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.

Twenty-year follow-up of the facial phenotype of Brazilian patients with Sotos syndrome.

Sotos syndrome is characterized by overgrowth starting before birth through childhood with intellectual disability and craniofacial anomalies. The majority of patients are large for gestational age with developmental delay or intellectual disability. The majority of cases are caused by pathogenic variants in NSD1. The most consistent physical features in this disorder are facial dysmorphisms including prominent forehead, downslanted palpebral fissures, prognathism with a pointed chin, and a long and narrow face. We present a follow-up to a cohort of 11 individuals found to harbor heterozygous, pathogenic, or likely pathogenic variants in NSD1. We analyzed the facial dysmorphisms and the condition using retrospective over 20 years. Among these patients, followed in our medical genetics outpatient clinic for variable periods of time, all had a phenotype compatible with the characteristic Sotos syndrome facial features, which evolved with time and became superimposed with natural aging modifications. We present here a long-term follow-up of facial features of Brazilian patients with molecularly confirmed Sotos syndrome. In this largest Brazilian cohort of molecularly confirmed patients with Sotos syndrome to date, we provide a careful description of the facial phenotype, which becomes less pronounced with aging and possibly more difficult to recognize in adults. These results may have broad clinical implications for diagnosis and add to the global clinical delineation of this condition.

Identification of a novel de novo nonsense mutation of the NSD1 gene in monozygotic twins discordant for Sotos syndrome.

INTRODUCTION: Sotos syndrome is a congenital overgrowth disorder characterized by facial gestalt, excessively rapid growth, acromegalic features and a non-progressive cerebral disorder with intellectual disability. METHODOLOGY: The identical male twins showed somewhat different clinical, cognitive and behavioural phenotypes. Abnormal clinical manifestations including seizures, scoliosis, enlarged ventricles, and attention-deficit/hyperactivity disorder (ADHD) were found in the proband (first twin), but not in the sibling (second twin). We used diagnostic exome sequencing (DES) to identify a heterozygous de novo mutation of the NSD1 gene in monozygotic twins with Sotos syndrome. RESULTS: DES revealed a novel nonsense mutation c.2596G>T (p.Glu866*) of the NSD1 gene in the proband, the first of monozygotic twins. Sanger sequencing analysis of the proband and his family members showed that this nonsense mutation was present in the proband and his sibling, but was absent in their parents, indicating that it occurred with de novo origin. CONCLUSION: This finding expands the phenotypic spectrum associated with variable expression of the Sotos syndrome caused by NSD1 mutation, and it adds further support for postconceptual mutation, epigenetic change and/or an environmental factor involved in the cause of the Sotos syndrome.