Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.


Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Chromosome 18p tetrasomy

Other Names for this Disease
  • Isochromosome 18p
  • Tetrasomy 18p
  • Tetrasomy chromosome 18p
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.


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.[1][2] 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).[1]
Last updated: 3/13/2009


  1. Chromosome 18, Tetrasomy 18p. National Organization for Rare Disorders (NORD). 2001; Accessed 3/13/2009.
  2. Tetrasomy 18p. Chromosome 18 Registry and Research Society. 2008; Accessed 3/13/2009.
Your Questions Answered
by the Genetic and Rare Diseases Information Center

Please contact us with your questions about Chromosome 18p tetrasomy. We will answer your question and update these pages with new resources and information.

Basic Information

  • The Chromosome 18 Registry & Research Society is an advocacy organization composed of parents of individuals with chromosome 18 abnormalities. Click on the link above to view their information page on tetrasomy 18p.
  • Genetics Home Reference (GHR) contains information on Chromosome 18p tetrasomy. This website is maintained by the National Library of Medicine.
  • The National Organization for Rare Disorders (NORD) is a federation of more than 130 nonprofit voluntary health organizations serving people with rare disorders. Click on the link to view information on this topic.

In Depth Information

  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Chromosome 18p tetrasomy. Click on the link to view a sample search on this topic.