ClinVar

Description

Variant summary: NRAS c.112-20dupC alters a nucleotide located close to a canonical splice site and therefore could affect mRNA splicing, leading to a significantly altered protein sequence. 5/5 computational tools predict no significant impact on normal splicing. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 0.00015 in 273884 control chromosomes, predominantly at a frequency of 0.00026 within the Non-Finnish European subpopulation in the gnomAD database. The observed variant frequency within Non-Finnish European control individuals in the gnomAD database is approximately 104 fold of the estimated maximal expected allele frequency for a pathogenic variant in NRAS causing Noonan Syndrome and Related Conditions phenotype (2.5e-06), strongly suggesting that the variant is a benign polymorphism found primarily in populations of Non-Finnish European origin. To our knowledge, no occurrence of c.112-20dupC in individuals affected with Noonan Syndrome and Related Conditions and no experimental evidence demonstrating its impact on protein function have been reported. A ClinVar submission (evaluation after 2014) cites the variant as likely benign. Based on the evidence outlined above, the variant was classified as benign.