Chronic Hand Eczema: From Nosological Ambiguity to Therapeutic Identity in the Era of Targeted Topical JAK Inhibition

Chronic hand eczema (CHE) is a persistent and relapsing inflammatory dermatosis characterized by substantial functional impairment, psychosocial distress, and occupational disability. Although epidemiologically common and clinically burdensome, CHE has long suffered from nosological ambiguity, frequently interpreted as a localized manifestation of atopic dermatitis, psoriasis, allergic contact dermatitis, or cumulative irritant dermatitis. The recent regulatory approval of topical delgocitinib, a pan-Janus kinase (JAK) inhibitor specifically indicated for moderate-to-severe CHE inadequately controlled by topical corticosteroids, has reshaped both therapeutic strategy and conceptual framing of the disease. The introduction of a targeted therapy dedicated to CHE has reinforced its clinical identity while simultaneously highlighting its internal biological heterogeneity. Beneath the umbrella term “chronic hand eczema” lie distinct phenotypes characterized by variable barrier dysfunction, immune polarization, and environmental interaction. This review integrates current knowledge on epidemiology, pathophysiology, diagnostic stratification, therapeutic algorithms, phase III registrative evidence, emerging real-world data, and the central role of barrier restoration. Particular attention is devoted to the hand as a specialized barrier organ and to the interplay between inflammation and epidermal structural integrity. In the era of targeted therapy, precise diagnostic framing and barrier-oriented management are indispensable to optimize outcomes.