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Partial trisomy 13q identified by sequential fluorescence in situ hybridization
V V Rao1, N J Carpenter, M Gucsavas
1H.A. Chapman Institute of Medical Genetics, Children's Medical Center, Tulsa, Oklahoma, USA.
Insights
A rare genetic condition, partial trisomy 13q, was identified in a 19-month-old boy due to a chromosome 1 and 13 translocation. This chromosomal abnormality led to multiple congenital anomalies, including omphalocele and heart defects.
Area of Science:
- Genetics
- Pediatrics
- Cytogenetics
Background:
- Trisomy 13 (Down syndrome) is a well-known chromosomal disorder.
- Partial trisomy 13q, where only a segment of the 13th chromosome's long arm is duplicated, is less common.
- Accurate diagnosis of chromosomal abnormalities is crucial for understanding associated phenotypes.
Observation:
- A 19-month-old boy presented with omphalocele, malrotation, microcephaly, micrognathia, low-set ears, rocker-bottom feet, and congenital heart disease.
- Karyotypic analysis revealed an unbalanced karyotype (46,XY,-1,+der(1)) suggesting an extra chromosome segment.
- Conventional cytogenetics failed to identify the origin of the extra material on chromosome 1q.
Findings:
- Fluorescence in situ hybridization (FISH) confirmed the extra material on chromosome 1q was the terminal long arm of chromosome 13.
- The infant was diagnosed with partial trisomy 13q (q32-qter).
- The abnormality resulted from a probable balanced translocation between chromosomes 1 and 13 in the parents.
Implications:
- This case highlights the utility of advanced techniques like FISH in diagnosing complex chromosomal rearrangements.
- Understanding partial trisomy 13q is essential for genetic counseling and managing associated congenital anomalies.
- Further research into the specific breakpoints and their phenotypic correlations in partial trisomy 13q is warranted.
Abstract:
We report on a 19-month-old boy with partial trisomy 13q resulting from a probable balanced translocation involving chromosomes 1 and 13. The infant presented with omphalocele, malrotation, microcephaly with overriding skull bones, micrognathia, apparently low-set ears, rocker-bottom feet, and congenital heart disease, findings suggestive of trisomy 13. Karyotypic studies from peripheral blood lymphocytes documented an unbalanced karyotype 46,XY,-1,+der(1). The mother's chromosomes were normal, and the father was not available. Conventional cytogenetic techniques were unable to identify the extra material on the terminal 1q. Using fluorescence in situ hybridization (FISH) on the GTL-banded metaphases, the extra material on 1q was identified as the terminal long arm of 13, thus resulting in partial trisomy 13 (q32-qter).