Terminology In Dermatology: Comprehensive Guide To Key Terms

Accurate description of skin conditions is fundamental to dermatological diagnosis and communication among healthcare professionals. Dermatologists assess lesions by their

distribution

,

morphology

,

arrangement

,

number

,

size

,

colour

, and involved sites, noting symmetry, shape, and pattern. Palpation reveals surface and deep characteristics, such as layer involvement, scale adherence, or crust contents. Special techniques like Wood’s light for pigment and infections, or dermoscopy for pigmented lesions, aid evaluation.

Structure of the Skin

The skin comprises three layers: the outer

epidermis

, middle

dermis

, and deep

subcutaneous tissue

(hypodermis). A basement membrane separates epidermis from dermis, facilitating communication.

• Epidermis: A ‘brick wall’ of keratinocytes producing keratin. Contains melanocytes (melanin for pigment), Langerhans cells (immune antigen presentation), and Merkel cells (sensory function). Subdivided into stratum basale (basal layer of proliferating cells), stratum spinosum (prickle cell layer with desmosomes for adhesion), stratum granulosum (granular layer with keratohyaline granules), and stratum corneum (horny layer of dead, keratinized cells that shed).
• Dermis: Connective tissue with collagen, elastin, fibroblasts, vessels, nerves, and appendages (sweat glands, hair follicles, sebaceous glands).
• Subcutaneous tissue: Fat and connective tissue insulating and cushioning.

Epidermal appendages include eccrine sweat glands, apocrine scent glands (axillae, groin), and pilosebaceous units.

Distribution

**Distribution** describes lesion scatter or spread. Lesions may be solitary or multiple, with patterns aiding diagnosis.

Term	Description	Examples
Generalised	Widespread, often symmetrical	Drug eruptions, viral exanthems
Localised	Confined to one area	Contact dermatitis
Dermatomal	Follows nerve root (e.g., shingles)	Herpes zoster
Extensor	Outer limb surfaces	Psoriasis
Flexural/Intertriginous	Skin folds	Flexural psoriasis, candidiasis
Follicular	Arising from follicles	Folliculitis
Seborrhoeic	Scalp, ears, eyebrows, nasolabial folds, sternum, interscapular	Seborrhoeic dermatitis
Symmetrical	Mirrored left/right	Atopic dermatitis
Truncal	Trunk predominant	Pityriasis rosea
Unilateral	One side	Naevus

Other patterns: acral (hands/feet), centrofacial (face centre), grouped (clusters), linear/striate (lines), palmoplantar (palms/soles), photo-aggravated (sun-exposed).

Configuration of Lesions

**Configuration** refers to lesion shape/outline, often grouped for diagnostic clues.

• Annular: Circular, ring-like (e.g., granuloma annulare).
• Arcuate: Partial ring, bow-like.
• Discoid/Nummular: Coin/disc-shaped (e.g., discoid eczema).
• Figurate: Geometric patterns (polycyclic, serpiginous).
• Gyrate: Whirling circle (e.g., erythema gyratum repens).
• Linear: Line-like (e.g., phytophotodermatitis).
• Reticulate: Net-like (e.g., livedo reticularis).
• Target: Concentric rings, iris-like (e.g., erythema multiforme).

Colour

Lesion colour provides diagnostic hints.

• Carotenaemia: Yellow/orange from beta-carotene excess.
• Erythema: Red from dilated vessels (blanching).
• Violaceous: Purple (e.g., lichen planus).
• Hyper pigmentation: Increased melanin (brown/black).
• Hypopigmentation: Reduced melanin; leucoderma (white).
• Purple (Purpura): Non-blanching extravascular blood.
• Xanthoderma: Yellow from lipids/xanthomas.

Morphology

**Morphology** classifies primary lesions by type and size.

Lesion Type	Size	Description
Macule/Patch	<1cm / >1cm	Flat, circumscribed colour change, non-palpable
Papule/Plaque	<1cm / >1cm	Palpable elevation, solid
Nodule/Tumour	>1cm	Deeper, larger solid elevation
Vesicle/Bulla	<1cm / >1cm	Fluid-filled, clear
Pustule	Varies	Pus-filled
Wheal	Varies	Oedematous, transient (urticaria)

Shape terms: acuminate (pointed), dome-shaped, filiform, flat-topped, oval/round, pedunculated (stalked), sessile, umbilicated (central dip), verrucous (wart-like).

Skin Surface

Surface features describe texture.

• Crust: Dried exudate/serum.
• Scale: Flaky keratin; types: desquamation (shedding), psoriasiform (large white/silver), pityriasiform (branny), lichenoid (adherent), keratotic (horny), exfoliation (peeling), maceration (moist peel), verrucous (warty).
• Other: Follicular plugging, hyperkeratosis.

Secondary Changes

Lesions evolve with secondary features.

• Erosion: Superficial epidermal loss, moist, re-epithelialises.
• Excoriation: Scratch mark.
• Fissure: Linear epidermal crack to dermis.
• Lichenification: Thickened, leathery from rubbing.
• Scar: Fibrous replacement post-injury.

Nails

Nail terminology includes onycholysis (nail-plate separation), onychomadesis (shedding), pachyonychia (thickening), Beau’s lines (transverse grooves from insult), splinter haemorrhages.

Mucocutaneous Membranes

Mucosal changes mirror skin but use terms like aphthae (ulcers), Koplik spots (measles).

Miscellaneous Terms

• Alopecia: Hair loss (scarring/non-scarring).
• Atrophy: Thinning.
• Comedo: Blackhead/whitehead.
• Induration: Hardening.

Frequently Asked Questions (FAQs)

What is a primary skin lesion?

Primary lesions are initial changes: macules, papules, vesicles, etc., unaltered by trauma.

How does distribution aid diagnosis?

Patterns like dermatomal (shingles) or flexural (candidiasis) narrow differentials.

What causes colour changes in skin?

Erythema (vascular), pigmentation (melanin), purpura (blood).

What are secondary skin changes?

Erosions, lichenification from evolution/scratching.

Why use standardised terminology?

Ensures precise communication; aligns with ICD-11, SNOMED.

Consult DermNet’s full glossary or A-Z index for more.