A de novo pure 21q22.3 deletion in a 9-year-old boy with buried penis: a case report and literature review

21q deletion has been associated with a wide range of clinical signs, from very mild to severe phenotypes, and with the progress of genetic technology, more patients with this deletion are being diagnosed. This study reports on a 9-year-old boy with a terminal deletion of 4.5 Mb on chromosome 21 in the locus of chr21: 43531239-48119895 (GRCh37/hg19). Dark skin, a buried penis, small testes, dental caries, microcephaly, a low auricle, mental and intellectual retardation, balance disorder and pituitary and callosum dysplasia were observed. The results of a literature review and observation of similar abnormalities, including hypoplasia of corpus callosum, in two patients with non-overlapping deletion regions suggest that there are multiple gene loci regulating brain development on 21q. By comparing the overlapped deletion region in 21q22.3 cases of brain anomalies and/or gonadal dysgenesis, we concluded there were two overlapped microdeletion regions (chr21:43531239-43792093 and chr21:46625055-46884297) that may be related to brain and gonadal development. The same 16.49 Mb deletion of chr21:31578129-48119895 (GRCh37/hg19) was shared in 10 cases, and 24 cases shared the same 5.59 Mb deletion of chr21:4247813048119895 (GRCh37/hg19) in DECIPHER (Database of Chromasomal Imbalance and Phenotype in Humans using Ensembl Resources), suggesting these were two commonly deleted regions of pure partial 21q. Those patients with the same breakpoints had different phenotypes suggesting the heterogeneity of 21q deletion.