Mutations in KCNQ1, KCNH2, and SCN5A are responsible for ∼80% of cases diagnosed with LQTS, leaving room for the discovery of additional causal genes for this disease.[9,10] In this study, we identified missense mutations G219E and T160M in KCNQ1 and TRPM4, respectively, in a proband from a family affected by LQTS and reprogrammed PBMCs from the proband and one healthy family member to generate functional hiPSCs-CMs. The gene discussed is TRPM4; the disease is familial long QT syndrome.