What investigations should be performed in a child with suspected progressive familial intrahepatic cholestasis (PFIC)?

Investigations for Suspected PFIC

In a child with suspected PFIC, initiate a systematic diagnostic approach starting with serum gamma-glutamyltransferase (GGT) measurement to differentiate PFIC subtypes, followed by early genetic testing using next-generation sequencing panels while simultaneously excluding extrahepatic biliary obstruction with ultrasound. 1

Initial Laboratory Assessment

Serum GGT is the critical first biochemical test as it distinguishes between PFIC subtypes:

• Low/normal GGT: PFIC1 (ATP8B1), PFIC2 (ABCB11), PFIC5 (NR1H4) 2
• Elevated GGT: PFIC3 (ABCB4) 2

Additional baseline laboratory investigations should include:

• Liver function tests: ALT, AST, alkaline phosphatase, conjugated and total bilirubin
• Serum bile acids: typically markedly elevated 3
• Alpha-fetoprotein: often elevated, particularly important for monitoring hepatocellular carcinoma risk in PFIC2 3
• Coagulation profile: PT/INR to assess synthetic function 3
• Fat-soluble vitamin levels: vitamins A, D, E, K due to malabsorption 2

Imaging Studies

Abdominal ultrasound is the first-line imaging modality to:

• Exclude extrahepatic biliary obstruction (biliary atresia, choledochal cysts) 4
• Assess for hepatosplenomegaly 3
• Evaluate liver parenchyma and portal vein patency

CRITICAL PITFALL: Normal ultrasound does NOT exclude PFIC. The biliary tree typically appears normal in PFIC as this is an intrahepatic cholestasis disorder 4.

Genetic Testing - The Definitive Diagnostic Tool

Genetic testing should be initiated early in the diagnostic work-up and should NOT be delayed 1. The 2024 EASL guidelines explicitly recommend:

• Next-generation sequencing (NGS) gene panels or whole-exome sequencing (WES) as the preferred approach 1
• Sanger sequencing of individual genes is now discouraged except possibly for ABCB4 testing in specific scenarios 1
• Testing should include: ATP8B1, ABCB11, ABCB4, NR1H4, TJP2, and other cholestasis-related genes 2

Key advantage: Genetic testing can be performed while awaiting other results and treatment can be initiated based on clinical suspicion 5.

Liver Biopsy

Liver biopsy should be performed when diagnosis remains unclear after initial work-up 4. The biopsy must:

• Contain ≥10 portal fields for adequate evaluation 4
• Include assessment of bile duct architecture
• Evaluate for fibrosis/cirrhosis progression

Specific histologic features:

• PFIC1 and PFIC2: Bland cholestasis, giant cell transformation, minimal inflammation
• PFIC3: Ductular proliferation, portal inflammation, periportal fibrosis 6, 7

Immunohistochemistry can be valuable:

• BSEP (bile salt export pump) staining for PFIC2
• MDR3 staining for PFIC3 7

Specialized Bile Analysis

Biliary lipid composition analysis (if available) can support diagnosis:

• Low phospholipid content suggests ABCB4 (MDR3) deficiency 7
• Requires specialized centers with expertise

Exclusion of Other Causes

Before confirming PFIC, systematically exclude other causes of infantile/childhood cholestasis 4:

Metabolic disorders:

• Alpha-1 antitrypsin deficiency: serum level and phenotype (not level alone as it's an acute phase reactant) 2
• Galactosemia, tyrosinemia: urine reducing substances, amino acids
• Cystic fibrosis: sweat chloride test
• Bile acid synthesis defects: urine and serum bile acid profile by mass spectrometry

Syndromic cholestasis:

• Alagille syndrome: clinical features (cardiac, facial, vertebral), JAG1/NOTCH2 testing 2

Infections:

• Bacterial sepsis, viral hepatitis, TORCH infections

Monitoring After Diagnosis

Once PFIC is suspected or confirmed, establish baseline measurements for disease monitoring 5:

• Pruritus severity scales (objective measurement tools)
• Growth parameters: height, weight, BMI
• Quality of life assessments
• Serum bile acid levels: for treatment response monitoring
• Liver imaging: for hepatocellular carcinoma surveillance, especially in PFIC2 (start from first year of life) 7

Practical Algorithm Summary

1. Cholestatic infant/child → Check GGT immediately
2. Ultrasound → Exclude extrahepatic obstruction
3. Initiate genetic testing (NGS panel/WES) → Do not wait for results to start treatment if clinical suspicion is high 5
4. Exclude common metabolic causes → α1-antitrypsin, infections, Alagille syndrome
5. Liver biopsy if diagnosis uncertain after above steps
6. Refer to specialized center for definitive management 5, 8

The 2024 EASL guidelines emphasize that genetic testing should occur early and management should take place in tertiary referral centers with expertise in cholestatic liver diseases 1. Treatment with ileal bile acid transport inhibitors can be initiated based on clinical presentation while awaiting genetic confirmation 5.