rs1554935136

Positions:

• chr11-6393629-G-A

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM1 PM2 PP3_Strong PP5_Very_Strong

The NM_000543.5(SMPD1):​c.1276G>A​(p.Gly426Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,132 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 Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: SMPD1 NM_000543.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 9.03

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 16 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 0 uncertain in NM_000543.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.949
• PP5: Variant 11-6393629-G-A is Pathogenic according to our data. Variant chr11-6393629-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 432163.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SMPD1	NM_000543.5	c.1276G>A	p.Gly426Ser	missense_variant	4/6	ENST00000342245.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SMPD1	ENST00000342245.9	c.1276G>A	p.Gly426Ser	missense_variant	4/6	1	NM_000543.5	P3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461132 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 726946

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000232

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type A Pathogenic:2

Likely pathogenic, no assertion criteria provided	clinical testing	Counsyl	Jan 31, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Mar 09, 2024	- -

Niemann-Pick disease, type B Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Kasturba Medical College, Manipal, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India

-

- -

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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 28, 2023

This sequence change replaces glycine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 426 of the SMPD1 protein (p.Gly426Ser). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with acid sphingomyelinase deficiency (PMID: 27338287). ClinVar contains an entry for this variant (Variation ID: 432163). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt SMPD1 protein function. For these reasons, this variant has been classified as Pathogenic. -

Sphingomyelin/cholesterol lipidosis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

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

Apr 15, 2024

Variant summary: SMPD1 c.1276G>A (p.Gly426Ser) results in a non-conservative amino acid change located in the Calcineurin-like phosphoesterase domain, ApaH type domain (IPR004843) of the encoded protein sequence. Four of four in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 249056 control chromosomes (gnomAD). c.1276G>A has been reported in the literature in several individuals affected with Niemann-Pick Disease, both in the homozygous state and in the compound heterozygous state with a pathogenic variant (Ranganath_2016). These data indicate that the variant is very likely to be associated with disease. The following publication has been ascertained in the context of this evaluation (PMID: 27338287). ClinVar contains an entry for this variant (Variation ID: 432163). Based on the evidence outlined above, the variant was classified as pathogenic. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

May 17, 2016

The G426S variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The G426S variant was not observed in approximately 6500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The G426S variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved across species. In silico analysis is inconsistent in its predictions as to whether or not the variant is damaging to the protein structure/function. Therefore, this variant is likely pathogenic; however, the possibility that it is benign cannot be excluded -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.50
BayesDel_addAF	Pathogenic	0.51	D
BayesDel_noAF	Pathogenic	0.49
CADD	Pathogenic	32
DANN	Uncertain	1.0
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.78
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.94	D;D
M_CAP	Pathogenic	0.47	D
MetaRNN	Pathogenic	0.95	D;D
MetaSVM	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-5.4	D;D
REVEL	Pathogenic	0.91
Sift	Benign	0.053	T;D
Sift4G	Pathogenic	0.0	D;D
Vest4		0.95
MVP		1.0
MPC		0.80
ClinPred		1.0	D
GERP RS		4.8
Varity_R		0.88
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.090		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: rs1554935136; hg19: chr11-6414859;