Liver kidney microsome type 1 (anti-LKM-1) antibodies are autoantibodies, proteins produced by the body's immune system that recognize 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 and measures the amount (titer) 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 is general agreement that there are two main types of autoimmune hepatitis (debate continues as to whether there is a distinct third type). Type 1 is the most common form of autoimmune hepatitis in the United States and is associated with the presence of smooth muscle antibodies (SMA) 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 young girls and is more common in Europe than in the United States.
How is it used?
The liver kidney microsome type 1 antibody (anti-LKM-1 or CYP2D6 antibody) test is primarily used along with a smooth muscle antibody (SMA) and an antinuclear antibodies (ANA) test to help diagnose autoimmune hepatitis and to differentiate between the two major types, type 1 and type 2.
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 ordered, 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 ordered?
The anti-LKM-1 test may be ordered when a healthcare practitioner is investigating an individual's liver disease and wants to distinguish between different causes of liver injury. It may be ordered along with other testing, such as an SMA and ANA test. These tests are usually ordered when a person presents with signs and symptoms, such as fatigue, weakness, and jaundice, and has abnormal findings on routine liver tests.
Signs and 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 (amenorrhea)
- Skin rashes
- Fluid buildup (edema)
Many of these signs and 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 high amount or titer of anti-LKM-1 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 rarely tested.
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 that person's prognosis. Levels may vary over time.
People with chronic hepatitis C may sometimes develop a different type of anti-LKM antibody, sometimes referred to as anti-LKM3. This type of antibody is not detected with the usual anti-LKM-1 test methods and is not typically tested for.
Should everyone with liver damage be tested for liver kidney microsome type 1 antibodies (anti-LKM-1)?
This is not usually necessary. Most cases of hepatitis will be due to another identifiable cause. However, if the person with symptoms is a young girl without other risk factors and/or the healthcare practitioner suspects an autoimmune process, then anti-LKM-1, ANA, and SMA testing may be performed.
Will anti-LKM-1 ever go away?
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 abuse. Since the treatment of hepatitis depends on the cause, it is very important that your healthcare practitioner understand the underlying cause(s) of your condition.
How fast 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 case, but it is usually manageable with proper treatment. Appropriate treatment is important to limit liver damage. For more information, consult with your healthcare provider 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 metabolizes 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.