Monosomy 7 in myeloid malignancies: parental origin and monitoring by real-time quantitative PCR.

Monosomy 7 is one of the most frequent chromosome changes observed in patients with myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML), and it may also be found superimposed to the Philadelphia chromosome in chronic myelocytic leukaemia (CML) in accelerated or blastic phase. It is even more common in secondary MDS/AML, and is associated with a variety of Mendelian and non-Mendelian predisposing disorders or in the so-called monosomy-7 families, where it recurs in subjects developing MDS/AML. Also partial monosomy 7 due to structural rearrangements (which thus has a different mechanism of origin as compared to monosomy, that is chromosome breakage vs non-disjunction) is frequently found in association with all the disorders mentioned above, but a single common region of deletion has not yet been identified. Familial cases indicated as unlikely the action of an oncosuppressor gene in the pathogenesis of MDS/AML associated with monosomy 7, and its role is thought to be mediated by gene dosage effects, recently investigated by microarray analysis. The presence of monosomy 7 portends a poor clinical outcome, both in MDS and in AML, and hence the clinical relevance of accurate monitoring of the abnormal clone during the course of the disease. We present here data concerning the methods to monitor the consistency of the monosomic clone and the parental origin of the chromosome 7 loss.