Trisomy 13 (Patau syndrome) is the third most common autosomal trisomy identified in liveborn infants, and the most severe. Affected children typically die within the first week of life, with only 5% surviving the first six months. In the majority of trisomy 13 infants cytogenetic studies demonstrate nondisjunction (47XX, +13); this chromosomal abnormality arises during maternal meiosis I and is associated with advanced maternal age.
The prominent phenotypic features of trisomy 13 are associated with an early defect in prechordal mesoderm development. As a result, the midface, eye, and forebrain are most markedly affected. The clinical manifestations of Patau syndrome include the abnormalities categorized by system below.
1. Head and neck: severe cleft lip and/or palate microphthalmia or anophthalmia, coloboma, cyclops, malformed or absent nose, deafness, scalp defects (aplasia cutis)
2. CNS: severe mental retardation microcephaly, holoprosencephaly (failure of brain to divide into hemispheres) absent olfactory nerve or bulb, neural tube defects
3. Extremities: polydactyly, rocker-bottom feet
4. Cardiac: PDA, atrial septal defect, ventricular septal defect
5. Renal: polycystic kidney disease
6. Gastrointestinal: abdominal wall defects associated with omphalocele or umbilical hernia, pyloric stenosis.
Clinical manifestations of trisomy 18 (Edwards syndrome) include
prominent occiput micrognathia,
small mouth low-set and malformed ears, and rocker-bottom feet.
Clenched hands with the index finger overriding the middle finger
and the fifth finger overriding the fourth finger are characteristic for this condition.
Meckel’s diverticulum and malrotation are common gastrointestinal abnormalities.
The prominent phenotypic features of trisomy 13 are associated with an early defect in prechordal mesoderm development. As a result, the midface, eye, and forebrain are most markedly affected. The clinical manifestations of Patau syndrome include the abnormalities categorized by system below.
1. Head and neck: severe cleft lip and/or palate microphthalmia or anophthalmia, coloboma, cyclops, malformed or absent nose, deafness, scalp defects (aplasia cutis)
2. CNS: severe mental retardation microcephaly, holoprosencephaly (failure of brain to divide into hemispheres) absent olfactory nerve or bulb, neural tube defects
3. Extremities: polydactyly, rocker-bottom feet
4. Cardiac: PDA, atrial septal defect, ventricular septal defect
5. Renal: polycystic kidney disease
6. Gastrointestinal: abdominal wall defects associated with omphalocele or umbilical hernia, pyloric stenosis.
Clinical manifestations of trisomy 18 (Edwards syndrome) include
prominent occiput micrognathia,
small mouth low-set and malformed ears, and rocker-bottom feet.
Clenched hands with the index finger overriding the middle finger
and the fifth finger overriding the fourth finger are characteristic for this condition.
Meckel’s diverticulum and malrotation are common gastrointestinal abnormalities.
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