4-987877-A-G

Variant names:

• chr4-987877-A-G
• rs780165694
• NM_000203.5:c.227A>G

Variant summary

Our verdict is Likely pathogenic. The variant received 9 ACMG points: 9P and 0B. PM1 PM2 PP3_Strong PP5

The NM_000203.5(IDUA):​c.227A>G​(p.Tyr76Cys) variant causes a missense change. The variant allele was found at a frequency of 0.0000178 in 1,459,692 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 Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. Y76Y) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000018 (0 hom.)
• Consequence: IDUA NM_000203.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:3
• Conservation: PhyloP100: 5.53
• Publications: 3 publications found

Genes affected

IDUA (HGNC:5391): (alpha-L-iduronidase) This gene encodes an enzyme that hydrolyzes the terminal alpha-L-iduronic acid residues of two glycosaminoglycans, dermatan sulfate and heparan sulfate. This hydrolysis is required for the lysosomal degradation of these glycosaminoglycans. Mutations in this gene that result in enzymatic deficiency lead to the autosomal recessive disease mucopolysaccharidosis type I (MPS I). [provided by RefSeq, Jul 2008]

SLC26A1 (HGNC:10993): (solute carrier family 26 member 1) This gene is a member of a family of sulfate/anion transporter genes. Family members are well conserved in their genomic (number and size of exons) and protein (aa length among species) structures, but have markedly different tissue expression patterns. This gene is primarily expressed in the liver, pancreas, and brain. Three splice variants that encode different isoforms have been identified. [provided by RefSeq, Jul 2008]

SLC26A1 Gene-Disease associations (from GenCC):

• nephrolithiasis susceptibility caused by SLC26A1

  Inheritance: AR Classification: MODERATE, LIMITED Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics

ACMG classification

Our verdict: Likely_pathogenic. The variant received 9 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 14 uncertain in NM_000203.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.951
• PP5: Variant 4-987877-A-G is Pathogenic according to our data. Variant chr4-987877-A-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 552686.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000203.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	IDUA	NM_000203.5	MANE Select	c.227A>G	p.Tyr76Cys	missense	Exon 2 of 14	NP_000194.2
	SLC26A1	NM_022042.4	MANE Select	c.*956T>C		3_prime_UTR	Exon 3 of 3	NP_071325.2
	IDUA	NR_110313.1		n.315A>G		non_coding_transcript_exon	Exon 2 of 14

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	IDUA	ENST00000514224.2	TSL:2 MANE Select	c.227A>G	p.Tyr76Cys	missense	Exon 2 of 14	ENSP00000425081.2
	IDUA	ENST00000247933.9	TSL:1	c.227A>G	p.Tyr76Cys	missense	Exon 2 of 14	ENSP00000247933.4
	SLC26A1	ENST00000398516.3	TSL:1 MANE Select	c.*956T>C		3_prime_UTR	Exon 3 of 3	ENSP00000381528.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.0000124 AC: 3 AN: 241606 AF XY: 0.00000759

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000292

Gnomad ASJ exome AF: 0.000204

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000178 AC: 26 AN: 1459692 Hom.: 0 Cov.: 30 AF XY: 0.0000207 AC XY: 15 AN XY: 726108

African (AFR) AF: 0.00 AC: 0 AN: 33462

American (AMR) AF: 0.0000224 AC: 1 AN: 44660

Ashkenazi Jewish (ASJ) AF: 0.0000766 AC: 2 AN: 26104

East Asian (EAS) AF: 0.00 AC: 0 AN: 39668

South Asian (SAS) AF: 0.00 AC: 0 AN: 86102

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51950

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5752

European-Non Finnish (NFE) AF: 0.0000189 AC: 21 AN: 1111662

Other (OTH) AF: 0.0000331 AC: 2 AN: 60332

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000434 Hom.: 0

Bravo AF: 0.0000113

ExAC AF: 0.0000166 AC: 2

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Mucopolysaccharidosis type 1 Pathogenic:2

May 09, 2025

Myriad Genetics, Inc.

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

NM_000203.3(IDUA):c.227A>G(Y76C) is a missense variant classified as likely pathogenic in the context of mucopolysaccharidosis type I. Y76C has been observed in cases with relevant disease (PMID: 21394825, 25009127, 31194252, 36299240). Relevant functional assessments of this variant are not available in the literature. Y76C has been observed in referenced population frequency databases. In summary, NM_000203.3(IDUA):c.227A>G(Y76C) is a missense variant that has been observed more frequently in cases with the relevant disease than in healthy populations. Please note: this variant was assessed in the context of healthy population screening.

Aug 06, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces tyrosine, which is neutral and polar, with cysteine, which is neutral and slightly polar, at codon 76 of the IDUA protein (p.Tyr76Cys). This variant is present in population databases (rs780165694, gnomAD 0.02%). This missense change has been observed in individual(s) with mucopolysaccharidosis type I (PMID: 21394825, 25009127; Invitae). ClinVar contains an entry for this variant (Variation ID: 552686). 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 IDUA protein function with a positive predictive value of 80%. For these reasons, this variant has been classified as Pathogenic.

Mucopolysaccharidosis, MPS-I-S;C0086431:Mucopolysaccharidosis, MPS-I-H/S;C0086795:Hurler syndrome Pathogenic:1

Mar 08, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

not specified Uncertain:1

Jun 13, 2025

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

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: IDUA c.227A>G (p.Tyr76Cys) results in a non-conservative amino acid change in the encoded protein sequence. Algorithms developed to predict the effect of missense changes on protein structure and function all suggest that this variant is likely to be disruptive. The variant allele was found at a frequency of 1.2e-05 in 241606 control chromosomes. c.227A>G has been reported in the literature as a compound heterozygous genotype in at-least two individuals affected with Mucopolysaccharidosis type I (Scheie syndrome) and has been subsequently cited by others (example, Bertola_2011, Tylki-Szymanska_2010, Yu Lin_2015, Clarke_2019, internal data). These data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 21394825, 31194252, 20217237, 25009127). ClinVar contains an entry for this variant (Variation ID: 552686). Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic.

not provided Uncertain:1

Mar 17, 2021

Revvity Omics, Revvity

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Hurler syndrome Uncertain:1

Jun 30, 2017

Counsyl

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

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.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.29
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.44
CADD	Pathogenic	29
DANN	Benign	0.93
DEOGEN2	Pathogenic	0.89	D
Eigen	Uncertain	0.52
Eigen_PC	Uncertain	0.43
FATHMM_MKL	Uncertain	0.81	D
LIST_S2	Uncertain	0.94	D
M_CAP	Pathogenic	0.51	D
MetaRNN	Pathogenic	0.95	D
MetaSVM	Pathogenic	0.83	D
MutationAssessor	Uncertain	2.6	M
PhyloP100		5.5
PrimateAI	Uncertain	0.71	T
PROVEAN	Uncertain	-4.3	D
REVEL	Pathogenic	0.84
Sift	Uncertain	0.0090	D
Sift4G	Uncertain	0.0040	D
Polyphen		1.0	D
Vest4		0.97
MutPred		0.72		Gain of loop (P = 0.1069)
MVP		0.98
MPC		0.85
ClinPred		0.95	D
GERP RS		3.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.44
gMVP		0.87
Mutation Taster		=23/77	disease causing

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: rs780165694; hg19: chr4-981665;