Monosomy 7 myelodysplasia and leukemia syndrome-2 (M7MLS2) is an autosomal dominant hematologic disorder characterized by onset of pancytopenia, acute myelogenous leukemia (AML), and variable features of myelodysplastic syndrome (MDS) usually in the first decades of life. Bone marrow cells show monosomy 7. Germline mutations in the SAMD9 gene, located on chromosome 7q, have a gain-of-function suppressive effect on the cell cycle, resulting in decreased cellular proliferation. It is hypothesized that this germline defect leads to selective pressure favoring somatic loss of the chromosome 7 harboring the mutant allele (adaptation by aneuploidy) (summary by Wong et al., 2018).
For a discussion of genetic heterogeneity of monosomy 7 myelodysplasia and leukemia syndrome, see 252270. [from
OMIM]