Is CTNS p.Leu303= (c.909C>T) pathogenic?

CTNS p.Leu303= (c.909C>T) is classified Likely benign in CTNS (ClinVar, Single submitter, 2 submitters; last evaluated 2023-04-06). Ultra-rare (popmax 0.0331%, mid); Associated with ocular cystinosis.

What condition is associated with CTNS p.Leu303= (c.909C>T)?

CTNS p.Leu303= (c.909C>T) is associated with ocular cystinosis, juvenile nephropathic cystinosis, cystinosis (ClinVar).

How common is CTNS p.Leu303= (c.909C>T) in the general population?

CTNS p.Leu303= (c.909C>T) is ultra-rare (popmax 0.0331%, mid) (gnomAD).

How is Cystinosis inherited?

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

CTNS p.Leu303=

c.909C>T · rs1252160181 · VCV1090762

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 2 submitters

gnomAD v4.1

Rare

ultra-rare (popmax 0.0331%, mid)

Conditions

ocular cystinosis

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 -0.17	GERP -0.7, phastCons 0.5
Overall
CADD	7.596	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0331% Middle Eastern · 2/6,036 alleles

Filtering AF 0.00584% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00243%

Overall 0.000547% 8/1,461,646 alleles · ultra-rare

Ancestry group	Frequency	1 in
Middle Easterngrpmax	0.0331%	3,018
European (non-Finnish)	0.000508%	196,669

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: CTNS
Protein: p.Leu303=
Coding: c.909C>T
MANE Select: NM_004937
dbSNP: rs1252160181
Type: single nucleotide variant
Location: chr17:3659914 (GRCh38)
Gene constraint: LOEUF 0.754 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 89.27 · 6 PDB
Residue 303: an α-helix; the pq-loop 2 domain

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

Disease context

ocular cystinosis — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: juvenile nephropathic cystinosis cystinosis

For Cystinosis (Orphanet):

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

Similar variants

CTNS p.Leu303Phe Uncertain significance ★★ ⚠ same residue
CTNS c.140+1G>T Pathogenic/Likely pathogenic ★★ same condition
CTNS c.140+2T>C Pathogenic/Likely pathogenic ★★ same condition
CTNS c.141-1G>A Pathogenic/Likely pathogenic ★★ same condition
CTNS c.141-24T>C Pathogenic ★★ same condition
CTNS c.225+3A>T Pathogenic/Likely pathogenic ★★ same condition
CTNS c.225+5G>A Likely pathogenic ★★ same condition
CTNS c.61+2T>C Likely 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/ctns-p-leu303 (accessed [today's date]).

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