49. A case study of trisomy 13 mosaicism

Abstract

A newborn male infant presented to the neonatal intensive care unit with respiratory distress, congenital heart disease (VSD, ASD, PDA), neonatal teeth, polydactyly in feet and hands, and undescended testes. Pregnancy was complicated by late prenatal care and history of substance abuse. Chromosomal microarray analysis (CMA) was performed on a peripheral blood specimen from this infant. Initially, the CMA software called a modest copy gain of 8 Mb with a mean log ration of 0.2, a value below our cutoff of >0.4. Upon closer examination of the scatter plot, a larger copy number gain of chromosome 13 was suspected. FISH was therefore ordered with probes for the long arm of chromosome 13 and results showed trisomy in 13% of cells, with the abnormal cells showing a der(13;13). Conventional cytogenetic analysis was subsequently performed and revealed a karyotype of 46,XY,der(13)t(13;13)(p11.2;q13) in 20% of cells examined.