These results offer two hypothetical scenarios: (1) a post-natal chromosomal rearrangement event, which would indicate that the NRAS subclonal mutation preceded the chromosomal aberration, a phenomenon recently described in an infant with acute myelomonocytic leukemia [16], or (2) undetectable rearranged blasts could have been present in both the neonatal twins. The gene discussed is NRAS; the disease is acute myelomonocytic leukemia M4.