Eczema/dermatitis Flashcards
What is dermaitis ?
- This refers to a group of itchy inflammatory skin conditions characterised variably by erythema, oedema, vesiculation (small fluid-filled blisters), scaling, fissuring & lichenification (thickening of skin)
- The terms dermatitis & eczema are used interchangably
Describe the histology of dermatitis/eczema in general
There is spongiosis with varying degrees of acantholysis & a superficial perivascular lympho-histocytic infiltrate
What are the different classifications of inflammatory dermatitis/eczema based on time ?
- Acute dermatitis/eczema = rapidly evolving red rash which may be blistered & swollen
- Chronic dermatitis/eczema = referring to a longstanding irritable area. It is often darker than the surrounding skin, thickened (lichenification) & scratched
What are the 2 main classifications of dermatitis/eczema ?
- Endogenous = mediated by inflammatory processes within or produced by the body
- Exogenous = mediated by inflammatory processes originating from causes outside the body
What are the main forms of endogenous eczema ?
- Atopic dermatitis
- Sebhorroeic dermatitis
- Discoid eczema (nummular dermatitis)
- Nodular purigo
- Lichen simplex chronicus
- Others
What are the main types of exogenous dermatitis/eczema ?
- Irritant contact dermatitis
- Allergic contact dermatitis
What is sebhorreic dermatitis ?
It is a chronic form of eczema/dermatitis that mainly affects the sebaceous gland rich regions of the scalp, face & trunk
What causes sebhorreic dermatitis ?
It is thought to be caused by an inflammatory reaction related to proliferation of a skin commensal called Malassezia furfur
What are the 2 forms of sebhorreic dermatitis ?
- Infatile (babies < 3months)
- Adult (tends to begin in late adolescence or the elderly)
What conditions is sebhorreic dermatitis in adults associated with ?
- HIV - if severe or widespread
- Parkinsons disease
Describe the distribution of infantile sebhorroeic dermatitis
- Commonly on the scalp as ‘cradle cap’
- Also face, neck, nappy area & limb flexures
What are the clinical features of sebhorreic dermatitis
Scalp:
- ‘Cradle cap’ = erythematous rash with scales which are yellow-brown & greasy
Elsewhere:
- well-defined areas of erythema ‘salmon-pink’ & scaling (smaller & whiter)
In infantile dermatitis the patient is usually well & itching is relatively mild/negligable
Describe the distribution of adult sebhorroeic dermatitis
Mainly affects the scalp, face (esp periorbital, nasolabial & auricular areas) & upper trunk
What are the clinical features of adult sebhorroeic dermatitis ?
- Well-defined patches of erythema with scaling & flaking of the skin
- Scales may be white/yellow or oily/dry
- Mild itch
- Scalp lesions may cause dandruff
- Ottitis externa & blepharitis may develop
How is sebhorroeic dermatitis diagnosed ?
Clinically
What is the treatment of infantile sebhorroeic dermatitis ?
For scalp:
- 1st line = topical emollient (e.g. olive/veg oil) & brush gently & wash with baby shampoo
- 2nd line = topical imidazole cream (clotrimazole 1% or miconazole)
Elsewhere:
- 1st line = bathing using emollient + barrier emollent (e.g. zinc & caster oil or parrafin ointments) + consider topical imidazole (clotrimazole 1% or miconazole)
- If nappy rash develops consider low potency TCS (hydrocortisone 1%)
What is the treatment of adult sebhorroeic dermatitis on the scalp & beard ?
- 1st line = ketonazole 2% shampoo or selenium sulphide shampoo
- 2nd line = other medicated shampoo e.g. zinc, pyrithione, coal tar, or salicylic acid
Adjunct if severe itch then add short course of TCS e.g. betatheasone valivate 0.1% or mometasone furate 0.1%
What is the treatment of adult sebhorroeic dermatitis on the face & body ?
1st line = topical anti-fungals - ketonazole 2% cream or imidazole (clotrimazole 1% or miconazole) + midly potent TCS (hydrocortisone 0.5% or 1%)
What condition may patients with sebhorroeic dermatitis develop later in life ?
Psoriasis or atopic eczema
What is discoid (nummular) eczema/dermatitis ?
An endogenous type of eczema/dermatitis in which there are scattered, roundish plaques or eczema
Note - usually plaques are less well-defined and have a finer more powdery scale than psoriasis
Who most commonly gets discoid eczema ?
- Can affect children & adults
- In males > 50 it is associated with chronic alcoholism
Describe the typical distribution of discoid eczema
Usually affects the limbs esp the legs. However, may affect trunk
What are the clinical features of discoid eczema ?
- Well-circumscribed round or oval plaques which are inflammed
- Very itchy
- May be 1. eudative = oozy papules, blisters & plaques or 2. dry = erythematous, dry plaques
- Plaques can be clear in centre ==> resembling ringworm
How is discoid eczema diagnosed/investigated?
- Diagnosed clinically
- But, skin scrappings doen to rule out tinea corporis (ringworm)
Pic shows discoid eczema presenting similar to ringworm


