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Skin Lesions: Morphology and Description

Skin Lesions: Morphology and Description

Skin Lesions: Morphology and Description

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Primary Lesions (Flat & Raised) - Spot On!

Primary and Secondary Skin Lesions Diagram

  • Flat (Non-Palpable): Circumscribed skin color change.
    • Macule: <1cm. E.g., freckle, lentigo, junctional nevus.
    • Patch: >1cm (large macule). E.g., vitiligo, café-au-lait.

      ⭐ A herald patch in Pityriasis Rosea is a classic patch lesion.

  • Raised (Palpable, Solid): Elevated above skin.
    • Papule: <1cm, solid. E.g., wart, lichen planus, molluscum.
    • Plaque: >1cm, solid, plateau-like (confluence of papules). E.g., psoriasis, chronic eczema.
    • Nodule: >0.5-1cm, solid, deeper in dermis/subcutis. E.g., erythema nodosum, dermatofibroma.
    • Tumor: >2cm (large nodule), solid, deep & wide. E.g., lipoma, large basal cell carcinoma.
    • Wheal: Transient, edematous, erythematous papule/plaque; evanescent & often pruritic. E.g., urticaria. (📌 Wheals are Welts)

Primary Lesions (Fluid & Follicular) - Bubble Trouble!

  • Vesicle: Circumscribed, elevated, clear fluid-filled lesion, <1 cm. Ex: Varicella, Herpes zoster.
  • Bulla: Large vesicle; circumscribed, elevated, clear fluid-filled, >1 cm. Ex: Bullous pemphigoid, Burns.
  • Pustule: Circumscribed, elevated lesion containing visible pus (not clear fluid). Ex: Pustular psoriasis, Folliculitis.
  • Cyst: Nodule; epithelial-lined cavity with liquid/semi-solid material (keratin, sebum). Ex: Epidermal inclusion cyst.
  • Comedo: Hair follicle plugged with keratin & sebum.
    • Open (blackhead): Dilated orifice, oxidized plug.
    • Closed (whitehead): Constricted orifice, non-oxidized.
  • Burrow: Serpiginous or linear track in epidermis by parasite. Ex: Scabies mite.

    ⭐ Burrows are pathognomonic for scabies.

  • Telangiectasia: Persistent dilation of small superficial blood vessels. Fine, red lines. Ex: Rosacea, CREST.

Primary and Secondary Skin Lesions Diagram

Secondary Lesions - Skin's Story Continues

  • Scale: Stratum corneum flakes (e.g., psoriasis).
  • Crust: Dried exudate (serum, pus, blood); e.g., impetigo (honey-colored).
  • Erosion: Epidermal loss; no scar (e.g., pemphigus).
  • Ulcer: Dermis/subcutis loss; scars (e.g., stasis ulcer).
  • Fissure: Linear skin crack; often painful (e.g., hand eczema).
  • Atrophy: Skin thinning; shiny, fragile (e.g., senile, steroid).
  • Scar: Post-injury fibrous tissue.
    • Hypertrophic: Raised, firm; within wound.
    • Atrophic: Depressed, thin; e.g., acne.
  • Excoriation: Linear erosion from scratching.
  • Lichenification: Thick epidermis, ↑skin lines from chronic rubbing.

    ⭐ Lichenification (thickened skin with exaggerated skin markings) is a hallmark of chronic rubbing, as seen in atopic dermatitis.

  • Keloid: Scar extending beyond original wound borders. Primary and Secondary Skin Lesionsoka

Lesion Configuration & Description - Map The Marks

Arrangement: How lesions are grouped.

TermDescriptionExample(s)
AnnularRing-shapedTinea corporis
ArcuateArc-shapedUrticaria
LinearStraight lineKoebner, Lichen striatus
Grouped/HerpetiformClustered (often vesicles)Herpes simplex/zoster
SerpiginousSnake-like, wavyCutaneous larva migrans
ReticularNet-like, lacyLivedo reticularis
Dermatomal/ZosteriformFollows a dermatomeHerpes zoster
Targetoid/IrisConcentric rings, "bull's eye"Erythema multiforme
TermDescriptionExample(s)
-------------------------------------------------------------------------------------------
LocalizedLimited to one areaImpetigo
GeneralizedWidespreadViral exanthem
SymmetricalAffects both sides equallyPsoriasis, Vitiligo
AsymmetricalPredominantly one sidePityriasis rosea (herald patch)
FlexuralIn skin folds (axillae, groin)Atopic dermatitis
ExtensorOn extensor surfaces (knees, elbows)Psoriasis
Sun-exposedAreas exposed to sunlightPhotodermatitis
IntertriginousIn body folds where skin rubsCandidiasis
AcralDistal extremities (hands, feet)Hand, Foot & Mouth Disease
  • Also Note Other Features:
    • Color: e.g., erythematous, violaceous, hyper/hypopigmented.
    • Shape: Overall form, e.g., round, oval, polycyclic, umbilicated.
    • Size: Measure in mm or cm.
    • Surface: e.g., smooth, rough, verrucous, scaly, crusted.
    • Consistency: e.g., soft, firm, fluctuant, indurated.
    • Borders: e.g., well-demarcated (sharp) vs. ill-defined (blurry).

⭐ Koebner phenomenon (isomorphic response): appearance of new lesions of a pre-existing dermatosis along lines of trauma. This is an exam-favourite fact!

High‑Yield Points - ⚡ Biggest Takeaways

  • Macule (<1cm) & Patch (>1cm): Flat, non-palpable, color change.
  • Papule (<1cm) & Plaque (>1cm): Elevated, palpable, solid lesions.
  • Vesicle (<1cm) & Bulla (>1cm): Fluid-filled, circumscribed elevations.
  • Pustule: Contains pus; Wheal: Transient, edematous, itchy elevation.
  • Lichenification: Thickened skin with exaggerated lines from chronic rubbing.
  • Erosion: Partial epidermal loss; Ulcer: Full-thickness epidermal loss, may scar.
  • Scale: Flakes of stratum corneum; Crust: Dried exudate (serum, blood, pus).

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Practice Questions: Skin Lesions: Morphology and Description

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Flashcards: Skin Lesions: Morphology and Description

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Lichen _____ presents with tiny pinhead-sized flesh-colored papules mainly on the dorsum of forearms or penis

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Lichen _____ presents with tiny pinhead-sized flesh-colored papules mainly on the dorsum of forearms or penis

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