Early onset or syndromic epilepsy

Gene: ATP6V1A

Green List (high evidence)

Comment on mode of inheritance: There are more than 30 individuals reported in literature with heterozygous de novo missense variants in ATP6V1A and a Developmental and epileptic encephalopathy (including early onset seizures in at least 28 cases). There are also 6 probands reported with biallelic ATP6V1A variants, of which only 2 presented with seizures. Hence, the mode of inheritance should be changed to
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted. As this is a demotion of the BIALLELIC MOI, an expert_review tag was also added.

Created: 9 Sep 2026, 1:05 p.m. | Last Modified: 9 Sep 2026, 1:05 p.m.

Panel Version: 9.78

BIALLELIC CASES:
PMID: 33320377 Vogt et al., 2021
Report of three affected individuals with a severely progeroid form of congenital cutis laxa with generalized muscular hypotonia (2 sibs from a Hungarian family and a boy from a consanguineous Turkish family). Method: WES. No seizures noted in either family.

Male proband from Family A showed generalized cutis laxa with redundant skin and muscular hypotonia, progeroid appearance, bilateral leg weakness, bilateral contractures of his hips and knees; muscle biopsy revealed increased connective and fatty tissue, increased variability of fiber size, rounded fibers, some central nuclei and degenerating fibers with vacuoles. CK was strongly elevated. He died at 8 days of age due to cardiac and respiratory failure. His brother was similarly affected, but his symptoms improved and he is alive at 17 years old. Although weak muscle tone and thin skin remained, he has normal cognition and attends high school. Proband was comp het for ATP6V1A variants: c.317 T > C, p.(Leu106Ser) & c.1513_1514del, p.(Asp505*)

Male proband from Family B presented at birth with generalized muscular hypotonia, retrognathia and severe cutis laxa. He had normal speech and cognitive development. General muscular hypotonia and weakness were noted at age 4 years. Cranial MRI showed a cortical atrophy. His CK was elevated. His muscle weakness improved over time - he had normal endurance and muscle strength without any progression or loss of motor functions at 15yo. He was found to be homozygous for ATP6V1A: c.284 T > A, p.(Met95Lys).

PMID: 28065471 Van Damme et al., 2017
Report of 5 families with syndromic cutis laxa and biallelic variants in ATP6V1E1 (2 families from Iran and Kuwait) and ATP6V1A (3 families from Germany, Turkey, and Pakistan). 2/3 families with ATP6V1A variants were consanguineous, and the probands were homozygous for the same ATP6V1A variant: c.215G>A, p.Gly72Asp. The German proband was homozygous for c.1012C>T, p.Arg338Cys.
Patient phenotypes: cutis laxa 3/3, severe hypotonia 3/3, cardiac abnormalities 3/3, aortic dilation 1/3, seizures 2/2 (1 not determined), contractures 1/3, MRI abnormalities (3/3 - 1 mild with an anatomical variant of the cavum septum pellucidum).
All parents reported to be unaffected.

MONOALLELIC CASES:
PMID: 40225911 Ma et al., 2024
Literature review of 31 previously reported cases with monoallelic de novo missense ATP6V1A variants and a Developmental and epileptic encephalopathy (DEE), plus two new cases with de novo heterozygous variants: c.1061G>T/p.(Trp354Leu) and c.746C>T/p.(Pro249Leu).
Common patient features from literature review: seizures (28/33), global developmental delay (29/33), hypotonia in infancy (24/33). Seizures mostly started within first 3 years of life (23/33). Most patients had no speech or poor language skills, which correlated with seizure severity. Brain MRI of 22 patients showed: hypomyelination in 13 patients, mild brain and cerebellar atrophy in 13 patients, thin corpus callosum in 4 patients, and bilateral lateral ventricle body broaden in one patient.

ATP6V1A is associated with Cutis laxa, autosomal recessive, type IID and AD Developmental and epileptic encephalopathy 93 in OMIM (Accessed 9th Sept 2026).

Created: 9 Sep 2026, 11:05 a.m. | Last Modified: 9 Sep 2026, 12:54 p.m.

