Etiology and pathology Primary trisomy 8 or more common chimera trisomy 8 syndrome is a very common autosomal abnormal disease. The incidence of children is about 1/25000- 1/50000. About 10% is a primary autosomal triad. At least 5: 1 male advantage. The complete trisomy of chromosome 8 is very rare after birth, although only 10% is found in cases of spontaneous abortion.

The average life expectancy of patients with clinical manifestations is normal. Most full-term babies have normal birth weight. Usually have moderate mental retardation. The forehead of patients with this syndrome is often high and protruding. The face is long. The external ear is underdeveloped. 50% cases have mild orbital widening and strabismus. Corneal opacity is more common. In 60% cases, the base of the nose is wide and the tip of the nose is upturned.

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The skull is often square, the corpus callosum is missing, and the mandible is small and backward. The patient may have cleft palate deformity. About 70% patients have finger and toe contracture deformity. About 35% patients are slender, accompanied by thoracic stenosis and slender pelvis; 65% cases have spinal deformity, mainly scoliosis. Widening of ribs, extra ribs, costal sulcus 1, spina bifida occulta, butterfly vertebral body and patella are common malformations.

25% cases have congenital heart abnormalities, mainly ventricular septal defect, patent ductus arteriosus, pulmonary artery stenosis, aortic stenosis, complete pulmonary vein connection abnormality and main artery abnormality. Hydronephrosis and/or hydroureter are common. 50% patients have cryptorchidism. 40% cases have hydronephrosis, hydronephrosis or ureteral obstruction.