Trisomy 21 and isodicentric chromosome 21 in Kostmann syndrome following treatment with G-CSF

A child with Kostmann syndrome, or severe congenital neutropenia, developed myelodysplastic syndrome after 6 years of treatment with rhG-CSF. The bone marrow karyotype showed acquired trisomy 21, and in some cells pentasomy 21 due to two isodicentric chromosomes 21. This is the second report of a patient with Kostmann syndrome and acquired trisomy 21.