Autoimmune Hepatitis: Evidence‑Based Diagnostic and Therapeutic Guidelines

Diagnostic Workup

The diagnosis requires elevated serum IgG, disease‑specific autoantibodies, compatible interface hepatitis on liver biopsy, and exclusion of alternative liver diseases; liver biopsy is mandatory for confirmation【@1】.
Screen for ANA, SMA, and anti‑LKM‑1 antibodies by indirect immunofluorescence on rodent tissue; a titer ≥ 1:40 is considered positive (≥ 1:80 yields two diagnostic points)【@3】.
If the initial panel is negative, test for anti‑SLA/LP antibodies and atypical ANCA because ≈ 15 % of patients are antibody‑negative at presentation【@3】.
Type 1 AIH is defined by ANA and/or SMA positivity; SMA showing a vascular/glomerular (VG) or vascular/glomerular/tubular (VGT) pattern is highly specific for AIH【@3】.
Type 2 AIH (predominantly in children/adolescents) is characterized by anti‑LKM‑1 and/or anti‑LC1 antibodies【@3】.
Anti‑SLA/LP antibodies are highly specific for AIH and are associated with more severe disease and higher relapse rates; detection requires molecular‑based assays【@3】.
Serum IgG > 1.1 × upper limit of normal supports the diagnosis, although 10 % of patients have normal IgG at presentation and 25‑39 % of acute‑onset cases may also have normal IgG【@4】.
ALT/AST and bilirubin levels should be recorded, recognizing a spectrum from asymptomatic to fulminant disease【@1】.
Systematically exclude viral hepatitis (HBV, HCV, HAV, HEV, CMV), metabolic dysfunction‑associated steatotic liver disease, alcohol‑related liver disease, and drug‑induced liver injury; coexistence is possible【@1】.
Review all medications and supplements for agents that can cause drug‑induced autoimmune‑like hepatitis (e.g., nitrofurantoin, minocycline, methyldopa, hydralazine, anti‑TNF agents, statins, immune‑checkpoint inhibitors)【@5】.
Screen for overlap with primary biliary cholangitis by testing anti‑mitochondrial antibodies and anti‑sp100/gp210; 4‑9 % of AIH patients have detectable AMA【@1】.
Liver biopsy is required in every case to confirm AIH, assess fibrosis stage, and differentiate from other disorders【@1】.
Histology typically shows interface hepatitis with lymphoplasmacytic infiltrates rich in plasma cells; acute presentations may show pan‑lobular hepatitis with less portal inflammation【@3】.
Features such as emperipolesis and rosettes are no longer considered specific for AIH and should not be used for diagnosis【@3】.
Apply the simplified diagnostic criteria (definite AIH score ≥ 7) using points for autoantibody titers, IgG level, histology, and exclusion of viral hepatitis【@1】.

Initial Management Strategy

First‑line induction for all patients with active AIH (including those with cirrhosis) is prednisolone combined with azathioprine, aiming for normalization of transaminases and IgG within 6–12 months【@2】.
Prednisolone 40 mg/day (or 0.5–1 mg/kg/day) plus azathioprine 1 mg/kg/day is the standard starting regimen in patients without contraindications【@2】.
In non‑cirrhotic adults, budesonide 9 mg/day may replace prednisolone to reduce systemic steroid exposure; budesonide is contraindicated in cirrhosis due to impaired first‑pass metabolism【@2】.
Azathioprine dose should be titrated up to 2 mg/kg/day as prednisolone is tapered, with regular blood‑count monitoring for bone‑marrow suppression【@7】.
TPMT activity must be measured before initiating azathioprine to identify patients at risk for severe myelosuppression【@2】.
Bone protection: calculate FRAX score for adults starting steroids and consider early bisphosphonate therapy in high‑risk patients; supplement vitamin D and ensure adequate calcium intake【@7】.

Special Clinical Presentations

Acute severe AIH (jaundice, INR ≥ 1.5, no encephalopathy): start prednisolone 40 mg/day if INR < 2.5 and sepsis excluded; ≈ 35 % may require early liver transplantation【@7】.
Acute liver failure (including encephalopathy): refer urgently to a transplant center【@7】.
Decompensated cirrhosis with MELD < 27: initiate prednisolone after a negative septic screen and discuss transplant options if MELD does not improve【@7】.
Drug‑induced autoimmune‑like hepatitis: discontinue the offending agent and perform liver biopsy if transaminases do not improve within one week; if jaundice, advanced fibrosis, or persistent enzyme elevation occurs, start prednisolone 0.5 mg/kg/day (max 40 mg)【@5】.

