Atopic Dermatitis: Causes, Symptoms, and Treatment

ATOPIC DERMATITIS
PAIRACH SUPSONGSERM
FELLOW IN TRAINING
ALLERGY AND CLINICAL IMMUNOLOGY
KING CHULALONGKORN MEMORIAL HOSPITAL
11 SEPTEMBER 2020

OUTLINE
• Introduction
• Epidemiology
• Pathophysiology and mechanisms of disease
• Natural history
• Clinical signs and Diagnosis
• Differential diagnosis
• Treatment
• Long-term outcomes
• Prevention
• Quiz

INTRODUCTION
• Atopic dermatitis (Atopic eczema) is one of the most
common inflammatory disorders
• Affecting up to 20% of children and 10% of adults
in high-income countries
• Characterised by intense itching and recurrent
eczematous lesions and has a heterogeneous clinical
presentation
• The usual age of onset is in early childhood,
typically at age 3–6 months (Can occur at any age)
• Atopic dermatitis in adults is common, including both
persistent and new onset forms
Langan SM, et al. Atopic dermatitis. Lancet 2020.

INTRODUCTION
• The causes of atopic dermatitis are complex and
multifactorial
• Loss-of-function mutations in the gene encoding
filaggrin (FLG) are the most strongly and consistently
reported genetic variants
• The increasing global prevalence of the disorder
highlights the role of environmental factors
• Individuals with atopic dermatitis are at increased
risk of having asthma, allergic rhinitis, and food
allergy, and could be at increased risk of a wide
range of health and psychosocial outcomes

EPIDEMIOLOGY
Weidinger S, et al. Atopic dermatitis. Nature Reviews (Disease Primers) 2018.

EPIDEMIOLOGY
Siriwaradon N, et al. Allergic Diseases : Insight and Reallity in Thailand. J ALLERGY CLIN IMMUNOL 2006.
Kulthanan K, et al. Adult-onset atopic dermatitis: a cross-sectional study of natural history and clinical manifestation. Asian Pac J Allergy Immunol 2007.

EPIDEMIOLOGY
• Although the prevalence of atopic dermatitis has plateaued in many high-income
countries, it continues to increase in low-income and middle-income countries
• The striking increase in prevalence over the past 30 years suggests that
environmental factors are important in the aetiology of atopic dermatitis
• The so-called hygiene hypothesis is frequently discussed as a possible explanation,
supported by an inverse socioeconomic gradient and an association with number of
siblings

PATHOPHYSIOLOGY AND MECHANISMS OF DISEASE
Atopic Dermatitis
Immunological
dysregulation
and
inflammation
Epidermal
barrier
dysfunction
Skin
microbiome
abnormalities

PATHOPHYSIOLOGY AND MECHANISMS OF DISEASE
• Genetic risk factors
• Epidermal barrier dysfunction
• The role of the microbiome
• Immunological dysregulation and inflammation
• Role of allergens
• Immunopathologic features
Boguniewicz M, et al. Atopic Dermatitis. Middleton’s Allergy (9th Edition) 2019.

PATHOPHYSIOLOGY AND MECHANISMS OF DISEASE:
GENETIC RISK FACTORS
• Atopic dermatitis has strong heritability (75% in twin studies), suggesting that genetic factors are
an important contributor
• Genome-wide association studies have identified 34 loci that cumulatively account for less than
20% of atopic dermatitis heritability
• These genomic regions contain multiple genes with roles in immune responses
> Type-2 differentiation
> T-cell activation
> Innate immunity
> The epidermal differentiation complex

Weidinger S, et al. Atopic dermatitis. Nature Reviews (Disease Primers) 2018.

GENETIC RISK FACTORS > FILAGGRIN

GENETIC RISK FACTORS > FILAGGRIN
• The strongest genetic risk for atopic dermatitis yet identified is associated with mutations in the skin barrier
protein filaggrin (Encoded by the FLG gene)
• Loss-of-function mutations in FLG cause a 50% decrease in protein expression in the heterozygous state and a
total loss of protein expression in the homozygous or compound heterozygous states
• Loss-of-function mutations in FLG cause the mild, semi-dominant, mendelian disorder of keratinisation ichthyosis
vulgaris
• FLG loss-of-function mutations confer a 3–5 times higher risk of atopic dermatitis in individuals who have them
than in individuals who do not, and predispose these individuals to asthma and peanut allergy
• FLG mutations were found in European, Japanese, Han Chinese populations (20-40% of AD patients)

GENETIC RISK FACTORS > OTHER GENETIC LOCI OF RELEVANCE
• Chromosome 5q31.1
> IL-4
> IL-13
> RAD50
• Chromosome 11q13.5
> EMSY
> LRRC32

