Dermatologists are currently recommended to assay for thiopurine methyltransferase (TPMT) activity prior to optimizing azathioprine treatment, in order to avoid it in those who are null for TPMT.2 Furthermore, in patients with late‐stage melanoma, dermato‐oncologists screen for the BRAF V600E mutation prior to prescribing vemurafenib. This evidence concerns the gene TPMT and melanoma.