Paracentric inversions in man

Area of Science:

• Human Genetics
• Cytogenetics
• Reproductive Biology

Background:

• Paracentric inversions are chromosomal rearrangements that can impact reproductive outcomes.
• Previous studies have indicated potential risks associated with these inversions, but comprehensive data is limited.

Purpose of the Study:

• To analyze the incidence and consequences of paracentric inversions in a large patient cohort.
• To investigate the association between paracentric inversions and adverse reproductive outcomes, including congenital malformations and fetal loss.

Main Methods:

• Review of constitutional chromosome analyses from 51,000 patients (1970-1985).
• Identification of index patients with paracentric inversions.
• Analysis of offspring and parental phenotypes for associated abnormalities.

Main Results:

• 18 index patients with paracentric inversions were identified.
• A significant incidence (26%) of mental retardation and/or congenital malformations was observed in offspring of phenotypically normal carriers.
• High rates of early fetal loss were noted in carrier parents, potentially due to unbalanced gametes from meiotic crossing-over.

Conclusions:

• Paracentric inversions in parents, even if phenotypically normal, are associated with increased risks for offspring.
• Meiotic crossing-over within the inversion loop may lead to unbalanced gametes and subsequent developmental issues or fetal loss.
• Further investigation into non-disjunction tendencies in carriers is warranted.