Background: Psoriasis is a skin condition characterized by the development of raised, red, and scaly plaques over time. Multiple comorbidities, including Crohn's disease, cancer, obesity, and cardiovascular disease, are more common in those with psoriasis. It is well-known that proteases, of which cathepsin S is a part, degrade damaged and undesired proteins. More and more evidence points to its role in a wide range of pathological states and inflammatory disorders. Purpose: The cathepsin-S serum level in psoriasis patients and how it relates to the severity of the illness will be reviewed in this study. Final thoughts: It is possible that serum cathepsin-S is involved in psoriasis. The possible use of cathepsin-S as a biomarker for psoriasis severity is supported by the link between the two.Background: Psoriasis is a skin condition characterized by the development of raised, red, and scaly plaques over time. Multiple comorbidities, including Crohn's disease, cancer, obesity, and cardiovascular disease, are more common in those with psoriasis. It is well-known that proteases, of which cathepsin S is a part, degrade damaged and undesired proteins. More and more evidence points to its role in a wide range of pathological states and inflammatory disorders. Purpose: The cathepsin-S serum level in psoriasis patients and how it relates to the severity of the illness will be reviewed in this study. Final thoughts: It is possible that serum cathepsin-S is involved in psoriasis. The possible use of cathepsin-S as a biomarker for psoriasis severity is supported by the link between the two.