Trisomy 13 syndrome (also known as Patau's syndrome) is the third most common multiple malformation syndrome. Most affected infants have full trisomy 13 at birth; a few have the rare mosaic partial trisomy 13 syndrome (with varying phenotypes) or translocation types. Infants with this disorder typically have brain and facial abnormalities as well as major cardiac, GI, and limb malformations. Full trisomy 13 syndrome is fatal. Many trisomic zygotes are spontaneously aborted; 50% to 70% of infants with full trisomy 13 syndrome die within 1 month after birth and 75% by the first year. Only isolated cases of survival beyond 5 years have been reported in full trisomy 13 patients. All survivors have profound mental retardation.
Approximately 75% of all cases of trisomy 13 syndrome are caused by chromosomal nondisjunction. About 20% are due to chromosomal translocation involving a rearrangement of chromosomes 13 and 14. About 5% are estimated to be mosaics; the clinical effects in these cases may be less severe.
Incidence is estimated to be 1 in every 5,000 neonates. The risk of chromosomal abnormalities typically increases with advanced maternal age; however, the mean maternal age for this abnormality is about 31 years.
Infants with trisomy 13 syndrome may present with microcephaly, varying degrees of holoprosencephaly, sloping forehead with wide sutures and fontanel, and a scalp defect at the vertex. Micro-ophthalmia, cataracts, and other eye abnormalities are seen in most patients with full trisomy 13. Bilateral cleft lip with associated cleft palate is seen in at least 45% of patients. Most are born with a congenital heart defect, especially hypoplastic left heart, ventricular septal defect, patent ductus arteriosus, or dextroposition, which may significantly contribute significantly to the cause of death.
Other possible findings include a flat and broad nose, low-set ears and inner ear abnormalities, polydactyly of the hands and feet, club feet, omphaloceles, neural tube defects, cystic hygroma, genital abnormalities, cystic kidneys, hydronephrosis, and musculoskeletal abnormalities. Affected infants may also experience failure to thrive, seizures, apnea, and feeding difficulties.
Multiple marker maternal serum screening tests, involving different combinations of alpha-fetoprotein, human chorionic gonadotropin (HCG) or free beta-HCG in some labs, and unconjugated estriol, may be abnormal in some pregnant women with an affected fetus; however, these tests aren't diagnostic.
Ultrasound commonly reveals multiple abnormalities in the fetus; however, because many multiple malformation syndromes have similar features, the diagnosis should be based on karyotype, done either prenatally or on peripheral blood lymphocytes or skin fibroblasts in a neonate or an aborted fetus. The neonate may have a single umbilical artery at birth. Magnetic resonance imaging or a computed tomography scan of the head may reveal a structural abnormality of the brain (holoprosencephaly) where the two cerebral hemispheres are fused.
Supportive care is the only treatment for the infant with trisomy 13 syndrome.
❑ Maintain the infant's fluid balance, and position him for comfort.
❑ Refer the parents to early intervention if the infant is medically stable.
❑ Provide the family with emotional support.
❑ Allow adequate time for the parents to bond with and hold their child.
❑ Refer the parents of an affected infant for genetic counseling to explore the cause of the disorder and to discuss the risk of recurrence in future pregnancies.
❑ Refer the parents to a social worker or grief counselor for additional support if needed.
❑ Refer the parents to the Support Organization for Trisomy 18, 13 and Related Disorders (S.O.F.T.) national support group to allow them interaction with other parents of infants with trisomy 18 and trisomy 13.
Review other book chapters online related to Sex chromosome conditions:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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