A patient has a history of relapsed AML (leukemia) treated with allogeneic stem cell transplant. They now have a lichenoid reaction in the mouth. What is the MOST likely cause?

Correct answer: A. Graft vs Host Disease (GvHD)

• A. Correct. GRAFT VS HOST DISEASE (GvHD) is the most likely cause of a lichenoid reaction in a patient who has received an ALLOGENEIC (donor) stem cell transplant. Oral GvHD classically presents as lichenoid changes, ulceration, and dryness. Chronic GvHD is the leading cause of lichenoid oral lesions in transplant recipients.
• B. Incorrect. AML recurrence does not typically manifest as a lichenoid reaction — GvHD is the far more likely explanation in this clinical context.
• C. Incorrect. Medication-induced candidiasis causes pseudomembranous white patches (candidiasis), not a lichenoid reaction.
• D. Incorrect. The patient's history of allogeneic transplant is the key — leukoplakia is not associated with stem cell transplant.