Incidental X Linked Findings A female fetus with a gain in the DMD gene

In prenatal diagnosis, chromosomal microarray analysis (CMA) has not yet fully replaced conventional cytogenetic but has rapidly become the recommended genetic test in pregnancies with ultrasound abnormalities. This methodology allows the identification of pathogenic small copy number variation (CNVs) in 5-10% of pregnancies with ultrasound abnormalities and a normal karyotype, increasing the diagnostic yield. However, this increased resolution can also result in the detection of incidental findings. Here we report a fetus referred for prenatal diagnosis due to skeletal dysplasia. Affymetrix Cytoscan HD chromosome microarray analysis was performed and a 204 kb gain was detected at Xp21.1 region (chrX: 31993622_32191110 [GRCh37]) in a female fetus, encompassing the intron 44 of the DMD gene, for the largest gene transcript. Nevertheless, if we considered the smaller transcripts it encompasses exon 1. The gain was maternally inherited. The DMD gene is involved on Becker muscular dystrophy, Cardiomyopathy, dilated, 3B and Duchenne muscular dystrophy. Intron 44 is a preferential breakpoint in about 30% of all DMD deletions, being the DMD transcript NM_004006.2 responsible for dystrophin expression in the skeletal muscle.The FGFR3 gene sequencing revealed the presence of the c.1118A >G, p.Y373C mutation associated to Thanatophoric Dysplasia, type 1 (TD1) justifying the ultrasound abnormalities.With this case, we reinforce that the discovery of CNVs in prenatal CMA goes beyond the correlation with the CNV and the ultrasound abnormalities. Incidental findings can also have a larger impact to the family clinical managing, even if not for the ongoing pregnancy for the reproductive future of the couple.