EPIDERMAL BARRIER DYSFUNCTION
• Epidermal barrier dysfunction is consistently observed in affected and
unaffected skin of patients with atopic dermatitis
Epidermal barrier dysfunction
Elevated transepidermal water loss and pH
Increased permeability
Reduced water retention
Altered lipid composition

EPIDERMAL BARRIER DYSFUNCTION
• Disruption of barrier function in atopic dermatitis is multifactorial
> Genetic factors (FLG mutations)
> Physical damage (Scratching)
> Microbial dysbiosis (S. aureus, Malassezia)
> Type 2 immune activity (Downregulation of skin barrier genes and stratum
corneum lipids)
> Keratinocytes in the stressed epidermal barrier send proinflammatory (Th2
cytokines) and pruritogenic signals

THE ROLE OF THE MICROBIOME
• Atopic dermatitis is associated with a
disordered microbiome, with S. aureus being a
dominant colonizer and pathogen
• Colonisation rates on bacterial cultures
> Non-lesional skin 39%
> Lesional skin 70%
• There is a loss of community diversity preceding
flares, and the microbiome becomes S. aureus
dominant with regression after treatment and a
return to baseline severity
EDSLEV SM, et al. Skin Microbiome in Atopic Dermatitis. Acta Derm Venereol 2020.

EDSLEV SM, et al. Skin Microbiome in Atopic Dermatitis. Acta Derm Venereol 2020.

THE ROLE OF THE MICROBIOME
• Cutaneous yeasts such as Malassezia species could trigger or exacerbate
cutaneous inflammation in atopic dermatitis
• The mechanisms are poorly understood

IMMUNOLOGICAL DYSREGULATION AND INFLAMMATION

IMMUNOLOGICAL DYSREGULATION AND INFLAMMATION >
ROLE OF IMMUNOGLOBULIN E IN CUTANEOUS INFLAMMATION
• IgE-dependent biphasic reactions are frequently associated with clinically significant
allergic reactions and may contribute to the inflammatory process of AD
• Immediate-type reactions related to mediator release by mast cells bearing
allergen-specific IgE may result in the pruritus and erythema that occur after
exposure to relevant allergens
• IgE-dependent late-phase reactions can then lead to more persistent symptoms
• Epidermal LCs in AD skin express IgE on their cell surface and are significantly more
efficient than IgE-negative LCs at presenting allergen to T cells

ROLE OF ALLERGENS
• Foods
> Patients with AD and positive food allergen skin tests could have negative food
challenges to the implicated allergen
> Double-blind placebo-controlled food challenges can confirm food allergy
> 33% of infants and young children with AD will show clinically relevant reactivity
to a food allergen
> Elimination of food allergens results in amelioration of skin disease and a
decrease in spontaneous basophil histamine release

ROLE OF ALLERGENS
• Aeroallergens
> Exacerbation of AD can occur with exposure to allergens such as house
dust mites, animal danders, and pollens
> The severity of AD has been correlated with the degree of sensitization to
aeroallergens
> Environmental control measures aimed at reducing dust mite allergen have
been shown to result in clinical improvement in AD patients

ROLE OF ALLERGENS
• Microbial agents
> Elevated allergen-specific IgE levels
>> S. aureus toxins
>> Malassezia sympodialis
>> Trichophyton rubrum

IMMUNOPATHOLOGIC FEATURES

NATURAL HISTORY
Fishbein AB, et al. Update on Atopic Dermatitis: Diagnosis, Severity Assessment, and Treatment Selection. J ALLERGY CLIN IMMUNOL PRACT 2020.
• AD can have heterogeneous
trajectories
> Early transient disease
> Relapsing-remitting AD
> Chronic persistent AD
> Long periods of remission
followed by recurrence

NATURAL HISTORY
• Active AD beyond childhood is common
• Predictors of persistent AD activity into
adulthood
> Concurrent asthma/AR
> Young age of onset
> Low socioeconomic status
> Non-white ethnicity

Kapur S, et al. Atopic dermatitis. Allergy Asthma Clin Immunol 2018.

TREATMENT
• Atopic dermatitis management aims to
> Improve symptoms
> Establish long-term disease control
• Management plans should be patient-centred
> Avoidance of individual trigger factors
> Skin barrier restoration
> A step-up and step-down approach (According to severity)

แนวทางการดูแลรักษาโรคผื่นภูมิแพ้ผิวหนัง (Atopic Dermatitis).

TREATMENT
• Barrier repair and maintenance therapy
• Topical anti-inflammatory therapies
• Phototherapy
• Conventional systemic treatments
• Targeted monoclonal antibodies
• Probiotics

TREATMENT:
BARRIER REPAIR AND
MAINTENANCE THERAPY
• Effects of moisturisers
> Increased hydration
> Reduced xerosis, itch, and flares
> Reduced need for anti-inflammatory medication
• Available moisturisers contain varying amounts of
emollient, occlusive, and humectant components
• Moisturisers with fewer ingredients and without
fragrances is recommended to avoid irritants and
allergic reactions
• Moisturisers should be used liberally, twice or three
times daily, including after bathing
แนวทางการดูแลรักษาโรคผื่นภูมิแพ้ผิวหนัง (Atopic Dermatitis).

