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International Psoriasis Council

Advancing Knowledge. Improving Care.

How Psoriasis Severity Is Defined, And What NPF’s Endorsement of IPC’s Framework Means

In 2020, the International Psoriasis Council (IPC) introduced a new way to define psoriasis severity, shifting the focus from labels alone to treatment candidacy. Under this approach, patients are classified as candidates for topical therapy or candidates for systemic therapy based on three criteria: body surface area greater than 10 percent, involvement of special (now called high-impact) sites, or failure of topical therapy.

Since its publication, this definition has been widely adopted in clinical guidelines worldwide, helping clinicians make clearer, more consistent treatment decisions.

Recently, the National Psoriasis Foundation (NPF) Medical Board formally endorsed the IPC definition and introduced two refinements. First, NPF aligned the IPC framework with familiar language by describing patients as having “mild” or “moderate to severe” psoriasis, corresponding to candidates for topical or systemic therapy. Second, NPF adopted the term “high-impact sites” in place of “special areas,” a change the IPC supports because it more clearly reflects the real-life effect of psoriasis on patients.

NPF also reaffirmed the IPC’s updated definition of failure of topical therapy, which is now defined as the inability to reach clear or nearly clear skin after two consecutive four-week courses of topical treatment.

Together, these steps strengthen a shared framework that clinicians, patients, and health care systems can understand and apply more easily.

“This alignment between IPC and NPF matters,” said IPC President Bruce Strober, MD. “When major organizations use the same language and criteria, it reduces confusion and helps patients get to the right treatment sooner.”

By using familiar terms like “mild” and “moderate to severe,” and by emphasizing high-impact sites, the NPF’s endorsement makes the IPC definition more accessible without changing its clinical foundation. The core message remains the same: severity should be defined not just by surface area, but by how the disease affects the person and whether topical treatment is enough.

IPC welcomes NPF’s endorsement and the refinements that make this framework clearer for everyone involved, from clinicians and researchers to patients and policymakers. Shared definitions support better care, better communication, and better outcomes for people living with psoriasis.

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