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Visual Diagnosis · Observation before conclusion

See the evidence. Defend the pattern.

Train your eye to observe, describe, compare, and reason—without turning one photograph into a diagnosis.

Start a visual caseLearn the framework

Designed for: medical students, rotators, interns, and residents refreshing visual reasoning. No image-identification experience is required.

Visual diagnosis reasoning boardThree original abstract lesion diagrams progress through observation, comparison, and focused reasoning.LOOK CLOSERWHAT DO YOU SEE?WHAT SEPARATES IT?WHAT FITS?SEE + DESCRIBEDIFFERENTIATEDEFEND
Original DermPrep schematic; no patient image or third-party clinical photograph.
PurposeBuild structured visual reasoning.
CompetenciesObserve · describe · compare · defend.
PrerequisiteDerm Foundations recommended.
TimeQuick 5 · Core 20 · Deep 35 min.

Choose your depth

Enter anywhere. Keep the same reasoning sequence.

Each mode ends with a usable observation, not a memorized picture.

Quick · 5 minutesLearn the visual scan

One framework, one model description, one question.

Core · 20 minutesReason through cases

Progressive reveal, feedback, comparison, and communication.

Deep Dive · 35 minutesCalibrate the differential

Variation, mimics, changed evidence, and learner-level next steps.

Quick mode · The DermPrep visual scan

Do not name it yet.

  1. 1What do you see?Pause before interpretation.
  2. 2Primary lesionFlat, solid and raised, fluid-filled, or deep?
  3. 3Color + surfaceName hue, scale, crust, erosion, or other change.
  4. 4ConfigurationHow do the lesions relate to one another?
  5. 5DistributionWhere are they, and what is spared?
  6. 6Additional featuresBorder, symmetry, depth, evolution, symptoms, mucosa, nails.
  7. 7Focused differentialMost likely, important alternative, dangerous mimic when relevant.
  8. 8Defend + next stepName the discriminating clue and what you would discuss with your supervisor.

Say it like this

“There are multiple, sharply demarcated, annular pink-brown plaques with peripheral scale on the trunk. The advancing scaly border supports a dermatophyte infection, although confirmation may require bedside testing.”

Learning objective

Recognize → describe → compare → reason → communicate.

By the end, you should be able to complete a morphology-first description, generate a focused differential, identify the feature that changes it most, state why alternatives fit less well, and communicate an appropriate supervised next consideration.

Foundation

Notice

Morphology, color, surface, configuration, distribution.

Rotation

Describe

Complete sentence, common mimics, focused differential.

Advanced rotation

Discriminate

History, distribution, and next diagnostic considerations.

Resident

Integrate

Dermoscopy, pathology, treatment implications, uncommon mimics—only where supported.

Core mode · Progressive reveal

Case Lab

Answer in order. The diagnosis stays hidden until you describe the evidence.

Foundation · Original schematic case

Start with the objective features

Text equivalent: several annular pink-brown plaques with relative central clearing and surface change at the edge.
1. What is the primary lesion?
3. Which clue matters most?
What changes your mind?

New information: bedside microscopy from the active edge does not show fungal elements, and similar plaques are present on both extensor elbows with nail pitting.

Reassess: the additional distribution and nail findings make psoriasis more plausible. One image never carries the whole diagnosis.

Compare mode

Similar at first glance. Different at the clue.

Predict the distinction before opening each answer.

Psoriasis vs dermatophyte infection

Looks similar: scaly plaques.

Reveal the discriminating approach

Look for: where scale sits, border behavior, distribution, associated scalp or nail findings, exposures, and the role of testing. Avoid diagnosing either from one isolated feature.

Common error: calling every annular plaque “ringworm” or every thick scaly plaque “psoriasis.”

Vesicle vs pustule

Looks similar: small elevated lesions with visible contents.

Reveal the discriminating approach

Look for: clear/serous versus purulent-appearing contents, follicular relationship, surrounding inflammation, and clinical context.

Describe: “grouped clear vesicles” versus “follicular pustules.”

Erosion vs ulcer

Looks similar: loss of the skin surface.

Reveal the discriminating approach

Look for: depth. An erosion is superficial epidermal loss; an ulcer extends into at least the dermis.

Common error: using the terms as synonyms without assessing depth.

