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Double mosaic aneuploidy: 45,X/47,XY,+8 in a male infant
B Schofield1, A Babu, D Punales-Morejon
1Division of Medical Genetics, Beth Israel Medical Center, New York, New York 10003.
Insights
This study details a rare case of mosaic trisomy 8 syndrome in a 13-month-old boy, presenting unique genital abnormalities and kidney issues. The findings highlight complex chromosomal mosaicism and its potential developmental impact.
Area of Science:
- Genetics
- Developmental Biology
- Pediatric Urology
Background:
- Mosaic trisomy 8 syndrome is a rare chromosomal disorder characterized by the presence of both normal and trisomic (three copies) chromosome 8 cell lines.
- This condition can lead to a wide spectrum of developmental abnormalities, varying in severity based on the proportion and distribution of trisomic cells.
Observation:
- A 13-month-old male presented with features of mosaic trisomy 8 syndrome, including partial penoscrotal transposition, a retractile left testis, and an absent right testis.
- Imaging revealed a bladder utriculum abnormality and bilateral hydronephrosis secondary to vesicoureteral reflux.
- Karyotyping demonstrated mosaicism (45,X/47,XY,+8) in peripheral blood, with varying cell line distributions in skin fibroblasts, left testicle, utriculum, and vas deferens tissue.
Findings:
- The patient exhibited complex chromosomal mosaicism with distinct cell line compositions across different tissues.
- Surgical specimens confirmed the presence of both 45,X and 47,XY,+8 cell lines in the left testicle and utriculum, with only the 45,X line detected in the vas deferens.
- This specific pattern of mosaicism, particularly involving sex chromosomes and chromosome 8, is previously unreported.
Implications:
- The findings suggest a potential novel mechanism for mosaicism origin, possibly involving an abnormal zygote with subsequent chromosome loss.
- Understanding the tissue-specific distribution of chromosomal abnormalities is crucial for diagnosing and managing complex genetic syndromes.
- This case underscores the importance of comprehensive genetic analysis in patients with congenital anomalies and ambiguous genitalia.
Abstract:
We report on a 13-month-old boy with abnormalities consistent with mosaic trisomy 8 syndrome and male genitalia with partial penoscrotal transposition without hypospadias, a retractile left testis in inguinal canal, and an absent right testis. A voiding cystourethrogram showed an outpouching close to the lower right side of the bladder (utriculum) and bilateral hydronephrosis secondary to vesicoureteral reflux. Peripheral blood karyotype was 45,X/47,XY,+8. The karyotype of cultured skin fibroblasts was 47,XY,+8 with no 45,X cells detected among 20 cells counted. Tissues removed during surgery documented a 45,X/47,XY,+8 complement in the left testicle and utriculum, but only a 45,X line among 20 cells counted from vas deferens tissue. A possible mechanism for the origin of this previously unreported mosaicism might be an abnormal zygote with a 47,XY,+8 complement with subsequent simultaneous loss of chromosome Y and 8 in a cell at a very early embryonic stage.