chr2-218814379-G-T

Variant names:

• chr2-218814379-G-T
• rs587778779
• NM_000784.4:c.1185-1G>T

Variant summary

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

The NM_000784.4(CYP27A1):​c.1185-1G>T variant causes a splice acceptor, intron change. The variant allele was found at a frequency of 0.00000137 in 1,461,784 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: CYP27A1 NM_000784.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 6.72
• Publications: 2 publications found

Genes affected

CYP27A1 (HGNC:2605): (cytochrome P450 family 27 subfamily A member 1) This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This mitochondrial protein oxidizes cholesterol intermediates as part of the bile synthesis pathway. Since the conversion of cholesterol to bile acids is the major route for removing cholesterol from the body, this protein is important for overall cholesterol homeostasis. Mutations in this gene cause cerebrotendinous xanthomatosis, a rare autosomal recessive lipid storage disease. [provided by RefSeq, Jul 2008]

CYP27A1 Gene-Disease associations (from GenCC):

• cerebrotendinous xanthomatosis

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), Myriad Women’s Health, Genomics England PanelApp, G2P

ACMG classification

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

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 2-218814379-G-T is Pathogenic according to our data. Variant chr2-218814379-G-T is described in ClinVar as Pathogenic. ClinVar VariationId is 65835.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000784.4. 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
	CYP27A1	NM_000784.4	MANE Select	c.1185-1G>T		splice_acceptor intron	N/A	NP_000775.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CYP27A1	ENST00000258415.9	TSL:1 MANE Select	c.1185-1G>T		splice_acceptor intron	N/A	ENSP00000258415.4
	CYP27A1	ENST00000494263.5	TSL:2	n.1810G>T		non_coding_transcript_exon	Exon 6 of 7

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461784 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727194

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

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53416

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1111914

Other (OTH) AF: 0.00 AC: 0 AN: 60394

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.0296732), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cholestanol storage disease Pathogenic:5

Aug 01, 2013

GeneReviews

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: curation

Dec 21, 2022

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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 65835). This variant is also known as IVS6-1G>T. Disruption of this splice site has been observed in individual(s) with cerebrotendinous xanthomatosis (PMID: 14741198, 25983621). This variant is not present in population databases (gnomAD no frequency). This sequence change affects an acceptor splice site in intron 6 of the CYP27A1 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in CYP27A1 are known to be pathogenic (PMID: 9392430, 10775536, 26937392).

Dec 30, 2023

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Apr 07, 2014

Unidad de Genómica Médica UC, Pontificia Universidad Católica de Chile

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

The homozygous c.1185-1G>T variant causes skippig of exon 7 and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

Apr 08, 2025

Myriad Genetics, Inc.

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

NM_000784.3(CYP27A1):c.1185-1G>T is a variant in a canonical splice site classified as pathogenic in the context of cerebrotendinous xanthomatosis. c.1185-1G>T has been observed in a case with relevant disease (PMID: 14741198). Relevant functional assessments of this variant are not available in the literature. c.1185-1G>T has not been observed in referenced population frequency databases. In summary, NM_000784.3(CYP27A1):c.1185-1G>T is a variant in a canonical splice site in a gene where loss of function is a known mechanism of disease, is predicted to disrupt protein function, and 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.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	34
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
PhyloP100		6.7
GERP RS		5.8
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.98		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.35		Position offset: 39
DS_AL_spliceai		0.98		Position offset: 1

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

Other links and lift over

dbSNP: rs587778779; hg19: chr2-219679102;