Primary biliary cirrhosis, a chronic autoimmune condition of small and medium-sized intrahepatic biliary ducts most prevalent in middle-aged women, often presents with pruritus and fatigue, is characterised by antimitochondrial antibodies and cholestatic pattern of LFT derangement.
Description
Primary Biliary Cirrhosis (PBC), increasing referred to as Primary Biliary Cholangitis, is a chronic, progressive autoimmune disease characterised by granulomatous destruction of the small intrahepatic bile ducts. It predominantly affects middle-aged women and can lead to cirrhosis and end-stage liver disease if untreated.
Pathogenesis
The precise pathogenesis of PBC remains poorly understood. However, it is widely accepted that a combination of genetic predisposition, environmental triggers, and immune-mediated responses contribute to the disease progression. The typical histological finding is lymphocytic cholangitis which affects the small interlobular bile ducts. Bile duct injury and the subsequent cholestasis result in fibrosis, which can eventually progress to cirrhosis.
Epidemiology, Risk Factors & Associations
- PBC has a strong female predilection (female to male ratio 9:1)
- The disease often presents between the ages of 40 and 60, and rarely in children.
- It is more prevalent in Northern Europe and North America (40 per 100,000 and 39 per 100,000 respectively).
- Genetic predisposition is suggested by its association with HLA DR8 and DQw4.
- Environmental risk factors such as smoking and urinary tract infections have been implicated, but causality is unclear.
- There is a strong association with other autoimmune diseases such as:
- Sjögren’s syndrome (44% of patients with PBC)
- Systemic sclerosis (12%)
- Hashimoto’s thyroiditis (10%).
- Systemic lupus erythematosus (9%).
- Autoimmune hepatitis (overlap syndrome) (10%)
- Raynaud phenomenon
- Coeliac Disease
- Other associations include:
- Cholelithiasis
- Interstitial lung disease associated with primary biliary cholangitis
- Pulmonary hypertension
- Hepatocellular carcinoma
- Hepatic osteodystrophy
- Kayser-Fleischer rings
Clinical Features
Patients with PBC can present with a variety of symptoms including:
- Fatigue (most common)
- Pruritus, typically worse at night, another major clinical presenting symptom.
- Jaundice, indicative of advanced disease
- Hepatomegaly or splenomegaly may be detected on physical examination.
Complications
The major complications of PBC include:
- Cirrhosis and its complications such as ascites, variceal bleeding, hepatic encephalopathy, and hepatocellular carcinoma (although less common compared to other causes of cirrhosis)
- Fat-soluble vitamin deficiencies (A, D, E, K) due to malabsorption
- Metabolic bone disease (osteoporosis, osteomalacia) due to vitamin D deficiency.
Pathological Features
Histopathology
- Early: Diffusely enlarged liver with uniform and prominent regenerative nodules and lace-like fibrosis. Inflammation and granuloma formation predominantly in small bile ducts.
- Late stages: Small, cirrhotic liver with widened fissures and signs of portal hypertension.
- Non-suppurative destructive cholangitis (lymphocytic infiltration of the bile duct epithelium) is a key feature
- Granulomas present in about half the cases
- Progression leads to periportal fibrosis and eventually cirrhosis
Biochemistry
- Anti-mitochondrial antibodies (AMA): Present in 90-95% of patients (highly sensitive and specific)
- Antinuclear antibodies (ANA): Present in 70% which may indicate overlap with autoimmune hepatitis and worse prognosis.
- Cholestatic LFT derangement: Marked increase in alkaline phosphatase (ALP) and elevated gamma-glutamyl transferase (GGT)
- Elevated IgM levels
Genetics
- Genetic predisposition suggested by the higher concordance rate in monozygotic twins
- Association with HLA DR8 and DQw4
- Some studies suggest an association with IL12A and IL12RB2 gene polymorphisms
Radiological Features
General Features
- Lymphadenopathy is a more prominent feature compared to other aetiologies of chronic liver disease
US
- The liver may have a normal appearance in early disease
- In advanced disease, the liver can be heterogeneous with coarsened echotexture and nodular contour due to cirrhosis.
- Increased echogenicity of periportal tracts (periportal halo).
- Signs of portal hypertension (splenomegaly, ascites, or varices)
CT
- Normal or reduced liver size, with a nodular surface in the case of cirrhosis
- Enlarged caudate lobe – a common finding in cirrhotic patients.
- Evidence of portal hypertension such as ascites, varices, splenomegaly.
MRI
- T2: Parenchymal lace-like fibrosis and periportal halo sign (oedema and inflammation)
- Cirrhosis and associated complications such as ascites or varices can also be seen
- MRCP can evaluate for the presence of bile duct abnormalities, although these are not usually seen in PBC as the disease primarily affects small bile ducts not well visualised on imaging.
Hepatobiliary Scintigraphy
Although not routinely used, it can show delayed excretion of tracer which improves after administration of phenobarbital.
Liver Elastography
- Increased liver stiffness can suggest cirrhosis
- It may be helpful in monitoring disease progression.
Grading and Staging
Histological staging of PBC is based on the Ludwig system:
- Stage 1: Portal inflammation
- Stage 2: Periportal or portal-portal septa, with intact lobular architecture
- Stage 3: Fibrosis with architectural distortion; no obvious cirrhosis
- Stage 4: Cirrhosis
Differential Diagnosis
- Autoimmune Hepatitis: Characterised by interface hepatitis on biopsy, elevated transaminases, and presence of specific autoantibodies like anti-smooth muscle antibody (SMA) or anti-liver kidney microsome type 1 (LKM1)
- Primary Sclerosing Cholangitis: Features multiple strictures and dilations (beads on a string) on cholangiography, predominance in males, and association with inflammatory bowel disease (particularly ulcerative colitis).
- Drug-induced liver injury: History of potential drug exposure is key.
Management
- Patients with suspected PBC should be referred to a hepatologist for confirmatory testing and treatment.
- Initial diagnostic tests include liver function tests, serologic tests for AMA, and liver biopsy for definitive diagnosis.
- Ursodeoxycholic acid (UDCA) is the first-line treatment, with obeticholic acid and fibrate as second-line options for those who don’t respond.
- Liver transplantation may be indicated in advanced cases.
- Regular surveillance for hepatocellular carcinoma is necessary in those with cirrhosis.