The goal of this clinical trial is to analyse efficacy and safety of ixekizumab in participants with refractory guttate psoriasis. The main question it aims to answer is:

What percentage of participants achieved more than 90% reduction from baseline in Psoriasis Area Index （PASI 90） after 12 weeks of ixekizumab treatment? Participants will receive a 12-week treatment of ixekizumab, with follow-up visits every 2 weeks during the treatment period. Keep a diary of their symptoms and Psoriasis Area Index.

This study was a single-arm, open-label, single-center multi-dose trial. Approximately 50 participants are scheduled to receive subcutaneous injection of ixekizumab for 12 weeks, with follow-up every 2 weeks during the treatment period. After the treatment period, the primary endpoint was assessed at week 16, and patients who achieved PASI 90 response were followed up at week 34 and week 52 to the medical center to assess disease recurrence or progression. To evaluate the efficacy of ixekizumab in the treatment of refractory guttate psoriasis.

Inclusion Criteria:

1. Patients voluntarily participate in the study and sign an informed consent form;
2. Age between 18 and 70 years, both genders are eligible;
3. Clinically diagnosed with guttate psoriasis;
4. Previously treated with traditional therapies for plaque psoriasis for more than 4 weeks (including antibiotics, topical corticosteroids, topical calcipotriene, phototherapy);
5. Current PASI score ≥ 3 or DLQI score ≥ 6;
6. Investigator assesses participants's suitability for treatment with ixekizumab;
7. No prior use of biologic agents for treatment;
8. Basic understanding of the purpose of the trial, its effects, and potential adverse events, and willing to sign the informed consent form according to the principles of the Helsinki Declaration;
9. Agree to receive regular treatment, follow-up, and undergo relevant examinations according to the clinical research protocol.

Exclusion Criteria:

1. Presence of other psoriasis phenotypes such as plaque, pustular, erythrodermic, or psoriatic arthritis;
2. Concomitant severe skin diseases, tumors, other systemic diseases (such as inflammatory bowel disease), or mental disorders;
3. Concurrent infections such as tuberculosis, HIV, hepatitis B, hepatitis C, etc.;
4. Allergy to ixekizumab;
5. Received systemic corticosteroids or immunosuppressive/immunomodulatory drugs for psoriasis treatment within the previous 4 weeks (including but not limited to methotrexate, cyclosporine, acitretin, azathioprine, hydroxychloroquine, apremilast, JAK inhibitors, etc.);
6. Participation in another clinical trial within the past 3 months;
7. Pregnant, lactating women, or those planning to become pregnant during the trial;
8. Other circumstances deemed inappropriate for inclusion by the investigator.