Complete monosomy 21 confirmed by FISH and array‐CGH

Monosomy 21 Seen in Live Born Is Unlikely to Represent True Monosomy 21: A Case Report and Review of the Literature

“…The high level of double rings in some tissues in our patient may have contributed to the patient's provisional clinical diagnosis of Down syndrome when the ring chromosome 21 is larger in size (i.e., less genomic imbalance due to monosomy) and demonstrates duplication (such as double rings) that includes the DSCR; the patient is more likely to have characteristics consistent with Down syndrome [ 28 ]. However, the phenotype of patients previously reported as full monosomy 21 appears to share features common to Down syndrome, such as heart defects, clinodactyly, simian crease, and upslanting palpebral fissures [ 1 – 3 , 5 , 8 – 10 , 12 , 13 , 23 ]. As discussed, however, the presence of an additional cell line has not been excluded in many of these previously reported cases.…”

High‐level mosaic monosomy 21 in a 13‐year‐old girl: Case report and review of the literature

“…To the best of our knowledge, only nine cases of full monosomy 21 have been reported to date since the 1980s, when more modern techniques became available to confirm such a diagnosis. All patients with full monosomy 21 died within a few days after birth (Cheng et al, 2006; Kulharya et al, 2012; Mori et al, 2004; Pelissier et al, 1987; Shah et al, 2010) or gestation ended in spontaneous miscarriage (Chang et al, 2001; Joosten et al, 1997; Ma et al, 2001) or elective termination of pregnancy (Manolakos et al, 2010), which is evidence that full monosomy 21 is incompatible with life. There have been cases previously diagnosed as non‐mosaic full monosomy 21, which were later reclassified as partial deletions because of molecular testing (Burgess et al, 2014).…”