MTX Hair Thinning — SCE Rheumatology MCQ

Correct answer: C — Low-dose methotrexate can cause diffuse hair thinning through its anti-folate action, and folic acid supplementation may reduce this toxicity.

Explanation lettering: C = shown as A · D = shown as B · B = shown as C · E = shown as D · A = shown as E

Low-dose methotrexate is a recognised cause of diffuse, non-scarring hair thinning, attributable to its anti-folate effect on rapidly dividing hair-matrix cells. The UK SmPC states that in rheumatoid arthritis folic or folinic acid supplementation may reduce methotrexate toxicity, explicitly including alopecia, and UK practice is to co-prescribe weekly folic acid on a different day from methotrexate. NHS guidance confirms the hair loss is unlikely to be permanent and that dose reduction or a change of medicine can be considered if it is troublesome, so option B is correct. Options A and D wrongly deny a well-documented DMARD adverse effect; rheumatoid activity itself does not explain new diffuse thinning temporally linked to methotrexate. Option C is wrong because the alopecia is non-scarring and generally reversible after folic acid optimisation, dose reduction or withdrawal. Option E is wrong because alopecia occurs with both oral and parenteral methotrexate.

Reference: Methotrexate 2.5 mg Tablets, Summary of Product Characteristics (electronic medicines compendium), sections on toxicity and folic acid supplementation. https://www.medicines.org.uk/emc/product/511/smpc