How might a balanced chromosomal translocation lead to a spectrum of intellectual disabilities in newborns?

Intellectual disability (ID) consists of a broad range of disorders characterized by low general intellectual functioning (IQ below 70). ID etiologic causes are heterogeneous, ranging from environmental to chromosomal and monogenic conditions. Although many autosomal genes responsible for ID are expected, but only a small number of these have been identified and up to now most progress has been made in the area of X-linked translocation ID; but many autosomal chromosome genes play a crucial role in the development of a central nervous system. Any change which lead to lose or reduce the function or change the expression of them; high or low, even have a damaging effect on the functional protein might lead to different phenotype like developmental delay, growth retardation or intellectual disabilities.

In this paper, we discuss the importance of balanced chromosomal translocations in the etiologic cause of newborn intellectual disabilities. Balanced translocation is the result of breaking off two chromosomes and reattached in a way that the sections of two chromosomes have switched places. These rearrangements are found as de novo events in 1/2,000 live births and give rise to some congenital anomalies which is the product of submicroscopic deletions, duplications, inversion or disruption, activation, or inactivation of a gene or different genes located at or near the breakpoints in the basepair level. These apparently balanced translocations due to positional effect lead to occur abnormal phenotype. In conclusion, Cryptic genomic imbalances cause mentality are very rare condition but new technologies like NGS long-read genome sequencing could detect rapid breakpoint effects on live birth healthy and discover a new way for prenatal diagnosis.