Atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disease that typically manifests for the first time in early childhood. Although it often improves during adolescence, it may also become a chronic condition that extends into adulthood. Atopic dermatitis is often associated with other atopic diseases, such as asthma or allergic rhinitis. Although the underlying etiology is not completely understood, genetic components, as well as exogenous and endogenous triggers, are believed to play a role. The main symptoms of atopic dermatitis include severe pruritus and dry skin. Primary treatment involves managing the pruritus and moisturizing the skin. Topical steroids and calcineurin inhibitors may be added if treatment with moisturizers is insufficient. In severe cases, systemic therapy with steroids is required. The main complication of atopic dermatitis is the development of secondary infections.

• Prevalence: About 8–12% of children and 6–9% of adults are affected. ^[1][2]
• Age ^[3]
  • Onset of symptoms usually occurs between 3–6 months of age.
  • Disease often improves with age.

Epidemiological data refers to the US, unless otherwise specified.

The etiology of atopic dermatitis is not completely understood. However, genetic factors (polygenic inheritance), as well as exogenous and endogenous triggers, may play a role.

• Genetics (polygenic inheritance) ^[3]
  • Inherited predisposition for increased IgE formation and sensitization (type 1 hypersensitivity reaction)
  • Mutation in the filaggrin gene → abnormalities in epidermal skin barrier formation → entry and interaction of antigens with immunogenic cells ^[4]
  • Approx. 70% of patients have a family history of atopic disease; (including eczema, asthma, allergies) ^[5]
• Triggers ^[3]
  • Exposure to indoor dust
  • Heat
  • Extremely dry or humid climate
  • Emotional stress
  • Skin irritation
  • Infections
• Other factors ^[6]
  • Impaired skin barrier (permits entry of pathogens)
  • Proinflammatory Th1 and Th2 lymphocytic response

• Main symptoms: intense pruritus and dry skin
• Infantile AD (age < 2 years) ^[7]
  • Eczema: over the face, head, and extensor surfaces of the extremities that usually spares the diaper area
  • May begin as cradle cap ^[8]
  • Dennie-Morgan fold: increased folds below the eye
  • Occasionally, lesions appear on the trunk.
• Childhood AD (age 2 to 12 years)
  • Eczema: flexural creases (antecubital fossa and popliteal fossa), skin folds, extensor surface of hands
  • Lesions usually become lichenified (thickening of the skin with accentuated skin markings)
• Adult/adolescent AD (age > 12 years) ^[7]
  • Lichenified lesions and pruritus of flexor surfaces of the extremities
  • The antecubital fossa is frequently involved.
  • Adult AD may also present as nummular eczema.
• Associated findings ^[9][10]
  • Atopic triad: triad of asthma, allergic rhinitis, and atopic dermatitis that is linked to allergen-triggered IgE-mast cell activation
  • Food allergies
  • Xerosis
  • White dermographism: a physical finding of transiently blanched skin after skin stroking
    • Caused by cutaneous vasoconstriction
    • Normal variant, but more common in patients with atopic dermatitis
  • Dermatographism: formation of urticaria after minor pressure is applied to the skin, likely mediated by local histamine release
  • Hertoghe sign: thinning or loss of the outer third of the eyebrows
  • Keratosis pilaris: keratinized hair follicles ("rough bumps") typically distributed over extensor arms and thighs

The symptoms of atopic dermatitis are variable and often change in the course of a lifetime. Itching and dry skin are usually the main symptoms.

The diagnosis of atopic dermatitis is usually based on patient history and clinical appearance. The American Academy of Dermatology suggests the use of several clinical criteria that need to be fulfilled in order to establish the diagnosis.

Clinical criteria ^[11]

• Essential features
  • Pruritus
  • Eczema
• Important features
  • Early age of onset
  • Atopy
    • Personal and/or family history
    • Immunoglobulin E reactivity (↑ serum IgE)
  • Xerosis

Histopathology ^[12]

• Not part of the diagnostic criteria
• Spongiotic dermatitis: epidermal intercellular edema widening the intercellular space between keratinocytes
  • Epidermal infiltration by lymphocytes is common.
  • Chronic fluid accumulation leads to the formation of intraepidermal vesicles
• Acanthosis and hyperkeratosis (in chronic eczema)

Severity assessment ^[11]

• Scoring system (SCORAD = scoring atopic dermatitis)

• Seborrheic dermatitis: Lesions are usually dry in atopic dermatitis and more greasy in seborrheic dermatitis. ^[13]
• Psoriasis
  • Onset is generally after adolescent years.
  • Lesions are typically covered with white or silvery scales and are commonly located on the extensor surface of extremities.
• Other eczematous diseases ^[14]
  • Contact dermatitis (e.g., allergic contact eczema)
  • Nummular dermatitis
• Infectious differentials ^[13]
  • Mycoses
  • Scabies

The differential diagnoses listed here are not exhaustive.

General measures ^[11]

• Avoid triggers:
  • Allergic trigger factors (pets, dust mites, pollen, certain foods)
  • Irritants (clothing, chemicals)
  • Heat
• Keep the skin moist
• Manage/eliminate stress
• Breastfeeding recommended during infancy

Management of AD based on disease severity ^[15][16]

• Secondary infections
  • Bacterial: staphylococcal skin infections ^[17]
  • Viral: eczema herpeticum ^[18]
  • Fungal: tinea (especially Trichophyton rubrum)
• Psychosocial complications ^[2]
  • Sleep problems
  • Decreased quality of life

We list the most important complications. The selection is not exhaustive.

The symptoms of atopic dermatitis usually improve with age and often resolve completely after puberty. ^[3]