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Ibrutinib Side Effects — RACP Adult Medicine MCQ

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ModerateHaematologyIbrutinib Side EffectsRACP Adult Medicine

A 55-year-old man on ibrutinib for CLL develops easy bruising and petechiae despite a normal platelet count (180 × 10⁹/L). He also has AF with rapid ventricular response. He is not on anticoagulation. Bleeding time is prolonged. What is the most likely drug-related side effect?

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Correct answer: A — Ibrutinib-induced platelet dysfunction

Ibrutinib inhibits BTK but also off-target inhibits collagen receptor signalling in platelets (via TEC kinase), causing platelet dysfunction with bleeding despite normal platelet count. AF is another common ibrutinib side effect (~10%). Ibrutinib increases major bleeding risk, particularly with concurrent anticoagulation. Second-generation BTKi (acalabrutinib, zanubrutinib) have less platelet dysfunction and AF.

Reference: ALLG – 2024 – CLL; iwCLL 2024; NCCN 2025