Trisomy 14 mosaicism: A case without evidence of neurodevelopmental delay and a review of the literature

Trisomy 14 mosaicism is a rare chromosomal defect with only 20 cases reported in the literature. We describe a child with trisomy 14 mosaicism who has some previously described and some novel phenotypic features. Trisomy 14 mosaicism was demonstrated in both blood lymphocytes and from skin fibroblasts, and with normal parents and siblings. This child had no evidence of neurodevelopmental delay at 6 years of age on formal testing, suggesting that mental retardation is not universal in this condition. This child did not demonstrate neurodevelopmental delay, which as been reported universally among children with trisomy 14 mosaicism.