Autoimmune Liver Disease — Written Clinical Reasoning

SAQ 1 — AIH-PBC overlap in a 54-year-old woman (15 marks, 30 minutes)

Prompt: Outline your assessment, the diagnostic reasoning, the integrated management plan addressing each problem, and the communication framework. Justify each decision with reference to evidence. ^[1]

Model Answer

Step 1 — The diagnostic synthesis (4 marks): ^[1]

This woman has an AIH-PBC overlap syndrome. The reasoning: she has features of BOTH diseases. For PBC, she has a cholestatic LFT pattern (ALP and gamma-GT disproportionately raised), a positive AMA at a high titre, a raised IgM, and the florid duct lesion on biopsy. For AIH, she has a hepatocellular component (the ALT of 180), a markedly raised IgG, positive ANA and SMA, and interface hepatitis with a plasma-cell infiltrate on biopsy. ^[1]

I would apply the Paris criteria for AIH-PBC overlap: two of three AIH features (moderate/severe interface hepatitis; ALT above five times the upper limit; IgG above twice the upper limit OR positive SMA) AND two of three PBC features (ALP above twice the upper limit; AMA positive; florid duct lesion). She meets two of three AIH items (interface hepatitis, positive ANA/SMA with raised IgG — her ALT of 180 is below the five-times threshold) and all three PBC items (ALP 520, AMA positive, florid duct lesion) ^[7]. The diagnosis is therefore definite overlap. The normal ultrasound excludes biliary obstruction. An MRCP is not required (her ducts are normal and she has no IBD to raise PSC), but I would send an IgG4 to exclude IgG4-sclerosing cholangitis, which can coexist with a cholestatic picture and is steroid-responsive.

The IAIHG position statement (Boberg 2011) cautions that overlap is partly a research concept and that patients should be treated for their predominant feature, but in this case the features of both diseases are clearly present and a combined strategy is justified ^[7].

Step 2 — The problem list (2 marks): ^[1]

1. AIH-PBC overlap syndrome with cholestatic and hepatocellular components — the central problem.
2. Cirrhosis or pre-cirrhosis — the jaundice (bilirubin 75) and the low albumin suggest synthetic dysfunction; I would stage with elastography (FibroScan) and review the biopsy for fibrosis.
3. Pruritus — a major quality-of-life issue; needs active management.
4. Osteoporosis risk — from the cholestasis AND the corticosteroids I will need to use.
5. Fat-soluble vitamin deficiency — likely given the cholestasis and jaundice.
6. Portal hypertension and HCC surveillance — once cirrhosis is confirmed.
7. Psychosocial impact and communication — a complex chronic diagnosis with lifelong therapy. ^[1]

Step 3 — The integrated management plan (6 marks): ^[1]

Pillar 1 — Ursodeoxycholic acid (UDCA) for the PBC component: I would start UDCA at 13 to 15 mg/kg/day in divided doses, first-line for all stages of PBC. The 1994 Lindor NEJM trial showed UDCA slows histological progression and reduces the need for transplant in PBC ^[2]. This is non-negotiable first-line therapy and will be continued lifelong.

Pillar 2 — Immunosuppression for the AIH component: I would add prednisolone 0.5 to 1 mg/kg/day (typically 40 to 60 mg daily) plus azathioprine 1 to 2 mg/kg/day. Critically, I would check thiopurine methyltransferase (TPMT) activity before starting azathioprine — TPMT deficiency causes fatal myelosuppression ^[5]. I would monitor the full blood count weekly for the first month, then monthly. In a patient without cirrhosis I would consider budesonide (a first-pass corticosteroid) to spare the steroid side effects, but given her possible cirrhosis (low albumin, jaundice) I would use prednisolone, as budesonide is ineffective in cirrhosis due to portosystemic shunting.

Pillar 3 — Staging and surveillance: FibroScan to stage fibrosis; upper GI endoscopy for variceal surveillance if cirrhosis is confirmed; baseline DEXA for bone density; six-monthly ultrasound plus alpha-fetoprotein once cirrhosis is confirmed; annual fat-soluble vitamin levels. ^[1]

Pillar 4 — Symptom control: For the pruritus, cholestyramine first-line (given separately from UDCA by at least 2 to 4 hours), then rifampicin 150 to 300 mg twice daily with liver function monitoring, then opioid antagonists (naltrexone) or sertraline. For the fatigue, there is no specific therapy — I would address sleep, mood and deconditioning, and exclude other causes (anaemia, hypothyroidism, vitamin D deficiency). ^[1]

Pillar 5 — Bone and nutritional health: Calcium and vitamin D supplementation; a bisphosphonate if the DEXA shows osteoporosis. Replace vitamins A, D, E and K as needed. For the corticosteroids, add bone protection, monitor blood glucose and blood pressure, and consider a PPI for gastroprotection. ^[1]

Pillar 6 — Second-line consideration: If her biochemistry does not normalise on UDCA plus immunosuppression, I would consider adding obeticholic acid for the PBC component — but ONLY if her cirrhosis is compensated (Child-Pugh A). OCA is contraindicated in decompensated (Child-Pugh B and C) cirrhosis because it can precipitate liver failure ^[3].

Step 4 — Communication (3 marks): ^[1]

I would explain the diagnosis in plain language: her immune system is attacking both the bile ducts and the liver cells, which is why she has features of two diseases, and the treatment needs to address both. I would explain that the UDCA is for the bile duct disease (lifelong), and the prednisolone and azathioprine are for the immune attack on the liver cells (at least 24 months before considering withdrawal). I would be honest about the chronicity, the surveillance burden, the corticosteroid side effects, and the transplant possibility if the disease progresses. I would involve the GP, the dietitian, the physiotherapist (for deconditioning), and a hepatology nurse specialist. I would document the shared decisions and review them as the biochemistry responds. ^[1]