Terminology used in skin diseases

June 6, 2021


Identification and classification of a patient’s skin lesions are important steps in the diagnosis of any skin disorder. Few simple terms can be used to describe the cutaneous findings in most skin diseases.

  • Macule / Patch: A flat circumscribed area of discoloration 0.5 cm or less is a macule. More than 0.5cm is known as a patch.
  • Papule / Plaque : An elevated solid lesion up to 0.5cm or less is called papule; color varies. Papules greater than 0.5cm are called plaque, such as Nevi, acne, warts, skin tags, and others.  Papules may become confluent and form plaques. Warts are Papular lesions with coarse or roughened surfaces.
  • Wheal (Hives): A firm plaque resulting from infiltration of the dermis with fluid. Wheals are transient and may last only a few hours.
  • Maculopapular: A raised and discolored circumscribed lesions.
  • Nodule:  Solid elevated lesion more than 0.5cm in diameter. A large nodule is referred to as a tumor.
  • Blisters: A small visible fluid or blood-filled blister 0.5 cm or less is a vesicle. More than 0.5cm blister is called Bullae. Blistering occurs due to loss of cell adhesion within the epidermis or subepidermal region. The clinical presentation depends on the site or level of blistering within the skin which in turn reflects the underlying cause.
  • Cyst: Fluid-filled sac in the tissue more than 0.5 cm.
  • Pustule : A pus filled blister as in folliculitis, chicken pox.
  • Scales: Loose or adherent excess dead epidermal cells that are produced by abnormal keratinization and shedding.  The term hyperkeratotic is used for small areas of thick adherent scales. e g. In Psoriatic lesions.
  • Crust (a scab): Dried exudate on skin. Yellow, brown, black, or green surface deposit of serum, pus, and /or blood.
  • Scar:  An abnormal formation of connective tissue implying dermal damage. The depressed or elevated proliferation of connective tissue that has replaced inflamed or traumatized skin.
  • Eschar: Black, hard crust resulting from tissue necrosis of the epidermis and /or dermis. Such as skin lesions in Anthrax disease.
  • Erythema: Redness
  • Erythroderma: Widespread redness with scaling.
  • Petechia/ Purpura / Ecchymoses:  Petechia is bruised (blood in the dermis) and tiny macules (less than 0.5 cm). Purpura is greater than 0.5 cm, and sometimes may be palpable. Bruises greater than 1cm are known as ecchymoses.
  • Telangiectasia: Dilated superficial blood vessels in the skin.
  • Atrophy: A depression in the skin resulting from thinning of epidermis and dermis.
  • Vitiligo: Loss of pigment in an area of skin due to the destruction of melanocytes.
Telangiectasia      –      scales     –     annular rings                                        
  • Atopy: The word atopy implies a capacity to hyper-react to common environmental factors.                             
  • Eczema (Dermatitis): Inflammation of the skin.
  • Excoriation: Linear or punctate erosions due to scratching. e. g in allergic skin conditions.
  • Erosion: A focal loss of superficial epidermis. Erosion does not penetrate below the dermo-epidermal junction so heals without scarring.
  • Ulcer: A focal loss of epidermis and dermis.  Ulcers heal with scaring.
  • Fissure: Linear, sharply defined loss of epidermis and dermis.
  • Lichenification: Thickening of the epidermis with accentuation of skin markings induced by scratching. Skin lines are accentuated so the surface looks like a washboard.
  • Comedone: A plug of the sebaceous and keratinous material lodged in the opening of the hair follicle. The follicular orifice may be dilated (blackhead) or narrowed ( whitehead or closed comedones).
  • Milia: A small superficial keratin cyst with no visible opening.
  • Annular lesion: Lesions occurring in rings. For example in Tinea corporis.
  • Discoid / Round shape: Round with a uniform appearance.
  • Oval shape: oval with uniform appearance throughout the lesion
  • Targetoid shape: Target-like with distinct zones. As in Erythema multiforme.
  • Arcuate shape: Arc shaped.
  • Serpiginous shape: Waves or snake-like.
  • Linear/Streak: a thin straight line of the lesion.
  • Discrete/isolated: Separated from one another.
  • Grouped lesions: Clustered next to each other. As in Herpes Simplex vesicles.
  • Dermatomal lesions: Distributed along a dermatome. As in Herpes zoster.
  • Reticular: Lace or net-like such as in vasculitis.
  • Symmetrical: Uniform distribution on both sides of the body.
  • Generalized/ Disseminated: Spread over wide areas of the body.
  • A photo distributed: Located in areas of sunlight exposure.

Cellulitis / Erysipelas: Cellulitis is Inflammation of subcutaneous tissue, due to bacterial infection and erysipelas is a bacterial infection of the dermis and upper subcutaneous tissue.

Folliculitis, Furuncles, and Carbuncles

Folliculitis is a superficial inflammation of hair follicles, deeper inflammation called furuncles (boils). Furuncle is painful, erythematous, tender, papular lesions. A Carbuncle is a tender nodular lesion caused by infection of a group of hair follicles with intense deep inflammation.

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