Successful Addition of Topical Tapinarof for Residual Psoriatic Lesions During Apremilast Therapy: A Case Report.

In some patients with psoriasis, residual skin lesions persist despite systemic treatment with apremilast. However, switching to biological agents may be challenging due to comorbidities, or dose reduction may be required due to side effects, leading to relapses. We report the case of an 86-year-old male with plaque psoriasis and psoriatic arthritis who achieved complete clearance after the addition of topical tapinarof to his apremilast regimen. Although his skin and joint symptoms initially improved with apremilast, mild residual cutaneous lesions recurred after three years (psoriasis area and severity index (PASI) 2.4). Due to a history of gastric cancer, the patient declined biologics. Following the initiation of topical tapinarof, PASI 0 was achieved within 1.5 months. This improvement allowed for a stepwise tapering of both agents; apremilast was eventually reduced to 30 mg every other day (QOD), and tapinarof application was reduced to QOD. The patient has maintained PASI 0 for over one year without recurrence of treatment-related adverse events. The complementary actions of systemic phosphodiesterase 4 inhibition and local aryl hydrocarbon receptor activation, along with tapinarof's durable remittive effect, may have facilitated this successful long-term remission despite the reduced dosage. However, as this is a single-case observation involving mild residual disease (PASI 2.4), the findings should be interpreted with caution. It remains possible that the topical treatment alone or the low baseline disease burden contributed to the rapid response. Further large-scale studies are needed to confirm the efficacy, safety, and generalizability of this combination strategy.