Inverse Flexural Psoriasis

A 46-year-old obese woman with type 2 diabetes and a history of mild plaque psoriasis presents with a 6-month history of painful, shiny red patches in her inframammary folds, axillae, and groin. She has been treated repeatedly with topical antifungals without benefit. On examination, the structure marked **A** shows sharply demarcated, smooth, beefy red, glazed-appearing plaques with a characteristic lack of scale, sharp margins respecting the fold depth, and central linear fissures. KOH mount is negative for pseudohyphae. Which of the following is the most likely diagnosis?