Tuberculosis — SCE Infectious Diseases MCQ

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A 40-year-old man on treatment for drug-susceptible pulmonary TB develops acute visual symptoms at week 6 of treatment. He reports decreased visual acuity and difficulty distinguishing red from green. Which anti-TB drug is most likely responsible?

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Correct answer: A — Ethambutol

Ethambutol causes dose-dependent optic neuritis presenting with decreased visual acuity, central scotomata, and red-green colour blindness. Visual acuity (Snellen chart) and colour vision (Ishihara plates) should be tested at baseline and monthly during treatment. The drug should be stopped immediately if visual symptoms occur and the patient referred to ophthalmology. The effect is usually reversible if detected early.

Reference: NICE NG33 2016 – Tuberculosis; BNF 2024 – Ethambutol