Panel Version: 9.76

Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted

Phenotypes
Developmental and epileptic encephalopathy 93, OMIM:618012; developmental and epileptic encephalopathy 93, MONDO:0020632

Publications

• 28065471
• 33320377
• 40225911

I don't know

Review and rating collated by Tracy Lester (Oxford Medical Genetics Laboratories Oxford University Hospitals NHS Foundation Trust, 2019_02_06) on behalf of Wessex and West Midlands GLH for GMS Neurology specialist test group, for Clinical Indication R59 'Early onset or syndromic epilepsy'. Review contributors: John Taylor and Helen Lord. Suggested gene rating: Green.

Created: 6 Aug 2019, 8:38 p.m. | Last Modified: 6 Aug 2019, 8:38 p.m.

Panel Version: 1.189

Green List (high evidence)

AD infantile or early childhood epileptic encephalopathy 3 - delayed psychomotor development, early onset refractory seizures and ID. Fassio et al, 2018 - 4 unrelated patients aged 8-14 with early onset epileptic encephalopathy. Patients of Italian, Mexican, Turkish and Japanese descent. 4 diff de novo het missense variants idenitifed In vitro expression studies done in 2 of these - support pathogenicity.

Created: 6 Aug 2019, 8:31 p.m. | Last Modified: 6 Aug 2019, 8:31 p.m.

Panel Version: 1.188

Mode of inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal

Phenotypes
Cutis laxa, type IID, 617403; Epileptic encephalopathy, infantile or early childhood, 618012

Publications

• 29668857

Comment when marking as ready: Associated with phenotype in OMIM and not in Gen2Phen. At least 4 variants were identified in unrelated cases of Epileptic encephalopathy, infantile or early childhood, 3 618012, one variant (c.1045G>A, NM_001690.3, p.D349N) appear give gain of function results in in vitro analysis, whereas the others had loss of function. Two homozygous variants were reported in two unrelated cases of Cutis laxa, autosomal recessive, type IID 617403 who both had seizures as part of their phenotypes.

Created: 18 Nov 2018, 10:49 p.m.

Comment on phenotypes: Monoallelic variants associated with Epileptic encephalopathy, infantile or early childhood, 3 618012 and biallelic variants associated with Cutis laxa, autosomal recessive, type IID 617403. Both phenotypes include seizures.

Created: 18 Nov 2018, 10:44 p.m.

Green List (high evidence)

Heterozygous mutations in ATP6V1A cause Epileptic encephalopathy, infantile or early childhood, type 3 (MIM 618012).

PMID: 29668857 reports on 4 individuals from 4 families with de novo pathogenic variants in ATP6V1A. The phenotype was consistent with a developmental encephalopathy with epilepsy.

All patients were found to harbor missense variants. The variants resulted in altered lysosomal homeostasis, abnormal neuritogenesis and synaptic density. However in one of the variants tested (p.Asp100Tyr) pathogenicity was mediated by loss-of-function mechanism while for another (p.Asp349Asn) by gain-of-function mechanism.

Differences in severity were noted, with two variants (incl. Asp100Tyr) being associated with a more severe phenotype and the two other (incl. Asp349Asn) with milder degrees of ID and epilepsy.

Biallelic ATP6V1A mutations cause Cutis laxa type IID (MIM 617403). PMID: 28065471 is the first report on 3 individuals from 3 different families (2 of which were consanguineous). All patients were homozygous for ATP6V1A pathogenic variants. All three presented with hypotonia, one (or possibly two) with developmental delay and two with seizures although the developmental phenotype is not further commented on. (Additional patients described in the article harbored mutations in other genes and were not considered).

As a result, this gene can be considered for inclusion in this panel as green.
Sources: Literature, Expert Review

Created: 17 Nov 2018, 7:53 a.m.

Mode of inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal

Phenotypes
# 618012 EPILEPTIC ENCEPHALOPATHY, INFANTILE OR EARLY CHILDHOOD, 3 - IECEE3; # 617403 CUTIS LAXA, AUTOSOMAL RECESSIVE, TYPE IID - ARCL2D

Publications

• 29668857
• 28065471