(a) Patients with myelodysplastic syndrome (MDS) who have mono-alleleic mutations in TP53 have similar outcomes to TP53-unmutated MDS. Conversely, bi-allelic loss caused by either (b) multiple mutations of TP53, copy-neutral loss of heterozygosity or (c) mono-allelic mutation of TP53 with deletion of the other TP53 allele, will result in no wildtype TP53 expression, and these groups are associated with inferior clinical outcomes.