BI02 Abrocitinib-induced Kaposi sarcoma in a patient with severe atopic dermatitis

Abstract Kaposi sarcoma (KS) is a human herpesvirus (HHV)-8-associated angioproliferative disorder. It can be classified into four types: classic, endemic, iatrogenic and HIV associated. Iatrogenic KS is most commonly observed in organ transplant recipients receiving prolonged immunosuppression. There are a small number of reports of KS occurring in patients treated with Janus kinase (JAK) inhibitors for immune-mediated inflammatory disease. To our knowledge, we report the first case of abrocitinib-induced KS, in a young patient with severe atopic dermatitis. A 31-year-old man of Asian Chinese descent with severe refractory atopic dermatitis presented with multiple progressively enlarging pigmented nodules over several months. His medical history included asthma and gout, and prior treatments for his skin included ciclosporin, methotrexate and mycophenolate mofetil, all of which were discontinued due to treatment failure. He achieved good disease control with abrocitinib for 2 years before the development of these lesions. The patient denied systemic symptoms such as weight loss or night sweats. Clinical examination revealed multiple pigmented nodules on the right medial ankle, left heel, left tragus and right chest, with no mucosal involvement or palpable lymphadenopathy. Histopathological analysis of incisional biopsies showed spindle cell proliferation with prominent slit-like vascular spaces within a cellular dermal nodule. Immunohistochemistry confirmed the presence of HHV-8, establishing a diagnosis of KS. HIV serology was negative. Staging computed tomography (CT) revealed numerous small cutaneous and subcutaneous nodules in the neck, consistent with possible metastases. He was found to have small pulmonary nodules, which were deemed to be of uncertain significance, and a repeat CT scan was organized for 3 months later. Abrocitinib was discontinued due to its likely contribution to iatrogenic immunosuppression, and the patient was referred to oncology. Chemotherapy with doxorubicin (25 mg m−2 every 2 weeks) was initiated, with a planned total of 10 cycles. This case highlights a potential association between JAK inhibitors, such as abrocitinib, and the development of KS in patients with severe AD requiring prolonged immunosuppression. Previous reports have demonstrated complete resolution of KS following the discontinuation of JAK inhibitors, emphasizing the reversible nature of the iatrogenic variant. This case highlights the importance of close monitoring for malignancies in patients receiving JAK inhibitors, particularly those with extensive immunosuppressive treatment histories. Balancing disease control with the risks of malignancy poses a significant challenge in managing complex cases of severe AD.