A rare genetic chromosomal anomaly syndrome resulting from a partial deletion of the long arm of chromosome 21. The disease has characteristics of pre and post-natal growth delay, short stature, intellectual disability, developmental delay with severe language impairment, thrombocytopenia and craniofacial dysmorphism which may include microcephaly, downslanted palpebral fissures, low-set ears, broad nose, thin upper vermillion and downturned corners of the mouth. Brain MRI abnormalities (such as agenesis of the corpus callosum) behavioural problems and seizures may be associated. [from
SNOMEDCT_US]