may be LKM-3 in the case of hepatitis delta infection, but they have no specific diagnostic relevance. The ANA test is often performed along with an SMA test. It is a marker of an autoimmune process and is associated with several autoimmune disorders, including type 1 autoimmune hepatitis.
Should everyone with liver damage be tested for anti-liver kidney microsomal type 1 antibodies (anti-LKM-1)?
Will anti-LKM-1 ever go away?
Not usually. Levels may vary over time, but once the autoantibodies have developed, they may present throughout a person's life. Sometimes longer term immune suppression does diminish antibody production including auto-antibodies, but there is not a good correlation between the antibody persistence and disease activity.
Can I have more than one cause of hepatitis?
Yes. For instance, autoimmune hepatitis can co-exist with a viral hepatitis, such as hepatitis B or hepatitis C, and can become worse with liver damage caused by alcohol misuse. Since the treatment of hepatitis depends on the cause, it is very important that your doctor understand the underlying cause(s) of your condition.
How quickly does autoimmune hepatitis progress?
The course and severity of autoimmune hepatitis is hard to predict. It may be acute or chronic. Some people will have no or few symptoms for many years and are diagnosed when routine liver tests are abnormal. Those with type 2 autoimmune hepatitis often have a more severe course, but it is usually manageable with proper treatment. Appropriate treatment is important to limit liver damage. For more information, consult with your hepatologist and see the related links.
If this antibody targets CYP450 2D6, why is it called anti-liver kidney microsome-1 (anti-LKM-1)?
This antibody was originally detected using tissue from the liver and kidney, hence the name anti-LKM-1. However, the specific protein in those tissues that the antibody targets (the major antigen) has since been identified as cytochrome P450 2D6 (CYP2D6). This protein is a major enzyme that metabolises about 25% of drugs as well as toxic substances. It is primarily found in cells of the liver and kidney, mainly within structures called microsomes.