A liveborn case of 49,XXXY, + 18

Area of Science:

• Genetics
• Developmental Biology
• Pediatrics

Background:

• Trisomy 18 (Edwards syndrome) is a genetic disorder caused by the presence of all or part of a third copy of chromosome 18.
• Sex chromosome aneuploidies, such as Klinefelter syndrome (47,XXY) or Turner syndrome (45,X), involve abnormalities in the number of sex chromosomes.
• The co-occurrence of autosomal and sex chromosome aneuploidies is rare, particularly in liveborn infants.

Observation:

• A liveborn male infant presented with trisomy for both the X chromosome (47,XXY karyotype) and chromosome 18 (47,XY,+18 karyotype).
• The infant exhibited multiple congenital anomalies, with several features overlapping with those typically seen in trisomy 18.
• The proband survived for only 2 days post-delivery.

Findings:

• This case represents the first documented instance of a liveborn male infant with concurrent trisomy X and trisomy 18.
• The genetic analysis confirmed a mosaic or non-mosaic trisomy for both chromosomal abnormalities.
• Both parents were found to have normal karyotypes, suggesting the aneuploidy arose de novo during gametogenesis or early embryogenesis.

Implications:

• This case expands the known spectrum of chromosomal abnormalities compatible with live birth.
• Understanding the phenotypic impact of combined aneuploidies is crucial for genetic counseling and prenatal diagnosis.
• Further research is needed to elucidate the mechanisms leading to simultaneous autosomal and sex chromosome aneuploidies and their developmental consequences.