A Rapid and Marked Response to Guselkumab in Extensive Plaque Psoriasis: A Case Report.

Psoriasis is a chronic immune-mediated inflammatory skin disease associated with significant morbidity and impaired quality of life. The introduction of biologic therapies, particularly interleukin (IL)-23 inhibitors such as guselkumab, has significantly improved outcomes in patients with moderate-to-severe disease, achieving high rates of skin clearance. However, clinical response is typically gradual, with maximal improvement occurring after 12-16 weeks, and rapid, near-complete clearance following a single dose remains uncommon and not well described. We present the case of a 58-year-old female with severe plaque psoriasis involving approximately 90% of body surface area (BSA), associated with intense pruritus and pain due to skin breakdown. Prior treatments had failed to achieve adequate disease control. Guselkumab was initiated according to standard dosing protocols. At the four-week follow-up after a single injection, the patient demonstrated a marked clinical response, with a reduction in BSA involvement from 90% to 5%, along with significant improvement in erythema, scaling, and plaque thickness, and substantial symptomatic relief. No adverse effects were observed. This report highlights an unusually rapid and pronounced response to guselkumab. However, given the single-case design, this observation should be interpreted with caution and may represent a hypothesis-generating finding that underscores interindividual variability in treatment response. Further studies are needed to better understand predictors of rapid response and their implications for personalized management of psoriasis.