Acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), primary myelofibrosis (PMF)

In AML, the frequency of monosomal karyotype increases with age: 4% in patients ≤ 30 years; 6-10% in patients ≤ 60 years and 13-20% above 60 years.
The frequency of MK cases is significantly higher in t-AML compared with de novo AML (24% vs 10%).
In MDS, MK frequency among patients with a complex karyotype is 83%. In children with advanced MDS MK frequency is 15%.
In PMF patients, MK is present in 42% of complex karyotype cases.

Monosomal karyotype is associated with prior chemotherapy or history of abnormal blood counts (Estey, 2010).

Very poor prognosis, worse with advanced age.
In comparison with non-MK patients, AML, MDS and PMF patients with a monosomal karyotype have lower overall survival rates. In MDS and PMF, the risk of leukemic transformation is higher in MK patients than in patients with non-MK complex karyotypes.
In MK-AML, overall survival at 4 years after diagnosis is 3-4% (vs 26-27% for non-CBF, non-MK AML patients) and event-free survival 2%. Overall survival decreases with advancing age: 17-40% for patients ≤ 30 years, 3-4% ≤ 60 years and 1% in patients older than 60 years. Complete remission rate is generally low, and also worse in older groups (24-52% under 60 years and 13-34% in patients older than 60 years).
In adult MDS patients with MK, 2-year survival is 6% (vs 23% for complex karyotype without monosomies) and 1-year leukemia risk is 32% (vs 14% for complex karyotype without monosomies). In advanced childhood MDS, the presence of a MK does not seem to be an independent adverse prognostic factor.
In PMF, the median survival for MK patients is 6 months, 2-year survival rate is 17% and 2-year leukemic transformation rate is 29% (vs 24 months, 51% and 8,3% in complex karyotype without monosomies).
As with most prognostic factors, the significance of monosomal karyotype seems to depend on the treatment strategy (Itzykson et al., 2011; Löwenberg et al., 2011).

Monosomal karyotype is defined as the presence of at least 2 autosomal monosomies or a single autosomal monosomy associated with at least one structural abnormality.