Dermatological Diagnosis

Examination Framework

1. Distribution

  • Identify where lesions occur on the body.

  • Look for:
    • Areas affected (e.g.
    – Sun-exposed vs.
    – Flexural vs.
    – Extensor vs.
    – Acral)

    • Symmetry
    – Bilateral & mirror-image → suggests systemic, autoimmune, or genetic disorders.
    – Asymmetric / unilateral → consider trauma, infection, arthropod bite, contact dermatitis.

    • Pattern / configuration
    – Linear, annular, arciform, serpiginous, grouped, dermatomal, blaschkoid, photodistributed, etc.

2. Morphology

  • Describe the primary lesion first, then add qualifying adjectives.
  • Essential elements:
    • Type & size of primary lesion
    • Colour
    • Surface changes
    • Edge / border
    • Associated features (scaling, crust, central clearing, umbilication, bleeding, tenderness, pruritus, etc.)

3. Arrangement & Evolution

  • Although not explicitly listed on the slide, always record:
    • Single vs. multiple
    • Discrete vs. confluent vs. coalescing into plaques
    • Evolution over time (acute, sub-acute, chronic; new vs. old lesions).

4. Other Relevant Structures

  • Examine and document:
    • Hair (alopecia, texture, colour change, scarring)
    • Nails (pitting, ridging, onycholysis, clubbing, peri-ungual erythema)
    • Accessible mucosae (oral, genital, conjunctiva for pigment, erosions, ulcerations)

Primary Skin Lesions (result from an initial pathologic process)

LesionKey Points
Macule• Well-circumscribed colour change without elevation or depression.
• Diameter <1\,\text{cm}.
Patch• Exactly like a macule but larger.
• Diameter >1\,\text{cm}.
Papule• Solid, elevated, palpable.
• Diameter <1\,\text{cm}.
Nodule• Solid, palpable, dome-shaped.
• Diameter >1\,\text{cm}.
Plaque• Plateau-like, slightly raised, well-circumscribed.
• Diameter >1\,\text{cm}.
Vesicle• Well-circumscribed, fluid-filled with clear serous fluid.
• Diameter <1\,\text{cm}.
Bulla• Same as vesicle but larger.
• Diameter >1\,\text{cm}.
Pustule• Vesicle/bulla containing yellow fluid (pus).
• Diameter
Wheal (Urtica)• Transient (<24\,\text{h}) pink/red swelling, usually pruritic, often with central pallor.
Telangiectasia• Persistent dilatation of superficial capillaries; blanchable fine red lines or networks.

Secondary Skin Lesions (evolve from primary lesions or external trauma)

• Scale
– Accumulated, abnormal stratum corneum (keratin).
– Silvery (psoriasis), greasy (seborrheic dermatitis), or fine (pityriasis versicolor).

• Crust
– Dried serum, blood, or pus on the surface ("scab").

• Excoriation
– Linear or punctate superficial erosion caused by scratching.

• Lichenification
– Chronic rubbing → thickened skin with exaggerated skin markings; leathery texture.

• Erosion
– Partial loss of epidermis only; heals without scarring.

• Ulcer
– Full-thickness epidermal loss with at least partial dermal destruction; heals with scarring.

• Necrosis
– Death of tissue; black eschar or gangrene.

• Scar (Cicatrix)
– Permanent fibrotic change following dermal damage. Hypertrophic, atrophic, keloidal.

• Atrophy
– Thinning of epidermis, dermis, or subcutis; appears shiny, wrinkled, and may reveal vessels.

Colour Descriptors

  • Erythematous (red, blanching)
  • Violaceous (purple)
  • Hyper- or hypopigmented vs. depigmented
  • Brown (melanin, hemosiderin)
  • Yellow (lipid, bilirubin, pseudomonas)
  • Black (necrosis, melanin)

Surface & Edge Qualifiers

  • Surface: smooth, verrucous, greasy, crusted, scaly, keratotic, umbilicated, punched-out.
  • Edge: well/ill-defined, active/migrating, serpiginous, undermined, rolled.

Practical Application Tips

• Always begin with “Site, Size, Shape, Colour, Surface, and Secondary change.”
• Use \text{cm} ruler or dermatoscope scale to record exact lesion size.
• Photograph lesions next to a scale for progression monitoring.
• Symmetry suggests systemic etiology, asymmetry favors localized pathology.
• Document mucosal, nail, and hair changes even when the complaint is "skin only"—they offer diagnostic clues (e.g.
nail pitting → psoriasis).

Clinical Reasoning Connections

  • Macules & patches without texture change → consider pigment disorders (vitiligo, melasma) or vascular causes.
  • A papule that coalesces into plaque + silvery scale + extensor distribution → classic psoriasis.
  • Vesicles in a dermatomal arrangement → herpes zoster.
  • Large bullae in elderly + "negative" Nikolsky sign → bullous pemphigoid.
  • Wheals lasting >24\,\text{h} or leaving bruises → think urticarial vasculitis.

Ethical & Practical Considerations

• Accurate morphological terminology allows clear inter-professional communication and avoids misdiagnosis.
• Detailed description forms a medico-legal record and guides biopsy site selection.
• Recognizing telangiectasia may prompt evaluation for systemic sclerosis or chronic liver disease.
• Identifying necrosis early (e.g.
in purpura fulminans) can be life-saving.

Quick Reference Mnemonic

"D R E M A S" → Distribution, Region (site), Edge, Morphology, Associated changes, Size/Surface.

End-of-Examination Checklist

  1. Stand back → general distribution.
  2. Close-up → primary lesion morphology.
  3. Look & feel adjunct structures (hair, nails, mucosae).
  4. Photograph & measure.
  5. Decide if biopsy, culture, or serology indicated.