rs1051771

Description

Ser1799Ser in exon 42 of TSC2: This variant is not expected to have clinical sig nificance because it does not alter an amino acid residue and is not located wit hin the splice consensus sequence. It has been identified in 9.9% (848/8596) of European American chromosomes from a broad population by the NHLBI Exome Sequenc ing Project (http://evs.gs.washington.edu/EVS; dbSNP rs1051771).

This alteration is classified as benign based on a combination of the following: population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

Likely benign based on allele frequency in 1000 Genomes Project or ESP global frequency and its presence in a patient with a rare or unrelated disease phenotype. NOT Sanger confirmed.

Variant summary: The TSC2 c.5397G>C (p.Ser1799Ser) variant involves the alteration of a non-conserved nucleotide, resulting in a synonymous change. One in silico tool predicts a polymorphism outcome for this variant. 4/5 splice prediction tools predict no significant impact on normal splicing. However, these predictions have yet to be confirmed by functional studies. This variant was found in 8759/114222 control chromosomes (440 homozygotes) at a frequency of 0.076684, which is approximately 1115 times the estimated maximal expected allele frequency of a pathogenic TSC2 variant (0.0000688), indicating this variant is a benign polymorphism. In addition, multiple clinical diagnostic laboratories/reputable databases classified this variant as benign. Taken together, this variant is classified as benign.

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease.