Treatment goals for psoriasis: Should PASI 90 become the standard of care?

Psoriasis is a chronic, immune-mediated inflammatory disorder affecting 2--3% of general population, being both physically and emotionally debilitating. Due to the rapid advances in the understanding of psoriasis pathogenesis, several targeted medications, aiming specific components of the immune system, have been and are currently being developed. These biologic therapies are a major technological advancement over traditional immunosuppressive medications and have revolutionized the treatment of psoriasis. Currently available biologic agents for psoriasis treatment have shown to be very effective, even long-term, with a favorable safety profile. The most widely used instrument for objective measurement of psoriasis severity and extension is the Psoriasis Area and Severity Index (PASI), which was developed in 1978. Even though it has a number of limitations (non-linearity because of the surface score, notorious floor effect and poor sensitivity to change for relatively small areas of involvement, lack of ponderation of the different qualities of the lesions and functional impairment associated with lesions involving visible areas, such as, the hands, feet, nails or genital areas and reduced reproducibility due to the variability associated to the determination of BSA), PASI has been considered the gold standard of psoriasis severity scale for decades.