Ibrutinib skin toxicities: Report of two cases.

Ibrutinib is a Bruton tyrosine kinase inhibitor used to treat many hematologic conditions, most commonly B-cell lymphomas and leukemias. Reportedly, skin rash is an adverse event in up to 27% of treated patients. Histopathologic description of these lesions is limited. We present two cases of ibrutinib-associated skin toxicities showing diverse histopathologic features. Case 1: A 72-year-old man was started on ibrutinib for chronic lymphocytic leukemia. Two months later, he developed multiple erythematous crusted papules on the chest, abdomen, and extremities. Biopsies revealed varied histopathology including poorly formed granulomatous dermatitis, epidermal necrosis, ulceration, and panniculitis. Ibrutinib was discontinued and his skin lesions resolved within 1 month. Case 2: A 48-year-old man received ibrutinib after failing standard therapy for primary central nervous system EBV positive diffuse large B-cell lymphoma. Two months after initiation of ibrutinib, he developed multiple firm, red, non-tender nodules on the forehead, buttock, and thigh. Biopsies revealed "pseudolymphoma"-like reaction with dense pandermal lymphohistiocytic inflammation and granulomas. His skin toxicity resolved without cessation of therapy. Awareness of the spectrum of histopathologic features that may be encountered in skin lesions of patients treated with ibrutinib, as illustrated by these two cases, will be critical for optimal patient management.