Psoriasis — Clinical and Types

A 38-year-old man presents with a 6-month history of erythematous, well-demarcated plaques with silvery scale over his elbows, knees, and scalp. Auspitz sign is positive. He denies systemic symptoms. Serology for HIV and streptococcal infection is negative. What is the most appropriate next step in management?

Which of the following is the hallmark histopathological finding in psoriasis?

A 38-year-old man presents with erythematous, well-demarcated plaques with silvery scales on his elbows, knees, and scalp for the past 6 months. Dermoscopy shows regular psoriasiform acanthosis. What is the most common clinical type of psoriasis in this patient?

Among patients with psoriasis, which is the most common site of involvement?

A 42-year-old woman with a 10-year history of plaque psoriasis now presents with sudden onset of widespread erythema, pustules, and systemic symptoms (fever, malaise). She had recently stopped her oral corticosteroid therapy. What is the most appropriate investigation to confirm the diagnosis of pustular psoriasis?