RHO-Related Retinopathy

👪

Inheritance

2

Autosomal dominant inheritance HP:0000006

Most RHO-related disease is autosomal dominant; gain-of-function and dominant negative mechanisms underlie both the RP4 and CSNBAD1 branches.

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:29042326 SUPPORT Human Clinical

"whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity."

This review directly supports autosomal dominant inheritance as the principal mode across both the degenerative and stationary RHO branches.

Autosomal recessive inheritance HP:0000007

Rare null or severe hypomorphic RHO alleles can produce autosomal recessive RP through loss of rhodopsin function.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:29042326 SUPPORT Human Clinical

"Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity."

This review identifies loss-of-function as the mechanism underlying the rare recessive RP branch within the RHO family.

◆

Subtypes

2

Retinitis Pigmentosa 4 MONDO:0013395

The dominant branch: autosomal dominant progressive rod-cone dystrophy presenting with childhood or early-adult nyctalopia, followed by progressive peripheral field loss and late central visual impairment. A generalized phenotype (75% of patients) progresses faster than a sector phenotype (25%), with median age to low vision at 52 years based on central visual field.

Show evidence (2 references)

PMID:32301896 SUPPORT Human Clinical

"Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"

Multicenter natural-history cohort of 100 RHO-associated RP patients documents RP4 as the major subtype with two recognized severity classes.

PMID:29042326 SUPPORT Human Clinical

"Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."

This comprehensive review establishes RP4 as the dominant disease branch within the RHO family.

Congenital Stationary Night Blindness Autosomal Dominant 1 MONDO:0012498

Rare gain-of-function RHO branch (G90D, T94I) causing congenital, non-progressive night blindness without retinal degeneration. Constitutive rhodopsin activation generates dark continuous noise that saturates rod phototransduction in the absence of light. The absence of degeneration is definitional for CSNBAD1 as an entity rather than a prediction for every carrier of the variants named: in the largest p.G90D cohort characterized to date only 20% were classified as CSNB while 53.3% had classic retinitis pigmentosa, so p.G90D carriers specifically may progress and be reclassified (see the evidence below and the caveat on the Congenital night blindness phenotype). T94I, A292E, and A295V have not been associated with degeneration.

Show evidence (4 references)

PMID:38743626 SUPPORT Model Organism

"G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization."

Knock-in mouse study mechanistically demonstrates that constitutive G90D-rhodopsin activity in darkness is the proximal cause of the stationary night-blindness phenotype.

PMID:29042326 SUPPORT Human Clinical

"Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP)."

This review explicitly places CSNBAD1 within the RHO mutation spectrum as a distinct gain-of-function subtype.

PMID:33669941 SUPPORT Human Clinical

"Nevertheless, the high occurrence of degeneration in our p.G90D cohort warrants caution in diagnosing p.G90D patients with CSNB without a longer follow up into adulthood."

Qualifies the "without retinal degeneration" clause of this description at the genotype level rather than supporting it. In this cohort of 15 p.G90D carriers only 20% were classified as CSNB while 53.3% had classic RP, so the authors advise against a CSNB diagnosis in p.G90D without long follow-up. Graded PARTIAL because CSNBAD1 as an entity remains defined as non-progressive (the same paper states "CSNB is considered a non-progressive rod dysfunction without retinal degeneration" and notes that other RHO-CSNB variants have not been associated with degeneration) — progressors are reclassified as RP rather than counted as degenerating CSNBAD1. The tension is between the nosological category and the genotype's real range, and both halves are recorded here rather than one being dropped.

+ 1 more reference

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Pathophysiology

4

Rhodopsin Misfolding and ER Stress

The majority of pathogenic RHO variants, most prominently P23H, produce misfolded rhodopsin that is retained in the endoplasmic reticulum rather than delivered to photoreceptor outer segments. Accumulation of misfolded rhodopsin triggers the unfolded protein response and proteotoxic stress. A second group of variants (e.g., P347L) produce correctly folded but mistrafficked rhodopsin that fails to reach the outer segment due to disrupted C-terminal sorting signals. Both mechanisms impair rod photoreceptor homeostasis and converge on rod apoptosis.

retinal rod cell CL:0000604

RHO hgnc:10012 ↓ DECREASED

protein folding GO:0006457 ↓ DECREASED response to endoplasmic reticulum stress GO:0034976 ↑ INCREASED photoreceptor cell maintenance GO:0045494 ↓ DECREASED

Downstream

Rod Photoreceptor Apoptosis Persistent ER stress and proteotoxicity from misfolded or mistrafficked rhodopsin overwhelm the adaptive unfolded protein response and trigger programmed rod cell death.