TREATMENT:
TOPICAL ANTI-INFLAMMATORY THERAPIES >
TOPICAL CORTICOSTEROIDS
• Topical corticosteroids are widely endorsed as the first-line anti-
inflammatory treatment
• Twice-daily application on affected areas is recommended
• Local side-effects
> Skin atrophy
> Purpura
> Striae
> Telangiectasias
> Dyspigmentation
> Facial acneiform changes
• Systemic side-effects
> Hypothalamic–pituitary–adrenal suppression
> Growth retardation
Kapur S, et al. Atopic dermatitis. Allergy Asthma Clin Immunol 2018.

TREATMENT:
TOPICAL CALCINEURIN INHIBITORS
• Topical calcineurin inhibitors
> Tacrolimus
> Pimecrolimus
• Equal to or less effective than moderately potent topical corticosteroids
• Advantage
> No skin atrophy
> Useful at susceptible sites (Face, intertriginous areas)
• Disadvantage
> Side effects are burning and pruritus
> High cost

TREATMENT:
TOPICAL ANTI-INFLAMMATORY THERAPIES
• Topical corticosteroids and topical calcineurin inhibitors can be proactively
applied to previously active sites for 2 days every week to reduce flares,
particularly when flares occur on the same body sites

TREATMENT:
CRISABOROLE
• Crisaborole ointment
> A topical inhibitor of the intracellular
enzyme phosphodiesterase 4)
> Treatment of patients aged 2 years or
older with mild-to-moderate AD

TREATMENT:
TOPICAL FORMULATIONS OF INHIBITORS OF THE JAK-STAT AND
SPLEEN TYROSINE KINASE PATHWAYS
• Ruxolitinib (JAK1 and JAK2 inhibitor)
• Delgocitinib (Pan-JAK inhibitor)

TREATMENT:
PHOTOTHERAPY
• Phototherapy
> Narrow-band ultraviolet B
> Medium-dose ultraviolet A1
• Usually 3–5 applications a week for a
total of 2–3 months
• Adverse effects
> Photodamage
> Skin carcinogenesis
> Melanoma induction

TREATMENT:
CONVENTIONAL SYSTEMIC TREATMENTS
• Systemic corticosteroids
> Short-term flare treatment
> Starting another systemic therapy
> Systemic side effects
• Ciclosporin
> Rapid onset of action
> Mean improvement of clinical severity scores of 55% from baseline after 6–8 weeks of treatment
> End-organ toxicity (Nephrotoxic) and cumulative risk of malignancy
> Continuous use for no longer than 1–2 years

TREATMENT:
CONVENTIONAL SYSTEMIC TREATMENTS
• Azathioprine and methotrexate
> Work slowly
> Maximum benefits
>> Azathioprine 4–8 weeks
>> Methotrexate 8–12 weeks
• Mycophenolate mofetil
> Alternative treatment option

TREATMENT:
TARGETED MONOCLONAL ANTIBODIES
• Dupilumab (Fully human monoclonal
antibody against IL-4Rα)
> Inhibits both IL-4 and IL-13
signaling
> Moderate-to-severe AD in
patients aged 6 years and older in the
USA and in patients aged 12 years
and older in the EU
> Side effect: conjunctivitis

TREATMENT:
TARGETED MONOCLONAL ANTIBODIES
• Omalizumab
> Case reports and small case series in AD patients treated with
omalizumab have shown both clinical benefit and lack of improvement
> An option for select patients with severe, recalcitrant AD

TREATMENT:
PROBIOTICS
• Lactobacilli and bifidobacteria are gut microorganisms hypothesized to
educate the neonatal immune system by converting the Th2-biased prenatal
responses into balanced immune responses
• A Cochrane review concluded that probiotics are not an effective treatment
for eczema in children, and that probiotic treatment carries a small risk of
adverse events

LONG-TERM OUTCOMES
• Patients with AD increased risk of asthma, AR, and food allergies (Particularly
in those with severe and early-onset AD)
• Allergic eye disease can complicate AD: keratoconjunctivitis, keratoconus,
cataract
• Psychosocial problems: psychological stress, low self-esteem, sleep deprivation

PREVENTION
• Two pilot studies suggested that regular use of a moisturizer soon after birth
could reduce the incidence of AD during the treatment period
• A more recent study using a ceramide-dominant emollient in the first 6 months
of life showed a trend toward reduced incidence of AD and food sensitization
at age 12 months
• Early treatment of the skin barrier in at-risk infants may prevent development
of AD and allergic sensitization

QUIZ

Thank You for Your Attention…

Atopic Dermatitis: Causes, Symptoms, and Treatment

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