Cases/Infectious Disease and Travel Health

Spreading Rash After A Tick Bite — Free SCA Practice Case

Walker with a spreading rash after a tick bite

Station Timer

12:00

Golden Minute

Initial Introduction

•Introduce yourself

•Ask an open question — "How can I help you today?"

•Listen — don't interrupt

•Catch early cues

Data Gathering

History, ICE & Diagnosis

Clinical Management

Diagnosis, Plan & Decisions

Safety Net

Follow-up & Close

12:00

Golden Minute

Materials for Candidate

Please review before starting the consultation

Patient Profile

Full Name

Brian Foster

Age

52 years

Consultation Type

Telephone

Age

Situation

Telephone Consultation. The patient has sent in a photograph of a rash and booked an urgent call.

Reason for Encounter

"I've got a strange circular rash on my leg that's been getting bigger. I was bitten by a tick when I was out walking a couple of weeks ago and I'm worried it's Lyme disease."

Medical Records

●PMH: Nil significant.
●Medications: None.
●Allergies: NKDA.

Photograph (sent in before the call)

A single, roughly circular, expanding area of erythema on the left calf, approximately 8 cm across, with some central clearing (a target/"bull's-eye" appearance); no significant scaling or weeping; no pustules.

Patient Script

For the friend playing the patient role

Character Overview: You are Brian, a 52-year-old keen hill walker. You spend most weekends out on the moors and in woodland. About two weeks ago you found a tick attached to your left calf after a walk and removed it. A few days ago a red mark appeared where the bite was and it has been slowly spreading outwards in a ring. You feel largely well but have had a couple of days of mild flu-like achiness. You have read about Lyme disease and are worried.

Opening Sentence: "Hi Doctor. I sent in a photo of my leg. About two weeks ago I picked up a tick on a walk — pulled it off myself. Then a few days ago this red patch came up where the bite was, and it's been spreading outwards in a circle, sort of like a target. I've read that's a sign of Lyme disease. Should I be worried?"

History if Asked (Data Gathering Phase)

●The rash: "It started as a small red spot at the bite site and has slowly spread outwards over about four or five days. It's now a good few inches across, with a paler centre — like a bull's-eye. It's not really itchy or painful, more just there."
●The tick bite: "I found the tick attached to my calf after a walk in woodland about two weeks ago. I'm not sure how long it had been on — could have been a while. I pulled it off with tweezers; I think I got it all out."
●Systemic symptoms: "I've felt a bit flu-ish the last couple of days — achy, tired, mild headache. No high fever."
●Walking/exposure: "I'm out walking most weekends, moorland and woods. I get the odd tick — comes with the territory."
●Previous rashes: "No, I don't get eczema or skin problems. This is new and different from anything I've had."

ICE — Ideas, Concerns, Expectations

The patient does not volunteer this information unprompted. These responses surface only when the candidate directly explores his perspective.

●Ideas: Brian has read that a spreading "bull's-eye" rash after a tick bite is Lyme disease and thinks that is what he has. "I'm fairly convinced it's Lyme — the bull's-eye ring after a tick bite is exactly what I read about."
●Concerns: He is worried about the serious long-term complications of untreated Lyme disease he has read about (joints, nerves, heart). "What worries me is the long-term stuff — I've read it can cause nerve and joint problems, even heart problems, if it's not treated."
●Expectations: He wants confirmation and, if it is Lyme, prompt antibiotic treatment. "I want to know if it's Lyme, and if it is, to get started on antibiotics quickly before it does any damage."

If Asked — Medical History and Systemic Screen

The patient confirms these details only when directly asked.

●General health: "Fit and well normally, no medical problems, no regular medications."
●Allergies: "None — I can take any antibiotics as far as I know."
●Neurological symptoms: "No facial weakness, no numbness or tingling, no visual problems."
●Joint symptoms: "A bit of general achiness, but no swollen joints."
●Cardiac symptoms: "No palpitations, no dizziness, no blackouts, no breathlessness."
●Other bites/rashes elsewhere: "Just the one rash, at the bite site on my calf."

If Asked — Rash Characterisation and Red-Flag Screen

The patient answers these only when directly asked.

●If asked about the rash expanding over time: "Yes — it's definitely got bigger over several days, from a small spot to a big ring."
●If asked about itch, pain, heat, or weeping: "No, it's not itchy or sore, not hot or weepy — just a spreading red ring with a paler middle."
●If asked about central clearing / target appearance: "Yes, the middle's gone paler, so it looks like a target."
●If asked about fever: "Mildly feverish and achy, but nothing high."
●If asked about facial droop, neck stiffness, severe headache (neuroborreliosis/meningism): "No, nothing like that."
●If asked about palpitations/fainting (carditis): "No, none of that."
●If asked about when the tick was removed and how long attached: "About two weeks ago; I don't know how long it was on — possibly overnight."

