D1.230 - Acute Localized Exanthemathous pustulosis induced by Pertuzumab and Trastuzumab with positive Lymphocyte Transformation test

Acute Localized Exanthematous Pustulosis (ALEP) is a delayed skin reaction characterized by multiple sterileand nonfollicular pustules on an erythematous and oedematous restricted skin area. It is considered a limited variant of Acute Generalized Exanthematous Pustulosis (AGEP). We report a case of ALEP developed after pertuzumab and trastuzumab administration with a positiveresults to Lymphocyte Transformation test (LTT).A 52-year-old woman, with no history of atopy, affected by cancer of right breast (cT2N+) luminal B HER 2positive. A few days after the administration of the third cycle of chemotherapy with carboplatin, paclitaxel,pertuzumab and trastuzumab, the patient suffered multiple itching pustulosis lesions on her face with mildconjunctival affectation. She was treated with doxycycline, oral and topical corticosteroids with quickly improvement and resolution in a week accompanied by epidermal desquamation of pustular lesions.Routine laboratory test showed normal values. Pustular secretion cultures from exudate were negative.Allergic study was performed one month after the reaction. Skin Prick test (SPT) and intradermaltest (ID) at the recommended concentration for all the implicated drugs was performed. Prick test concentrations used were:  oxaliplatin 5 mg/ml, paclitaxel 6 mg/ml, pertuzumab 1,6 and 30 mg/ml and trastuzumab 21 mg/ml. The concentrations used for intradermal test were: oxaliplatin 0.5 and 5 mg/ml, paclitaxel 0.6 mg/ml, pertuzumab 0.016 and 0.3 mg/ml and trastuzumab 0.21 mg/ml. All skin test were negative at inmediate and delayed (24 hours) readings.Subsequently, at least one month after the suspension of any corticosteroids, Lymphocyte TrasformationTest (LTT) was performed with oxaliplatin, pertuzumab and trastuzumab. LTT confirmed a positive response to pertuzumab and trastuzumab, Based on the clinical history and allergological study, the patient was diagnosed with an ALEP to pertuzumab and trastuzumab. To our knowledge this is the first case of ALEP for Pertuzumab and Trastuzumab with positive result to in-vitro LTT suggesting a T cell-mediated type IV hypersensitivity.