Hand and foot malformations
Gene: SMARCA2
Heterozygous pathogenic SMARCA2 variants cause Nicolaides-Baraitser syndrome (MIM #601358). DD/ID are universal features. A dominant-negative or gain-of-function effect appear to be the most likely mechanism (Abdul-Rahman O. - PMID: 26468571). Please also note that Cappuccio et al (2020 - PMID: 32694869) report on individuals with de novo SMARCA2 variants with features of a novel, blepharophimosis-intellectual disability syndrome (BIS) but whose clinical presentation did not fit a diagnosis of Nicolaides-Baraitser (NB) syndrome. Clinical details on 14 subjects with BIS were provided, DD/ID being a universal feature (14/14 - moderate to severe ID). Compared to other syndromes with blepharophimosis, lack of ptosis (observed in only 14% in this cohort), epicanthus inversus and limb abnormalities were proposed to distinguish BIS from other recognizable syndromes with blepharophimosis. All individuals with BIS were found to harbor de novo missense variants. These clustered outside the helicase domain and localized within exons 8,9 and 19. Few (6) additional individuals with de novo missense variants (in ex. 8, 14, 19) did not fit either diagnosis (NB or BIS) with the SNVs classified as VUS. According to Cappuccio et al, most individuals with diagnosis of NB syndrome harbor variants spanning exons 15 to 25 [corresponding to the ATPase domain, which in turn is split in a Helicase ATP-Binding domain (720-912) and a helicase C-terminal domain (1080-1164)]. Most NB-associated variants are missense and rarely in-frame exon deletions. As also commented on, CNVs (deletions or duplications) encompassing SMARCA2 have been reported in individuals with DD/ID although these did not fit a diagnosis of NB syndrome (and CNVs were rather not intragenic/limited to SMARCA2) [cited PMIDs: 31530938, 28846756]. Transcriptomic and methylation signatures confirmed molecular stratification of affected individuals with SMARCA2-related disorders (and controls).Created: 26 Jul 2020, 11:39 p.m. | Last Modified: 26 Jul 2020, 11:39 p.m.
Panel Version: 0.3513
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Phenotypes
Nicolaides-Baraitser syndrome, MIM #601358; Blepharophimosis-intellectual disability syndrome
Publications
Mode of pathogenicity
Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments
Gene: smarca2 has been classified as Green List (High Evidence).
Mode of pathogenicity for gene: SMARCA2 was changed from to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments
Publications for gene: SMARCA2 were set to
Gene: smarca2 has been classified as Green List (High Evidence).
gene: SMARCA2 was added gene: SMARCA2 was added to Hand and foot malformation. Sources: Expert list Mode of inheritance for gene: SMARCA2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Phenotypes for gene: SMARCA2 were set to Nicolaides-Baraitser syndrome MIM#601358