Autoimmune Hepatitis (AIH) in Pediatrics

Autoimmune hepatitis is a chronic, immune‐mediated inflammatory liver disease of unclear origin. In children it ranges from asymptomatic enzyme elevations to fulminant liver failure, and requires prompt diagnosis and long‐term immunosuppression to prevent progression to cirrhosis.

Definition and Key Features

• Progressive inflammatory disorder characterized by:

  • Markedly elevated aminotransferases

  • Hypergammaglobulinemia (especially IgG)

  • Presence of non–organ-specific autoantibodies

  • Characteristic interface (piecemeal) hepatitis on biopsy

  • Response to immunosuppressive therapy (steroids ± azathioprine or alternatives)

Epidemiology

• Affects all ethnicities, with a 3:1 female predominance.

• Prevalence estimates:

  • ~1/200,000 in general U.S. pediatric population

  • Up to 20/100,000 in adolescent girls in high‐incidence areas (e.g., Spain)

• Accounts for ~20% of chronic hepatitis cases in North American and Western European children.

Pathogenesis

1. Genetic predisposition

   • Strong HLA associations:

     • Type 1 AIH: HLA-DRB1 *03 and *04

     • Type 2 AIH: HLA-DRB1 *07 and *03

   • HLA-DR7 linked to more aggressive disease and poorer prognosis.

2. Environmental triggers

   • Molecular mimicry from viral infections (HAV, HBV, HCV, HSV, CMV, EBV)

   • Drug‐induced AIH (minocycline, nitrofurantoin, statins, anti-TNF agents)

3. Immune injury

   • Loss of tolerance leads to T-cell–mediated cytotoxicity and autoantibody production.

Serologic Markers & Autoantibodies

• Type 1 AIH: ANA ± SMA
• Type 2 AIH: anti-LKM1 or anti-LC1
• Anti-SLA: marker of severe disease (in type 1 or 2)
• Anti-asialoglycoprotein receptor: may appear when others are negative
• p-ANCA: seen in AIH–PSC overlap

Clinical Presentation

• Acute form (40%): Nausea, vomiting, malaise → jaundice in ~40%.

• Insidious form (30%): Fatigue, poor weight gain, intermittent jaundice.

• Asymptomatic: Detected by routine labs.

• Complications at presentation:

  • Portal hypertension (10–15%): splenomegaly, variceal bleeding, ascites

  • Acute liver failure (10–15%): INR > 1.5, encephalopathy

Associated autoimmune conditions (40% of patients):

• Thyroiditis, type 1 diabetes, vitiligo, inflammatory bowel disease

• Primary immunodeficiency syndromes (APECED, IPEX, CVID, hyper-IgM syndrome)

Diagnostic Evaluation

Laboratory Tests

• ↑ AST/ALT (often >10× ULN)

• ↑ IgG (≥1.1× upper limit)

• ↑ total protein with low albumin

• Cholestatic enzymes (GGT, ALP) may be modestly elevated

• Cytopenias if hypersplenism present

• Prolonged INR in ALF or vitamin K deficiency

Autoantibody Testing

• ANA, SMA, LKM1, LC1, and anti-SLA panels

• Use indirect immunofluorescence (rodent tissue or HEp-2 cells) or ELISA with validated cut-offs

Scoring Systems

• Simplified International Autoimmune Hepatitis Group (IAIHG) criteria: combine autoantibodies, IgG, histology, and exclusion of viral hepatitis.

Histopathology

• Interface hepatitis: lymphocyte and plasma cell infiltrate at portal–lobular interface

• Bridging necrosis/inflammation, periportal fibrosis, and possible cirrhosis

• Plasma cell predominance is highly suggestive

Type 1 vs. Type 2 AIH

AIH–PSC Overlap Syndrome

• Features of both AIH and primary sclerosing cholangitis (PSC):

  • Labs: Cholestatic enzymes (↑ GGT), elevated IgG, positive ANA/SMA/p-ANCA

  • Imaging: MRCP or ERCP: multifocal strictures and beading of bile ducts

  • Histology: interface hepatitis + periductal “onion skin” fibrosis

• Management: Standard AIH immunosuppression + ursodeoxycholic acid (UDCA 10 mg/kg b.i.d.)

