Trisomy 13 was initially described by Patau and colleagues259 in 1960. Although the major diagnostic criteria include microphthalmia, cleft lip/palate, and Polydactyly, nearly every organ system may be involved. Most infants have normal birth weights and are hypotonic; about half have a cleft lip/palate. Many have a face with sloping forehead and bulbous nose (Fig. 3-9). Life-threatening abnormalitites include cardiovascular and central nervous system malformations; perinatal death is common, and 95% die by age 3 years. Additional anomalies include polycystic renal cortices, biseptate uterus in females, undescended testes and abnormal insertion of phallus in males, hyperconvex nails, muscle and skeletal abnormalities, capillary cutaneous defects, and cutaneous scalp defects. The central nervous system is markedly affected, with defects including absence of rhinencephalon, union of ventricles and thalami, defects of corpus callosum, falx cerebri, and commissures, and arhinencephaly with absence of olfactory nerves and lobes; microcephaly is common.
vitreous, intraocular cartilage, and retinal dysplasia (Fig. 3-9).7,137,156 Pathologically, intraocular cartilage and evidence of bilateral persistent hyperplastic primary vitreous may be evident.57-184
Although most children with trisomy 13 have 47 chromosomes, a small number have 46 chromsomes with a Robertson-ian translocation, which usually occurs de novo but, rarely, may be inherited from a carrier parent. The incidence increases with maternal age.
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