Increased epidermal filaggrin in chronic idiopathic urticaria is associated with severity of urticaria

Background: Chronic idiopathic urticaria (CIU) and atopic dermatitis (AD) are common allergic skin diseases associated with severe pruritus. AD skin is characterized by filaggrin deficiency, but it has not been studied in CIU.

Objective: To compare the expression of filaggrin in skin from patients with CIU, patients with AD, and normal controls and to investigate whether altered filaggrin expression is associated with CIU severity.

Methods: Skin biopsies were obtained from 16 patients with CIU, 11 patients with AD, and 14 normal controls. Filaggrin expression was evaluated using real-time reverse transcriptase polymerase chain reaction and immunostaining. Urticaria activity score, transepidermal water loss, and skin pH were measured.

Results: FLG gene expression was significantly greater in lesional CIU skin compared with lesional AD skin (P < .01). The staining intensity of filaggrin was significantly increased in lesional CIU skin compared with skin from normal controls (P < .01) and lesional AD skin (P < .001). A significant correlation was observed between filaggrin staining intensity and urticaria activity score in patients with CIU (r = 0.538, P < .05). Transepidermal water loss was significantly increased in lesional skin of patients with AD compared with skin from normal controls (P < .01) and lesional skin from patients with CIU (P < .01). Skin pH was significantly decreased in lesional skin from patients with CIU compared with skin from normal controls (P < .01) and patients with AD (P < .001).

Conclusion: Filaggrin is overexpressed in lesional CIU skin, and increased filaggrin expression is positively correlated with urticaria severity in CIU. Altered filaggrin expression has physiologic effects on transepidermal water loss and pH in the skin of patients with CIU, suggesting increased barrier function compared with skin from patients with AD.