Ixekizumab is an IgG4 monoclonal antibody that binds to interleukin 17A indicated for the treatment of plaque psoriasis in adults and children, psoriatic arthritis and axial spondyloarthritis in adult patients. Immune system disorders such as angioedema or anaphylaxis have been reported with ixekizumab.

Our patient was a 53-year-old woman diagnosed with spondyloarthritis B27+ receiving treatment with subcutaneous ixekizumab 160 mg by subcutaneous injection (two 80 mg injections) at week 0, followed by 80 mg (one injection) at weeks 2, 4, 6, 8, 10, and 12, then maintenance dosing of 80 mg (one injection) every 4 weeks (Q4W).

After first administration, the patient showed an extensive local reaction in the injection site (>10cm) that progressively increased its size till fifth administration. In this administration, the patient also experienced severe dyspnea and flushing. Due to the absence of response to other agents and the severity of her spondyloarthritis, the patient was derived to Allergology Unit for desensitization.

The results of prick  (5 x 5) (ixekizumab concentration 80 mg/ml) and intradermal skin tests (1:100; 12x12) with ixekizumab were positive in our patient (negative in ten healthy controls). Polysorbate 80 prick-test were negative. Total IgE level was 130,00 UI/ml and specific IgE against hamster epithelium and latex were negative. Triptase level was 5,9 ug/l.

The patient was planned to undergo ixekizumab desensitization according to an 8-step protocol, previous informed consent. Premedication consisting of ebastine, acetylsalicylic acid, montelukast and methylprednisolone one hour before desensitization was administered.

Eight step desensitization protocol was performed with a total duration of one hour and 45 minutes and a total ixekizumab dose of 80 mg. Dose steps were 0.008, 0.08, 0.8, 1.6, 4.8, 12.8, 25.6 and 34.31 mg. TAB were performed after and before desensitization, being the percentage of activate basophils 88% and 59%, respectively. Ixekizumab desensitization protocol was safe and well tolerated.

Our 8-step protocol desensitization to ixekizumab resulted safe and effective in our patient and it has allowed the continuation of treatment with ixekizumab. Our experience may be helpful for similar clinical cases. A careful risk/benefit ratio should be considered, and an accurate informed consent is mandatory.