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Trisomy-12p syndrome: Family study and prenatal diagnosis
Insights
Trisomy-12p, a genetic condition, presents a distinct syndrome in infants. This occurs due to a parent
Area of Science:
- Human Genetics
- Clinical Cytogenetics
- Pediatric Medicine
Background:
- Genetic counseling is crucial for families with balanced translocations.
- Unexplained infant phenotypes necessitate thorough cytogenetic investigation.
Observation:
- An infant presented with unusual facies, abdominal distension, and hypotonia.
- Initial karyotyping suggested trisomy-21, inconsistent with clinical presentation.
Findings:
- Maternal balanced translocation t(12;14)(p11;q11) was identified.
- The infant inherited the translocation, resulting in partial trisomy 12p.
Implications:
- Trisomy-12p is confirmed as a recognizable genetic syndrome.
- Reciprocal translocations carry a significant risk (50%) of abnormal offspring.
- Prenatal diagnosis via amniocentesis is recommended for at-risk pregnancies.
Abstract:
A young unrelated Indian couple produced a baby who had an unusual facies, marked abdominal distension and muscular hypotonia. At 8 weeks cytogenetic investigation revealed what appeared to be trisomy-21. Because this did not agree with the clinical signs the parents were tested and the mother was found to have a balanced translocation between chromosomes 12 and 14; her karyotype was 46,XX,rcp(12; 14)(p11; q11) and it was realized that her son had inherited her translocation chromosome involving the short arms of chromosomes 12 and 14. He thus had trisomy-12p. The present case and 10 others reported in the literature confirm that trisomy-12p produces a recognizable syndrome. Parents carrying a balanced translocation have a 50:50 risk of producing an abnormal infant at every pregnancy because both the trisomic and monosomic conditions may be viable. Amniocentesis for fetal karyotyping must be recommended to the couples concerned.