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Monosomy 7 myelodysplasia and leukemia syndrome 1(M7MLS1)

MedGen UID:
Concept ID:
Disease or Syndrome
Synonyms: CHROMOSOME 7q DELETION; Familial Mosaic Monosomy 7 Syndrome; Monosomy 7 of bone marrow
Gene (location): SAMD9L (7q21.2)
Monarch Initiative: MONDO:0009646
OMIM®: 252270


Monosomy 7 myelodysplasia and leukemia syndrome-1 (M7MLS1) is an autosomal dominant hematologic disorder with highly variable manifestations. Most patients present in early childhood with pancytopenia and dyspoietic or dysplastic changes in the bone marrow. These abnormalities are almost always associated with monosomy 7 in the bone marrow. In severely affected individuals, the phenotype progresses to frank myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML). Less severely affected individuals may have transient thrombocytopenia or anemia, or have normal peripheral blood counts with transient bone marrow abnormalities or transient monosomy 7. Germline mutations in the SAMD9L 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). Monosomy 7 or partial deletion of the long arm of chromosome 7 (7q-) is a frequent cytogenetic finding in the bone marrow of patients with myelodysplasia and acute myelogenous leukemia. Furthermore, monosomy 7 or 7q- is the most frequent abnormality of karyotype in cases of AML that occur after cytotoxic cancer therapy or occupational exposure to mutagens. The age distribution of de novo cases shows peaks in the first and fifth decades. Monosomy 7 is found in about 5% of de novo and 40% of secondary cases of AML. These findings suggest that loss of certain genes at this region is an important event in the development of myelodysplasia (summary by Shannon et al., 1989). Genetic Heterogeneity of Monosomy 7 Myelodysplastic and Leukemia Syndrome See also M7MLS2 (619041), caused by germline mutation in the SAMD9 gene (610457) on chromosome 7q21. [from OMIM]

Clinical features

From HPO
Acute myeloid leukemia
MedGen UID:
Concept ID:
Neoplastic Process
A clonal expansion of myeloid blasts in the bone marrow, blood or other tissues. The classification of acute myeloid leukemias (AMLs) encompasses four major categories: 1) AML with recurrent genetic abnormalities; 2) AML with multilineage dysplasia; 3) Therapy-related AML; 4) AML not otherwise specified. The required bone marrow or peripheral blood blast percentage for the diagnosis of AML is 20% (WHO classification)
MedGen UID:
Concept ID:
Congenital Abnormality
Clonal hematopoietic stem cell disorders characterized by dysplasia (ineffective production) in one or more hematopoietic cell lineages, leading to anemia and cytopenia.
MedGen UID:
Concept ID:
Disease or Syndrome
A reduction in the number of circulating thrombocytes.
Increased mean corpuscular volume
MedGen UID:
Concept ID:
Larger than normal size of erythrocytes.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

Recent clinical studies


Eggermann K, Meyer R, Begemann M, Dey D, Bültmann E, Kurth I, Korenke GC, Knopp C
Genes (Basel) 2022 Dec 14;13(12) doi: 10.3390/genes13122356. PMID: 36553623Free PMC Article

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