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Unusual mosaic trisomy 13 through 13/13 translocation and monosomy 13 with a small ring
S M Jalal1, J A Martin, T R Benjamin
1Cytogenetics Laboratory, Mayo Clinic, Rochester, MN 55905.
Insights
This study reports the first case of de novo mosaicism involving a 13q13q translocation and a ring chromosome 13. The infant presented with severe dysmorphic features and congenital anomalies, surviving for three months.
Area of Science:
- Genetics
- Developmental Biology
- Clinical Medicine
Background:
- Mosaicism, a condition where an individual has two or more cell lines with different genetic makeup, can lead to complex phenotypes.
- Chromosomal abnormalities, particularly those involving chromosome 13, are associated with severe developmental disorders.
Observation:
- The study describes a rare case of de novo mosaicism (46,XX,t(13q13q)/46,XX,-13,+r(13)) in an infant.
- The two cell lines were observed at frequencies of 34% and 66%.
- The infant exhibited significant dysmorphic features including encephalocele, abnormal ears, iris coloboma, and underdeveloped kidneys.
Findings:
- The infant presented with multiple congenital anomalies and dysmorphic features, indicative of a severe genetic disorder.
- The presence of both a 13q13q translocation and a ring chromosome 13 in a mosaic pattern was identified.
- The ring chromosome 13 is hypothesized to be a secondary anomaly resulting from the 13q13q translocation.
Implications:
- This case highlights the phenotypic variability and severity associated with complex chromosomal mosaicism involving chromosome 13.
- Understanding the mechanisms of ring chromosome formation in the context of translocations is crucial for genetic counseling.
- Further research into mosaic chromosomal abnormalities can improve diagnostic approaches and management strategies for affected individuals.
Abstract:
Apparently the first patient with de novo mosaicism 46,XX,t(13q13q)/46,XX,-13,+r(13) is described. The two cell lines were present at a frequency of 34% and 66%, respectively. The infant survived for about three months. The prominent dysmorphic features were: birth-weight and head circumference below the 3rd centile, encephalocele, multiple skin tags of low set dysplastic ears, coloboma of the left iris, short upward slanting palpebral fissures, and prominent nasal root. An imperforate anus, recto-vaginal fistula, enlarged adrenals, missing/hypoplastic kidneys, and limb anomalies were also present. It is postulated that the ring is a secondary anomaly arising from the 13q13q translocation.