Improvement of hereditary palmoplantar keratoderma with oral trametinib.

We report a child with a past medical history notable for congenital deafness, palmoplantar keratoderma (PPK), and hypothalamic glioma who initiated a MEK inhibitor trametinib for cancer-directed therapy at 11 years of age and was incidentally noted to have marked improvement in his PPK. Trametinib withdrawal led to worsening in the patient's PPK. We speculate that the patient's PPK improved because of trametinib, given the temporal relationship between trametinib therapy and PPK severity, observed both after introduction and withdrawal of trametinib therapy. The upregulation of MAPK signaling may be involved in the pathogenesis of keratinocyte proliferation in at least some forms of PPK, given that downstream inhibition of MAPK signaling led to an improvement in the patient's PPK.