Chromosome 18, Tetrasomy 18p
Tetrasomy 18p, Chromosome 18p tetrasomy
Type of disease: Rare conditions
Tetrasomy 18p is a chromosomal disorder in which the short arm of the 18th chromosome (18p) appears four times (tetrasomy) rather than the normal two times in cells of the body. The symptoms of tetrasomy 18p vary from case to case but may include craniofacial abnormalities; malformations of the spine, hands, or feet; neuromuscular abnormalities; kidney malformations; moderate to severe mental retardation; limitations in speech; and/or behavioral abnormalities. In most cases, tetrasomy 18p is the result of a spontaneous (de novo) genetic change (mutation) early in embryonic development that occurs for unknown reasons (sporadic). Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.