Responses to Management (The Negotiation Phase)

●If the Doctor diagnoses Lyme disease clinically from the erythema migrans rash: "So you can tell just from the rash? Don't I need a blood test to confirm it?" (The tested point is explaining that erythema migrans is a clinical diagnosis and that antibiotics should be started without waiting for serology.)
●If the Doctor prescribes doxycycline: "How long do I take the antibiotics for? Are there any side effects I should know about?" (The tested point is prescribing the correct regimen and counselling, e.g. doxycycline and sun sensitivity.)
●If the Doctor explains a blood test now could be falsely negative: "But wouldn't a blood test make sure? Why wouldn't it show up?"
●If the Doctor safety-nets for disseminated Lyme: "What are the warning signs I should watch for if the antibiotics don't sort it?"
●If the Doctor gives tick-prevention advice: "I walk every weekend — how do I avoid this happening again?"

Mark Scheme

Domain 1: Data Gathering and Diagnosis

0 / 16 indicators checked+0−0

Positive (0/8)

Negative (0/8)

Domain 2: Clinical Management and Medical Complexity

0 / 18 indicators checked+0−0

Positive (0/9)

Negative (0/9)

Domain 3: Relating to Others

0 / 12 indicators checked+0−0

Positive (0/6)

Negative (0/6)

Clinical Learning Points

Erythema Migrans and the Clinical Diagnosis of Lyme Disease

●Erythema migrans is the characteristic early rash of Lyme disease: a red rash that increases in size over days to weeks, often ≥5 cm, sometimes with central clearing (a target/bull's-eye), appearing 1–4 weeks (up to 3 months) after a tick bite. It is usually not itchy, hot, or painful.
●Per NICE NG95, Lyme disease should be diagnosed clinically and treated without laboratory testing when erythema migrans is present.

Why Not to Rely on Serology Early

●Antibody tests (ELISA, then immunoblot) can be falsely negative in early Lyme disease before antibodies develop. Where erythema migrans is present, do not delay treatment for testing.
●Serology has a role when there is no erythema migrans but Lyme is suspected (with repeat testing/immunoblot if initially negative and suspicion persists).

Antibiotic Treatment (NICE NG95)

●First-line (early Lyme, adult): doxycycline 100 mg twice daily or 200 mg once daily for 21 days.
●Alternatives: amoxicillin 1 g three times daily for 21 days (e.g. pregnancy, young children where doxycycline is contraindicated); azithromycin if both are unsuitable.
●Counsel on doxycycline photosensitivity and completing the course.

Distinguishing Erythema Migrans from Mimics

●Not every rash after a tick bite is Lyme disease. Consider eczema/dermatitis, cellulitis, ringworm (tinea), and localised insect-bite reactions — which differ in features (itch, scaling, heat, rapid onset, or a small fixed reaction). Erythema migrans is a slowly expanding, non-itchy, non-painful ring, often with central clearing.

Disseminated Lyme Disease

●Untreated Lyme disease can disseminate: neuroborreliosis (facial palsy, meningitis, radiculopathy), Lyme carditis (heart block — palpitations, syncope), and Lyme arthritis (swollen joints).
●Safety-net for these features; they warrant urgent review and often specialist involvement.

Jarisch–Herxheimer Reaction

●A transient worsening of symptoms can occur within the first day or two of starting antibiotics; warn the patient so it is not mistaken for treatment failure or an allergy.

Tick-Bite Prevention and Removal

●Advise covering skin, using insect repellent, and checking for ticks after being in tick habitats.
●Remove ticks promptly with fine-tipped tweezers, gripping close to the skin and pulling steadily upward; clean the area. Prompt removal reduces transmission risk. Seek review if a rash or symptoms develop.

Common Candidate Mistakes in This Case

●Delaying treatment to await serology: failing to recognise erythema migrans as a clinical diagnosis and treating promptly.
●Wrong regimen: incorrect antibiotic, dose, or duration, or too short a course.
●Missing dissemination screening/safety-netting: not asking about or warning of neuroborreliosis, carditis, and arthritis.
●Over-diagnosing every post-tick rash as Lyme — or missing a genuine one: failing to distinguish erythema migrans from mimics in either direction.
●No prevention advice: neglecting tick prevention in a patient with ongoing high exposure.

Free MRCGP SCA practice case for GP registrars covering Spreading Rash After A Tick Bite — Infectious Disease and Travel Health. Includes candidate brief, patient script, marking scheme mapped to the RCGP SCA marking domains, and learning points. Built directly from the RCGP curriculum topic stations listed under "How this might be tested in the MRCGP SCA," part of a free library of 79 SCA practice cases for simulated consultation assessment preparation.

← Back to Free SCA Practice Cases