[Genetics of partial trisomies. Trisomy 4p].

Area of Science:

• Human Genetics
• Clinical Genetics
• Teratology

Background:

• Trisomy 4p is a chromosomal disorder characterized by the duplication of genetic material on the short arm of chromosome 4.
• This condition presents with a range of phenotypes, influenced by the extent of the chromosomal duplication.
• Understanding genotype-phenotype correlations is crucial for genetic counseling and clinical management.

Observation:

• This study analyzed two cytogenetically distinct variants of trisomy 4p, including cases with and without proximal 4q involvement.
• Data were compiled from the Minsk Teratologic Center and a review of 64 international literature cases.
• Phenotypic similarity was mathematically evaluated based on intrapair, within-family, and interfamilial comparisons.

Findings:

• Phenotypic similarity is significantly greater in trisomy 4p patients with duplicated distal segments (4p15(16)----pter).
• As the size of the trisomic segment increases, the degree of phenotypic similarity among patients decreases.
• A significant excess of within-family similarity over interfamilial similarity was observed.

Implications:

• The findings highlight the critical role of the size and location of duplicated chromosomal segments in determining phenotypic expression in trisomy 4p.
• The greater intrafamilial similarity suggests a potential influence of shared genetic background (genofond) within families.
• This research contributes to a better understanding of trisomy 4p, aiding in more precise genetic prognostication and counseling.