Possible genotype–phenotype correlations with coagulation defects in the context of RASopathies were initially hypothesized for PTPN11 and SOS1. A study performed on 27 NS patients identified a PTPN11 mutation in 21 and bleeding defects in 9, and therefore a correlation between PTPN11 mutations and bleeding defects in the context of NS was hypothesized. Here, SOS1 is linked to RASopathy.