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Down syndrome with XO/XX mosaicism
Acta Paediatrica Academiae Scientiarum Hungaricae
|January 1, 1979
Summary
A 2-month-old girl with Down syndrome (DS) exhibited mosaicism for trisomy 21. Despite the genetic findings, she showed no signs of infantile Turner syndrome (TS).
Area of Science:
- Genetics
- Pediatrics
- Developmental Biology
Background:
- Down syndrome (DS) is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.
- Mosaicism refers to the presence of two or more cell lines with different genetic makeup within an individual.
- Infantile Turner syndrome (TS) is a condition that affects females and results from a missing or partially missing X chromosome.
Observation:
- A 2-month-old female infant was diagnosed with Down syndrome.
- Genetic analysis revealed a mosaic karyotype: 47, XX, +21/46, X, +21.
- The infant presented without any clinical manifestations suggestive of infantile Turner syndrome.
Findings:
- The patient displayed a mix of cells, with some having an extra copy of chromosome 21 (trisomy 21) and others having a normal female karyotype with an additional X chromosome.
- The specific genetic makeup, 47, XX, +21/46, X, +21 mosaicism, indicates a complex chromosomal abnormality.
- Crucially, the absence of Turner syndrome symptoms in an infant with this specific mosaicism is a significant clinical observation.
Implications:
- This case highlights the variability in clinical presentation of chromosomal abnormalities, even with mosaicism.
- Understanding such genetic mosaics is crucial for accurate diagnosis and prognosis in pediatric genetics.
- Further research may elucidate the mechanisms underlying the lack of Turner syndrome features in the presence of X chromosome variations and trisomy 21 mosaicism.