Eczema Flashcards
Atopic dermatitis aka
atopic eczema
Eczema patients often have a personal or family history of other atopic diseases such as (2)
asthma or allergic rhinitis (hay fever)
Eczema typically affects what areas
- in infants (4)
- in children (4)
Infants typically show involvement of the cheeks, forehead, scalp, and extensor surfaces
Skin flexures
- popliteal fossa
- antecubital fossa
- wrists
- ankles
2 key pathogenic factors of the development of eczema
Epidermal barrier dysfunction
+
Immune dysregulation following allergen exposure –> INFLAMMATION
How does mutation of the filaggrin gene contribute to eczema
Loss-of-function mutation in the structural protein filaggrin predisposes to a less effective mechanical barrier against the environment –> INCREASED SENSITISATION to cutaneous antigens
also causes lower lower levels of natural moisturising factor in stratum corneum –> DRY SKIN
Pathological (histological) findings in atopic dermatitis (atopic eczema) (3)
Spongiosis (intercellular oedema in the epidermis) - manifests as intra-epidermal vesicles
Acanthosis (thickening of epidermis)
Inflammation - lymphocytic infiltrate
Acute v chronic eczema
Acute eczema is used to describe a flare-up of symptoms, e.g. sudden onset of lots of vesicles, swelling and oedema
Chronic is used to describe the condition when the patient develops signs of chronic inflammation (e.g., lichenification)
- spongiosis is mild (little intra-epidermal vesicles)
- LOTS of acanthosis
Chronic eczema typically affects what areas
neck, upper back, and arms, as well as the hands and feet.
Typical clinical features of eczema (2)
Pruritus
Xerosis (dry skin)
Clinical features of acute eczema (5)
- erythema
- scaling
- papules
- vesicles
- crusting
Clinical features of chronic eczema (3)
lichenification (thickened and leathery skin, often resulting from continuously rubbing/scratching the skin)
plaques
hypopigmentation
Name some exogenous/external types of eczema
Contact dermatitis (irritant or allergic)
Lichen simplex
Photoallergic eczema
Name some endogenous/internal types of eczema apart from atopic eczema
Discoid eczema Venous eczema Seborrhoiec dermatitis/eczema Pompholyx eczema Asteatotic eczema
Allergic contact dermatitis (a type of contact dermatitis) is what type hypersensitivity reaction
Type 4 - delayed hypersensitivity
Describe how the type 4 hypersensitivity reaction works in allergic contact dermatitis, e.g. reaction to metal in necklace
Antigen presenting cells take hapten/ allergen to LN and present to naive T cells
Clonal expansion of these T cells, released into blood stream
When these T cells next encounter hapten –> mast cell degranulation, vasodilatation and neutrophils
Irritant contact dermatitis (a type of contact dermatitis) is when the skin is injured by what 2 factors
Friction - e.g. microtrauma
Environmental factors
- cold
- chemicals, e.g. acid, detergents
Investigation of allergic contact dermatitis
Patch testing - looking for delayed hypersensitivity reaction
Seborrhoeic dermatitis in infants manifests as what
aka CRADLE CAP in babies
- rough scaly greasy patches on the scalp usually
- and also maybe scaling on forehead/eyebrows
Seborrhoiec dermatitis in adults is different from infants as it usually goes away itself in infants, what is it defined as in adults
Chronic dermatitis characterised by erythematous and greasy scaly patches
Seborrheic dermatitis is associated with proliferation of what fungus + what does this cause
malassezia furfur
Clinical features of seborrhoeic dermatitis (4)
Red, sharply marginated lesions covered with greasy looking scales
- on the scalp
- on the nose
- on the nasolabial folds
- behind ear
Itchy scalp
White flakes in hair
Treatment of seborrhoeic dermatitis
- in infants (cradle cap) (1)
- in children/adults if only scalp affected (1)
- in children/adults if non-scalp areas affected (2)
Infants
-emollient
Scalp affected
-medicated shampoo (anti fungal - ketoconazole)
Non-scalp affected
-topical corticosteroids or anti fungal
Explosive often generalised onset of SD may be a marker of what infection
HIV
Characteristic clinical feature of discoid eczema
Distinctive circular or oval patches of itchy, reddened, swollen and cracked skin
Initially, these patches are often swollen, blistered (covered with vesicles)
Over time, the patches may become dry, crusty, cracked and flaky
