Introduction

Autoimmune hepatitis 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 AIH, 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

  • Auto-immune hepatitis is rare. It 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.

  • Very rarely, AIH may be the result of Hep A, Hep B, EBV
  • More commonly AIH is caused by Hep C
 

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:
  • Liver-specific problems:
 

Prognosis

  • Many patients will have severe cirrhosis by the time of diagnosis
  • About 25% of patients will have a liver transplant

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