ClinVar Genomic variation as it relates to human health

Variant summary: NPC1 c.2731G>A (p.Gly911Ser) results in a non-conservative amino acid change in the encoded protein sequence. Three of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00097 in 251484 control chromosomes, predominantly at a frequency of 0.011 within the African or African-American subpopulation in the gnomAD database, including 2 homozygotes. The observed variant frequency within African or African-American control individuals in the gnomAD database is approximately 4.0 fold of the estimated maximal expected allele frequency for a pathogenic variant in NPC1 causing Niemann-Pick Disease Type C phenotype (0.0027), strongly suggesting that the variant is a benign polymorphism found primarily in populations of African or African-American origin. To our knowledge, no occurrence of c.2731G>A in individuals affected with Niemann-Pick Disease Type C and no experimental evidence demonstrating its impact on protein function have been reported. Five clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as benign. Based on the evidence outlined above, the variant was classified as benign.

NPC1: BS1, BS2

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). No publications were found based on this search. Allele frequency data from public databases was too high to be consistent with this variant causing disease. Therefore, this variant is classified as benign.