Erythema is redness caused byvascular dilatation.
A plaque is an elevated area of skingreater than 2 cm in diameter butwithout substantial depth.
A papule is a small solid elevationof skin, less than0.5 cm in diameter.
A macule is a small ﬂat area ofaltered colour ortexture.
A vesicle is a circumscribedelevation of skin, lessthan 0.5 cm in diameter, andcontaining ﬂuid.
A bulla is a circumscribedelevation of skin over0.5 cm in diameter and containingﬂuid.
A pustule is a visible accumulationof pus in theskin.
An abscess is a localized collectionof pus in acavity, more than 1 cm in diameter.Abscesses are usually nodules, andthe term ‘purulent bullatimes used to describe a pus-ﬁlledblister that ion top of the skin rather thanwithin it.
A wheal is an elevated whitecompressible evanes-cent area produced by dermaloedema. It is oftensurrounded by a red axon-mediated ﬂare. Althoughusually less than 2 cm in diameter,some wheals arehuge.
Angioedema is a diffuse swellingcaused by oedemaextending to the subcutaneoustissue.
A nodule is a solid mass in theskin, usually greaterthan 0.5 cm indiameter, in both width and depth,which can be seen to be elevated orcan be palpated.
A tumour is harder to deﬁne as theterm is based more correctly onmicroscopic pathology than onclinical morphology. We keep ithere as a convenient term todescribe an enlargement of thetissues by normal orpathological material or cells thatform a mass, usuallymore than 1 cm in diameter.Because the word ‘tumour’can scare patients, tumours maycourteously be called‘large nodules’, especially if theyare not malignant.
A papilloma is a nipple-likeprojection from theskin.
Petechiae are pinhead-sizedmacules of blood in theskin.
The term purpura describes alarger macule orpapule of blood in the skin. Suchblood-ﬁlled lesionsdo not blanch if a glass lens ispushed against them(diascopy).
An ecchymosis is a largerextravasation of bloodinto the skin.A haematoma is a swelling fromgross bleeding.
A comedo is a plug ofgreasykeratin wedged ina dilated pilosebaceous oriﬁce.Open comedones areblackheads. The follicle opening ofa closed comedois nearly covered over by skin sothat it looks like apinhead-sized, ivory-colouredpapule.
Telangiectasia is the visibledilatation of smallcutaneous blood vessels.
Poikiloderma is a combination ofatrophy, reticulatehyperpigmentation andtelangiectasia.
A scale is a ﬂake arising from the horny layer. A keratosis is a horn-like thickening of the stratum corneum. A crust may look like a scale, but is composed of dried blood or tissue ﬂuid. An ulcer is an area of skin from which the whole of the epidermis and at least the upper part of the dermis has been lost. Ulcers may extend into subcutaneous fat, and heal with scarring. An erosion is an area of skin denuded by a complete or partial loss of only the epidermis. Erosions heal without scarring.
An excoriation is an ulcer or erosion produced by scratching. A ﬁssure is a slit in the skin. A sinus is a cavity or channel that permits theescape of pus or ﬂuid. A scar is a result of healing, where normal structures are permanently replaced by ﬁbrous tissue. Atrophy is a thinning of skin caused by diminution of the epidermis, dermis or subcutaneous fat. When the epidermis is atrophic it may crinkle like cigarette paper, appear thin and translucent, and lose normal surface markings. Blood vessels may be easy to see in both epidermal and dermal atrophy. Licheniﬁcation is an area of thickened skin with nincreased markings. A stria (stretch mark) is a streak-like linear atrophic pink, purple or white lesion of the skin caused by changes in the connective tissue. Pigmentation, either more or less than surrounding skin, can develop after lesions heal.