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Trisomy 12p and monosomy 4p: phenotype-genotype correlation
Daniela Gambel Benussi1, Paola Costa, Marcella Zollino
1S.C. Genetica Medica, IRCCS Burlo Garofolo, Trieste, Italy.
Insights
This study details a rare genetic condition involving partial 4p monosomy and 12p trisomy. The case helps refine understanding of the critical genetic regions influencing 12p trisomy syndrome phenotypes.
Area of Science:
- Human Genetics
- Clinical Cytogenetics
- Developmental Biology
Background:
- 4p Monosomy, known as Wolf-Hirschhorn syndrome (WHS), and 12p Trisomy syndrome are discussed, with WHS characterized by growth/mental retardation, hypotonia, seizures, and a 'Greek helmet' facial appearance.
- Phenotypic variability in 12p Trisomy syndrome is often linked to the extent of associated partial monosomies, highlighting the complexity of chromosomal abnormalities.
Observation:
- A clinical and molecular cytogenetic analysis was performed on a 4-year-old girl presenting with macrosomy, facial dysmorphisms, epilepsy, and intellectual disability.
- The patient was found to have an unbalanced translocation, t(4;12)(p16.3;p13.3), resulting in concurrent partial 4p monosomy and partial 12p trisomy.
Findings:
- The patient exhibited several phenotypic characteristics consistent with 12p Trisomy syndrome, suggesting a significant contribution from the duplicated 12p region.
- The molecular cytogenetic findings provide a detailed characterization of this rare unbalanced translocation, linking specific chromosomal segments to observed clinical features.
Implications:
- This case contributes to a more precise definition of the critical duplicated region on chromosome 12p responsible for the 12p Trisomy syndrome phenotype.
- Understanding such complex chromosomal rearrangements is crucial for accurate genetic diagnosis, counseling, and potential therapeutic strategies for affected individuals.
Abstract:
4p Monosomy and 12p trisomy have been discussed and redefined along with recently reviewed chromosomal syndromes. 12p Trisomy syndrome is characterized by normal or increased birth weight, developmental delay with early hypotonia, psychomotor delay, and typical facial appearance. Most likely, the observed phenotypic variability depends on the type and extent of the associated partial monosomy. Partial deletions of the short arm of one chromosome 4 cause the Wolf-Hirschhorn syndrome (WHS). Affected patients present Greek helmet face, growth and mental retardation, hypotonia, and seizures. The combination of these characteristics constitutes the phenotypic core of WHS. We present a clinical and molecular cytogenetic characterization of a 4-year old mentally retarded girl with macrosomy, facial dysmorphisms, and epilepsy, in whom an unbalanced t(4;12)(p16.3;p13.3) translocation was detected, giving rise to partial 4p monosomy and partial 12p trisomy. Because the patient shows most of the phenotypic characteristics of 12p trisomy, this case could contribute to a better definition of the duplicate critical region that determines the phenotype of the 12p trisomy syndrome.
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