rs1554934193

Variant names:

• chr11-6391574-G-A
• rs1554934193
• NM_000543.5:c.509G>A

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.509G>A​(p.Trp170*) variant causes a stop gained change. The variant allele was found at a frequency of 0.000000685 in 1,460,652 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SMPD1 NM_000543.5 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 4.53
• Publications: 0 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 11-6391574-G-A is Pathogenic according to our data. Variant chr11-6391574-G-A is described in ClinVar as Pathogenic. ClinVar VariationId is 529233.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.509G>A	p.Trp170*	stop_gained	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.509G>A	p.Trp170*	stop_gained	Exon 2 of 6	1	NM_000543.5	ENSP00000340409.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460652 Hom.: 0 Cov.: 34 AF XY: 0.00000138 AC XY: 1 AN XY: 726548

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000299 AC: 1 AN: 33466

American (AMR) AF: 0.00 AC: 0 AN: 44594

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26122

East Asian (EAS) AF: 0.00 AC: 0 AN: 39664

South Asian (SAS) AF: 0.00 AC: 0 AN: 86084

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53258

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5566

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111578

Other (OTH) AF: 0.00 AC: 0 AN: 60320

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type A Pathogenic:2

-

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Mar 17, 2017

Natera, Inc.

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Niemann-Pick disease, type A;C0268243:Niemann-Pick disease, type B Pathogenic:1

Aug 06, 2018

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. Loss-of-function variants in SMPD1 are known to be pathogenic (PMID: 12369017, 15221801). This variant has been observed to be homozygous in an individual affected with Niemann-Pick type A (PMID: 19405096). This variant is also known as p.W168X in the literature. ClinVar contains an entry for this variant (Variation ID: 529233). This variant is not present in population databases (ExAC no frequency). This sequence change creates a premature translational stop signal (p.Trp170*) in the SMPD1 gene. It is expected to result in an absent or disrupted protein product. -

not provided Pathogenic:1

Nov 14, 2024

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Nonsense 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); This variant is associated with the following publications: (PMID: 25525159, 19405096) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.62	D
BayesDel_noAF	Pathogenic	0.49
CADD	Pathogenic	40
DANN	Uncertain	1.0
Eigen	Pathogenic	0.95
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Uncertain	0.88	D
PhyloP100		4.5
Vest4		0.92
GERP RS		5.1
PromoterAI		0.0029	Neutral
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: rs1554934193; hg19: chr11-6412804; COSMIC: COSV54968404; COSMIC: COSV54968404;