PDE4 inhibitors have garnered increasing interest due to their remarkable safety record and ease of prescription, as demonstrated by the growing body of literature highlighting their off-label applications, including aphthous stomatitis, psoriasis, AD, hidradenitis suppurativa, sarcoidosis, lichen planus, discoid lupus erythematosus, and others [14,15]. This evidence concerns the gene PDE4A and Alzheimer disease.