Mosaic trachea in a child with trisomy 9 mosaicism

Humans with mosaic karyotypes may present with milder forms of birth defects than one would see in non-mosaic individuals. Mosaicism may also affect tissues, resulting in different parts of an organ manifesting varied phenotypes. We present the case of a child born with mosaic trisomy 9 and multiple congenital anomalies. Her trachea displays segmental abnormalities that suggest tissue mosaicism. We describe the endoscopic and cytogenetic findings in this child and propose a possible genetic mechanism to account for the unusual malformations.