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Nuchal thickening in Jacobsen syndrome
S M McClelland1, A P Smith, N C Smith
1Department of Radiology, Aberdeen Royal Infirmary, UK.
Summary
A routine ultrasound detected nuchal thickening, which led to genetic testing. This revealed Jacobsen syndrome (del(11)(q23)) in a male fetus, confirmed by autopsy.
Area of Science:
- Prenatal diagnosis
- Medical genetics
- Fetal pathology
Background:
- Routine detailed ultrasound at 20 weeks' gestation is a standard prenatal screening tool.
- Nuchal thickening can be an indicator of various fetal abnormalities.
- Normal maternal serum alpha-fetoprotein and low Down's syndrome risk do not exclude other genetic conditions.
Observation:
- An apparently isolated finding of nuchal thickening was observed during a routine 20-week detailed ultrasound.
- Maternal alpha-fetoprotein levels were within the normal range.
- The calculated risk for Down's syndrome was low (1 in 6800).
Findings:
- Amniocentesis revealed a karyotype of 46,XY, del(11)(q23).
- This chromosomal abnormality is characteristic of Jacobsen syndrome.
- Fetal autopsy at 23 weeks confirmed the phenotype and internal abnormalities consistent with Jacobsen syndrome.
Implications:
- This case highlights the importance of further investigation even with seemingly isolated ultrasound findings and low risk for common aneuploidies.
- Jacobsen syndrome, though rare, should be considered in the differential diagnosis of nuchal thickening.
- Accurate prenatal diagnosis through genetic analysis is crucial for genetic counseling and management.