Mechanism underlying pruritus in recessive dystrophic epidermolysis bullosa: Role of interleukin-31 from mast cells and macrophages.

Background: Pruritus is a highly burdensome symptom in patients with epidermolysis bullosa, especially recessive dystrophic epidermolysis bullosa (RDEB); however, only a few studies have assessed the molecular pathogenesis of RDEB-associated pruritus. Interleukin (IL)-31 is a key cytokine implicated in pruritus associated with dermatologic diseases such as atopic dermatitis and prurigo nodularis.

Objective: To investigate the role and cellular source of IL-31 in RDEB-associated pruritus.

Methods: Serum and skin samples were obtained from 11 RDEB patients and 11 healthy controls. Pruritus visual analogue scale scores were determined. Serum levels of IL-31 and thymic stromal lymphopoietin (TSLP) were examined by enzyme-linked immunosorbent assay (ELISA). The expression of IL-31 and other pruritus mediators in the skin were examined through immunofluorescence staining, and their correlation with pruritus severity was analysed.

Results: Serum IL-31 and TSLP were elevated in RDEB patients. IL-31 expression was increased in RDEB skin and positively correlated with pruritus severity. Most of the IL-31-expressing cells were mast cells, and some were CD206(+) M2-like macrophages. The number of substance P(+) cells was also increased in the patients' skin, and most of them were mast cells. The number of substance P(+) mast cells was correlated with the number of IL-31(+) dermal infiltrates. The number of IL-4Rα- and IL-13-expressing cells and expression of TSLP and periostin increased in RDEB skin, but without a correlation to pruritus score.

Conclusion: The increased production of skin IL-31 from mast cells and M2-like macrophages may be the mechanism underlying pruritus in RDEB.