Atopic Dermatitis

Question 1

What is atopic dermatitis

Answer 1

Chronic relapsing skin disorder with intense itch
Usually associated with family history of atopic disease
-atopic march (AD, asthma, rhinitis)

Question 2

Describe the epidemiology of AD

Answer 2

Generally found in childhood
-most within 1st year of life, 1 to 5

Rarely occurs for the 1st time during adulthood

Prevalence increasing

Question 3

What 3 factors contribute to the aetiology of AD

Answer 3

Environmental

• allergens, irritants, dietary factors
• infections, stress
• pollutants, weather change

Genetic

• FHx, genetic disposition
• defective skin barrier
• abnormal Th2, IgE immune response

Question 4

Describe how gene mutations contribute to barrier dysfunction
-how common is this mutation

Answer 4

Normal functioning of filaggrin

• converted from profilaggrin between the stratum granulosum and corneum
• in corneum => incooporated into lipid envelope for skin barrier function
• releases AA that aid in water retention

Abnormal functioning

• abnormal barrier => increased AG entry, Th2 response
• increased dryness

10% of us have the mutation
40% of mutation carriers have eczema
-more likely to have atopic triad

Question 5

Describe the pathophysiology behind AD

Answer 5

Impaired stratum corneum barrier function

• decreased functional filaggrin =>
• increased protease => corneocyte dysadhesion
• abnormal lipids => increased SC permeability

Environmental factors

• altered skin microbiome (more S aureus)
• damage to epidermal barrier and increased skin barrier penetration of AG => immune activation

Both contribute to immune dysregulation
-keratinocyte derived pro Th2, ILC cytokines => acute innate, adaptive and chronic responses

Question 6

Describe the presentation of AD in different age group[s

• infant
• child
• adults

Answer 6

Infant => forehead, cheeks, extensor surfaces
-papules, vesicles that crust

Child => flexor surfaces, face, neck

Adult => hands, neck, shoulders, flexor surfaces

May also have

• periorbital eczema
• xerosis (general dryness)
• excoriations and prurigo (due to intense itch)
• impetiginization

If chronic
-lichenification (increased skin markings)

Question 7

Describe the prognosis of AD

Answer 7

Chronic disease with recurrent flares

• most children outgrow it
• adults may continue to have localised dermatitis on hands

Frequent skin infections, S aureus colonization
-eczema herpeticum <= herpes virus

Question 8

Describe the comorbidities that accommpany AD

Answer 8

Obesity, smoking => increased risk for AD

Atopic

• atopic triad
• allergic conjunctivitis, rhinosinusitis, esophagitis
• allergy contact dermatitis

Infection (cutaneous, extracutaneous)

AI

Skin pain and itch

Sleep disturbances

Neuropsych

• anxiety, depression, suicide
• ADHD

Question 9

How would you treat AD

• topical
• systemic

Answer 9

Topical

• Emollients
• CS
• calcineurin inh (inhibits Tcell activation)
• antiseptic wash (for frequent infections)

Systemic

• short course prednisolone
• phototherapy
• methotrexate, ciclosporin, azothiopurine
• mycophenolate mofetil
• biologics

Question 10

What is dulipumab

• how does it work
• what are the side effects

Answer 10

IL4, 13 inh

Normally IL4 => Th2 activation

• produces IL4, IL5, IL13, IL31 => activates eosinophils, basophils, mast cells, IgE releasing B cells, T cells
• +ve feedback loop of IL4
• leads to weakening of epidermal barrier, reduction in antimicrobial peptides

Conjunctivitis
Enthesitis, arthritis

Question 11

When would you use dulipumab

Answer 11

Only recommended in

• moderate/severe AD in adults if
  
  • no response/contraindicated/not tolerant to at least 1 other systemic therapy

Stop dupilumab at 4 months if no response