Is ALG2 p.Leu66= (c.198A>G) pathogenic?

ALG2 p.Leu66= (c.198A>G) is classified Likely benign in ALG2 (ClinVar, Single submitter, 1 submitter; last evaluated 2024-12-05). Very rare (popmax 0.00268%, afr); Associated with ALG2-congenital disorder of glycosylation.

What condition is associated with ALG2 p.Leu66= (c.198A>G)?

ALG2 p.Leu66= (c.198A>G) is associated with ALG2-congenital disorder of glycosylation, congenital myasthenic syndrome 14 (ClinVar).

How common is ALG2 p.Leu66= (c.198A>G) in the general population?

ALG2 p.Leu66= (c.198A>G) is very rare (popmax 0.00268%, afr) (gnomAD).

How is ALG2-CDG inherited?

Typically Autosomal recessive (Orphanet). A genetic counselor can assess individual risk for a family.

ALG2 p.Leu66=

c.198A>G · rs374316187 · VCV1589256

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00268%, afr)

Conditions

ALG2-congenital disorder of glycosylation

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP -0.22	phastCons 0.26
Overall
CADD	6.472	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00268% African / African-American · 2/74,592 alleles

Filtering AF 0.000619% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000477%

Overall 0.00107% 17/1,583,704 alleles · very rare exomes 16/1,431,390 · genomes 1/152,314 · joint denominator

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.00268%	37,296
Remaining individualsnot grpmax-eligible	0.00162%	61,654
South Asian	0.00113%	88,826
European (non-Finnish)	0.00111%	90,112

Rarity supports pathogenicity (ACMG PM2); frequency above a disease-specific BA1/BS1 threshold argues against it. A variant frequent in one ancestry group can be near-absent in others, so a single global figure can mislead.

Variant & gene context

Gene: ALG2
Protein: p.Leu66=
Coding: c.198A>G
MANE Select: NM_033087
dbSNP: rs374316187
Type: single nucleotide variant
Location: chr9:99221697 (GRCh38)
Gene constraint: LOEUF 1.408 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 91.03

Full ALG2 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

ALG2-congenital disorder of glycosylation — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: congenital myasthenic syndrome 14

For ALG2-CDG (Orphanet):

Inheritance: Autosomal recessive
Onset: Infancy, Neonatal

Similar variants

ALG2 p.Ala29Pro Uncertain significance ★★ ⚠ same condition
ALG2 p.Ala36Val Uncertain significance ★★ ⚠ same condition
ALG2 p.Ala71Gly Uncertain significance ★★ ⚠ same condition
ALG2 p.Ala71Val Uncertain significance ★★ ⚠ same condition
ALG2 p.Arg129Gln Uncertain significance ★★ ⚠ same condition
ALG2 p.Arg130Gln Uncertain significance ★★ ⚠ same condition
ALG2 p.Arg251His Uncertain significance ★★ ⚠ same condition
ALG2 p.Arg378Cys Uncertain significance ★★ ⚠ same condition

Built on 18 open, versioned datasets — ClinVar, gnomAD, AlphaMissense, REVEL, ClinGen & more — plus Sugi Variant's own cross-source analysis. Source data 2026-01–2026-10, ClinVar 2026-10. Full sources & versions →

Cite Sugi Variant

Gür T. Sugi Variant: A Deterministic Per-Variant Germline Reference from a Knowledge Graph for Humans and AI Agents. 2026. doi:10.5281/zenodo.21509445. This variant: https://sugi.bio/variant/alg2-p-leu66 (accessed [today's date]).

Preprint & method: sugi.bio/variant/method Machine-readable: this page as Markdown