Is CLCN1 p.Pro883= (c.2649C>T) pathogenic?

CLCN1 p.Pro883= (c.2649C>T) is classified Likely benign in CLCN1 (ClinVar, Single submitter, 1 submitter; last evaluated 2023-07-29). Very rare (popmax 0.000678%, nfe); Associated with myotonia congenita, autosomal dominant.

What condition is associated with CLCN1 p.Pro883= (c.2649C>T)?

CLCN1 p.Pro883= (c.2649C>T) is associated with myotonia congenita, autosomal dominant, myotonia congenita, autosomal recessive (ClinVar).

How common is CLCN1 p.Pro883= (c.2649C>T) in the general population?

CLCN1 p.Pro883= (c.2649C>T) is very rare (popmax 0.000678%, nfe) (gnomAD).

How is Thomsen and Becker disease inherited?

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

CLCN1 p.Pro883=

c.2649C>T · rs146366176 · VCV2923412

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.000678%, nfe)

Conditions

myotonia congenita, autosomal dominant

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Splicing
SpliceAI	<0.2	no splice effect predicted · four deltas, not one · how we know
Constraint at this position
Conservation	phyloP -3.5	GERP -12
Overall
CADD	2.365	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.000678% European (non-Finnish) · 8/1,180,050 alleles

Filtering AF 0.000292% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000211%

Overall 0.000496% 8/1,614,102 alleles · very rare exomes 6/1,461,886 · genomes 2/152,216 · joint denominator

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: CLCN1
Protein: p.Pro883=
Coding: c.2649C>T
MANE Select: NM_000083
dbSNP: rs146366176
Type: single nucleotide variant
Location: chr7:143351647 (GRCh38)
Gene constraint: LOEUF 1.026 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 68.34 · 9 PDB
Residue 883: the 'disordered' region

Full CLCN1 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

myotonia congenita, autosomal dominant — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: myotonia congenita, autosomal recessive

For Thomsen and Becker disease (Orphanet):

Inheritance: Autosomal dominant, Autosomal recessive
Onset: Adolescent, Adult, Childhood, Infancy
Prevalence: 1-9 / 100 000 (Worldwide)

Similar variants

CLCN1 p.Pro883Thr Uncertain significance ★★ ⚠ same residue
CLCN1 c.1167-10T>C Pathogenic/Likely pathogenic ★★ same condition
CLCN1 c.1401+1G>T Pathogenic/Likely pathogenic ★★ same condition
CLCN1 c.1471+1G>A Pathogenic/Likely pathogenic ★★ same condition
CLCN1 c.180+1G>A Likely pathogenic ★★ same condition
CLCN1 c.180+3A>T Pathogenic/Likely pathogenic ★★ same condition
CLCN1 c.1930+1G>A Pathogenic/Likely pathogenic ★★ same condition
CLCN1 c.2172+1G>A Pathogenic ★★ 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/clcn1-p-pro883 (accessed [today's date]).

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