As winter's dry weather continues, psoriasis patients are feeling the pinch.

Psoriasis, a chronic inflammatory disease caused by an abnormal immune response, is an incurable condition that affects 0.5-1 percent of the Korean population. It is characterized by flare-ups and exacerbations and is known to worsen in about 65 percent of patients, especially in winter.

Notably, psoriasis often affects socially active people in their 20s, and its symptoms, which appear as red patches and thick flakes on the skin, greatly affect patients' quality of life.

According to a 2017 Korean study, about 80 percent of psoriasis patients experience decreased quality of life.

Against this backdrop, the Korean Society for Psoriasis announced a new expert consensus on psoriasis severity and treatment goals on Oct. 29, World Psoriasis Day.

Previously, patients had to meet the strict criteria of Psoriasis Area and Severity Index (PASI) of 10 points or more and Body Surface Area (BSA) of 10 percent or more to be classified as severe psoriasis. However, the new consensus classifies patients with PASI 10 or more or PASI 5 or more but less than 10 and psoriasis in special areas as severe psoriasis.

The latest consensus also refined treatment goals.

Instead of the previous PASI relative score, the consensus now refers to an absolute PASI score of 2 or less. For specialty site psoriasis, the goal is to achieve 10 percent or less of body surface area in the affected area and “none” or “almost none” for moderate. For nail psoriasis, a Nail Psoriasis Severity Index (NAPSI) score of 75 points was suggested as a goal.

Korea Biomedical Review spoke to Dr. Park Eun-ju, a professor of dermatology at Halyim University Sacred Heart Hospital and the public relations director at the Korea Society for Psoriasis, about effective psoriasis treatment and management, the significance of the new treatment standards, including specialty psoriasis, and the organization's efforts to improve the quality of life for psoriasis patients.

Question: Could you describe the disease burden of psoriasis and its prevalence in Korea?

Answer: Psoriasis has a prevalence of 1-5 percent in the Western world and 0.5-1 percent in Korea. Although the prevalence rate in Korea may seem relatively low, in absolute numbers, many patients have psoriasis. In particular, the symptoms of flaky skin significantly reduce patients' quality of life, and it is often misunderstood as an infectious disease, adding to social stress.

Psoriasis is a chronic inflammatory disease that can affect the skin, the cardiovascular system, joints, and even the eyes. Therefore, it is essential to treat psoriasis by managing systemic inflammation and preventing complications, not just improving skin symptoms.

Despite all the publicity and education provided by the Korean Society for Psoriasis, some patients still visit a doctor only when the disease is severe. It is unfortunate that patients who have been suffering from the disease for 20 to 30 years or more may no longer seek treatment possibilities. However, younger patients with recent onset are more likely to have access to treatment information and seek medical attention on time.

Q: What are the goals of psoriasis treatment, and what is the treatment strategy?

A: The main goals of psoriasis treatment are to maintain clear skin for a long period and to control flare-ups and complications of the disease. However, clear skin can vary from patient to patient and country. Some patients are satisfied with a significant improvement in symptoms compared to the past when the disease was severe, while others are still very stressed if only one or two skin lesions remain. Therefore, patients' subjective expectations and psychological impact should be considered when setting treatment goals.

Q: You mentioned that the definition of “clear skin” varies by patient and country. We are curious about how they define it in Korea.

A: Although 'clear skin' is not defined numerically in Korea, PASI 75 is used as the insurance coverage criteria for biologics. As such, the primary goal of treatment has traditionally been to reach PASI 75, but with the recent introduction of several new drugs, the goal is increasingly being raised to PASI 90.

Psoriasis experts believe it's time to adjust the treatment goal. This is already happening in other countries, and the Korean Society for Psoriasis recently developed a new consensus on treatment goals and severity criteria.

Q: What does this expert consensus mean?

A: While not yet at the level of a guideline, the new consensus was developed based on input from experts in the field of psoriasis treatment in Korea and is the first step in clarifying the severity and treatment goals for psoriasis. It will take some time, but announcements will follow the consensus on topical treatments, systemic treatments, and biologics.

