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      Sotos syndrome

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      1 , , 1
      Orphanet Journal of Rare Diseases
      BioMed Central

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          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.

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          Most cited references55

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          Haploinsufficiency of NSD1 causes Sotos syndrome.

          We isolated NSD1 from the 5q35 breakpoint in an individual with Sotos syndrome harboring a chromosomal translocation. We identified 1 nonsense, 3 frameshift and 20 submicroscopic deletion mutations of NSD1 among 42 individuals with sporadic cases of Sotos syndrome. The results indicate that haploinsufficiency of NSD1 is the major cause of Sotos syndrome.
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            Genotype-phenotype associations in Sotos syndrome: an analysis of 266 individuals with NSD1 aberrations.

            We identified 266 individuals with intragenic NSD1 mutations or 5q35 microdeletions encompassing NSD1 (referred to as "NSD1-positive individuals"), through analyses of 530 subjects with diverse phenotypes. Truncating NSD1 mutations occurred throughout the gene, but pathogenic missense mutations occurred only in functional domains (P < 2 x 10(-16)). Sotos syndrome was clinically diagnosed in 99% of NSD1-positive individuals, independent of the molecular analyses, indicating that NSD1 aberrations are essentially specific to this condition. Furthermore, our data suggest that 93% of patients who have been clinically diagnosed with Sotos syndrome have identifiable NSD1 abnormalities, of which 83% are intragenic mutations and 10% are 5q35 microdeletions. We reviewed the clinical phenotypes of 239 NSD1-positive individuals. Facial dysmorphism, learning disability, and childhood overgrowth were present in 90% of the individuals. However, both the height and head circumference of 10% of the individuals were within the normal range, indicating that overgrowth is not obligatory for the diagnosis of Sotos syndrome. A broad spectrum of associated clinical features was also present, the occurrence of which was largely independent of genotype, since individuals with identical mutations had different phenotypes. We compared the phenotypes of patients with intragenic NSD1 mutations with those of patients with 5q35 microdeletions. Patients with microdeletions had less-prominent overgrowth (P = .0003) and more-severe learning disability (P = 3 x 10(-9)) than patients with mutations. However, all features present in patients with microdeletions were also observed in patients with mutations, and there was no correlation between deletion size and the clinical phenotype, suggesting that the deletion of additional genes in patients with 5q35 microdeletions has little specific effect on phenotype. We identified only 13 familial cases. The reasons for the low vertical transmission rate are unclear, although familial cases were more likely than nonfamilial cases (P = .005) to carry missense mutations, suggesting that the underlying NSD1 mutational mechanism in Sotos syndrome may influence reproductive fitness.
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              NSD1 is essential for early post-implantation development and has a catalytically active SET domain.

              The nuclear receptor-binding SET domain-containing protein (NSD1) belongs to an emerging family of proteins, which have all been implicated in human malignancy. To gain insight into the biological functions of NSD1, we have generated NSD1-deficient mice by gene disruption. Homozygous mutant NSD1 embryos, which initiate mesoderm formation, display a high incidence of apoptosis and fail to complete gastrulation, indicating that NSD1 is a developmental regulatory protein that exerts function(s) essential for early post-implantation development. We have also examined the enzymatic potential of NSD1 and found that its SET domain possesses intrinsic histone methyltransferase activity with specificity for Lys36 of histone H3 (H3-K36) and Lys20 of histone H4 (H4-K20).
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                Author and article information

                Journal
                Orphanet J Rare Dis
                Orphanet Journal of Rare Diseases
                BioMed Central (London )
                1750-1172
                2007
                7 September 2007
                : 2
                : 36
                Affiliations
                [1 ]Department of Medical Genetic, Hospital Necker-Enfants Malades, 149 rue de Sèvres, 75743 Paris Cedex 15, France
                Article
                1750-1172-2-36
                10.1186/1750-1172-2-36
                2018686
                17825104
                6dac6089-1b96-4849-8578-cad82ac3d799
                Copyright © 2007 Baujat and Cormier-Daire; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 3 July 2007
                : 7 September 2007
                Categories
                Review

                Infectious disease & Microbiology
                Infectious disease & Microbiology

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