MEKAR has been estimated to occur in up to 90% of patients receiving MEK inhibitor therapy, although the majority of cases are apparently asymptomatic and resolve without the need for intervention or compromising the therapeutic dose of cancer-directed therapy.19,23,30 Clinical trial data show a high incidence of MEKAR among treated patients but also indicate that only a minority of patients have symptomatic MEKAR. Here, MAP2K7 is linked to cancer.