Psoriasis treated with methotrexate — SCE Dermatology MCQ

Correct answer: C — Defer methotrexate and assess liver risk first

The correct answer is C, defer methotrexate and assess liver risk first. This man has multiple recognised risk factors for methotrexate related hepatotoxicity: alcohol intake of 35 units weekly, obesity (BMI 34), a raised ALT, and a FIB-4 score above the local referral threshold, indicating probable fibrosis risk that must be characterised before committing to a hepatotoxic drug. Current UK dermatology practice uses non-invasive fibrosis markers such as FIB-4 or transient elastography to risk-stratify patients before and during methotrexate, and an abnormal score should prompt further assessment (repeat testing, elastography, or hepatology referral) rather than proceeding blind. Starting an antifolate drug with unquantified fibrosis risk is unsafe and inconsistent with the pre-treatment work-up recommended for systemic methotrexate use in psoriasis. Why the other options are wrong: A, start methotrexate with no further assessment: ignores four independent hepatotoxicity risk factors (alcohol excess, obesity, raised ALT, high FIB-4) and breaches the standard pre-treatment liver risk assessment pathway. C, use methotrexate and add folic acid later: folic acid mitigates gastrointestinal and haematological toxicity but has no protective effect on methotrexate related liver fibrosis, so it does not address the actual contraindication risk here. D, switch to long-term oral prednisolone: chronic systemic corticosteroids are not indicated for plaque psoriasis and carry a recognised risk of triggering severe rebound or pustular psoriasis on withdrawal. E, prescribe topical calcipotriol as sole therapy: topical agents alone are inadequate for severe plaque psoriasis, which by definition requires systemic or biologic therapy for disease control. Key point: alcohol excess, obesity, raised ALT and an elevated FIB-4 score together mandate formal liver risk assessment before starting methotrexate, not immediate initiation or premature abandonment of systemic therapy.

Reference: British Association of Dermatologists guidance on methotrexate use in psoriasis (liver risk stratification with FIB-4/transient elastography); BNF methotrexate monitoring requirements, https://bnf.nice.org.uk/drugs/methotrexate/