Skin general

Question 1

What is a macule?

Answer 1

• A macule is a circumscribed area of change in skin colour without elevation or depression
• It can be well defined or ill defined
• It can be any colour or size.
• Examples include vitiligo, cafe-au-lait spots, mongolian spots and port-wine stains
• Causes of solitary macular rash include portwine stain, fixed drug eruption and erythema migrans
• Causes of localised macular lesions include solar lnetigines and fixed drug eruptions
• Causes of generalised macular rash include viral exanthem and drug eruptions

Question 2

What is a papule?

Answer 2

• A papule is a superficial elevated solid lesion generally <0.5cm in diameter which is palpable
• Causes for a solitary papule include dermal naevus, BCC
• Causes for localised papular rahs include condyloma lata and lichen planus
• Generalised papular rash causes include psoriasis, lichen planus and neurofibromatosis

Question 3

What is a plaque?

Answer 3

• A plaque is a plateau-like elevation above the skin surface that occupies a relatively large surface area in comparison to its height above the skin
• It is frequently formed by confluence of papules and is well demarcated
• Lichenification can be a feature which means the skin is thickened
• Lichenification is seen in atopic dermatitis, eczematous dermatitis, psoriasis and lichen simplex chronicus
• Bowens disease, superficial spreading melanoma and lichen simplex chronicus are the commonest causes of solitary plaques
• Psoriasis is the commonest cause of lcoalised plaque
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Question 4

What is a nodule?

Answer 4

• A nodule is a palpable, solid, round or ellipsoidal lesion that is larger than a papule.
• The depth of a lesion differentiates a nodule from a papule
• A solitary nodule can be a derma naevus, BCC and nodular melanoma
• Localised nodules are mostly metastatic cancers
• Generalised nodules can be lipomas and metastatic melanomas

Question 5

What is a wheal?

Answer 5

• A wheal is a rounded or flat topped pale red papule or plaque that characteristically disappears within 24-48 hrs
• A rash consisting of wheals is called an urticarial exanthem or urticaria

Question 6

What is a vesicle-bulla (blister)?

Answer 6

• A vesicle (<0.5cm) or a bulla (>0.5cm) is a circumscribed, elevated superficial cavity containing fluid
• The roof of vesicle/bulla is so thin that it is transparent and the serum or blood can be seen
• They are always superficial and well defined
• Localised vesicular/bullous lesions can be caused by herpes zoster and herpes simplex.
• Generalised vesicular/bullous lesions are caused by varicella/bullous pemphigoid

Question 7

What is a pustule?

Answer 7

• A pustule is a circumscribed, superficial cavity of skin that contains a purulent exudate
• Pustules differ from vesicles in that they have a turbid content
• The causes for localised pustular lesions include herpes zoster, impetigo and folliculitis barbae
• The causes of generalised pustular lesions include pustular pasoriasis and small pox

Question 8

What is a crust?

Answer 8

• A crust develops when serum,blood or purulent exudate dries on the skin surface
• If the crusts are thick and involves necrosis, it is called ecthyma
• Honey coloured superficial crusts occur in impetigo

Question 9

What is a scale?

Answer 9