Cryptic chromosomal rearrangements in children with idiopathic mental retardation in the czech population
Abstract
Chromosomal aberrations are the most commonly known cause of mental retardation. Standard cytogenetic banding techniques hold resolution limits of 5 - 8 Mb, and thus are not powerful enough to detect chromosomal rearrangements below 5 Mb in size.
It is for this reason these types are referred to as "cryptic" rearrangements. Cryptic rearrangements were scanned using the multiplex ligation probe amplification method in a cohort of 64 probands with mental retardation or developmental delays in combination with at least one of the following symptoms: hypotonia after birth, congenital anomalies, or face dysmorphisms; but without a positive cytogenetic finding.
The study contributes to the knowledge of microdeletion syndromes and helps disclose their natural phenotypic variability. In total, 10 positives (16 %) were detected, particularly 3 duplications and 6 different deletions, 1 of these in 2 probands.
Besides the well-characterized syndromes, less-often described rearrangements with ambiguous phenotype associations were also detected. Some rearrangements, particularly duplications, are associated with vague phenotypes; and their frequency could be underestimated.