Mild disease

For mild disease, which affects 70% to 80% of patients with psoriasis, first-line management remains topical treatments. Glucocorticoids and vitamin D derivatives, or their combination, are typically sufficient for mild psoriasis. Topical calcineurin inhibitors (tacrolimus or pimecrolimus) are reserved for difficult anatomic sites, such as the face and intertriginous areas, which are more prone to the adverse effects of the other topical agents.2 For the scalp, combinations of corticosteroids and vitamin D3 analogues are most effective, though very potent corticosteroids alone are more effective than vitamin D3 derivatives.9

Moderate-to-severe disease 

There is no single definition in the literature of what constitutes moderate-to-severe psoriasis. The Psoriasis Area and Severity Index (PASI), percentage of BSA affected, and the Dermatological Life Quality Index provide physicians with some metrics to differentiate mild disease from moderate-or-severe psoriasis. However, these guidelines and their numeric cutoffs are cumbersome to calculate and use in daily practice and may not take into account the full clinical and subjective picture of disease burden. For example, although predominant psoriatic nail involvement may not constitute a significant percentage of BSA, it can negatively affect quality of life and be difficult to treat topically.2,10 The Consensus Guidelines of the National Psoriasis Foundation Medical Board thus define moderate-to-severe psoriasis as disease that “cannot or would not be expected to achieve adequate control using topical agents, with adequacy defined by the patient’s own perception of the disease and its burdens.”10

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Patients with moderate-to-severe psoriasis are often treated with a combination of phototherapy and topical or systemic therapy. Table 1 summarizes some key points regarding systemic therapies discussed in this article. 

Click to enlarge.

Click to enlarge. 

Narrow-band UV-B (311 nm and 313 nm) is the more widely used phototherapy, whereas photochemotherapy, such as PUVA (320-400 nm), is used less frequently. Although phototherapy is effective, it is time consuming, as it is performed 2 to 5 times per week in a clinical environment. Therefore, phototherapy is mainly used for acute disease control rather than chronic management.2,11

PUVA increases the risk of skin cancers, especially after 200 treatments, which also limits its chronic use.11 Absolute contraindications to phototherapy include genetic defects that increase light sensitivity or risk of skin cancer, lupus erythematosus, and pregnancy or lactation (for pregnancy, the contraindication applies to oral PUVA only). Phototherapy was developed based on the observation that exposure to sunlight helped reduce the symptoms of many skin diseases. Phototherapy has been shown to inhibit keratinocyte proliferation, induce apoptosis in cells of the immune system, and inhibit Th1 and Th17 proliferation, as well as stimulation of the Th2 system.2,12