Korean Society for Psoriasis proposes new severity criteria to include special areas

In Korea, psoriasis leaves a mark on lives as deeply as on skin.

For a young man in the food industry, each workday means sealing his hands in gloves, trapping moisture and triggering irritation until the itch becomes unbearable.

Another man in his 30s, coping with severe scalp psoriasis, constantly battled a cascade of flakes, tying up his hair to conceal them during job interviews. When questions about his appearance inevitably surfaced, he’d shrug them off, masking his frustration and embarrassment.

Psoriasis affecting what the International Psoriasis Council defines as "special areas"—the scalp, palms, soles, nails, and genitals—can profoundly impact quality of life, with visible lesions often leading to social discomfort, especially in professional and social settings.

Previously, the criteria for severe psoriasis in Korea were rigid, requiring a psoriasis area severity index (PASI) score of 10 or higher. However, with 80 percent of Korean psoriasis patients reporting moderate-to-severe effects not only on their skin but on their quality of life, a revised severity classification and updated treatment goals have been proposed.

“In Korea, the existing criteria measured only the extent of psoriasis but lacked the ability to evaluate the severity and thickness of lesions,” said Bang Chul-hwan, director of information at the Korean Society for Psoriasis and professor of dermatology at Catholic University of Korea Seoul St. Mary’s Hospital, at a press conference hosted by the Korean Society for Psoriasis on Tuesday marking World Psoriasis Day. 

The society’s revised guidelines now adopt a more flexible approach, recognizing psoriasis in special areas or cases of localized treatment resistance as indicators of moderate severity.

Previously, moderate to severe psoriasis in Korea required not only a PASI score of 10 or higher but also a body surface area (BSA) of over 10 percent. Supplementary criteria included a physician global assessment (PGA) of moderate or higher and a quality of life assessment score of 10 or above.

For biological agents to be covered by insurance, patients must meet criteria such as having severe psoriasis for over six months, a PASI score of 10 or higher, a BSA of 10 percent or more, and having undergone phototherapy or systemic therapy for more than three months. 

However, a systematic literature review, conducted with input from over 70 domestic experts, has led to new criteria for classifying moderate to severe psoriasis. The revised criteria now state that either a PASI score of 10 or higher, or a PASI score between 5 and 10 with significant localized psoriasis, qualifies for the new classification.

“The shift from ‘and’ to ‘or’ criteria introduces much-needed flexibility,” Bang said. He explained that by simplifying and reducing the number of severity indicators, the new guidelines allow for the inclusion of psoriasis in special areas, where the condition can be particularly disruptive.

This adjustment aligns with recent European updates, where moderate-to-severe psoriasis is now classified based on a PASI score of 10 or higher, BSA over 10 percent, or a dermatology life quality index score of 10 or above. 

Bang said the updated Korean guidelines aim to focus on the quality-of-life impacts without over-categorizing cases as ‘severe.’ “We want a balanced approach that recognizes the unique challenges of psoriasis in special areas while preventing overclassification,” he said.

Bang added that this is just the beginning.

If the new approach proves effective within Korea’s healthcare framework, it could eventually pave the way for biological treatments and other therapies for patients struggling with severe psoriasis. “Developing evidence to support this is a long-term objective,” he said.

Additionally, the treatment goals have been raised from the previous PASI 75 (indicating a 75 percent improvement) to PASI 90 or higher, with a target of achieving an absolute score of PASI 2 or lower for some patients. 

According to Bang, moving to an absolute PASI score was “essential,” as relative improvements may not capture patient satisfaction when initial scores are particularly high or low. “By setting an absolute score as a goal based on the patient’s condition, we can establish a more practical target compared to relative scores, thereby more effectively improving the quality of life for psoriasis patients,” he said.