Atopic Dermatitis (Eczema): Filaggrin Deficiency, Epidermal Barrier Dysfunction & Clinical Therapy

1. Pathophysiology & The Defective Epidermal Barrier

Atopic Dermatitis (AD) is a chronic, relapsing, pruritic inflammatory skin disorder affecting up to 20% of pediatric populations and 10% of adults worldwide. At the molecular foundation lies loss-of-function mutations in the FLG gene encoding filaggrin, leading to impaired stratum corneum aggregation, decreased natural moisturizing factor (NMF), elevated transepidermal water loss (TEWL), and increased allergen penetration.

2. Clinical Presentation Across Age Cohorts

Morphological distribution evolves characteristically across life stages:

• Infantile Phase (0–2 years): Acute edematous, weeping erythema predominantly localized to facial convexities (cheeks, forehead) and extensor limbs, typically sparing the diaper region.
• Childhood & Adolescent Phase: Chronic lichenified plaques and excoriations localized to flexural folds (antecubital and popliteal fossae, posterior neck, wrists).
• Adult Phase: Prominent localized dermatosis of hands, periocular tissue, and flexural creases accompanied by generalized severe xerosis.

3. Clinical Management & Stepwise Therapeutic Escalation

Therapy adheres to structural barrier restoration combined with targeted anti-inflammatory intervention:

• Intensive Emollient Regimens: Daily application of ceramide-dominant, fragrance-free ointments within 3 minutes of lukewarm bathing ("soak and seal").
• Topical Calcineurin Inhibitors (Tacrolimus 0.03–0.1%, Pimecrolimus 1%): Non-steroidal anti-inflammatory agents preferred for delicate facial and intertriginous zones.
• Topical PDE-4 Inhibitors (Crisaborole 2%): Non-steroidal option reducing cyclic AMP-driven cytokine cascades.
• Systemic Biologics & JAK Inhibitors: Dupilumab (IL-4Rα antagonist) and tralokinumab (anti-IL-13) providing steroid-sparing disease control for moderate-to-severe disease.