3q29 microduplication syndrome (also known as 3q29 duplication syndrome) is a condition that results from the copying (duplication) of a small piece of chromosome 3 in each cell. The duplication occurs on the long (q) arm of the chromosome at a position designated q29.

The features associated with 3q29 microduplication syndrome vary widely. Some individuals with this chromosomal change have very mild or no related signs and symptoms, and the duplication is discovered because they undergo genetic testing only after a family member is diagnosed. Other people with a 3q29 microduplication have delayed development (particularly speech delay) and intellectual disability or learning difficulties. Although most affected individuals have no major birth defects, eye abnormalities, heart defects, and an unusually small head (microcephaly) can occur. 3q29 microduplication syndrome may increase the likelihood of being overweight or having obesity, although it is hard to determine whether these weight issues are caused by the duplication.

3q29 microduplication syndrome appears to be very rare. Fewer than 30 affected individuals have been described in the medical literature.

Most people with 3q29 microduplication syndrome have an extra copy of about 1.6 million DNA building blocks (base pairs), also written as 1.6 megabases (Mb), at position q29 on chromosome 3. However, the duplication can vary in size. It affects one of the two copies of chromosome 3 in each cell.

The segment that gets duplicated is surrounded by short, repeated sequences of DNA that make it prone to rearrangement during cell division. The rearrangement can lead to missing or extra copies of DNA at 3q29. (A missing copy of this segment causes another condition called 3q29 microdeletion syndrome.)

The chromosome segment most commonly duplicated in people with 3q29 microduplication syndrome contains about 20 genes. Some of these genes are thought to be involved in brain and eye development. However, it is unknown which specific genes, when abnormally copied, are related to the varied signs and symptoms of 3q29 microduplication syndrome. It is also unclear why some people with a duplication at 3q29 have no associated health problems. It is possible that genetic changes outside the 3q29 region can influence the features of this condition.

Genetic Testing Information

• Genetic Testing Registry: Chromosome 3q29 microduplication syndrome

Genetic and Rare Diseases Information Center

• 3q29 microduplication syndrome

Patient Support and Advocacy Resources

• National Organization for Rare Disorders (NORD)

Catalog of Genes and Diseases from OMIM

• CHROMOSOME 3q29 DUPLICATION SYNDROME

Scientific Articles on PubMed

• PubMed

• Ballif BC, Theisen A, Coppinger J, Gowans GC, Hersh JH, Madan-Khetarpal S, Schmidt KR, Tervo R, Escobar LF, Friedrich CA, McDonald M, Campbell L, Ming JE, Zackai EH, Bejjani BA, Shaffer LG. Expanding the clinical phenotype of the 3q29 microdeletion syndrome and characterization of the reciprocal microduplication. Mol Cytogenet. 2008 Apr 28;1:8. doi: 10.1186/1755-8166-1-8. Citation on PubMed or Free article on PubMed Central
• Goobie S, Knijnenburg J, Fitzpatrick D, Sharkey FH, Lionel AC, Marshall CR, Azam T, Shago M, Chong K, Mendoza-Londono R, den Hollander NS, Ruivenkamp C, Maher E, Tanke HJ, Szuhai K, Wintle RF, Scherer SW. Molecular and clinical characterization of de novo and familial cases with microduplication 3q29: guidelines for copy number variation case reporting. Cytogenet Genome Res. 2008;123(1-4):65-78. doi: 10.1159/000184693. Epub 2009 Mar 11. Citation on PubMed or Free article on PubMed Central
• Lisi EC, Hamosh A, Doheny KF, Squibb E, Jackson B, Galczynski R, Thomas GH, Batista DA. 3q29 interstitial microduplication: a new syndrome in a three-generation family. Am J Med Genet A. 2008 Mar 1;146A(5):601-9. doi: 10.1002/ajmg.a.32190. Citation on PubMed