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Balanced double complex translocations [46,XX,t(1p;6p;7p;3q;11p)(11q;22p;21q)] in an infant with multiple congenital
Insights
This study details a rare case of de novo double complex translocations in an infant, involving a record eight breakpoints. This genetic anomaly is associated with a severe multiple congenital anomalies syndrome.
Area of Science:
- Human Genetics
- Cytogenetics
- Pediatric Medicine
Background:
- Complex chromosome rearrangements (CCRs) are rare structural variations.
- De novo CCRs present diagnostic challenges and can lead to severe phenotypes.
- Understanding the breakpoints in CCRs is crucial for genetic counseling and prognosis.
Observation:
- A 1-month-old female infant presented with a de novo balanced double complex translocation [46,XX,t(1p;6p;7p;3q;11p) (11q;22p;21q)].
- The infant exhibited a multiple congenital anomalies syndrome, including microcephaly, corneal staphyloma, and limb abnormalities (hypoplastic thumbs, ectrodactyly, brachydactyly, syndactyly).
- This case involves eight distinct breakpoints (1p22, 3q27, 6p21, 7p15, 11p15, 11q11, 21q11, 22p11), the highest number reported in human CCRs.
Findings:
- The identified breakpoints are not associated with known fragile sites.
- The complex chromosomal rearrangement appears to have occurred spontaneously (de novo) in this patient.
- The extreme complexity of the translocation, with eight breakpoints, is unprecedented in human CCRs.
Implications:
- This case expands the known spectrum of complex chromosome rearrangements and their associated phenotypes.
- Detailed characterization of such rearrangements aids in understanding gene disruption and dosage effects.
- Further research into the mechanisms of de novo CCR formation is warranted.
Abstract:
We describe a 1-month-old female infant with balanced double complex translocations [46,XX,t(1p;6p;7p;3q;11p) (11q;22p;21q)]. She had a multiple congenital anomalies syndrome of microcephaly, unilateral corneal staphyloma, hypoplastic thumbs, ectrodactyly of the right foot, brachydactyly of the left third toe, and syndactyly between the left fourth and the fifth toes. The complex chromosome rearrangements of the patient involve 8 breakpoints, the greatest number of breakpoints in complex chromosome rearrangements of humans known to us. The 8 breakpoints are 1p22, 3q27, 6p21, 7p15, 11p15, 11q11, 21q11, and 22p11. These are not related to any confirmed fragile sites. These double complex translocations seemed to have occurred de novo.