Show evidence (1 reference)

PMID:29042326 SUPPORT Human Clinical

"Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."

This review supports the breadth of RHO missense variation underlying the RP4 pathophysiology trunk.

Rod Photoreceptor Apoptosis

Proteotoxic or homeostatic failure in rod photoreceptors, driven by misfolded or mistrafficked rhodopsin, leads to rod-selective apoptotic cell death. This node is the shared convergence point for all RP4-causing RHO variants regardless of upstream mechanism class.

retinal rod cell CL:0000604

neuron apoptotic process GO:0051402 ↑ INCREASED photoreceptor cell maintenance GO:0045494 ↓ DECREASED

Downstream

Night blindness Primary rod photoreceptor loss from apoptosis produces nyctalopia, the earliest and most consistent presenting symptom of RP4, reflecting direct rod-mediated scotopic dysfunction.

Secondary Cone Degeneration and Progressive Vision Loss Primary rod loss deprives cones of rod-derived trophic support and disrupts the retinal environment, driving secondary cone degeneration and loss of central vision.

Show evidence (1 reference)

PMID:32301896 SUPPORT Human Clinical

"Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"

This natural-history cohort supports progressive rod-driven degeneration as the central RP4 pathological process.

Secondary Cone Degeneration and Progressive Vision Loss

Following primary rod loss, photoreceptor degeneration extends to involve cones, producing progressive central visual field constriction and eventual loss of visual acuity. Retinal remodeling with pigment migration produces characteristic bone-spicule pigmentation on fundus examination.

retinal rod cell CL:0000604 retinal cone cell CL:0000573

photoreceptor cell maintenance GO:0045494 ↓ DECREASED

Downstream

Progressive peripheral visual field loss Advancing rod-cone degeneration constricts peripheral visual fields progressively, with median age for low vision (central visual field <20°) of 52 years in the generalized phenotype.

Reduced visual acuity Late cone involvement and macular degeneration produce central visual acuity loss. Median age to mild visual acuity impairment is 72 years.

Show evidence (1 reference)

PMID:32301896 SUPPORT Human Clinical

"Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%), in terms of decline rates of the BCVA (P < 0.001) and V4e retinal seeing areas (P < 0.005)."

Structural OCT data link photoreceptor-RPE complex thinning to visual acuity loss, supporting progressive cone involvement in the late stage.

Constitutive Rhodopsin Activation in Darkness

Gain-of-function RHO variants (G90D, T94I) shift the receptor toward an active conformation in the absence of photon absorption. This generates dark continuous phototransduction noise that saturates the rod signaling cascade, mimicking constant low-level illumination and abolishing the rod's capacity for dark-adapted detection of dim light. Unlike RP4, this branch does not cause photoreceptor degeneration.

retinal rod cell CL:0000604

RHO gain-of-function variant hgnc:10012 ↕ DYSREGULATED

G protein-coupled opsin signaling pathway GO:0016056 ↕ DYSREGULATED phototransduction GO:0007602 ↕ DYSREGULATED

Downstream

Congenital night blindness Persistent constitutive rhodopsin activation desensitizes rods in darkness, causing non-progressive congenital night blindness without retinal structural degeneration.

Show evidence (2 references)

PMID:38743626 SUPPORT Model Organism

"dark continuous noise comprising low-amplitude unitary events occurring at a very high molecular rate equivalent in effect to ~40,000-fold of R* s-1 from WT-Rho."

Quantitative mouse data establish that the extraordinary magnitude of constitutive G90D noise explains profound rod desensitization in CSNB.

PMID:29042326 SUPPORT Human Clinical

"Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP). Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or..."

This review places gain-of-function constitutive activation as the mechanistic basis distinguishing CSNBAD1 from the RP4 branch.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

8

Eye 7

Night blindness VERY_FREQUENT Nyctalopia HP:0000662

Show evidence (1 reference)

PMID:29042326 SUPPORT Human Clinical

"Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."

Regraded to PARTIAL: the sentence links RHO mutations to RP but says nothing about nyctalopia. Treating it as SUPPORT for night blindness relies on the classical definition of RP supplying the missing step, which is reasoning rather than evidence. Same generic-definitional-snippet pattern as the companion item on the Night blindness causal edge.

