Autoimmune Hepatitis
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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.

  • Very rarely, AIH may be the result of Hep A, Hep B, EBV
  • More commonly AIH is caused by Hep C
Autoimmune Hepatitis histology
Autoimmune Hepatitis histology – showing the characters feature of portal mononuclear cell inflammatory infiltrate extending into the lobule (interface hepatitis).

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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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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