Trisomy 13 is a very rare and lethal autosomal chromosomal malformation syndrome. Its incidence is 1/12,000 births. In this paper, we present a new trisomy 13 case associated with unusual and undescribed findings. This patient was the first child of unrelated parents with advanced maternal and paternal age, at 36 and 38 years, respectively. Unfortunately, the parents did not accept the prenatal diagnosis. The baby was born after 34 weeks of gestation by cesarian section. His birth weight was 1,865 g and he demonstrated typical craniofacial abnormalities for trisomy 13 such as severe microphthalmia, microcephaly and scalp defects, and peripheral chromosome analysis revealed trisomy 13. He died of congenital heart disease and sepsis on the 12th hospital day. A complete autopsy revealed a scalp and a skull defect at the vertex, aplasia of the 5th finger nails, a complex heart disease including pulmonary trunk atresia, patent foramen ovale, membranous ventricular septal defect (VSD), main aorticopulmonary collateral artery (MAPCA) and aortic dextroposition, arrhinencephaly, partial agenesis of the corpus callosum, and neuronal heterotopias in the cerebellum. He also had bilateral cystic renal dysplasia, Meckel’s diverticulum, right inguinal hernia, ectopic splenic tissue in the pancreas, and ectopic thymus tissue adjacent to the thyroid.

To our knowledge, this is a unique trisomy 13 case with numerous common and uncommon features including a bone defect in the skull, partial agenesis of the corpus callosum, aplasia of the 5th finger nails, and a complex heart disease including pulmonary atresia, patent foramen ovale, membranous VSD, MAPCA and aortic dextroposition, which have not been published previously in the relevant literature all together.

Postmortem examination is thus very important in this syndrome for demonstrating the many unrecognized malformations[5]. Furthermore, unrecognizable lethal syndromes should also be evaluated with postmortem chromosomal analysis and autopsy. Otherwise, severe anomalies such as arrhinencephaly, Meckel’s diverticulum, cardiac malformations and kidney abnormalities likely go undetected.

Though the prognosis of cases with Patau syndrome is poor, a small number of patients have recently been reported to have had a long survival by Tunca et al.[7], Iliopoulos et al.[8] and Duarte et al[9]. The absence of holoprosencephaly is an important factor for determination of long survival since lobar or semilobar holoprosencephaly may lead to early fetal death[10,11].

Tennstedt et al.[5] reported congenital heart defects and extracardiac malformations associated with chromosomal abnormalities in a study performed on 815 fetuses, and chromosomal anomalies were detected in 33% of the cases in whom karyotyping was possible. Of 19 cases with chromosomal abnormalities, six were demonstrated to be trisomy 13 with various cardiac malformations. Common cardiovascular anomalies observed in trisomy 13 are summarized in Table I. The present case had a complex cardiac anomaly consisting of pulmonary trunk atresia, patent foramen ovale, membranous VSD, MAPCA, and aortic dextroposition, which has not been described previously as seen in Table I.

Table I: Common Cardiovascular Anomalies in Trisomy 13 (Gorlin et al.[2])

Table II describes the comparison of the clinical findings of our patient with the frequency of various defects reported in the literature. Our case had all of the characteristic findings plus bilateral absence of olfactory tractus, nail dysplasia in the 5^th fingers and a scalp and occipital bone defect. The scalp defects are known to constitute 85% of all solitary lesions of aplasia cutis congenita, and several factors such as intrauterine trauma, vascular compromise or teratogens have been implicated in the pathogenesis of these lesions[12]. However, the etiology of scalp and skull defect in trisomy 13 is still unclear.

Table II: Comparison of the Present Case with the Frequency of Various Defects Reported in Trisomy 13 (Gorlin et al.[2])

Prenatal ultrasonography (USG) may be very helpful for the diagnosis of trisomy 13 (Patau) syndrome. Unfortunately, the parents of the present case did not accept the prenatal diagnosis. Prenatal USG, particularly threedimensional (3D) sonography, permits a more detailed evaluation than routine 2D sonography[13,14]. Visualization of the facial dysmorphisms in the fetus will help them accept prenatal genetic counseling approaches such as amniocentesis and therapeutic abortion, and it may also facilitate their granting permission for a postmortem study.

In conclusion, the presented case is a complete autopsy that demonstrated very well several common and uncommon findings in trisomy 13 syndrome, such as a complex heart disease, malformations of the central nervous system, pancreas, kidney, and 5^th finger nails, and defects of the scalp and calvaria.