Synopsis
Use anatomical distribution, lesion configuration and surface change to narrow dermatological differentials while avoiding pattern labels that conceal incomplete examination.
- 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.
Key red flags
Generalised skin pain, rapidly extending erythema, confluent purpura, mucosal loss, erythroderma or a dermatomal eruption affecting the eye requires urgent action.
Unilateral grouped vesicles with neuropathic pain in a sensory distribution supports herpes zoster, especially when lesions stop near the midline.
Investigation priorities
Capture involved and spared anatomy before treatment.
Management branches
The patient is stable and the result will alter diagnosis, referral or follow-up.
- Define the question for Distribution, configuration and surface change, explain the process and obtain valid consent before exposing, touching, photographing or sampling skin.
- Choose 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.
- Interpret 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.