Keywords: PI3K inhibitor; PI3K, phosphoinositide 3-kinase; PRP, pityriasis rubra pilaris; TCS, topical corticosteroid; TMP-SMX, trimethoprim/sulfamethoxazole; duvelisib; follicular lymphoma; phosphoinositide 3-kinase inhibitor; pityriasis rubra pilaris; psoriasiform; psoriasis.