Progressive peripheral visual field loss VERY_FREQUENT Constriction of peripheral visual field HP:0001133

Show evidence (1 reference)

PMID:32301896 SUPPORT Human Clinical

"Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"

The multicenter cohort confirms progressive peripheral field loss as the dominant early functional deficit in RP4, with rate varying by phenotype class.

Rod-cone dystrophy VERY_FREQUENT HP:0000510

Show evidence (1 reference)

PMID:29042326 SUPPORT Human Clinical

"Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."

Regraded to PARTIAL: the sentence establishes that RHO mutations cause a degenerative retinal condition, but says nothing about the rod-first sequence with secondary cone involvement that defines a rod-cone dystrophy. It supports the classification only via the general meaning of "retinitis pigmentosa", not by stating the ordering this node asserts.

Reduced visual acuity FREQUENT HP:0007663

Show evidence (1 reference)

PMID:32301896 SUPPORT Human Clinical

"For the best-corrected visual acuity (BCVA), the median age to reach mild impairment (20/67 ≤ BCVA < 20/40) was 72 years, whereas this could not be computed for lower acuities."

Natural-history data directly quantify the late onset of central acuity loss (median 72 years to mild impairment), supporting a predominantly rod-first degenerative trajectory with late cone and macular involvement.

Reduced rod electroretinogram VERY_FREQUENT Abnormal electroretinogram HP:0000512

Show evidence (2 references)

PMID:33669941 SUPPORT Human Clinical

"The function of the rod system, as revealed by dark-adapted (DA) full-field ERG (ffERG), was highly dysfunctional in all patients."

Direct human RHO source for this node: dark-adapted full-field ERG was highly dysfunctional in every patient tested in this p.G90D cohort, and the patients with classic RP specifically showed undetectable rod-specific (DA 0.01) responses. That is the scotopic rod ERG reduction this phenotype asserts, observed rather than inferred.

PMID:32301896 SUPPORT Human Clinical

"Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%), in terms of decline rates of the BCVA (P < 0.001) and V4e retinal seeing areas (P < 0.005)."

Regraded to PARTIAL: this natural-history cohort quantifies decline in BCVA and V4e visual-field area, not electroretinography — the cached record contains no ERG content beyond a MeSH keyword. It corroborates progressive rod-cone functional loss in RP4, which is what the ERG is a readout of, but it does not itself evidence a reduced rod ERG. The PMID:33669941 item above carries that observation.

Riggs-type electroretinogram VERY_FREQUENT Abnormal electroretinogram HP:0000512

Show evidence (4 references)

PMID:30051303 SUPPORT Human Clinical

"CSNB from abnormalities in phototransduction can be recessive or dominant and is much less common. This produces a Riggs type of ERG with loss of the rod a-wave as well as the b-wave."

Establishes the electrophysiological dichotomy in CSNB: phototransduction defects (the class to which gain-of-function RHO CSNBAD1 belongs) produce a Riggs-type ERG with loss of the rod a-wave, whereas the "negative" Schubert-Bornschein ERG with a preserved large a-wave arises from photoreceptor-to-bipolar-cell transmission defects.

PMID:38743626 SUPPORT Model Organism

"One well-studied rhodopsin point mutant, G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization."

Sources the disease-level step directly for RHO rather than by inference from the CSNB class: a rhodopsin point mutant causes CSNB through constitutive activity in darkness that desensitizes rods. That is a phototransduction-level lesion, which is what produces the Riggs-type ERG pattern rather than an inner-retinal transmission defect. The companion PMID:30051303 item carries only the class-level ERG dichotomy.

PMID:33669941 SUPPORT Human Clinical

"CSNB caused by RHO mutations is of the Riggs type, electroretinographically characterized by the complete loss of rod-specific ERG activity. DA bright flash (3.0) ERG typically exhibits a reduced DA a-wave and low b-wave, while the LA cone-specific responses are largely normal, reflecting..."

Human RHO-specific source for this node: a clinical cohort of p.G90D patients states directly that RHO-related CSNB is of the Riggs type, with loss of rod-specific ERG activity and a reduced dark-adapted a-wave together with a low b-wave, while cone responses are largely preserved. This supplies the human counterpart to the G90D knock-in mouse item above, which CLAUDE.md requires for a human phenotype.

+ 1 more reference

Congenital night blindness VERY_FREQUENT Nyctalopia HP:0000662

The largest p.G90D cohort characterized to date (PMID:33669941, 15 patients from three families) classified only 20% as CSNB, with 53.3% developing classic retinitis pigmentosa, and cautioned against diagnosing p.G90D patients with CSNB without long follow-up into adulthood. Other RHO-CSNB variants (T94I, A292E, A295V) have not been associated with progressive disease.

