WHAT IS ECZEMA?

Dr Diana Purvis

Paediatric Dermatologist

What is eczema?

• Clinical features

• Epidemiology

• Prognosis

• Etiology and pathogenesis

• Immunology

• Skin barrier

Eczema

• From the Greek: ‘to boil over’

Eczema

• From the Greek: ‘to boil over’

• Pruritic papulovesicular dermatitis characterised by

erythema, oedema and a serous exudate in the

epidermis, an inflammatory infiltrate in the dermis, oozing

and vesiculation, and crusting and scaling; and later by

lichenification, thickening, signs of excoriations and

altered pigmentation. • TheFreeDictionary.com

Eczema

• From the Greek: ‘to boil over’

• Pruritic papulovesicular dermatitis characterised by

erythema, oedema and a serous exudate in the

epidermis, an inflammatory infiltrate in the dermis, oozing

and vesiculation, and crusting and scaling; and later by

lichenification, thickening, signs of excoriations and

altered pigmentation. • TheFreeDictionary.com

• “The itch that rashes”

• Itchy skin condition plus three of

• History of involvement of the creases

• Personal history of atopy (or 1st degree relative if <4 years)

• Generally dry skin

• Visible flexural eczema

• Onset under 2 years of age • UK Working Party, BJD 1994

Diagnostic criteria for atopic eczema

Features of eczema

Major features: • Pruritis

• Rash

• face and extensors in infants

• flexural in older children

• Chronic or chronically relapsing

• Personal or family history of other atopic disease

Other common features: • Dryness

• Dennie-Morgan folds

• Allergic shiners

• Facial pallor

• Pityriasis alba

• Keratosis pilaris

• Icthyosis vulgaris

• White dermatographism

• Conjunctivitis

• Keratoconus and cataracts

• Elevated serum IgE

• Skin prick test positivity

Eczema - subtypes

• Eczema / atopic dermatitis

• Seborrhoeic dermatitis

• Discoid, nummular eczema

• Dyshidrotic eczema / pompholyx

• Contact dermatitis

• Varicose eczema

• Asteatotic eczema

Infant Child/adolescent Adult

Prognosis

• Outcome of any individual is difficult to predict

• Spontaneous resolution in 40-60% of infants, especially with mild

disease

• 20% have resolved by adolescence, 65% less severe

• Prevalence is 2 – 3% in adults

• Adults whose childhood eczema has remitted can present with

hand dermatitis

• Poor prognosis:

• Generalised eczema

• Associated asthma and hayfever, high IgE levels

• Family history of troublesome eczema

• Early age of onset

Epidemiology of eczema

• Prevalence of has increased three-fold since 1960s

• 10-20% of children in industrialised countries eg Europe, USA

• 1-3% of adults

• Lower prevalence in agricultural economies eg China, Africa

• Environmental factors seem critical in disease expression

• Risk factors include:

• Small family size

• Increased income and education

• Migration from rural to urban environments

• Increased use of antibiotics

The hygiene hypothesis

• The ‘Western lifestyle’ predisposes to allergic disease

• Lack of early childhood exposure to infectious agents, symbiotic

microorganisms and parasites

• Suppresses the natural development of Th1 predominant

immune response

• Promotes a Th2 dominant or allergic response

• Supported by reduced risk of eczema with:

• owning a pet

• attending daycare

• use of probiotics

The atopic march

How atopic is atopic eczema?

