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MDR-TB — SCE Infectious Diseases MCQ

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HardTuberculosisMDR-TBSCE Infectious Diseases

At week 8 of BPaLM therapy for rifampicin-resistant TB, haemoglobin falls from 125 to 84 g/L and the patient develops symmetrical painful distal paraesthesia. QTc and liver tests are unchanged. Which component most plausibly explains both toxicities?

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Correct answer: C — Linezolid through mitochondrial ribosomal inhibition and impaired haematopoiesis

Linezolid inhibits mitochondrial protein synthesis and prolonged exposure can cause myelosuppression, peripheral neuropathy, optic neuropathy and lactic acidosis. Full blood counts and active neurological and visual monitoring are essential, with dose interruption or reduction decided by the specialist TB team. Bedaquiline and moxifloxacin are particularly relevant to QT monitoring but do not explain this paired syndrome.

Reference: Linezolid SmPC: https://www.medicines.org.uk/emc/product/13583/smpc; NHS England BPaLM policy: https://www.england.nhs.uk/publication/clinical-commissioning-policy-bpalm-bpal-for-patients-aged-%E2%89%A5-14-years-with-suspected-functional-or-confirmed-rr-tb-mdr-tb-or-pre-xdr-tb/