The phenotypic and cytogenetic spectrum of partial trisomy 9

A new patient with trisomy for the chromosome segment 9pter→q22 is compared to 19 previously reported cases of partial trisomy 9. Manifestations such as microcephaly, prominent nasal root, bulbous nose, and down‐turned corners of the mouth are common to patients with trisomic segments extending from 9p21 to 9q13, while intra‐uterine growth retardation, cleft lip/palate, skeletal anomalies, and heart defects are more common with trisomic segments extending through 9q22‐9q32. A graphic method illustrates this progression in the partial trisomy 9 malformation spectrum as the triplicated chromosome region extends from bands 9q21 to 9q32. More severe and random defects are observed with complete trisomy 9 or tetrasomy 9p, suggesting an extreme excess of material greatly increases developmental variability.