Deep Dive · Representation and uncertainty

Variation is not the same as a mimic.

Variation

The same disease can look different across skin tones, ages, body sites, stages, treatments, and severity. Color words should describe what is visible—not assume inflammation is always bright red.

Mimic

A different disease can produce a similar visual pattern. Separate it by looking for the highest-value difference in morphology, distribution, history, symptoms, evolution, or testing.

Representation standard: future clinical-image cases should include rights-cleared examples across skin tones and phenotypes. Until that collection is approved, this page uses original schematics and text equivalents rather than presenting one photograph as universal.

Why not?

A defensible answer explains why the leading possibility fits, why reasonable alternatives fit less well, and which finding carries the most weight. “It looks like it” is not a reasoning statement.

SupportsThe morphology and distribution that fit.
Argues againstThe expected clue that is absent or contradicted.
UnresolvedThe history, exam, dermoscopy, microscopy, culture, biopsy, or evolution still needed.

Clinical communication

What would you say?

Weak

“The patient has a circular rash. It looks fungal.”

Better

“There are several annular pink-brown plaques with relative central clearing and scale concentrated at the peripheral border on the trunk. A dermatophyte infection is a leading consideration; I would discuss bedside testing and the focused differential with my supervising clinician.”

Why the second is stronger: it separates observation from interpretation, uses morphology-based language, calibrates certainty, and states a learner-appropriate next action.

Know / Say / Do

Know

Visual recognition narrows a differential; it does not replace context or confirmation.

Say

Lead with morphology and distribution, then state what the evidence supports.

Do

Examine appropriate additional sites and discuss next diagnostic considerations with your supervising clinician.

Common mistakes and correction

Train the process, not the picture.

Naming before noticing

Tempting because: recognition feels fast.

Correct: commit to one objective sentence before the differential.

Giant differential lists

Tempting because: more names feel safer.

Correct: most likely, important alternative, and dangerous mimic when relevant—each tied to a clue.

One-image certainty

Tempting because: atlases show classic examples.

Correct: ask how the pattern may vary and what different disease can mimic it.

Color-only reasoning

Tempting because: color is immediate.

Correct: integrate surface, palpability, configuration, distribution, and evolution.

Don’t miss

Escalate promptly through the supervising team when a patient appears systemically unwell or has a painful or rapidly progressive eruption, extensive blistering or skin detachment, mucosal involvement, concerning non-blanching lesions, or another urgent feature.

Retrieval practice

Try one question.

You see a sharply demarcated scaly plaque. Which next observation best improves the differential?

30-second recap

  • Describe before you diagnose.
  • Use morphology, color, surface, configuration, and distribution.
  • Build a focused differential around discriminating clues.
  • Reassess when history, examination, or testing changes.
  • Communicate uncertainty and learner-level next steps clearly.

Attending-style questions

Be ready to defend the visual evidence.

What is the primary lesion, and what makes you call it that?

State whether it is flat or raised, solid or fluid-filled, superficial or deep, and the objective feature that supports the term.

Which single feature changes your differential most?

Choose one discriminating feature—such as border, scale, configuration, distribution, symmetry, evolution, or mucosal involvement—and explain its direction of effect.

What is a reasonable alternative, and why is it less likely?

Name the strongest alternative, then identify the observed or missing feature that lowers it.

What would you examine or discuss next?

Choose focused additional history, examination sites, or diagnostic considerations appropriate to your level and supervision.

Keep the learning loop moving

Your next best actions

Learn nextDerm Foundations · MorphologyPractice nextPimp Me · Visual patternsApply nextClinical Case · Scaly plaque

Also connects to Rotation Ready and related Derm Conditions.

Sources & page information
  1. Nast A, Griffiths CEM, Hay R, et al. The 2016 International League of Dermatological Societies’ revised glossary for the description of cutaneous lesions. Br J Dermatol. 2016;174(6):1351–1358.
  2. International League of Dermatological Societies. Glossary for Dermatology Terms.
  3. American Academy of Dermatology. Basic Dermatology Curriculum: Morphology.
  4. American Academy of Dermatology. Red scaly rash: the papulosquamous eruption.
  5. DermNet. Terminology in dermatology. Tertiary terminology cross-check.
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