The genetic basis of several diseases has been elucidated by rare cases involving large, cytogenetically visible deletions or translocations that identified specific chromosomal regions for further analysis.
The authors suggested that, based on the common clinical features in these individuals and several previously reported individuals with cytogenetically visible deletions of 2q32q33 [12]–[27], microdeletions of 2q32q33 constitute a distinct syndrome (OMIM 612313).
Several of the individuals previously reported with cytogenetically visible deletions of 2q32q33 have had dental abnormalities, including missing teeth, abnormally shaped teeth, malocclusion, and diastema [11], [14], [22], [23], [26], [28].
33 Visible deletions of every telomeric band have been identified.
Congenital anomaly register data showed the prevalence of microscopically visible deletions in the range of 0.3 to 2/10,000 births [ 18- 20].
The clinical phenotype appears to be more severely affected in cases with microscopically visible deletions, but not with larger submicroscopic deletions [ 29].
Rare pathological CNVs have also been identified, including cytogenetically visible deletions associated with spermatogenetic failure (Tiepolo and Zuffardi 1976) and anomalies of sex determination (Disteche et al. 1986) and three distinct cytogenetically undetectable deletions leading to spermatogenetic failure (Vogt et al. 1996), as well as insertions causing hearing impairment (Wang et al. 2013).
From the prevalence of microscopically visible deletions at birth (0.5 1.0 per 10 000) (Hamerton et al, 1975; Jacobs et al, 1992), we estimate that all or almost all cases born nationally in the early and middle 1990s were within our data set, but that there was underdiagnosis for earlier periods.
However, these studies were primarily designed to identify biallelic gene mutations by analyzing the residual non-deleted 5q31.2 allele using MDS samples, AML samples, or cell lines containing a cytogenetically visible 5q31.2 deletion, and they only examined 20 of the 28 5q31.2 genes [6], [7], [8], [9], [10].
