Introduction
Autoimmune hepatitis (AIH) is a cause of chronic hepatitis. It is also sometimes referred to as chronic active hepatitis. Any hepatitis that typically lasts >6 months is referred to as chronic.
It is characterised by:
- Increased IgG levels
- Antibodies against:
- Liver specific proteins
- Non-live specific proteins
- Mononuclear infiltrate within the liver
- Monocytes, macrophages, lymphocytes, plasma cells, macrophages and mast cells
There are three types of autoimmune hepatitis, which can be distinguished histologically:
- AIH – 1 – shows the presence of anti-smooth muscle antibodies (ASMA’s), andsometimes anti-nucelar antibodies (ANA’s)
- AIH – 2 – has liver-kidney microsomal type 1 antibodies (LKM-1) and sometimes anti-liver cytosol 1 antibodies (anti-LC1).
- AIH – 3 – has antibodies to soluble liver proteins or liver-pancreas antigen.
- Actin antibody is related to prognosis. Those with actin antibody presence are more likely to require transplant than those without.
- HLA-DR3 and HLA-DR4 are associated with increased risk for AIH.
- In HLA-DR3 patients the disease tends to occur earlier, and is more likely to require transplantation.
- ANA’s – antinuclear antibodies are present in many autoimmune diseases: Rheumatoid arthritis, SLE, scleroderma, polymyositis, dermatomyositis, as well as AIH. In many of these diseases the ANA blood test can help diagnosis.
Epidemiology
- Autoimmune hepatitis is rare. In Western Europe and the US there are <1 case per 100 000
- The M:F ratio is 1:3
- Peaks of incidence: Age 10-20, and 45-70. The lower peak is more common and:
- § Accounts for about half of cases
- § Typically premenstrual girls
- § 80% of AIH-2 patients are children
- Other autoimmune disease in the patient, or first degree relatives:
- 20% of patients have another autoimmune disease
- 40% of patients have a first degree relative with an autoimmune disease
Pathology
The disease is thought to occur in genetically pre-disposed individuals who come into contact with an environmental trigger.
Many patients with autoimmune hepatitis have a low CD8 count. They also often have a genetically determined reduced level of CD4 T cells, which are associated with fighting viral infection. Thus it may be possible that a viral infection triggers off the production of autoantibodies in susceptible individuals. For example, the hepatitis C virus has a close relation to LKM-1 antibody mentioned above.
Drugs and Environmental agents have also been cited as possible causes.
Presentation
- May initially be acute presentation, but will always eventually become chronic.
- Up to 50% of patients present as if an acute viral hepatitis.
- In other cases, there is typically an insidious onset
- Non-specific symptoms:
- Fatigue
- Anorexia
- Weight loss
- Amenorrhoea
- Behavioural changes
- Abdominal pain
- Liver-specific problems:
- Epistaxis – nose bleeds
- Easy bruising
- Jaundice
- Hepatomegaly / splenomegaly (50-60% of cases)
- Ascties
- Signs associated with chronic liver disease: Asterixis, Palmar erythema, Spider naevi
Prognosis
- Many patients will have severe cirrhosis by the time of diagnosis
- About 25% of patients will have a liver transplant
