Subacute Cutaneous Lupus Secondary to Trastuzumab Emtasine

There is a defined, but poorly described, relationship between Trastuzumab and Cutaneous Lupus Erythematosus, and whether Trastuzumab causes CLE or simply leads to dermatologic manifestations of latent Lupus Erythematosus has yet to be established. The link between the two seems now more relevant than ever, as Trastuzumab has recently been theorized as a possible therapy for Lupus Nephritis. As such, any cutaneous rash or skin lesion that appears after the administration of Trastuzumab should lead to suspicion of Cutaneous Lupus Erythematosus. We report a case of Cutaneous Lupus Erythematosus, proven by both skin biopsy and serology, in a female patient on her 9th cycle of Trastuzumab emtasine for breast cancer.