Saturday 30 October 2010
Partial monosomy 21 has been reported, but the phenotypes described are variable with location and size of the deletion.
2 patients with a partially overlapping microdeletion of 21q22 had a striking phenotypic resemblance. They both presented with severe psychomotor delay, behavioral problems, no speech, microcephaly, feeding problems with frequent regurgitation, idiopathic thrombocytopenia, obesity, deep set eyes, down turned corners of the mouth, dysplastic ears, and small chin. Brain MRI showed cerebral atrophy mostly evident in frontal and temporal lobes, widened ventricles and thin corpus callosum in both cases, and in one patient evidence of a migration disorder. A patient also presented with epilepsy and a ventricular septum defect. Another patient had a unilateral Peters anomaly. These patients present with a recognizable phenotype specific for this 21q22.1-q22.2 locus.
Microarray analysis showed a partially overlapping microdeletion spanning about 2.5 Mb in the 21q22.1-q22.2 region including the DYRK1A gene and excluding RUNX1.
Distinctive Phenotypic Abnormalities Associated with Submicroscopic 21q22 Deletion Including DYRK1A. Oegema R, de Klein A, Verkerk AJ, Schot R, Dumee B, Douben H, Eussen B, Dubbel L, Poddighe PJ, van der Laar I, Dobyns WB, van der Spek PJ, Lequin MH, de Coo IF, de Wit MC, Wessels MW, Mancini GM. Mol Syndromol. 2010 Sep;1(3):113-120. PMID: 21031080