11-6391795-G-T

Variant names:

• chr11-6391795-G-T
• rs120074122
• NM_000543.5:c.730G>T

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM2 PP3_Strong PP5_Very_Strong

The NM_001318088.2(SMPD1):​c.-232G>T variant causes a 5 prime UTR premature start codon gain change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 31)
• Consequence: SMPD1 NM_001318088.2 5_prime_UTR_premature_start_codon_gain
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 9.25

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]

ACMG classification

Verdict is Pathogenic. Variant got 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: BayesDel_addAF computational evidence supports a deleterious effect, 0.618
• PP5: Variant 11-6391795-G-T is Pathogenic according to our data. Variant chr11-6391795-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 370798.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.730G>T	p.Gly244*	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.730G>T	p.Gly244*	stop_gained	Exon 2 of 6	1	NM_000543.5	ENSP00000340409.4

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 36

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2

Oct 01, 2020

Revvity Omics, Revvity

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Aug 22, 2023

Clinical Genetics Laboratory, Skane University Hospital Lund

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Niemann-Pick disease, type A Pathogenic:2

Feb 13, 2024

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Apr 14, 2016

Counsyl

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Sphingomyelin/cholesterol lipidosis Pathogenic:1

Jan 22, 2020

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

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: curation

The p.Gly244Ter variant in SMPD1 (also known as p.Gly242Ter due to a difference in cDNA numbering) has been reported in 1 individual with Niemann-Pick disease (PMID: 29966168) and was absent from large population studies and no high quality genotypes at this site were noted to include this variant. This variant has been reported in ClinVar (VariationID: 370798) as likely pathogenic by Counsyl. This nonsense variant leads to a premature termination codon at position 244, which is 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. The phenotype of an individual compound heterozygous for this variant is highly specific for Niemann-Pick disease based on acid sphingomyelinase activity being <10% of normal, consistent with disease (PMID: 29966168). In summary, this variant meets criteria to be classified as pathogenic for Niemann-Pick disease in an autosomal recessive manner based on the prediction it causes loss of function, its absence in the general population, and the phenotype of an individual with the variant being highly specific for the disease. ACMG/AMP Criteria applied: PVS1, PM2_Supporting, PP4 (Richards 2015). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.62	D
BayesDel_noAF	Pathogenic	0.65
CADD	Pathogenic	41
DANN	Uncertain	0.99
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	1.0	D
Vest4		0.90
GERP RS		5.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs120074122; hg19: chr11-6413025; COSMIC: COSV54966614; COSMIC: COSV54966614;