PDE4A and psoriasis: Apremilast, a selective inhibitor of PDE4-cAMP signaling, represents an innovative therapeutic strategy for psoriasis in cases where other systemic therapies have failed or been contraindicated.[15] Growing evidence shows that patients with inflammatory diseases exhibit higher PDE-4 expression than healthy individuals, including but not limited to rheumatoid arthritis, chronic obstructive pulmonary disease, and autoimmune disease.[16] Currently, PDE-4 inhibitors show substantial potential in the treatment of IBD.