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.