Psoriasis is a skin condition characterized by red, raised, round lesions covered with silvery-white flakes that shed. These symptoms are primarily seen on areas that experience frequent friction or external irritation, such as the scalp, back, buttocks, and elbows. However, in some cases, the condition can spread across the entire body or affect the nails.

The severity of itching varies among individuals—some may not experience any itching, while others may suffer from intense pruritus. These symptoms generally persist for a long time, sometimes improving or worsening intermittently.

Beyond skin symptoms, psoriasis can also cause joint swelling, deformation, and pain, indicating that it is not solely a skin disease but may also involve systemic effects.

The exact cause of psoriasis remains unclear, but it is believed to result from a combination of genetic predisposition and various environmental factors.

Potential triggers include infections such as colds or tonsillitis, seasonal changes (especially winter), certain medications, smoking, unbalanced diets, stress, and metabolic syndrome (including obesity, dyslipidemia, hypertension, and diabetes).

An abnormal immune response leads to an excessive production of substances called “cytokines,” which prolong inflammation and cause the skin to become red. Additionally, the outermost layer of the skin, known as epidermal cells, proliferates abnormally.

Normally, epidermal cells regenerate every 28 to 40 days, but in individuals with psoriasis, this process is accelerated to just 4 to 5 days. As a result, immature epidermal cells accumulate on the skin surface, forming thickened layers that eventually shed as scales.

Psoriasis is classified into several types based on symptoms:

• Plaque Psoriasis (Psoriasis Vulgaris): This is the most common form, accounting for approximately 90% of cases, characterized by classic psoriatic lesions.
• Psoriatic Arthritis (PsA): About 15% of psoriasis patients develop this inflammatory arthritis, which causes swelling of fingers and toes, lower back pain at rest, and pain in the Achilles tendon or soles. Although similar to rheumatoid arthritis, it is a distinct condition.
• Guttate Psoriasis: This type is marked by small red spots and often appears suddenly after an infection (such as tonsillitis). In some cases, treating the underlying infection leads to improvement.
• Erythrodermic Psoriasis: This severe form causes widespread redness, fever, dehydration, and fatigue. Hospitalization may be required.
• Pustular Psoriasis: This type presents as white or yellow pustules on the skin. It can arise either as a progression of plaque psoriasis or suddenly without warning. Symptoms may include fever, generalized swelling, and joint pain, often requiring hospitalization. Some patients have a genetic predisposition, which can be tested.

Psoriasis treatments are classified into four main categories:

1. Topical Therapy
2. Phototherapy
3. Oral Medications
4. Biologic Therapy (Injectable Treatments)

Each treatment has its advantages and disadvantages. The optimal approach is determined by the severity of symptoms and the patient’s lifestyle, often involving a combination of therapies.

Our department has been particularly focused on phototherapy. We offer Narrowband UVB, PUVA baths (available on an outpatient basis), targeted phototherapy devices such as TheraBeam and VTRAC, and the XTRAC Excimer Laser, which is one of the few available in Japan.

We are also actively engaged in biologic therapy, which involves antibody-based drugs that directly target cytokines responsible for inflammation. Currently, all biologic drugs for psoriasis are administered via injection, with treatments targeting TNF-α, IL-12/23, and IL-17.

Although biologic therapy is expensive, it is particularly effective for patients with severe skin symptoms or psoriatic arthritis that has been difficult to manage with other treatments.

For oral medications, the PDE4 (Phosphodiesterase-4) inhibitor, introduced in 2017 as the first new oral drug for psoriasis in 25 years, is now widely used. In 2022, the Tyk2 (Tyrosine Kinase 2) inhibitor, which demonstrated superior efficacy to PDE4 inhibitors, was also introduced. Additionally, JAK (Janus Kinase) inhibitors are available for treating psoriatic arthritis.

JAK inhibitors block the intracellular signaling of cytokines that cause inflammation, offering a therapeutic effect comparable to biologic therapy. However, they are costly and may suppress immune function, requiring caution against infections.

Our department offers psoriasis consultations on all outpatient clinic days.

On Tuesdays, we provide a specialized psoriasis clinic (by appointment only). If joint symptoms are present, we conduct imaging tests such as joint ultrasound, X-rays, and MRI, and we also facilitate referrals to rheumatology specialists as needed.

Since 2019, our department has served as the main facility for the Western Japan Psoriasis Registry, a collaborative effort among dermatology institutions across western Japan. This registry is one of the largest psoriasis databases in Japan, collecting clinical data to optimize psoriasis treatment strategies.

By 2024, over 2,800 patients have participated.

All patient data is kept confidential, and we appreciate your cooperation in advancing psoriasis research.