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High-Yield Images: The “Spot” Diagnosis — Differences for MRCP Part 1

TL;DR: 

For MRCP Part 1, image-based (“spot”) questions reward rapid pattern recognition followed by precise differentiation between look-alike conditions. This guide explains the scope, highlights the most tested image themes, covers key differentiating features, and provides a mini-MCQ plus a practical checklist to help you convert images into marks.


Why image-based questions matter in MRCP Part 1

Image interpretation is a high-yield scoring area in MRCP Part 1. The images are rarely obscure; instead, they depict classic conditions with subtle differentiators. The exam tests whether you can (1) recognise the pattern quickly and (2) choose the single best diagnosis or next step, avoiding common traps.

Most candidates lose marks not because they have never seen the image, but because they confuse closely related differentials—for example, psoriasis vs seborrhoeic dermatitis, or basal cell carcinoma vs squamous cell carcinoma.

For syllabus context and weighting, review the official MRCP Part 1 overview from MRCP(UK):https://www.mrcpuk.org/mrcpuk-examinations/part-1


Scope of “spot” diagnoses you should expect

In MRCP Part 1, images are most commonly drawn from:

  • Dermatology

  • Ophthalmology

  • Rheumatology

  • Endocrinology

  • Neurology

Dermatology remains the single most frequent source, making it a reliable revision target.


10 high-yield image patterns you must recognise

  1. Psoriasis vulgaris – well-demarcated erythematous plaques with silvery scale on extensor surfaces

  2. Seborrhoeic dermatitis – greasy scale on scalp, eyebrows, and nasolabial folds

  3. Atopic eczema – flexural involvement with lichenification

  4. Malignant melanoma – asymmetry, border irregularity, colour variation

  5. Basal cell carcinoma – pearly papule with telangiectasia

  6. Squamous cell carcinoma – ulcerated or crusted lesion on sun-exposed skin

  7. Herpes zoster – unilateral dermatomal vesicular rash

  8. Erythema nodosum – tender red nodules on shins

  9. Rheumatoid nodules – firm nodules on extensor surfaces

  10. Xanthelasma – yellow plaques on eyelids suggesting dyslipidaemia

These images are repeatedly used because they are instantly recognisable when learned properly.


MRCP Part 1 candidate revising high-yield image-based spot diagnoses

The 5 most tested differentiations (and how to avoid traps)

1. Psoriasis vs seborrhoeic dermatitis

  • Psoriasis: thick silvery scale, extensor surfaces

  • Seborrhoeic dermatitis: greasy scale, sebaceous areasTrap: assuming scalp involvement always means psoriasis

2. Basal cell carcinoma vs squamous cell carcinoma

  • BCC: pearly, slow-growing, rarely metastasises

  • SCC: ulcerated, faster growth, metastatic potentialTrap: choosing BCC for any facial lesion

3. Eczema vs tinea corporis

  • Eczema: poorly demarcated, itchy, improves with steroids

  • Tinea: annular lesion with central clearingTrap: steroid use masking tinea (“tinea incognito”)

4. Herpes simplex vs herpes zoster

  • HSV: recurrent, grouped vesicles

  • Zoster: dermatomal, unilateral, painfulTrap: missing dermatomal distribution

5. Erythema nodosum vs vasculitis

  • Erythema nodosum: tender nodules, no ulceration

  • Vasculitis: purpura, ulcerationTrap: over-diagnosing vasculitis


Mini-MCQ (image-based concept)

A photograph shows a pearly, flesh-coloured papule with surface telangiectasia on the nose of a 72-year-old man.

What is the most likely diagnosis?

A. Squamous cell carcinomaB. Malignant melanomaC. Basal cell carcinomaD. Actinic keratosisE. Seborrhoeic keratosis

Correct answer: C. Basal cell carcinoma

Explanation: The pearly appearance with telangiectasia on sun-exposed skin is classic for basal cell carcinoma. Squamous cell carcinoma is more likely to appear ulcerated or crusted.

For more exam-style image MCQs, practise with a dedicated question bank such as:https://passmedicine.comor the Crack Medicine Qbank:https://crackmedicine.com/qbank/


Practical study checklist for image questions

Before exam day, ensure you can:

  • Identify the classic visual hallmark of common conditions

  • Name one key differentiator from the closest mimic

  • Link the image to a single best diagnosis, not a list

  • Avoid over-thinking rare conditions

  • Answer within 30 seconds per image

Use timed practice to simulate pressure—mock exams are particularly effective:https://crackmedicine.com/mock-tests/


How this fits your MRCP Part 1 revision strategy


Frequently Asked Questions

Are image questions common in MRCP Part 1?

Yes. They appear regularly and are considered high-yield because they test rapid clinical recognition.

Do I need to diagnose rare conditions from images?

No. The exam focuses on common, classic presentations, not zebras.

Is dermatology the most important image topic?

Yes. Dermatology images are the most frequent and predictable.

How can I improve my image interpretation quickly?

Repeated exposure with feedback—using MCQs and mock tests—is the fastest method.


Ready to start?

In MRCP Part 1, spot diagnoses are about disciplined pattern recognition, not guesswork. Learn the classics, master the differences, and practise under time pressure. Done well, image questions become one of the most reliable sources of marks.


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