22nd July 2023

Autoimmune hepatitis (AIH)

Background

The precise underlying aetiology of AIH is unknown, but it is thought to involve altered T-cell function. It is often associated with other autoimmune disorders.

Historically there are three types of AIH, classified by autoantibodies. However, more recently, it has been proposed that AIH type III is not a distinct subgroup, but rather should be included within AIH type I.

Assessment and diagnosis

Clinical presentation varies from asymptomatic to acute hepatitis, or most commonly, the insidious onset of chronic liver disease.

Symptoms include fatigue, anorexia, abdominal discomfort, nausea, pruritus, polyarthralgia of the small joints, amenorrhoea and fluctuating jaundice. One third of adults will have cirrhosis at the time of presentation. On examination, there may be stigmata of chronic liver disease.

Liver function tests will be abnormal at presentation. Often there is a significant transaminitis (elevated AST and ALT) alongside a more modest rise in bilirubin and ALP. However, AIH can also present with a cholestatic picture. Raised IgG is characteristic of AIH. A reduced albumin level and prolonged prothrombin time may also be seen.

The next stage of investigation is to test for the presence of autoantibodies (described in the table below). A liver biopsy should also be performed. Characteristic histological findings are of a periportal infiltrate with inflammation that extends beyond the limiting plate and interface hepatitis (previously known as piecemeal necrosis). In an acute hepatitis presentation, the histology may be atypical.

Other tests may be necessary to exclude other causes of liver disease. The diagnosis cannot be made from one test alone but is a clinical diagnosis based on a combination of features.

Table 1: Different types of AIH

Management

The mainstay of treatment is immunosuppression. In some cases, e.g. older patients with asymptomatic disease and mild hepatitis, it may be appropriate not to treat, but to actively monitor.

The recommended initial treatment is combination therapy of a corticosteroid plus azathioprine. Prior to treatment with azathioprine, patients should have thiopurine methyltransferase (TPMT) activity measured. TPMT deficiency can lead to bone marrow toxicity if an affected patient is given immunosuppressants.

For patients with decompensated liver disease or those with acute severe AIH, combination therapy is not the recommended first line, but instead corticosteroid monotherapy is preferred.

Long-term maintenance therapy may be required. Patients should be monitored for side effects relating to the use of corticosteroids and azathioprine.

It may also be appropriate to screen for HCC with regular AFP and liver ultrasound – as with any form of chronic liver disease.