Phenotype comparison among individuals with developmental delay/intellectual disability with or without genomic imbalances.
Clinical features alone can’t rule out genomic imbalances—order CMA for every DD/ID case.
01Research in Context
What this study did
Doctors looked at 137 people with developmental delay or intellectual disability. Half had known chromosome deletions or duplications. The other half had normal lab tests.
The team scored every person on 25 features like head size, seizures, and behavior problems. They wanted to see if the chromosome group looked different from the no-chromosome group.
What they found
Both groups looked the same. Same number of unusual faces, same seizure rates, same behavior issues.
Only one clue helped: people with chromosome problems had more first-degree relatives with learning issues. Everything else was a coin toss.
How this fits with other research
Cordova et al. (1993) already showed we underestimate what people with ID can do. C et al. now show we also underestimate how often genes drive the delay.
Cerutti et al. (2004) proved simple screeners catch psychiatric comorbidity in India. C et al. push the screen one step earlier: catch the gene change before you chase the mental-health fallout.
Together the papers say: stop guessing, start testing. Clinical eyes miss both hidden skills and hidden chromosomes.
Why it matters
If you wait for the "classic genetic look" you will miss cases. Order chromosomal microarray on every new DD/ID client. The test explains the delay, predicts medical risks, and gives families the why they keep asking for. One blood draw, one clear answer, better lifelong planning.
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02At a glance
03Original abstract
BACKGROUND: The chromosomal microarray analysis (CMA) is recommended as a first-tier test for individuals with developmental delay (DD)/intellectual disability (ID) and/or multiple congenital anomalies. However, owing to high costs, this technique is not widely performed for diagnostic purposes in several countries. The aim of this study was to identify clinical features that could favour the hypothesis of genomic imbalances (GIs) in individuals with DD/ID. METHODS: The sample consisted of 63 individuals, and all of them underwent a detailed evaluation by a clinical geneticist and were investigated by the CMA. They were divided into two groups. Group A composed of 20 individuals with pathogenic copy number variants (CNVs); and group B composed of 43 individuals with normal CMA results or variants of uncertain clinical significance (VUS). RESULTS: Pathogenic GIs were found in 20 cases (32%), including 11 individuals with an abnormal karyotype, VUS was found in five individuals (8%) and the results were normal in 38 individuals (60%). Major anomalies were found in 15/20 (75%) individuals in group A against 35/43 (81%) in group B. Dysmorphisms (≥5) were found in 17/20 (85%) in group A and 41/43 (95%) in group B. The most frequent major anomalies detected in group A were congenital heart disease, epilepsy and renal malformation; and in group B, they were malformations of central nervous system, congenital heart disease, microcephaly, epilepsy and hearing impairment. There was no significant statistical difference among the frequencies in groups A and B. CONCLUSIONS: Evidences point that every individual with DD/ID, with no specific clinical suspicion, should have screening for GIs as a first-tier test, regardless of the presence or absence of additional major anomalies or dysmorphisms. Future studies with a similar design would be helpful, especially in countries where the access to new technologies is still limited.
Journal of intellectual disability research : JIDR, 2019 · doi:10.1111/jir.12615