Psoriasis Targeted Therapy: Characterization of Interleukin 17A Expression in Subtypes of Psoriasis

Psoriasis is a chronic, inflammatory autoimmune disease that affects about 3% of the general population in the United States with 17% suffering from moderate to severe psoriasis. The disease process is believed to be mediated by tumor necrosis factor (TNF)-α and cytokines secreted by specialized T-cell populations including Interleukin (IL)-17, IL-22, and Interferon (IFN) γ. IL-17 plays an important role in psoriasis. In this study we evaluated the expression of IL-17A in variants of psoriasis including plaque, palmoplantar, scalp, pustular, and guttate subtypes via immunohistochemistry (IHC).

A search of the University of Miami Dermatopathology database was performed to identify all available patient specimens within the various subtypes of psoriasis. IL-17A IHC staining was performed using 4 μm paraffin skin sections. 1:25 dilution of IL-17A antibody was used. Stained slides were analyzed using a semi-quantitative scoring method ranging from negative to three plus.

Palmoplantar and pustular psoriasis cases showed consistently strong IL-17A staining. Plaque psoriasis cases showed intermittent to strong IL-17A staining. The results in the scalp and guttate psoriasis cases showed variable results.

The results of our study suggests the significant role of the cytokine IL-17A in the development of palmoplantar and pustular psoriasis. However, scalp and guttate subtypes showed variable expression from negative to strongly positive, which demonstrates a case by case basis expression of IL-17A. Therefore, exploring the IHC characterization of subtypes of psoriasis will help dermatologists better understand the pathogenesis of each subtype and help clinicians optimize treatments.