Abstract
Sotos syndrome is an overgrowth condition characterized by cardinal features including excessive growth during childhood, macrocephaly, distinctive facial gestalt and various degrees of learning difficulty, and associated with variable minor features. The exact prevalence remains unknown but hundreds of cases have been reported. The diagnosis is usually suspected after birth because of excessive height and occipitofrontal circumference (OFC), advanced bone age, neonatal complications including hypotonia and feeding difficulties, and facial gestalt. Other inconstant clinical abnormalities include scoliosis, cardiac and genitourinary anomalies, seizures and brisk deep tendon reflexes. Variable delays in cognitive and motor development are also observed. The syndrome may also be associated with an increased risk of tumors. Mutations and deletions of the NSD1 gene (located at chromosome 5q35 and coding for a histone methyltransferase implicated in transcriptional regulation) are responsible for more than 75% of cases. FISH analysis, MLPA or multiplex quantitative PCR allow the detection of total/partial NSD1 deletions, and direct sequencing allows detection of NSD1 mutations. The large majority of NSD1 abnormalities occur de novo and there are very few familial cases. Although most cases are sporadic, several reports of autosomal dominant inheritance have been described. Germline mosaicism has never been reported and the recurrence risk for normal parents is very low (<1%). The main differential diagnoses are Weaver syndrome, Beckwith-Wiedeman syndrome, Fragile X syndrome, Simpson-Golabi-Behmel syndrome and 22qter deletion syndrome. Management is multidisciplinary. During the neonatal period, therapies are mostly symptomatic, including phototherapy in case of jaundice, treatment of the feeding difficulties and gastroesophageal reflux, and detection and treatment of hypoglycemia. General pediatric follow-up is important during the first years of life to allow detection and management of clinical complications such as scoliosis and febrile seizures. An adequate psychological and educational program with speech therapy and motor stimulation plays an important role in the global development of the patients. Final body height is difficult to predict but growth tends to normalize after puberty.
Highlights
Sotos syndrome is a childhood overgrowth condition, first described in 1964 by Sotos et al [1], though the first patient described may have been reported in 1931 [2]
They confirmed that overgrowth, dysmorphism and learning disability were present in 90% of these NSD1-positive individuals, with a wide spectrum of associated features including macrocephaly, advanced bone age, neonatal jaundice and hypotonia, seizures, scoliosis, cardiac defects and genitourinary anomalies [10]
The reported incidence of advanced bone age in Sotos cases varies from 74% to 100% of cases, and this variability is probably related to the frequency, timing and method of assessment
Summary
Diagnosis is based on clinical exam and radiographic bone age (cf. clinical description). Sotos syndrome belongs to a group of overgrowth syndromes that have some clinical features in common such as pre- and/or postnatal overgrowth and/or advanced bone age. Many of these syndromes, can be excluded on the bases of other major clinical features. Alternate methods of feeding may need to be considered such as the use of a nasogastric tube Another common problem is gastroesophageal reflux which causes heartburn, vomiting, esophageal irritation and respiratory problems. Programs including infant stimulation, occupational therapy, speech therapy, and adaptive physical education play a significant role in the nurturing of a child with Sotos syndrome. Final body height is difficult to predict but growth in height tends to normalize after puberty
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