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Local inflammatory reaction following tick bite — MSRA MCQ

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ModerateInfectious DiseasesLocal inflammatory reaction following tick biteMSRA

A 36-year-old man presents the day after removing an attached tick from his lower leg following a walk in the New Forest. He removed the tick intact with fine-tipped tweezers approximately 18 hours ago. Since then, he has developed a 2.5 cm erythematous patch centred on the bite site. It is mildly warm and pruritic but not painful, and he feels well. There is no fever, headache, arthralgia, facial weakness or expanding rash elsewhere. He has no relevant medical history and takes no regular medication. What is the most appropriate management today?

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

Reveal the answer and explanation

Correct answer: A — Advise symptomatic treatment and safety-netting, without Lyme serology or antibiotic treatment

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

This is most consistent with a local inflammatory reaction to a tick bite. The rash developed within 18 hours, is small, itchy and mildly warm, with no systemic features. UKHSA guidance states that a reaction developing and receding within 48 hours of a tick bite, particularly if hot, itchy or painful, is likely to be a bite reaction rather than erythema migrans. Symptomatic treatment and clear safety-netting are appropriate: he should seek review if the rash persists, expands centrifugally, develops after several days, or systemic symptoms occur. Erythema migrans usually develops at least 3 days after an infected tick bite and is treated clinically without laboratory testing; therefore B would be appropriate for a delayed, expanding rash compatible with erythema migrans. C is inappropriate because early serology may be negative and testing is not indicated for this transient local reaction. D is attractive because post-exposure doxycycline is used in some high-incidence parts of the USA, but UKHSA states that prophylaxis is not recommended in the UK. E would be appropriate if there were progressive painful erythema, tenderness, spreading inflammation or systemic features suggesting cellulitis.

Reference: Lyme disease: differential diagnosis (Updated 20 April 2022) — https://www.gov.uk/guidance/lyme-disease-differential-diagnosis Lyme disease: management and prevention (Updated 14 April 2022) — https://www.gov.uk/guidance/lyme-disease-management-and-prevention Lyme disease: NICE guideline NG95, recommendations (2018) — https://www.nice.org.uk/guidance/ng95/chapter/Recommendations