NM_000543.5:c.518dupT

Variant names:

• chr11-6391579-A-AT
• rs786204733
• NM_000543.5:c.518dupT

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000543.5(SMPD1):​c.518dupT​(p.Ser174LeufsTer19) variant causes a frameshift change. The variant allele was found at a frequency of 0.0000062 in 1,612,284 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. F173F) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000055 (0 hom.)
• Consequence: SMPD1 NM_000543.5 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:8
• Conservation: PhyloP100: 5.69
• Publications: 1 publications found

Genes affected

SMPD1 (HGNC:11120): (sphingomyelin phosphodiesterase 1) The protein encoded by this gene is a lysosomal acid sphingomyelinase that converts sphingomyelin to ceramide. The encoded protein also has phospholipase C activity. Defects in this gene are a cause of Niemann-Pick disease type A (NPA) and Niemann-Pick disease type B (NPB). Multiple transcript variants encoding different isoforms have been identified. [provided by RefSeq, Jul 2010]

SMPD1 Gene-Disease associations (from GenCC):

• acid sphingomyelinase deficiency

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• Niemann-Pick disease

  Inheritance: AR Classification: DEFINITIVE Submitted by: Myriad Women’s Health
• Niemann-Pick disease type A

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Orphanet, G2P
• Niemann-Pick disease type B

  Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Orphanet, Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 11-6391579-A-AT is Pathogenic according to our data. Variant chr11-6391579-A-AT is described in ClinVar as [Likely_pathogenic]. Clinvar id is 189153.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMPD1	NM_000543.5	c.518dupT	p.Ser174LeufsTer19	frameshift_variant	Exon 2 of 6	ENST00000342245.9	NP_000534.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMPD1	ENST00000342245.9	c.518dupT	p.Ser174LeufsTer19	frameshift_variant	Exon 2 of 6	1	NM_000543.5	ENSP00000340409.4

Frequencies

GnomAD3 genomes AF: 0.0000132 AC: 2 AN: 152062 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000242

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000404 AC: 1 AN: 247298 AF XY: 0.00000747

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000898

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000548 AC: 8 AN: 1460222 Hom.: 0 Cov.: 34 AF XY: 0.00000551 AC XY: 4 AN XY: 726338

African (AFR) AF: 0.00 AC: 0 AN: 33458

American (AMR) AF: 0.00 AC: 0 AN: 44534

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26116

East Asian (EAS) AF: 0.00 AC: 0 AN: 39652

South Asian (SAS) AF: 0.00 AC: 0 AN: 86016

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53260

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5536

European-Non Finnish (NFE) AF: 0.00000720 AC: 8 AN: 1111356

Other (OTH) AF: 0.00 AC: 0 AN: 60294

GnomAD4 genome AF: 0.0000132 AC: 2 AN: 152062 Hom.: 0 Cov.: 33 AF XY: 0.0000269 AC XY: 2 AN XY: 74280

African (AFR) AF: 0.0000242 AC: 1 AN: 41396

American (AMR) AF: 0.00 AC: 0 AN: 15282

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5178

South Asian (SAS) AF: 0.00 AC: 0 AN: 4826

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10602

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000147 AC: 1 AN: 67986

Other (OTH) AF: 0.00 AC: 0 AN: 2092

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000151

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:8

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type A Pathogenic:4

May 13, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: SMPD1 c.518dupT (p.Ser174LeufsX19) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory. The variant allele was found at a frequency of 4e-06 in 247298 control chromosomes. c.518dupT has been reported in the literature in individuals affected with Niemann-Pick Disease Type A. These data indicate that the variant may be associated with disease. Four 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 pathogenic/likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Apr 25, 2021

Diagnostics Division, CENTRE FOR DNA FINGERPRINTING AND DIAGNOSTICS

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

- -

Jan 23, 2015

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Apr 22, 2023

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Niemann-Pick disease, type A;C0268243:Niemann-Pick disease, type B Pathogenic:2

Aug 29, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Ser174Leufs*19) in the SMPD1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in SMPD1 are known to be pathogenic (PMID: 12369017, 15221801). This variant is present in population databases (rs786204733, gnomAD 0.0009%). This premature translational stop signal has been observed in individual(s) with Niemann-Pick disease type A (PMID: 15221801). This variant is also known as c.512_513dupT p.F171fsX19. ClinVar contains an entry for this variant (Variation ID: 189153). For these reasons, this variant has been classified as Pathogenic. -

Feb 16, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Pathogenic:1

Jul 23, 2024

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Frameshift variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); Also known as c.512_513dupT, p.F171fsX19; This variant is associated with the following publications: (PMID: 34426522, 33675270, 12369017, 34273913, 37347058, 15221801) -

Sphingomyelin/cholesterol lipidosis Pathogenic:1

Jan 22, 2020

Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: curation

The p.Ser174LeufsTer19 variant in SMPD1 (also known as p.Ser172LeufsTer19 due to a difference in cDNA numbering) has been reported in one individual with Niemann-Pick disease (PMID: 15221801) and has been identified in 0.001% (1/111376) of European (non-Finnish) chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs786204733). Although this variant has been seen in the general population, its frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar (VariationID: 189153) as likely pathogenic by Counsyl. This variant is predicted to cause a frameshift, which alters the protein's amino acid sequence beginning at position 174 and leads to a premature termination codon 19 amino acids downstream. This alteration is then predicted to lead to a truncated or absent protein. Loss of function of the SMPD1 gene is an established disease mechanism in autosomal recessive Niemann-Pick disease. In summary, although additional studies are required to fully establish its clinical significance, this variant is likely pathogenic. ACMG/AMP Criteria applied: PVS1, PM2 (Richards 2015). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		5.7
Mutation Taster		=0/200	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs786204733; hg19: chr11-6412809;