Ruxolitinib, a small molecule JAK-1/2 inhibitor, was approved by the U.S. Food and Drug Administration (FDA) in November 2011, as the first therapeutic for the treatment of intermediate and high-risk myelofibrosis.  The Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway is one of the most well-studied intracellular signaling networks.  Recent advances in our understanding of the complexities of signal activation and regulation of gene expression has provided opportunities for targeted therapeutic interventions.  Although numerous inhibitors of the JAK/STAT pathway are currently being evaluated in clinical trials, ruxolitinib represents the first FDA approved in-class JAK inhibitor. We report a drug eruption associated with ruxolitinib.