Prenatal characterization of novel neurosonographic findings in a fetus with SOTOS syndrome

Sotos syndrome is a rare genetic disorder that occurs in less than 1 in 10,000 births. It is characterized by rapid growth during childhood (tall stature and unusually large head), typical facial dysmorphic features, neurodevelopmental delays of both mental and movement abilities, and learning disabilities. Prenatal diagnosis of Sotos syndrome is infrequent and sonographic findings are not well characterized as the condition is generally detected during childhood. We present a case in which routine third trimester ultrasound detected intracranial findings including ventriculomegaly, periventricular pseudocysts, and increased periventricular echogenicity. Although initially suspected to be the result of fetal infection with CMV, amniocentesis excluded fetal infection and microarray analysis detected a de novo 2.13 MB interstitial deletion of 5q35.2-35.3 involving several genes including the NSD1 gene, thus confirming the diagnosis of Sotos syndrome. This case provides novel characterization of the sonographic phenotype in a fetus with Sotos syndrome and discusses the differential diagnosis. What's already known about this topic?Soto's syndrome (deletion involving the NSD1 gene) is rarely diagnosed prenatally.Thus far, prenatal diagnosis was based on the presence of macrocephaly with or without ventriculomegaly and polyhydramnios.What does this study add?We provide detailed characterization of novel neurosonographic findings in fetus with Soto's syndrome.We report white matter involvement including periventricular pseudocysts and hyperechogenic periventricular echogenic enhancement of the parenchyma in a fetus with Soto's syndrome (deletion involving the NSD1 gene).Following exclusion of fetal infection, CMV being the most common, findings of white matter involvement on neurosonography require genetic counseling and consideration for microarray analyses and/or exome sequencing.