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Genetic and Rare Diseases Information Center (GARD)

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Chromosome 3p duplication

Other Names for this Disease
  • 3p duplication
  • 3p trisomy
  • Duplication 3p
  • Partial trisomy 3p
  • Trisomy 3p
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Your Question

My 9 month old son was recently diagnosed with trisomy 3p. I am having a hard time finding any information about the disorder. Any information you can share or direct me to would be most appreciated.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is chromosome 3, trisomy 3p?

Chromosome 3, trisomy 3p is a chromosome abnormality characterized by an individual having an extra copy of one of the short arms (or part of the short arm) of chromosome 3 (3p), thus having 3 copies (a trisomy) of the chromosome segment involved instead of the normal two copies. The most common features associated with the condition are intellectual disabilities; slow psycho-motor development; broad head (brachycephaly); prominent forehead (frontal bossing); square-shaped face; wide-set eyes (hypertelorism); epicanthic folds; full cheeks; short prominent philtrum; micrognathia and retrognathia; short neck; and congenital heart defects.[1] Depending on the nature and severity of features, life expectancy may be shortened. The presence of an extra copy of specific genes causes the features of the condition. It is usually inherited from a parent who carries a balanced translocation involving chromosome 3, which can result in the unbalanced translocation trisomy 3p in a child.[2]
Last updated: 2/1/2011

What are the signs and symptoms of chromosome 3, trisomy 3p?

There have been various signs and symptoms reported in individuals with trisomy 3p. The main features may include hypotonia (decreased muscle tone), intellectual disabilities, low birth weight, square-shaped face with microcephaly (abnormally small head), brachycephaly (broad-shaped head), frontal bossing (prominent forehead), temporal indentation, epicanthal folds, and hypertelorism (wide-spaced eyes) and/or telecanthus. The nose may be short with a large tip and prominent philtrum. The lips may be everted and the corners of the mouth may be down-turned. Cleft lip and/or palate are frequently present, and anomalies of the auricles (external ears) are common. A small, receding jaw (micrognathia and/or retrognathia) and short neck are typical. Congenital heart disease, most commonly septal defects, are frequent as well as genitourinary abnormalities. Cryptorchidism (undescended testes) and incomplete masculinization of the external genitalia may be present in males. Camptodactyly and minor limb anomalies may be present. Dermatoglyphics (scientific study of fingerprints) show a very high number of whorls. The mortality rate has reportedly been high (close to 50%); however, a large portion of the reported cases occurred several or more years ago, and advances in medical technology may have decreased the reported mortality rates. Although the reported cases in the literature have varied in terms of the amount of extra material present in each individual, the developmental defects and congenital malformations present have been fairly constant.[2]
Last updated: 5/25/2011

What causes chromosome 3, trisomy 3p?

The presence of the extra genetic material in the cells of an individual with trisomy 3p causes the clinical features (phenotype) of the condition. Researchers have concluded that although affected individuals differ with regards to the amount of extra material they have, there seems to be a specific "region" on the short arm of chromosome 3 (3p) that is responsible for the common features observed in affected individuals; this region is referred to as 3p25-~3pter.[2] To learn more about chromosomes and the terminology regarding chromosome abnormalities, click here.
Last updated: 2/1/2011

How is chromosome 3, trisomy 3p inherited?

Trisomy 3p can happen on its own as a new chromosome abnormality (referred to as de novo) in offspring, or it can be caused by a parent having a balanced translocation. In most cases, an individual who has trisomy 3p is the child of a parent who is a balanced translocation carrier.[2] People generally have 23 pairs of chromosomes and inherit one in each pair from each parent. Sometimes, a section from one chromosome of a particular pair changes places with a section from a chromosome of another pair. When the two breaks do not pass through a gene and there is no gain or loss of material it is called a balanced translocation. Someone with a balanced translocation (a carrier) usually has no health or developmental problems, although they may sometimes have difficulties when they want to have children. Balanced translocations happen naturally. They can be new (de novo) or they can be passed down in families from parent to child through the generations. New translocations occur when sperm or egg cells are forming or just after fertilization during the copying of the early cells that will become an embryo.[3] To read more about balanced translocations, click here.

Even though the chromosome rearrangement is balanced in a parent, it can result in an unbalanced rearrangement in a child. The child can receive too little, or an extra amount, of the chromosome material that is rearranged in the parent. Trisomy 3p often results from the child receiving an extra copy of some or all of the material on the short arm of chromosome 3. The chance that carrying a balanced translocation will cause a child to receive unbalanced chromosomal material varies from less than 1% to up to 20% according to the specific chromosomes involved in the translocation.[4]
Last updated: 6/10/2011

How can I find a genetics professional in my area?

Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:
Last updated: 10/18/2013