Interestingly, targeted deep sequencing was also able to detect persistence of some leukemia-related mutations (biCEBPα, TYK2 and SETD2) during relapse at a very low MF (0.08%, 0.4% and 0.07% respectively), further supporting the potential application of Next Generation Sequencing techniques in minimal residual disease monitoring [22] [23] [24]. The gene discussed is TYK2; the disease is leukemia.