Methods, Online Supplementary Table S1). We detected mutations in the TKD or the juxtamembrane domain (JMD) of FLT3 in 15/167 (9%) patients (Table 1). In children (patients> 1 year, n= 72), only one FLT3 aberration (TKD-D835H) was found (1/72, 1.4%). In infants (n= 95), FLT3-TKD mutations were identified in 12/95 (12.6%) patients. Seven of these had D835 substitutions and 4 had I836 deletions, all of which are activating. 9, 10 One infant had a novel 12-base pair (bp) deletion and 3-bp insertion involving codons D835 to S838 similar to the mutation reported by Taketani et al. 3 Notably, of the 12 infants with a FLT3-TKD mutation, only 3 suffered from relapse; 3-year cumulative incidence of relapse (CIR) 26±14%. In only 2/95 (2.1%) infant patients, alterations in the JMD of FLT3 were detected, namely one uncharacterized duplication, and one novel Y589_F594 deletion. Both patients relapsed. haematologica 2017; 102: e438