Monitoring Treatment Response

After 1 month, an inadequate response is defined as < 50 % reduction in ALT/AST【@7】.
After 6 months, inadequate response is failure to achieve normal ALT/AST and IgG levels【@7】.
In severe cases, weekly monitoring of transaminases and INR is recommended until a clear downward trend is documented【@4】.
For inadequate responders:
- Re‑evaluate the diagnosis and assess medication adherence【@2】.
- Measure azathioprine metabolites (thioguanine nucleotides) to guide dose optimization (target 235–450 pmol/8 × 10⁸ RBC)【@7】.
- Consider switching prednisolone to budesonide in non‑cirrhotic patients with significant steroid‑related adverse effects【@7】.
Steroid taper: once complete biochemical response is confirmed (repeat testing 2–4 weeks later), taper prednisolone slowly over 3 months in adults【@2】.
In children, maintain low‑dose steroids and discontinue only after specialist discussion【@2】.
Check morning serum cortisol before complete steroid withdrawal; low values warrant a short Synacthen test and endocrinology referral【@2】.

Second‑Line and Rescue Therapies

For azathioprine intolerance or persistent inadequate response, consider mycophenolate mofetil (MMF) or tacrolimus as second‑line agents【@2】.
MMF: 1–2 g/day in azathioprine‑intolerant patients; effective contraception is required because MMF is teratogenic【@2】.
MMF has a more favorable side‑effect profile than tacrolimus but may be less effective as rescue therapy【@7】.
Tacrolimus: target trough level 3–5 ng/mL for patients inadequately responding to optimized azathioprine; may be more effective than MMF as rescue therapy【@7】.
Third‑line options (cyclosporine, sirolimus, rituximab, infliximab) require specialist expertise before use【@2】.

Long‑Term Management and Surveillance

Maintain therapy for at least 3–5 years, and for at least 2 years after achieving complete biochemical response【@2】.
In patients with sustained response for 3–4 years, azathioprine can be withdrawn in a single step with continued monitoring for relapse and fibrosis progression【@2】.
Routine liver biopsy before treatment withdrawal is not required in adults, though it may be useful in selected cases【@2】.
Surveillance for complications (portal hypertension, hepatocellular carcinoma) should follow generic cirrhosis guidelines; perform 6‑monthly ultrasound for HCC in all cirrhotic patients unless contraindicated【@1】【@2】.
Non‑invasive fibrosis assessment (transient elastography or validated alternatives) every 2–3 years is recommended【@2】.

Relapse Management

Relapse is indicated by rising ALT/AST (with variable IgG); exclude other causes but liver biopsy is usually unnecessary【@2】.
Restart prednisolone (or budesonide in non‑cirrhotic patients) together with azathioprine or another steroid‑sparing agent if not already on therapy【@2】.
After achieving biochemical remission following relapse, continue long‑term maintenance with a steroid‑sparing agent rather than attempting withdrawal【@2】.

Preventive Care

Encourage regular cervical screening and HPV vaccination (up to age 45 for at‑risk groups) in women on long‑term immunosuppression【@2】.
Advise sun protection and vigilance for new skin lesions due to increased skin‑cancer risk with immunosuppression【@2】.
Promote a healthy lifestyle: balanced nutrition, smoking cessation, limited alcohol, regular physical activity, and maintenance of healthy body weight【@2】.
Ensure COVID‑19 vaccination, including a third dose for adequate humoral response in immunosuppressed patients【@5】.

Key Pitfalls to Avoid

Do not initiate immunosuppression based solely on low‑titer autoantibodies (1:40) in acute infectious hepatitis; defer AIH work‑up unless liver injury persists > 3 months or worsens【@4】.
Do not dismiss pan‑lobular hepatitis as “not AIH” in acute presentations; this pattern is recognized in acute‑onset AIH【@3】.
Do not rely on emperipolesis or rosettes for diagnosis, as they lack specificity【@3】.
Do not use budesonide in cirrhotic patients because of reduced first‑pass metabolism and risk of systemic exposure【@2】.
Do not prescribe MMF to women of child‑bearing potential without effective contraception due to teratogenicity【@2】.
Do not abruptly stop immunosuppression; always taper gradually to avoid precipitating acute‑on‑chronic liver failure【@1】.