What causes Tetrasomy 18p?
Causes. Tetrasomy 18p results from the presence of an abnormal extra chromosome , called an isochromosome 18p, in each cell. An isochromosome is a chromosome with two identical arms. Normal chromosomes have one long (q) arm and one short (p) arm, but isochromosomes have either two q arms or two p arms.
How common is Tetrasomy 18p?
Affected Populations Chromosome 18, Tetrasomy 18p is a very rare chromosomal disorder that appears to affect males and females equally. Approximately 40 cases have been reported in the medical literature.
What causes isochromosome?
An isochromosome is created when the centromere is divided transversely, or perpendicular to the long axis of the chromosome. The division is usually not occurring in the centromere itself, but in an area surrounding the centromere, also known as a pericentric region.
Can babies with trisomy 18 survive?
Fifty per cent of babies born with trisomy 18 survive beyond their first six to nine days. About 12% of babies born with trisomy 18 survive the first year of life. It is difficult to predict the life expectancy of a baby with trisomy 18 if the baby does not have any immediate life-threatening problems.
What is isochromosome 18p?
DISCUSSION Tetrasomy 18p is a structural chromosomal anomaly characterized by mental retardation, microcephaly, craniofacial anomalies, skeletal findings and occasionally renal and cardiac malformations. The isochromosome 18p i(18p) observed for our patient is monocentric, as demonstrated using centromere-specific FISH probes for chromosome 18.
What is tetrasomy 18p (18p syndrome)?
Background: Tetrasomy 18p is a very rare chromosomal disorder and is the result of a spontaneous mutation early in embryonic development in most of the cases.
What is chromosome 18p deletion?
Summary Summary. Chromosome 18p deletion is a chromosome abnormality that occurs when there is a missing (deleted) copy of genetic material on the short arm (p) of chromosome 18.
What does 18p mean in medical terms?
ABSTRACT. Background: Tetrasomy 18p is a very rare chromosomal disorder and is the result of a spontaneous mutation early in embryonic development in most of the cases. This condition is characterised by the presence of a supernumerary 18p isochromosome (i(18p)) in all or some cells of the affected individual.