Chromosome 18, Tetrasomy 18p
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NORD is very grateful to Shashikant Kulkarni, PhD, Director of CytoGenomics and Molecular Pathology, Director of Clinical & Molecular Cytogenetics, Department of Pathology, Washington University School of Medicine, for assistance in the preparation of this report.
Synonyms of Chromosome 18, Tetrasomy 18p
- Tetrasomy, Short Arm of Chromosome 18
- No subdivisions found.
Chromosome 18, Tetrasomy 18p is a very rare chromosomal disorder in which the short arm of the 18th chromosome (18p) appears four times (tetrasomy) rather than twice in cells of the body. Individuals with a normal chromosomal make-up (karyotype) have two 18th chromosomes, both of which have a short arm ("18p") and a long arm ("18q"). However, in individuals with Chromosome 18, Tetrasomy 18p, four short arms (18ps) are present in cells of the body rather than the normal two.
The symptoms of Chromosome 18, Tetrasomy 18p may vary from case to case. Many affected individuals may have abnormalities of the head and facial (craniofacial) area; malformations of the spine, hands, and/or feet; neuromuscular abnormalities, such as increased muscle tone (hypertonia), increased reflex reactions (hyperreflexia), and difficulty coordinating movement; kidney (renal) malformations; and/or additional physical abnormalities. In addition, children and adults with Chromosome 18, Tetrasomy 18p often exhibit moderate to severe mental retardation, limitations in speech, and/or behavioral abnormalities. In most cases, Chromosome 18, Tetrasomy 18p is the result of a spontaneous (de novo) genetic change (mutation) early in embryonic development that occurs for unknown reasons (sporadic).
Chromosome 18, Tetrasomy 18p Resources
(Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder [e.g., mental retardation, craniofacial abnormalities, kidney defects, etc.].)
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