A 45,X male with a Yp/18 translocation

Area of Science:

• Human Genetics
• Molecular Cytogenetics
• Reproductive Biology

Background:

• Investigating the genetic basis of sex determination in individuals with atypical chromosomal complements.
• Examining the role of Y chromosome material in male development.
• Understanding the mechanisms behind sex chromosome abnormalities and their phenotypic consequences.

Observation:

• A 45,X male patient was analyzed for Y-specific DNA.
• Positive hybridization signals for Yp fragments were detected.
• In situ hybridization localized Yp sequences to chromosome 18p, indicating a Y/18 translocation.

Findings:

• The Y/18 translocation involved the entire Yp region, including the Y centromere, replacing a segment of 18p.
• The translocated chromosome was functionally monocentric, with the chromosome 18 centromere being active.
• Gene dosage studies confirmed a deletion at 18p11.3, consistent with the 18p-syndrome.
• The patient exhibited clinical signs characteristic of the 18p-syndrome.

Implications:

• XO males typically have a maternally inherited X chromosome and maleness derived from a de novo Y/autosome translocation from the father.
• Y/autosome translocations can lead to autosomal deficiencies, potentially causing congenital malformations.
• This case highlights the complex genetic mechanisms underlying sex development and the phenotypic impact of chromosomal rearrangements.