Use of a topical Janus kinase inhibitor in immune checkpoint inhibitor-induced eczematous reaction: a case report.

In this report, we describe the case of a 28-year-old female with bilateral breast cancer in the setting of a BRCA1 mutation, who presented to dermatology with an eczematous reaction, ultimately diagnosed as a cutaneous immune-related adverse event (cirAE) secondary to an immune checkpoint inhibitor (ICI), pembrolizumab. Our case report highlights a novel therapeutic option for an eczematous cirAE: the topical JAK 1/2 inhibitor, ruxolitinib. CirAEs can occur in up to 55% of patients on ICIs, a class of medications seeing rapidly increasing use in cancer therapy, and prior research has demonstrated that ICI-induced dermatitis may involve different pathways than traditionally observed in their spontaneous counterparts. Specifically, marked Th1 skewing is noted in ICI-induced dermatitis, as opposed to a predominant Th2 response which typically characterizes spontaneous atopic dermatitis. To our knowledge, this is the first case report in the literature discussing use of a topical JAK inhibitor, ruxolitinib, in the treatment of topical steroid-refractory cirAEs. Furthermore, as topical JAK inhibitors are thought to not carry the risks of systemic JAK inhibitors, including malignancy, ruxolitinib cream is a promising therapeutic option for this challenging patient population.