Serum Substance P, Neuropathic Pain, and Central Sensitization Across Treatment Groups in Chronic Plaque Psoriasis

The goal of this observational study is to better understand whether blood levels of Substance P are related to pain, itching, altered pain sensations, central sensitization, psoriasis severity, and quality of life in adults with chronic plaque psoriasis. The main questions this study aims to answer are: Are serum Substance P levels associated with neuropathic pain features, central sensitization, psoriasis severity, pain, itching, and quality of life? Do serum Substance P levels and these clinical features differ among patients receiving different psoriasis treatments? Researchers will compare three groups of patients: those receiving IL-17 inhibitor treatment, those receiving conventional systemic treatment with methotrexate or acitretin, and those receiving topical treatment only or no current treatment. Participants will: Have their psoriasis severity assessed and complete questionnaires about pain, itching, central sensitization, and quality of life. Undergo a neurological examination. Participants who report pain will also be evaluated for neuropathic pain features using the DN4 questionnaire. Provide a blood sample for measurement of serum Substance P and routine laboratory tests. Undergo electromyography and nerve conduction studies if peripheral neuropathy is suspected during the neurological evaluation. No treatment will be assigned or changed as part of this study.