Efficacy of anti‐immunoglobulin E therapy in patients with prurigo: A pilot study

Objectives Chronic prurigo is a reactive skin disease marked by multiple pruriginous lesions such as papules, nodules, and erythema. We previously showed that basophil infiltration into the pruriginous lesions and basophil activation in blood are frequently observed. Therefore, basophils may be involved in the pathogenesis of chronic prurigo. In this study, we examined the efficacy of anti‐immunoglobulin E (IgE) therapy with omalizumab, which blocks basophil activation, in patients with prurigo. Methods Seven patients with chronic prurigo (prurigo chronica multiformis [PCM]: five patients; prurigo nodularis [PN]: two patients) and one patient with prurigo subacuta (PS) were enrolled. The infiltration of basophils into skin lesions was assessed by immunohistochemical analyses using a monoclonal antibody. All patients were treated three times with 300 mg omalizumab every 4 weeks, regardless of serum levels of total IgE. Skin symptoms were assessed using our unique skin scores before and after treatment with omalizumab. The efficacy of the treatment was determined according to the reduction ratio of skin scores as follows: high (ratio > 70%), moderate (70% ≥ ratio > 40%), mild (40% ≥ ratio > 10%), or none (10% ≥ ratio). Results All five patients with PCM were improved: The efficacy was high for three patients, moderate for one patient, and mild for one patient. In addition, the pruriginous lesions were improved mildly in the patient with PS, but not in those with PN. Conclusions Anti‐IgE antibody therapy with omalizumab may be effective for PCM but not for the other types of chronic prurigo. In this study, we examined the efficacy of anti‐IgE therapy with omalizumab, which blocks basophil activation, in patients with prurigo. Anti‐IgE antibody therapy with omalizumab was effective for prurigo chronica multiformis but not for the other types of chronic prurigo.