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Fever without an apparent source in an infant aged 1 to 3 months — MRCEM SBA MCQ

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EasyPaediatric emergenciesFever without an apparent source in an infant aged 1 to 3 monthsMRCEM SBA

A 7-week-old infant is brought to the emergency department with a temperature of 38.3°C measured in the axilla. He is alert, feeding normally and well perfused. Examination identifies no source of infection or respiratory signs. His white blood cell count is 17.2 × 10⁹/L and C-reactive protein is 6 mg/L. A urine sample is negative for nitrite and leucocyte esterase, and a blood culture has been taken. There is no contraindication to lumbar puncture, which can be performed promptly. What is the most appropriate management plan?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Admit, perform lumbar puncture promptly, then start intravenous cefotaxime and amoxicillin.

Although this infant appears well and has a low C-reactive protein and negative urine dipstick, he is aged between 1 and 3 months and his white blood cell count exceeds 15 × 10⁹/L. NICE recommends both lumbar puncture and parenteral antibiotics for a febrile infant in this age group who meets that white-cell threshold. When indicated, lumbar puncture should be performed without delay and, whenever possible, before antibiotics; it is promptly available here. NICE recommends a third-generation cephalosporin plus an antibiotic active against *Listeria* for infants younger than 3 months who require parenteral treatment. ([nice.org.uk](https://www.nice.org.uk/guidance/ng143/chapter/recommendations)) A is insufficient because a reassuring appearance does not remove the white-cell-based indications for investigation and treatment. C omits *Listeria* cover. D gives appropriate initial antibiotics but unnecessarily postpones a feasible lumbar puncture until a blood culture result. E uses oral rather than parenteral treatment. The infant requires paediatric inpatient assessment and ongoing review while results are obtained. ([nice.org.uk](https://www.nice.org.uk/guidance/ng143/chapter/recommendations))

Reference: NICE NG143, Fever in under 5s: assessment and initial management, recommendations 1.5.4 and 1.5.6 (Last updated 26 November 2021) — https://www.nice.org.uk/guidance/ng143/chapter/recommendations NICE NG143, Fever in under 5s: assessment and initial management, recommendations 1.5.5 and 1.5.7 (Last updated 26 November 2021) — https://www.nice.org.uk/guidance/ng143/chapter/recommendations