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Mosaicism for ring and isopseudodicentric chromosome 13
Insights
This study details a rare case of chromosome 13 mosaicism in an infant, specifically an isopseudodicentric/ring formation. This genetic anomaly explains the infant's multiple malformations due to chromosome 13 duplication-deficiency.
Area of Science:
- Cytogenetics
- Human Genetics
- Developmental Biology
Background:
- Routine cytogenetic evaluation is crucial for diagnosing genetic disorders in infants.
- Chromosome 13 abnormalities can lead to severe developmental issues and multiple malformations.
Observation:
- A three-month-old female infant presented with multiple congenital malformations.
- Initial cytogenetic analysis revealed mosaicism involving chromosome 13, specifically a dicentric/ring structure.
Findings:
- Further investigation identified the dicentric chromosome as an isopseudodicentric.
- The formation mechanism involves chromosome and chromatid breaks, bridging, breaking, and fusion, distinct from typical ring chromosome 13 formation.
- The infant's phenotype is consistent with a combined duplication-deficiency of chromosome 13.
Implications:
- This case highlights a rare mechanism of chromosome rearrangement in humans.
- Understanding isopseudodicentric/ring formation is vital for accurate genetic diagnosis and counseling.
- Phenotypic correlation in chromosomal mosaicism underscores the importance of detailed cytogenetic analysis.
Abstract:
A three-month-old female infant with multiple malformations was noted on routine cytogenetic evaluation to have dicentric/ring mosaicism of chromosome 13. Additional cytogenic investigations indicated that the dicentric could be further defined as an isopseudodicentric. Unlike the double chromosome break in the more common ring 13 cases, the mechanism for isopseudodicentric/ring generation is attributed to chromosome and chromatid breaks with subsequent bridging, breaking and fusion. The phenotypic features are those of a combined duplication-deficiency of chromosome 13.