First Case of Prenatal Diagnosis and Characterization by SNP Arrays of an Interstitial de Novo 6p 12.3-21.2 Duplication

In this paper we present the first case of prenatal diagnosis in a 20-week-old fetus, without apparent ultrasound abnormalities, of an interstitial “de novo” 6p 12.321.2 duplication with a size of 13 Mb. The chromosomal abnormality was discovered prenatally by karyotype and then characterized using SNP arrays in amniotic fluid cells. The clinical characteristics described for this type of alteration are: low birth weight, psychomotor retardation, prominent forehead, microcephaly due to craniosynostosis, flat occiput, microstomia, thin lips, malformed, low-set ears and thin and sparse hair, heart disease, hemangiomas and proteinuria. Unlike the cases published so far, which were all diagnosed postnatally, no major morphological abnormalities were observed from ultrasound exams or fetal autopsy. This fact is probably related to the gestational age at diagnosis (20 weeks), an age at which the most frequent clinical characteristics described in the literature have not yet developed. This is the first case of an interstitial “de novo” 6p 12.3-21.2 duplication diagnosed prenatally and characterized at the molecular level. Our observation emphasizes the importance of using SNP arrays for prenatal diagnosis, even in cases where the ultrasound screening is normal.