Show evidence (2 references)

PMID:33669941 SUPPORT Human Clinical

"All patients had night vision problems for as long as they could remember, which did not worsen with age."

Human RHO-specific source for congenital, non-worsening night blindness in a p.G90D cohort, and the basis for the VERY_FREQUENT band. The quoted sentence covers all 15 characterized p.G90D carriers, which is a wider denominator than this node's CSNBAD1 scope; within that scope the band rests on the 3/3 patients classified as CSNB, and it holds on either denominator. Replaces reliance on model-organism evidence alone for this human phenotype.

PMID:38743626 SUPPORT Model Organism

"Congenital stationary night blindness (CSNB) is an inherited retinal disease that causes a profound loss of rod sensitivity without severe retinal degeneration."

Regraded to PARTIAL: this is a class-level definitional statement about CSNB in general, not a RHO-specific or patient-level observation, so it frames the phenotype rather than establishing it for this subtype. The RHO-specific human step is carried by the PMID:33669941 item above.

Other 1

Spicular retinal pigmentation FREQUENT Spicular pigmentation of the retina HP:0007737

Show evidence (2 references)

PMID:29042326 SUPPORT Human Clinical

"Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."

Regraded to PARTIAL: this sentence never mentions pigmentation. Its only link to the claim is that the disease it names is "retinitis pigmentosa", so it supports the finding indirectly, through the disease definition, rather than reporting the fundus appearance. The companion PMID:33669941 item below carries the direct observation.

PMID:33669941 SUPPORT Human Clinical

"Bone spicule pigmentation was seen in all individuals with RP, localized in different areas depending on the pattern of retinal degeneration"

Direct human RHO source for this fundus finding: in the p.G90D cohort, bone-spicule pigmentation was present in every patient with an RP phenotype and in none of those diagnosed with CSNB. That observation both sources the finding for the RP4 branch and corroborates its absence from the CSNBAD1 branch, which is why the phenotype is scoped to RP4.

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Genetic Associations

1

RHO pathogenic variants (Causative)

Gene: RHO hgnc:10012

Autosomal dominant

Show evidence (2 references)

PMID:29042326 SUPPORT Human Clinical

"Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."

This review is the primary reference establishing RHO as the most common single adRP gene with a large pathogenic variant spectrum.

CGGV:assertion_29542633-051c-4b06-af52-d2c5a2a8ee90-2025-02-20T170000.000Z SUPPORT Other

ClinGen classifies the RHO–inherited retinal dystrophy gene-disease relationship as Definitive with semidominant inheritance, reflecting the predominance of AD disease alongside rare AR null-allele cases.

💊

Medical Actions

2

QR-1123

Action: Pharmacotherapy NCIT:C15986

QR-1123 is an investigational allele-selective RNase H-mediated gapmer ASO that targets and degrades the P23H mutant RHO mRNA while sparing wild-type RHO transcripts. It was administered as a single intravitreal injection. ProQR suspended the development program in April 2022 following a strategic restructuring after the ILLUMINATE trial failure for sepofarsen.

Show evidence (1 reference)

clinicaltrials:NCT04123626 SUPPORT Human Clinical

"This study evaluates the safety, tolerability and efficacy of QR-1123 injection in the eye (intravitreal; IVT) injections (one eye/unilateral) in subjects receiving a single dose or repeat doses."

AURORA Phase 1/2 first-in-human study confirms QR-1123 was clinically evaluated as an intravitreal ASO for adRP due to the P23H RHO mutation.

Low vision rehabilitation and supportive care

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Low vision aids, orientation and mobility training, and genetic counseling form the current standard of care for RP4. No approved pharmacotherapy exists.

Show evidence (1 reference)

PMID:32301896 SUPPORT Human Clinical

"Based on central visual fields, the optimal window of intervention for RHO-associated RP is before the 5th decade of life."

Natural-history data highlighting the optimal intervention window underscore the role of supportive care in managing this progressive disease pending disease-modifying therapies.

📊

Prevalence

2

IRD clinical genetics cohort (Foundation Fighting Blindness Consortium, 41 international centers, 33,834 patients)

4%

RHO was the fifth most common solved gene in a large multinational IRD cohort, accounting for 4% of all genetically solved cases. This ranks behind ABCA4, USH2A, RPGR, and PRPH2.

