Can NIPT predict Common imprinting disorders
| Disorder | Imprinted Region / Mechanism | Can Routine NIPT Predict It? | Important Limitation |
|---|---|---|---|
| Prader-Willi syndrome (PWS) | 15q11-q13 paternal expression loss | ⚠️ Sometimes | Large paternal deletion may be detected by CNV-NIPT; UPD and imprinting defects generally missed |
| Angelman syndrome (AS) | 15q11-q13 maternal expression loss | ⚠️ Sometimes | Same limitation; methylation/UPD cannot be reliably assessed |
| Beckwith-Wiedemann syndrome (BWS) | 11p15 imprinting abnormalities | ❌ Usually no | Many cases are methylation defects, paternal UPD, CNV, or CDKN1C variants |
| Silver-Russell syndrome (SRS) | 11p15 or 7p12 imprinting abnormalities | ❌ Usually no | Predominantly methylation/UPD abnormalities |
| Temple syndrome | 14q32 maternal UPD / imprinting | ❌ Usually no | UPD/imprinting defects generally invisible to standard NIPT |
| Kagami-Ogata syndrome | 14q32 paternal UPD / imprinting | ❌ Usually no | Same |
| Transient neonatal diabetes mellitus | 6q24 imprinting | ❌ Usually no | Methylation/UPD/paternal duplication mechanisms |
| Maternal UPD 14 / paternal UPD 14 | 14q32 | ❌ | Requires UPD/imprinting testing |
| Maternally inherited diabetes and deafness | mtDNA, not classic genomic imprinting | ❌ | Standard NIPT does not screen for this |
Routine NIPT is primarily looking at DNA dosage.
DNA dosage → DNA sequence → parental origin → methylation/imprinting
Could a more advanced NIPT detect imprinting disorders?
1. SNP-based NIPT
Instead of simply counting chromosome fragments, SNP-based NIPT can analyze allelic inheritance.
This potentially allows detection of:
• parental origin
• some UPD
• triploidy
• certain inherited variants.
Therefore, theoretically, it is much more useful for imprinting disorders than purely counting-based NIPT.
2. Methylation-based NIPT
Imprinting disorders are fundamentally disorders of differential DNA methylation.
BWS
11p15:
• IC1 methylation abnormality
• IC2 methylation abnormality
SRS
• 11p15 hypomethylation
• sometimes 7p12 UPD
Therefore, a cell-free DNA assay capable of reliably determining fetal-specific methylation patterns could theoretically screen directly for these conditions.
The difficulty is that maternal plasma contains predominantly maternal cfDNA, with only a fraction being fetal/placental.
So, the assay must distinguish: maternal methylation signal + placental/fetal methylation signal.
The placenta introduces another problem
NIPT is essentially a placental DNA test, not a direct fetal blood/tissue test.
That matters enormously for imprinting disorders because: placental mosaicism + imprinting abnormalities + fetal mosaicism can be discordant.
This can be especially relevant in:
• BWS
• confined placental mosaicism
• UPD
• trisomy rescue
• placental mosaicism involving chromosome 11 or 15.
A trisomy-rescue mechanism can produce: placental/fetal trisomy → rescue → UPD
The final fetus may have normal chromosome dosage but abnormal parental origin.
Where NIPT is actually useful
Level 1: Directly useful - Large deletions/duplications involving an imprinted region.
Example:
15q11-q13 deletion → possible PWS/Angelman
NIPT may detect the CNV.
Level 2: Indirectly useful - NIPT detects an abnormality that raises suspicion for an imprinting mechanism.
For example:
trisomy 15 / chromosome 15 abnormality
could trigger consideration of:
• UPD 15
• PWS
• Angelman syndrome.
Similarly, abnormalities involving chromosome 11 could occasionally prompt consideration of 11p15-related disease.
Level 3: Poorly detected
Pure:
• UPD
• methylation defect
• imprinting-center defect
• small pathogenic variant
The key concept
NIPT can detect some of the genomic architecture associated with imprinting disorders, but it generally cannot detect the imprint itself.
Deletion can sometimes be seen.
Duplication can sometimes be seen.
UPD is usually not seen.
Abnormal methylation is usually not seen.
Imprinting-center defects are usually not seen.