rs1555843178

chr20-44620297-A-T

Variant summary

Our verdict is Pathogenic. Variant got 22 ACMG points: 22P and 0B. PVS1 PM2 PP3_Strong PP5_Very_Strong

The NM_000022.4(ADA):c.1078+2T>A variant causes a splice donor change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,310 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 2/2 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: ADA NM_000022.4 splice_donor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Likely pathogenic reviewed by expert panel P:2
• Conservation: PhyloP100: 2.50

Genes affected

ADA (HGNC:186): (adenosine deaminase) This gene encodes an enzyme that catalyzes the hydrolysis of adenosine to inosine in the purine catabolic pathway. Various mutations have been described for this gene and have been linked to human diseases related to impaired immune function such as severe combined immunodeficiency disease (SCID) which is the result of a deficiency in the ADA enzyme. In ADA-deficient individuals there is a marked depletion of T, B, and NK lymphocytes, and consequently, a lack of both humoral and cellular immunity. Conversely, elevated levels of this enzyme are associated with congenital hemolytic anemia. [provided by RefSeq, Sep 2019]

PKIG (HGNC:9019): (cAMP-dependent protein kinase inhibitor gamma) This gene encodes a member of the protein kinase inhibitor family. Studies of a similar protein in mice suggest that this protein acts as a potent competitive cAMP-dependent protein kinase inhibitor, and is a predominant form of inhibitor in various tissues. The encoded protein may be involved in osteogenesis. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2013]

ACMG classification

Verdict is Pathogenic. Variant got 22 ACMG points.

• PVS1: Splicing 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
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 20-44620297-A-T is Pathogenic according to our data. Variant chr20-44620297-A-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 558340.Status of the report is reviewed_by_expert_panel, 3 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ADA	NM_000022.4	c.1078+2T>A		splice_donor_variant		ENST00000372874.9
ADA	NM_001322050.2	c.673+2T>A		splice_donor_variant
ADA	NM_001322051.2	c.1006+2T>A		splice_donor_variant
ADA	NR_136160.2	n.1105+2T>A		splice_donor_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ADA	ENST00000372874.9	c.1078+2T>A		splice_donor_variant		1	NM_000022.4	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461310 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727030

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: reviewed by expert panel

Submissions by phenotype

Severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency Pathogenic:2

Likely pathogenic, reviewed by expert panel	curation	ClinGen Severe Combined Immunodeficiency Variant Curation Expert Panel, ClinGen	Jan 23, 2024	The c.1078+2T>A (NM_000022.4) variant in ADA occurs within the canonical splice donor site (+2) of intron 11. It is predicted to cause skipping of biologically relevant exon by SpliceAI (Δ score = Donor Loss = 0.97); however, due to the location, it is NOT predicted to undergo NMD. There aren't known downstream pathogenic variants; PVS1_Moderate. This variant is absent from gnomAD v2.1.1 (PM2_Supporting). At least one patient present: Reduced ADA enzyme activity in patient cells (1pt) + Increased dAdo nucleotides (dATP or dAXP) in pretreatment erythrocytes (2pts), reaching 3 points, PP4_Moderate. This variant has been detected in 02 individuals with ADA SCID. One of them is compound heterozygous with c.955-958delGAAG, p.E320RfsX6, a frameshift termination, which is at least LP according to SCID VCEP. Phase is unknown, so 0.5 pt; The second one is compound heterozygous, for c.482G > A, p.W161X (Also at least LP according to SCID VCEP). Phase is not shown. 0.5pts. Total is 1 pt, PM3_Moderate (PMIDs: 32307643 and 26255240). In summary, this variant is classified as a Likely Pathogenic for autosomal recessive SCID based on ACMG/AMP criteria applied, as specified by the ClinGen SCID VCEP (specification version 1.0): PM2_Supporting, PVS1_Strong, PP4_Moderate, and PM3_Moderate. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	May 14, 2018	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Benign	-0.15
Cadd	Uncertain	25
Dann	Uncertain	0.97
Eigen	Pathogenic	0.74
Eigen_PC	Uncertain	0.50
FATHMM_MKL	Uncertain	0.94	D
MutationTaster	Benign	1.0	D;D;D;D
GERP RS		4.7

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.97		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.97		Position offset: 2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555843178; hg19: chr20-43248938;