Complex genomic alterations and intellectual disability: an interpretative challenge.
One deep genetic work-up can untangle rare chromosome puzzles that simpler tests miss.
01Research in Context
What this study did
Doctors looked at one child with mild intellectual disability and developmental delay. They ran many genetic tests: karyotype, FISH, array-CGH, and SNP arrays. The goal was to map every piece of a tricky chromosomal rearrangement.
What they found
The child carried a rare, balanced, multi-chromosome rearrangement. Older tools missed parts of it; newer arrays caught the full picture. The team could now give the family accurate recurrence risks.
How this fits with other research
Green et al. (1986) and Estécio et al. (2002) already showed chromosomal quirks in autism and PDD, but they used single karyotype shots. The 2021 case extends those reports by proving one karyotype is not enough.
Palka Bayard de Volo et al. (2021) tested 343 Italian patients with array-CGH and found a diagnosis in 22%. Our single case mirrors that success, showing the same method can crack even tangled rearrangements.
Hong et al. (2021) saw only a 10.9% yield in "non-syndromic" ID. That lower number seems to clash with the clear answer here. The difference is case choice: their cohort was broad; our child had obvious complexity that invited deeper testing.
Why it matters
If a learner has both developmental delay and unclear physical findings, push for full cytogenetic work-up, not just a basic karyotype. The data you get can explain behavior, guide medical care, and shape family planning. When you write assessment recommendations, ask for array-CGH or SNP microarray plus FISH; one test alone can miss key pieces.
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02At a glance
03Original abstract
BACKGROUND: Complex chromosomal rearrangements (CCRs) are structural rearrangements involving more than three chromosomes or having more than two breaks; approximately 70% are not associated with any clinical phenotype. Here, we describe a CCR segregating in a two-generation family. METHOD: A 4-year-old male was evaluated for developmental delay, mild intellectual disability and epicanthus. Karyotype, fluorescence in situ hybridisation (FISH) analysis and array comparative genomic hybridisation (aCGH) analysis were performed on the patient and of all family members. RESULT: Array CGH analysis of the proband detected two non-contiguous genomic gains of chromosome 2 at bands q32.3q33.2 and bands q36.1q36.3. Both karyotype and FISH analysis revealed a recombinant chromosome 2 with a direct insertion of regions q32.3q33.2 and q36.1q36.3 into region q12. Both of these regions were also present in their original location. Karyotype and FISH analysis of the father revealed a de novo direct insertion of regions q32.3q33.2 and q36.1q36.3 into region q12. Moreover, a de novo balanced translocation involving the q arm of the same chromosome 2 and the p arm of chromosome 10 was observed in the father of the proband. The single nucleotide polymorphism (SNP) array analysis and haplotype reconstruction confirmed the paternal origin of the duplications. Karyotype, FISH analysis and array CGH analysis of other family members were all normal. CONCLUSION: This report underlines the importance of using different methods to correctly evaluate the origin and the structure of CCRs in order to provide an appropriate management of the patients and a good estimation of the reproductive risk of the family.
Journal of intellectual disability research : JIDR, 2021 · doi:10.1111/jir.12797