Derm – Describing Lesions

General Terms

Lesion: An area of altered skin

Rash: An eruption

Naevus: A localised malformation of tissue structures

Comedone: A plug in a sebaceous follicle containing altered sebum, bacteria and cellular debris: can be present as open (blackhead) or closed (whitehead)  

Cyst: A papule or nodule that contains fluid so is fluctuant

Morphology – Primary lesions

Macule:  an area of colour change less than 1.5cm in diameter –  if you shut your eyes and ran your hand over it you’d not detect if – eg a freckle

Patch: A large area of altered colour or texture

Papule: A small solid palpable lesion less than 0.5cm in diameter  raised above the skin surface.

Nodule:  A solid raised lesion >0.5cm in diameter with a deeper component

Plaque: A palpable flat lesion over 0.5cm in diameter usually slightly raised above the skin surface.

Vesicle: A small fluid-filled blister less than 0.5cm in diameter.

Bulla: a large blister filled with clear fluid over 0.5cm in diameter

Pustule: vesicle containing pus less than 0.5cm in diameter

Abscess: localised accumulation of pus in the dermis or subcutaneous tissues

Wheal: transient raised lesion due to dermal oedema

Boil / Furuncle: Staph infection around or within a hair follicle

Carbuncle: Staph infection of adjacent hair follicles (multiple boils/furuncles)


Morphology – Secondary Lesions

(Lesions that evolved from the primary lesion)

Excoriation: Loss of epidermis following trauma

Lichenification: Well-defined roughening of skin with accentuation of skin markings

Scales: Flaskes of stratum corneum – like in psoriasis

Crust: Rough surfaces consisting of dried serum, blood, bacteria and cellular debris that has exuded through an eroded epidermis (eg from a burst blister)

Scar: New fibrous tissue which occurs post-wound healing – may be atrophic (thinning), hypertrophic (hyperproliferation within wound boundary) or keloidal (hyperproliferation beyond wound boundry)

Ulcer: Loss of epidermis and ermis (heals with scarring)

Fissure: An epidermal crack often due to excess dryness

Striae: Linea areas which profress from purple to pink to white. Has the histopathological appearance of a scar (associated with excessive steroid usages, glucocorticoid production, growth spurts and pregnancy)



Discrete: Individual lesions separated from each other

Confluent: Lesions merging together

Target: Concentric Rings (like a dartboard)

Linear: In a line

Annular: Like a circle or ring

Discoid / Nummular: A coin-shaped / round lesion


Generalised: All over body

Widespread: Extensive

Localised: Restricted to one area of skin only

Flexural: Body folds

Extensor: Knees / elbows / Shins

Pressure Areas: Sacrum, buttocks, ankles, heels

Dermatome: Area of skin supplied by a single spinal nerve

Photosensitive: Sun-exposed areas sucha as fa

Kobner Phenomenon: A linear eruption arising at site of trauma



Erythema: Redness (due to inflammation and vasodilation) which blanches on pressure

Purpura: red or purple colour (due to bleeding into the skin or mucous membranes) does not blanch on pressure – petechiae (small pinpoint macules) and Ecchymoses (larger bruise-like patches)

Hypo-pigmentation: Areas or pales skin

De-pigmentation: White skin due to absence of melanin

Hyper-Pigmentation: Darker skin which may be due to various causes (eg post-inflammatory)


Alopecia: Loss of hair

Hirsutism: Androgen-dependent hair growth in a female

Hypertrichosis: Non-androgen dependent pattern of excessive hair growth


Clubbing: Loss of angle between posterior nail fold and nail plate

Koilonychia: Spoon shaped depression of the nail plate (ass. with iron-deficiency anaemia, congenital)

Onycholysis: Separation of the distal end of the anil plate