PDE4A and rheumatoid arthritis: Indeed, selective PDE4 inhibitors have generated substantial interest as treatment for several autoimmune conditions including rheumatoid arthritis, ankylosing spondylitis, Alzheimer's disease, psoriasis, psoriatic arthritis, sarcoidosis, systemic lupus erythematosus, inflammatory bowel disease, atopic dermatitis, and multiple sclerosis [7].