The Support Organization for Trisomy 18, 13 and Related Disorders (SOFT)
~ Trisomy 13 Facts ~
Trisomy 13 syndrome is a disorder of human chromosomes which occurs in approximately
1 in 10,000 live born infants. Trisomy refers to three copies of a chromosome instead of the
normal two and in Trisomy 13 there is the presence of an extra #13 chromosome.
Approximately 80% of infants with Trisomy 13 syndrome will have a full trisomy (affecting all
cells) while the remainder will have a trisomy due to a rearrangement of cells called a
translocation (an attachment of all or part of one chromosome to another chromosome) or
have mosaicism (two different cell lines in an individual such as normal cells and trisomy
Infants born with Trisomy 13 have a recognizable pattern of physical features that often
allows the health professional to make the diagnosis of the syndrome.
(Genetic testing must be done to confirm diagnosis.) Notable physical birth defects and, sometimes, anatomic changes of internal organs are present. Findings of significance include small head size (microcephaly); small eyes (microphthalmia) or sometimes an absent eye or faulty
development of the retina. Cleft lip or cleft palate or both occur in about 60% of children. In addition, there are a number of less medically significant physical findings that are helpful in
diagnosis. These include variations of ear shape, changes on the palm of the hand, and
extra fingers and toes. Changes in foot development, including changes to the heel, the so-called rocker bottom foot, can occur.
About 80% of children with Trisomy 13 will have a congenital heart defect. This can include:
ventricular septal defect (VSD), an opening between the lower chambers of the heart which
prevents the heart from pumping blood correctly (a heart murmur is generally heard from
this finding); atrial septal defect (ASD), an opening between the two upper chambers of the
heart making it difficult for the heart to pump sufficient oxygen- rich blood to body tissues (a
heart murmur is often heard); patent ductus arteriosis (PDA), a defect involving the lack of
closure of the channel that usually closes near the time of birth and thus remains open; and
dextrocardia, which is a location of the heart on the right side of the chest. The majority of
heart lesions are usually not those that cause death in the neo-natal period but on occasion
more medically serious heart defects can occur in Trisomy 13.
D Trisomy Syndrome
(the last two terms are usually not used at the present time)
The major implications of Trisomy 13 involve a predisposition to the congenital malformations (birth defects) mentioned above, an increased mortality in infancy and
developmental and motor disability in older children. In addition, older infants can have
visual difficulties because of the findings mentioned above and a hearing loss. The
increased mortality is related to difficulties with breathing due either to interrupted breathing
(apnea) or problems of lung development. In addition, gastroesophageal reflux (backward
flow of a small amount of stomach contents upward to the throat) and feeding problems can
occur and predispose to aspiration (small amount of liquid inhaled or trickled into
the lungs) which can precipitate aspirational pneumonia.
Important and Common Birth Defects in Trisomy 13
Holoprosencephaly 60% (an anatomic defect of the brain involving failure of the forebrain to divide properly)
Kidney defects 30%
Skin defects of the scalp 20%
Common Disorders in infants and young children with Trisomy 13
Slow post natal growth
Source of information:
John C. Carey, MD, MPH, Medical Advisor for SOFT
Professor of Pediatrics and Genetics,
University of Utah
Support Organization for Trisomy 18, 13 and Related Disorders
2982 South Union St. Rochester, NY 14624
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