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[Tetrasomy 9p]
Summary
Tetrasomy 9p, a rare genetic condition involving an extra copy of chromosome 9p, presents with severe malformations. This case highlights the maternal origin of the extra chromosome and its distinct, more severe phenotype compared to trisomy 9p.
Area of Science:
- Genetics
- Cytogenetics
- Developmental Biology
Background:
- Tetrasomy for the short arm of chromosome 9 (9p) is an extremely rare chromosomal abnormality.
- Previous literature reports only ten additional cases of this condition.
Observation:
- A newborn male presented with multiple congenital malformations and an extra chromosome.
- Cytogenetic analysis of peripheral blood lymphocytes revealed tetrasomy 9p: 47,XY, + t(9;9)(pter----q13::p11----pter).
- C-banding confirmed the maternal origin of the extra chromosome.
Findings:
- The patient exhibited tetrasomy 9p, characterized by an additional copy of the short arm of chromosome 9.
- The phenotypic presentation was similar to trisomy 9p but included more severe additional malformations.
- The extra chromosome was identified as a result of a translocation, t(9;9)(pter----q13::p11----pter).
Implications:
- This case expands the understanding of tetrasomy 9p, a condition with limited documented instances.
- The findings suggest that tetrasomy 9p may lead to a more severe spectrum of developmental abnormalities than previously recognized.
- Further research into the genetic mechanisms and phenotypic variability of tetrasomy 9p is warranted.