Aetiology of common skin conditions

Question 1

psoriasis

Answer 1

chronic inflammatory skin disease caused by increased epidermal skin turnover - causes plaques involves relapse and remitting

chronic plaque - red plaques well defined edges with silvery scales, plaques can crack and bleed

guttate - acute form, pink scaly drop-like plaques that usually occur in children after streptococcal throat infection

flexural - shiny and moist , occur in skin folds e.g. armpit, groin etc.

Question 2

eczema

Answer 2

impaired barrier function
atopic eczema - caused by genetic factor
- dry, itchy, cracked skin

Question 3

dermatitis

Answer 3

allergic contact dermatitis - allergy of a usually harmless substance that has made skin contact
- e.g. plant, fragrance etc.
- activation of T cells releases cytokines

irritant contact dermatitis - no allergy involved, caused by a substance which is irritant to skin
- e.g. detergent, abrasives
- irritant removes lipids and oils from stratum corneum

Question 4

acne

Answer 4

skin eruption caused by inflammation of sebaceous glands
- occurs where sebaceous glands are most common e.g. skin, back

affects most people, common in puberty
- mild - non inflammatory, comedones <20
- severe - large nodule cysts, scarring, >125 lesions

blackheads
- small open follicular papule
- central black keratin plug
- pigmentation comes from oxidised melanin not dirt

white heads
- small closed papule
- no keratin plug