Autoimmune hepatitis

Pathogenesis and diagnostic criteria

The mechanism of AIH development represents a classical autoimmune triad: genetic predisposition + trigger exposure + breakdown of immune tolerance. Diagnosis relies on four key criteria:

1. Morphological: presence of periportal hepatitis according to histology.
2. Biochemical: hypergammaglobulinemia.
3. Immunological: presence of specific autoantibodies in serum.
4. Clinical and pharmacological: positive response to immunosuppressive therapy.

The most critical step is the exclusion of other diseases. Viral hepatitis, Wilson's disease (normal copper and ceruloplasmin levels required), $\alpha_1$-antitrypsin deficiency, biliary pathology, and toxic-alcoholic injury must be ruled out.

AIH classification

Depending on the produced autoantibodies and target antigens, AIH is divided into two main types (modern hepatology has abandoned the designation of a 3rd type due to the low specificity of the anti-SLA marker).

• Type 1 AIH (classic): accounts for over 90% of cases. It occurs at any age, but has two peaks (10–20 years and 45–70 years). The target antigen is a liver-specific protein. Antinuclear antibodies (ANA) and smooth muscle antibodies (SMA) are detected in the blood. The diagnostic titer for adults is $\ge$ 1:80, and for children $\ge$ 1:20.
• Type 2 AIH: a rare form (3–4%) characteristic of the pediatric profile (children aged 2 to 14 years). The target antigen is liver-kidney microsomes (LKM-1). The marker is anti-LKM-1 antibodies. This form is distinguished by a severe course, a high risk of fulminant hepatitis, and rapid progression to cirrhosis. It is frequently associated with other autoimmune pathologies (diabetes, vitiligo).

Clinical and laboratory presentation

The symptoms of AIH are extremely variable. In adults, the disease may begin latently (asthenia, right upper quadrant discomfort) or acutely, dominated by extrahepatic manifestations (fever, thyroiditis, ulcerative colitis), with jaundice appearing later. In children, AIH manifests abruptly in 50–65% of cases, mimicking acute viral hepatitis.

Laboratory profile:

• Cytolysis syndrome: transaminases (ALT, AST) elevated 5–10 times or more.
• Immune-inflammatory syndrome: hypergammaglobulinemia, predominantly due to the IgG fraction.
• Absence of pronounced cholestasis: alkaline phosphatase (ALP) is usually normal or slightly elevated (unlike sclerosing cholangitis), while GGT may be elevated.

Treatment strategy and prognosis

Immunosuppressive therapy is initiated immediately after confirmation of the diagnosis, regardless of the current clinical severity.

• Baseline therapy: glucocorticoids (prednisolone or methylprednisolone).
• Combination therapy: azathioprine is added to reduce the hormonal burden and enhance the effect.
• Second-line drugs: cyclosporine, budesonide, tacrolimus.

The main goal is absolute biochemical and histological remission. Patients require rigorous follow-up (monitoring of ALT/AST every 3 months, IgG every 6 months). In the event of established cirrhosis or hepatocellular decompensation, liver transplantation is indicated, after which 5-year survival exceeds 90%.

Class and exam questions

What else to study on this topic

• Scoring system for histological grading of AIH
• Differential diagnosis with pigmentary hepatoses
• Features of Wilson's disease in children
• Management protocols for patients with seronegative AIH
• Indications and timing of liver transplantation in autoimmune pathologies

Other topics in "Chapter 7. Digestive System Diseases"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.