• Up to 50% of hospital eczema patients are not sensitised,

even higher in community settings

• Population attributable risk for allergic sensitisation

causing eczema <50% in affluent countries, as low as

zero in non-affluent countries (ISAAC)

• Genetic risk

• “atopic disease” asthma, eczema, allergic rhinitis do tend to cluster

in families

H Williams, C Flohr J All Clin Imm 2006

Pathogenesis of eczema

Two hypotheses:

1) Inside-out

Immunological disturbance causes IgE-

mediated sensitisation, epithelial barrier

dysfunction is secondary

2) Outside-in

Epidermal barrier dysfunction allows

irritants and allergens into the skin, with

immunological disturbance secondary

Itch

Scratch

Leaky skin barrier

Inflammation

Immune dysfunction

Eczema Soap

Irritants

Infection

Allergens

House dust mite

Cat/dog fur

Itch

Scratch

Leaky skin barrier

Inflammation

Immune dysfunction

Eczema Soap

Irritants

Infection

Allergens

House dust mite

Cat/dog fur

Itch

Scratch

Leaky skin barrier

Inflammation

Immune dysfunction

Eczema Soap

Irritants

Infection

Allergens

House dust mite

Cat/dog fur

The skin as a barrier

The skin as a barrier

The stratum corneum

The skin barrier

• Skin barrier function maintained by:

• Regular desquamation

• Intercellular lipid bilayers

• Natural Moisturising Factors

• Production of antimicrobial peptides

The skin barrier is impaired in eczema

• Genetic defects • Filaggrin gene mutation in 30% of eczema patients

• Filaggrin involved in production of natural moisturising factors

• Other genes affecting stratum corneum function eg SPINK5, loricrin

• Reduced ceramides and water binding

• Decreased sebaceous secretion

• Impaired production of antimicrobial peptides • Defensins and cathelicidins

• Staphylococcus aureus colonisation in 90%

• Increased viral infections

The skin in eczema

1. Irvine et al. J Invest Dermatol 2006; 126: 1200–02. 2. Bieber T. N Engl J Med 2008; 358: 1483–94.

Gene-environment interaction

Genetic

background

Environmental

factors

Skin

barrier

Immune

system

Microbiological

agents (bacteria, virus, etc,)

Stress

Allergens (inhalative, food, contact)

Climate

Irritants

New discovery: filaggrin gene mutation

Itch

Scratch

Leaky skin barrier

Inflammation

Immune dysfunction

Eczema Soap

Irritants

Infection

Allergens

House dust mite

Cat/dog fur

What causes eczema?

Itch

Scratch

Leaky skin barrier

Inflammation

Immune dysfunction

Eczema Soap

Irritants

Infection

Allergens

House dust mite

Cat/dog fur

What causes eczema?

Itch

Scratch

Leaky skin barrier

Inflammation

Immune dysfunction

Eczema Soap

Irritants

Infection

Allergens

House dust mite

Cat/dog fur

What causes eczema?

Triggers

3/26/09 41

Brick => Corneocyte

Mortar => Lipid Lamellae

Cork MJ, Hunter LW & Danby SG; Academic Unit of Dermatology Research, The University of Sheffield.

Brick wall model of

the skin

The Normal Skin Barrier

3/26/09 42 Cork MJ, Hunter LW & Danby SG; Academic Unit of Dermatology Research, The University of Sheffield.

2/10/2015 43

Irritants &

allergens

Cork MJ, Hunter LW & Danby SG; Academic Unit of Dermatology Research, The University of Sheffield.

The skin barrier in atopic dermatitis

3/26/09 44

Broken

mortar

in AD

Cork MJ, Hunter LW & Danby SG; Academic Unit of Dermatology Research, The University of Sheffield.

TEWL

2/10/2015 The Academic Unit of Dermatology Research, The University of Sheffield. 45

Irritants &

allergens

46

Emollients

Cork MJ, Hunter LW & Danby SG; Academic Unit of Dermatology Research, The University of Sheffield.

NO itch

NO scratching

Effective skin barrier

NO inflammation

NO immune dysfunction

NO eczema

Emollients, treat inflammation

Avoid soap

and irritants,

treat

infection,

treat with

steroids,

immuno-

suppressant

Address allergens

minimise exposure,

immune modulation

Treat

inflammation,

cool,

antihistamines

Treat itch,

physical

barriers,

distraction