01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Map the eruption before magnifying an individual lesion. Symmetry, exposed versus covered sites, pressure areas, folds, extensor surfaces and dermatomal boundaries reveal exposures and mechanisms. Record notable sparing because it can be as discriminating as involvement.
Configuration emerges from lesion growth, coalescence, trauma or anatomical pathways. Linear disease may follow scratching, contact, a developmental line or a nerve. Surface change then refines probability: peripheral scale, greasy scale, crust, fissuring or central atrophy should be located within the pattern rather than listed separately.
Distribution, configuration and surface change should answer a defined clinical question and be integrated with history, examination and the consequences of error. Explain uncertainty, record the sampling or observation conditions, and arrange a result-review plan rather than treating an isolated finding as self-interpreting.
Key points
- Distribution records where lesions occur and where they are spared: flexural, extensor, acral, seborrhoeic, photodistributed, dermatomal, intertriginous or generalised.
- Configuration describes relations between lesions, including annular, arcuate, linear, grouped, reticulate, targetoid, discoid and confluent patterns.
- Inspect scalp, hair, nails, mucosae, palms, soles and skin folds when consented because hidden sites may separate close differentials.
- An annular outline is not a diagnosis: dermatophyte infection, granuloma annulare, eczema, urticaria and inflammatory dermatoses can all form rings.
- For Distribution, configuration and surface change, describe what is seen before assigning a diagnosis, and record site, extent, symptoms, duration and change over time.
- A technically adequate result in Distribution, configuration and surface change can still be misleading when the wrong lesion, site, preparation or clinical question was selected.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Atopic eczema often favours flexures while plaque psoriasis favours extensor sites, but age, treatment and severity can reverse textbook distributions.
Face, V-neck, forearms and hand backs with sharp clothing sparing suggests photosensitivity; examine covered sites and ask about medicines.
Unilateral grouped vesicles with neuropathic pain in a sensory distribution supports herpes zoster, especially when lesions stop near the midline.
A ring with an active scaly margin and central clearing suggests dermatophyte infection, but sampling is needed when appearance is altered.
Palms, soles, nails and mucosae can reveal infection, drug reaction, inflammatory disease or systemic involvement missed on trunk inspection.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Complete distribution diagramFirst step - Why
- Capture involved and spared anatomy before treatment.
- Interpretation and limitations
- Record symmetry, percentage area only when useful, hidden sites examined and consent; a partial diagram can falsely imply sparing.
- 02
Surface examination and magnification - Why
- Locate scale, crust, follicular change, atrophy or vesiculation.
- Interpretation and limitations
- Side lighting and dermoscopy may clarify surface architecture, but pattern recognition cannot substitute for sampling an uncertain infection.
- 03
Exposure and medicine timeline - Why
- Align distribution with contact, light, occupation and drug latency.
- Interpretation and limitations
- A plausible boundary or latency strengthens causation; absence of immediate symptoms does not exclude delayed allergic contact dermatitis.
- 04
Question-led scraping, swab or biopsy - Why
- Test the leading alternative when morphology overlaps.
- Interpretation and limitations
- Sample the active untreated edge for mycology, infected exudate for culture when indicated, or a representative lesion for histopathology.
04Clinical next stepsHow the result changes management or prompts escalation.
01Planned assessmentUse whole-skin pattern mapping systematicallyFirst stepThe patient is stable and the result will alter diagnosis, referral or follow-up.+
- 1Define the question for Distribution, configuration and surface change, explain the process and obtain valid consent before exposing, touching, photographing or sampling skin.
- 2Choose representative anatomy, optimise lighting or specimen technique, and document site, morphology, symptoms and relevant previous treatment. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
- 3Interpret the result beside the full clinical pattern, communicate uncertainty and arrange ownership of results and safety-netting. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
02Uncertain resultResolve discordance in Distribution, configuration and surface changeThe technical finding conflicts with the history, lesion evolution or wider examination.+
- 1Recheck identity, site, timing, preparation, treatment exposure and whether the selected target was genuinely representative. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
- 2Repeat or select a complementary test only when it can distinguish the remaining important alternatives. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
- 3Seek dermatology, pathology, microbiology or allergy advice when clinicopathological disagreement would change urgent care. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
03Urgent patternDo not let whole-skin pattern mapping delay escalationEscalationA rapidly progressive eruption, systemic illness, threatened vision or airway, or suspected aggressive malignancy is present. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.+
- 1Stabilise immediate physiological threats and obtain same-day senior or specialty assessment according to the dominant emergency. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
- 2DefinitiveTake time-critical images or specimens only when doing so will not postpone resuscitation, antimicrobials or definitive referral. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
- 3Record evolution and communicate the differential, outstanding results and explicit deterioration triggers during handover. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Record who will review the result arising from Distribution, configuration and surface change, the expected timescale and the action threshold before the patient leaves.
- Compare subsequent findings with the original site description, dimensions, symptoms and image or specimen identifiers for Distribution, configuration and surface change.
- Reassess earlier if rapid growth, bleeding, ulceration, fever, mucosal disease, eye symptoms or functional compromise develops. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
- Document technical limitations and previous treatment that could alter sensitivity or specificity of whole-skin pattern mapping.
- Close the loop after specialist or laboratory review, including clinicopathological disagreement and any need for repeat sampling. Apply that step specifically within the distribution, configuration and surface change assessment and its recorded clinical context.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Sparing is positive evidence
Unaffected eyelids, folds, pressure points or covered skin can reveal exposure geometry and should be explicitly documented.
Koebnerisation has several causes
Linear lesions after scratching occur in psoriasis, lichen planus and vitiligo and do not identify one disease.
Treatment redraws maps
Topical corticosteroid or antifungal exposure may suppress scale centrally while disease remains active at the margin.
Pigment can outlast activity
Brown, grey or lighter macules may mark previous distribution after erythema, elevation and itch resolve.
Patterns need chronology
A generalised eruption that began at one contact site differs from simultaneous lesions appearing across several regions.
07Common pitfallsFrequent interpretation and management errors.
- 01
Declaring a photo-distribution without asking about windows, clothing, sunscreen and occupational exposure.
- 02
Calling every ring tinea and starting combination steroid treatment before obtaining a scraping from the active edge.
- 03
Recording body-surface percentage without stating whether erythema is difficult to see in deeply pigmented skin.
- 04
Missing nail, scalp, oral or genital involvement because examination was limited to the presenting forearm.
- 05
Using a configuration name as a final diagnosis despite incompatible symptoms, tempo or surface change.