To gather information about the mutational landscape at a very early time point in the post-natal life of children who subsequently developed MLL-AF4 infant leukaemia, Gale and colleagues retrospectively analysed routine blood spot screening tests, which were taken hours after birth, and detected the leukaemia-specific MLL-AF4 fusion in these children (Gale et al., 1997). The gene discussed is KMT2A; the disease is leukemia.