Trisomy 9: predominance of cardiovascular, liver, brain, and skeletal anomalies in the first diagnosed case

A pathologic study of the first case of trisomy 9 is presented. The patient, a 26 day old male infant, was found at autopsy to have primarily cardiovascular, liver, brain, and skeletal abnormalities. The cardiac findings included double outlet right ventricle, preductal coarctation of the aorta, patent ductus arteriosus, and ventricular septal defect. Skeletal anomalies consisted of lack of a pubic arch, hypodevelopment of the left tibia, absence of the left fibula, missing tarsal and calcaneal bones bilaterally, a left foot having a single toe with a metatarsal and two phalangeal bones, absence of the distal phalangeal bones of four toes on the right foot, bilateral radial head dislocations, and micrognathia. Liver findings included bile duct proliferation, canalicular cholestasis, mild portal mononuclear inflammatory infiltrate, and fatty change in the absence of biliary tract obstruction. Findings in the brain included a large fourth ventricle between widely separated cerebellar hemispheres, which suggested the Dandy-Walker malformation. The cerebellum, however, was well formed histologically and the roofing membrane appeared to be arachnoid.