Reactive Arthritis (Keratoderma Blennorrhagicum)

A 26-year-old HLA-B27 positive man presents with a 4-week history of asymmetric oligoarthritis, conjunctivitis, dysuria with sterile urethral discharge, and hyperkeratotic erythematous scaly pustular plaques on the palms and soles with thick keratotic margins resembling shells — consistent with keratoderma blennorrhagicum secondary to reactive arthritis triggered by prior Shigella infection. The skin biopsy shows parakeratosis, Kogoj pustules, and dermal lymphocytic infiltrate. Which of the following represents the **first-line topical management** for the palmoplantar keratodermic lesions marked **A** in the diagram?