Case report. Trisomy 9 syndrome.

Two cases of trisomy 9 are described. Patient 1 is the fourth case of complete trisomy 9 to be reported, and the third reported to have been born alive. This patient showed an anomaly of the perineum, with a short distance between the anus and vulva, and the circular muscle around the anus was missing. Like earlier cases of complete trisomy 9, this girl died in the neonatal period. Patient 2, with a trisomy 9 mosaicism, had a mesenterium commune. The two above-mentioned malformations have not been described previously as part of the syndrome. The features of the trisomy 9 syndrome and the differences between infants with trisomy 9 and trisomy 9 mosaicism are discussed.