The consensus document clarifies the severity criteria and treatment goals. Currently, patients are considered to have severe psoriasis if they have a PASI of 10 or greater or a BSA of 10 percent or greater. While meeting these criteria may qualify for special consideration, they do not fully account for the impact on quality of life. For example, a patient with scalp-wide lesions that make socializing difficult may not be considered severe unless they meet the PASI 10 and BSA 10 percent criteria.

To address this limitation, the new consensus document considers the impact of specialty site psoriasis in determining severity. Specifically, patients with a PASI of 5 to 10 should be considered to have severe psoriasis even if they do not have a PASI of 10 or BSA of 10 percent if they have 30 percent or more involvement in specialty areas or if their Physician Global Assessment (PGA) is severe.

In conclusion, the consensus is significant because it complements existing criteria to improve the quality of life for patients with specialty lesions and ensure that they receive appropriate treatment.

Q: What are these special areas?

A: Patients' quality of life is significantly impaired when psoriasis involves the nails. In addition, psoriasis often occurs around the less visible genitals, and this often leads to significant difficulties with sex life. The scalp, palms, and soles of the feet are also special areas, and patients with lesions in these areas can be psychologically debilitated and experience great discomfort.

Q: Why was this published as an expert consensus rather than a guideline?

A: Because it would be very difficult and overwhelming to cover everything at once, this is an expert consensus statement rather than a guideline, which is a simpler format. We are currently in the process of clarification through research papers.

Q: We understand that this expert consensus reflects international standards. How have international severity criteria changed?

A: The International Psoriasis Council (IPC) considers a PASI score of 10 or BSA of 10 percent or a Dermatology Life Quality Index (DLQI) score of 10 or more severe. This means that the criteria are very broad and include quality of life. The presence of special sites and response to treatment are also included in the definition of severe psoriasis. It's also considered severe if topical treatments don't work.

In addition, the new definition is more specific than before: Not all patients can be considered severe even if they have special areas, but only if the area involved exceeds 30 percent. So, if you have a small lesion on your scalp, it's not considered a special site. These criteria are similarly applied in Europe; our consensus statement reflects and further refines them.

Q: Why did the goal of psoriasis treatment change from a relative improvement rate (PASI 75) to an absolute value (PASI 2), and what are the clinical implications of this change?

A: The consensus proposes that the goal of treatment should be an absolute PASI score of 2 rather than a relative percentage improvement of PASI 75, 90, or 100 to compensate for the limitations of relative assessment. For example, if a patient with an initial PASI score of 40 improves to 10 points, they are considered to have reached a PASI of 75, but a PASI of 10 is still high. Conversely, for a patient with an initial PASI of 5, achieving a PASI of 75, a relative improvement rate, may be more difficult.

Therefore, the absolute value criterion is meaningful because it allows us to systematically manage all patients regardless of their initial PASI score and aim for a higher quality of life. A PASI score of 2 reflects a substantial improvement in a patient's symptoms, indicating that only two or three lesions remain throughout the body. Therefore, while a reduction from a PASI score of 40 to 10 was previously considered a sufficient improvement, the new criteria require more aggressive treatment to achieve the more stringent goal of a PASI score 2.

Q: How does the new consensus differ from the previous reimbursement criteria, how is it being implemented in clinical practice, and what is the psoriasis society doing to help?

A: With the existing reimbursement and special criteria for calculation, it is important to reach the primary goal of PASI 75. If you don't reach PASI 75, it becomes difficult to maintain your insurance coverage. However, it's also important to explain to patients that they can get better and make the case for any necessary medication changes.

While the current settlement may not bring immediate change, the psoriasis society continues to work toward improving reimbursement criteria in the long term. Notably, we are considering ways to support patients with specialty lesions and severity scores between 5 and 10 who have a high financial burden and use many off-label medications.