Ring 21 is an unstable structural abnormality of chromosome 21 that can lead to RUNX1 gene amplification. We present a unique case with a carrier patient of a constitutional ring chromosome 21 (partial monosomy and trisomy 21) with dysmorphic features and congenital malformations phenotype, who developed acute myeloid leukaemia with myelodysplasia-related changes and two ring 21 chromosomes with RUNX1 amplification. The patient's constitutional ring 21 chromosome showed alterations in tumour suppressor genes, and oncogenes, but not in RUNX1. RUNX1 gene expression at acute myeloid leukaemia diagnosis, showed no upregulation, so other genes may also be the genetic amplification targets in this patient. Copyright © 2016 John Wiley & Sons, Ltd.
Keywords: AML; RUNX1 amplification; r(21).
Copyright © 2016 John Wiley & Sons, Ltd.