Management

Treatment Goals

• Complete biochemical remission (normal ALT/AST, bilirubin)

• Immunologic remission (normal IgG, negative/slightly positive autoantibodies)

• Histologic improvement or stability

• Prevent progression to cirrhosis and avoid relapse

First-Line Therapy

1. Prednisone

   • 2 mg/kg/day (max 60 mg) for induction, given AM

   • Taper to 0.5 mg/kg/day by week 4, then to 5–10 mg/day maintenance

2. Azathioprine

   • Start 1–2 mg/kg/day once prednisone dose is ≤20 mg/day

   • Check TPMT activity before initiation to guide dosing

3. Duration: Minimum 24 months of combined therapy and ≥12 months of complete remission before considering taper

Updated Alternatives & Add-Ons

• Mycophenolate mofetil (MMF)

  • 600 mg/m² b.i.d.; effective in azathioprine‐intolerant or refractory patients

• Budesonide

  • No longer first‐line per EASL 2025 due to limited pediatric data and safety concerns

• Tacrolimus or sirolimus

  • Consider in refractory cases or azathioprine/MMF intolerance

• UDCA (10 mg/kg b.i.d.)

  • For overlap with PSC or persistent cholestasis

Monitoring

• Biochemical response: evaluate ALT/AST monthly during induction, then every 3 months

• Immunologic markers: IgG and autoantibodies every 6–12 months

• Bone density: baseline and periodic DEXA in long-term steroid use

• Growth and pubertal development: assess at each visit

• Screen for steroid toxicities: glucose, blood pressure, cushingoid features

Treatment Endpoints

• Complete biochemical response: normalize ALT/AST within 12 months

• Histologic remission: repeat biopsy if clinically indicated (persistent activity despite normal enzymes)

• Tapering: consider very gradual withdrawal after 2 years of remission; relapse rates exceed 50%

Liver Transplantation

• Indications (2–3% of pediatric AIH):

  • Acute fulminant AIH unresponsive to steroids

  • Decompensated cirrhosis or portal hypertension complications

  • Hepatocellular carcinoma

• Post‐transplant recurrence: Occurs in ~30%; managed with standard immunosuppression

Key Takeaways

• Early recognition and a high index of suspicion are critical in children with unexplained hepatitis.

• A combination of clinical, serologic, and histologic criteria guides the diagnosis.

• Long-term immunosuppression is standard; MMF is now endorsed as a safe alternative first‐line agent in azathioprine‐intolerant patients.

• Overlap with PSC requires addition of UDCA.

• Multidisciplinary care—including hepatology, rheumatology, and transplant teams—ensures optimal outcomes.

References:

1. EASL Clinical Practice Guidelines on Autoimmune Hepatitis, May 2025.

Autoimmune hepatitis

1. Elevated aminotransferases
2. Serum IgG
3. Non-organ specific antibodies (ANA, SMA, LKM, LC1)
4. Interface hepatitis
5. Responsive to treatment with immunosuppresive medication

• Type 1: ANA and smooth muscle antibody (SMA)
• Older children
• Chronic presentation (Cirrhosis more common)
• Common overlap with Sclerosing cholangitis
  
• May be able to wean off immunosuppresion
  
• Type 2: LKM and Liver cytosol 1 antibody (LC1)
• Younger children
• Acute presentation /ALF more common
• Lifelong immunosuppression

• Female > Male
• 20% of chronic hepatitis in caucasians

• genetically susceptible individual
• unknown trigger initiates autoimmune activity causing liver damage
• viral
• medications (minocycline, nitrofurantoin, statins, anti-TNF, adalimumab, infliximab)

• 40% Acute hepatitis - malaise, nausea. vomiting, jaundice
  
• 30% Insidious onset - asymptomatic or wt loss, jaundice over weeks - months
• 10-15% will have complications of portal hypertension (hypersplenism, ascites, and GI bleed)
• 10-15% acute liver failure - ALF

• Increase GGT with elevated tranaminases
• Increased IgG and autoantibodies
• imaging reveals characteristic irregular narrowing +/- strictures of the extrahepatic and/or intrahepatic bile ducts by MRCP or ERCP
• Treat with immunosuppression and urosdiol

1. Prednisone 2mg/kg once daily in AM - max dose 40-60mg (monitor for side effects)
2. Budesonide (high hepatic first pass effect) lower side effects , used with azathioprine
3. Ursodiol (if overlap SC)
4. Thiopurine methyltransferase TMPT activity prior to starting azathioprine
5. Transplant
1. acute/fulminant liver failure
2. failure of medical therapy
3. HCC
4. AIH may recur in 33%