A 32-year-old man with newly diagnosed pulmonary tuberculosis is started on standard four-drug therapy (HRZE). After 2 weeks of treatment, he develops acute onset jaundice, dark urine, and right upper quadrant tenderness. Liver function tests show ALT 320 U/L, AST 380 U/L, total bilirubin 4.2 mg/dL, and alkaline phosphatase 95 U/L. Hepatitis A, B, and C serology are negative. What is the most appropriate next step in management?

Explanation

## Clinical Context This patient presents with **drug-induced liver injury (DILI)** occurring within 2 weeks of starting standard antitubercular therapy. The pattern of transaminitis with hyperbilirubinemia and clinical jaundice indicates hepatocellular injury, most likely from isoniazid, rifampicin, or pyrazinamide. ## Management Algorithm for TB-DILI ```mermaid flowchart TD A[TB-DILI suspected]:::outcome --> B{ALT/AST > 5× ULN<br/>or ALT/AST > 3× ULN<br/>+ symptoms?}:::decision B -->|Yes| C[STOP all drugs<br/>immediately]:::urgent C --> D[Await LFT<br/>normalization]:::action D --> E[Rechallenge with<br/>individual drugs]:::action E --> F{Identify culprit<br/>agent}:::decision F -->|Identified| G[Restart TB regimen<br/>without culprit]:::action F -->|None identified| H[Restart full therapy<br/>with caution]:::action ``` ## Key Management Principles **Key Point:** When ALT/AST exceed 3× upper limit of normal (ULN) WITH symptoms, or 5× ULN regardless of symptoms, all antitubercular drugs must be **stopped immediately**. This is non-negotiable. **High-Yield:** The correct approach is **complete cessation** followed by **individual drug rechallenge** (sequential introduction) to identify the hepatotoxic agent: - Start with least hepatotoxic drug (usually ethambutol) - Add second drug after 3–5 days if LFTs remain stable - Reintroduce isoniazid, rifampicin, and pyrazinamide one at a time - Whichever drug causes LFT rise again is the culprit **Clinical Pearl:** Isoniazid and rifampicin are the most common culprits (~60% of TB-DILI cases), followed by pyrazinamide. Ethambutol rarely causes hepatotoxicity. ## Why This Patient Needs Full Cessation This patient meets criteria for **severe DILI**: - ALT 320 U/L (>5× ULN if ULN ~60) - Clinical jaundice (bilirubin 4.2 mg/dL) - Symptomatic (jaundice, RUQ pain) Continuing any drug risks acute liver failure. Selective discontinuation (option C) is inadequate because it does not identify the culprit and may continue exposure to the offending agent. ## Rechallenge Protocol Timeline | Day | Action | LFT Check | |-----|--------|----------| | 0 | Stop all drugs | Baseline | | 3–7 | LFTs normalize | Confirm | | 7–10 | Start ethambutol (safest) | Day 10 | | 14 | Add second drug if stable | Day 14 | | 21 | Add third drug if stable | Day 21 | | 28 | Identify culprit if any rise | Day 28 | [cite:Harrison 21e Ch 158] ## Why Each Distractor Is Wrong **Option A (Continue therapy):** Continuing drugs in the face of severe hepatocellular injury (ALT >300, jaundice, symptoms) risks progression to acute liver failure and death. This violates the cardinal rule of DILI management: **stop the offending drug(s) immediately**. **Option B (Discontinue HRZE, restart with EFQ):** While fluoroquinolones are less hepatotoxic, this approach skips the critical step of identifying which drug caused the injury. The patient may still have latent sensitivity to one of the original drugs, and fluoroquinolones are not first-line for drug-susceptible TB. Restarting without rechallenge risks recurrence. **Option C (Discontinue INH + RIF only):** This is a compromise that fails on two counts: (1) it does not identify the culprit (could be PZA), and (2) continuing PZA and ETH alone is suboptimal for TB treatment if INH and RIF are truly the problem. The standard approach is **complete cessation**, not selective discontinuation.