Chapter 14: Psoriasis – Drug Therapy & Clinical Management

Psoriasis is a chronic, debilitating T cell-mediated disease involving complex inflammatory dysregulation and hyper-proliferation of epidermal keratinocytes, commonly presenting as well-demarcated erythematous plaques with silvery-white scales. This condition, which affects 2% to 3% of the U.S. population, often necessitates lifelong management aimed at symptom control and remission, as it is associated with significant emotional impact and the risk of developing psoriatic arthritis. Treatment selection is stratified by disease severity, primarily based on the percentage of Body Surface Area (BSA) affected, utilizing topical, phototherapy, and systemic modalities. For localized or mild disease (typically under 10% BSA), first-line therapy centers on high-potency topical corticosteroids, often used briefly and then rotated with adjunct treatments such as emollients or Vitamin D analogs (calcipotriene) to minimize adverse effects like skin atrophy. Systemic agents are reserved for generalized or unresponsive disease, requiring baseline laboratory work before initiation. These include traditional therapies like the antifolate methotrexate and the immunosuppressant cyclosporine, which carry risks of hepatic or renal toxicity, respectively. Systemic retinoids, like acitretin, are highly teratogenic and strictly contraindicated with alcohol and during pregnancy. Newer systemic options include the oral phosphodiesterase 4 inhibitor, apremilast, which uniquely requires no initial lab studies. For moderate to severe cases, targeted Biologics are employed, designed to inhibit key pro-inflammatory cytokines, including TNF-alpha (e.g., Infliximab, Adalimumab), IL-12/23 (Ustekinumab), IL-17 (Secukinumab), and IL-23 (Risankizumab). Due to the immunosuppressive nature of most systemic and biologic therapies, mandatory testing for tuberculosis (TB) and hepatitis B/C is required before treatment begins. Patient education is crucial, focusing on avoiding known triggers—such as stress, smoking, and certain medications (like beta blockers)—and understanding that consistent adherence is necessary for managing this chronic, waxing-and-waning condition.