Show evidence (1 reference)

PMID:39908130 SUPPORT Human Clinical

"The most common genetic etiologies were ABCA4 (17%), USH2A (9%), RPGR (6%), PRPH2 (5%), and RHO (4%)."

The FFB Consortium gene poll provides the most current large-scale estimate of RHO burden across all inherited retinal disease.

Autosomal dominant RP (adRP) cohorts, Western populations

RHO mutations are the single most frequent cause of adRP, accounting for approximately 20–26% of adRP cases in North American and European cohorts. The P23H variant (c.68C>A) alone accounts for approximately 2,000–3,000 clinically affected patients in the United States.

Show evidence (2 references)

PMID:29042326 SUPPORT Human Clinical

"Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."

This comprehensive review establishes RHO as the leading single-gene cause of adRP across Western populations.

PMID:39278389 SUPPORT Human Clinical

"The estimated clinical prevalence of adRP due to RHO P23H based on literature review was approximately 2000-3000 patients."

Meta-analysis and population genetics modeling provide an independent US-specific estimate for the P23H variant alone.

🔬

Clinical Trials

1

NCT04123626 PHASE_I SUSPENDED

AURORA: first-in-human Phase 1/2 study of intravitreal QR-1123 (single and repeat doses) in adults with adRP due to the P23H RHO mutation. Open-label single-dose cohorts and double-masked repeat-dose cohorts. Program suspended by ProQR in April 2022.

Target Phenotypes: Rod-cone dystrophy HP:0000510 Night blindness HP:0000662

Show evidence (1 reference)

clinicaltrials:NCT04123626 SUPPORT

"This study evaluates the safety, tolerability and efficacy of QR-1123 injection in the eye (intravitreal; IVT) injections (one eye/unilateral) in subjects receiving a single dose or repeat doses."

AURORA (NCT04123626) was the sole clinical trial of QR-1123 and the most advanced ASO program for RHO-related RP to date.

{ }

Source YAML

click to show

name: RHO-Related Retinopathy
creation_date: "2026-06-22T00:00:00Z"
category: Mendelian
description: >
  RHO-related retinopathy is an umbrella of inherited retinal diseases caused by
  pathogenic variants in RHO, which encodes rhodopsin, the rod photoreceptor
  visual pigment. The dominant subtype is retinitis pigmentosa 4 (RP4), a
  progressive rod-cone dystrophy in which misfolded or mistrafficked rhodopsin
  drives proteotoxic stress and rod photoreceptor apoptosis, followed by
  secondary cone degeneration and irreversible vision loss. A minority of RHO
  variants are gain-of-function substitutions (G90D, T94I) that constitutively
  activate rhodopsin in darkness, producing congenital stationary night
  blindness autosomal dominant 1 (CSNBAD1), a non-progressive condition without
  retinal degeneration. With over 150 identified pathogenic variants, RHO
  mutations are collectively the most common cause of autosomal dominant RP and
  account for approximately 4% of all genetically solved inherited retinal
  disease.
disease_term:
  preferred_term: RHO-related retinopathy
  term:
    id: MONDO:0700380
    label: RHO-related retinopathy
synonyms:
- RHO-associated retinal dystrophy
- rhodopsin-associated retinitis pigmentosa
parents:
- Ophthalmological Disease
- Retinal Dystrophy
- Inherited retinal dystrophy
has_subtypes:
- name: RP4
  display_name: Retinitis Pigmentosa 4
  subtype_term:
    preferred_term: retinitis pigmentosa 4
    term:
      id: MONDO:0013395
      label: retinitis pigmentosa 4
  description: >
    The dominant branch: autosomal dominant progressive rod-cone dystrophy
    presenting with childhood or early-adult nyctalopia, followed by progressive
    peripheral field loss and late central visual impairment. A generalized
    phenotype (75% of patients) progresses faster than a sector phenotype (25%),
    with median age to low vision at 52 years based on central visual field.
  evidence:
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"
    explanation: >
      Multicenter natural-history cohort of 100 RHO-associated RP patients
      documents RP4 as the major subtype with two recognized severity classes.
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."
    explanation: >
      This comprehensive review establishes RP4 as the dominant disease branch
      within the RHO family.
- name: CSNBAD1
  display_name: Congenital Stationary Night Blindness Autosomal Dominant 1
  subtype_term:
    preferred_term: congenital stationary night blindness autosomal dominant 1
    term:
      id: MONDO:0012498
      label: congenital stationary night blindness autosomal dominant 1
  description: >
    Rare gain-of-function RHO branch (G90D, T94I) causing congenital,
    non-progressive night blindness without retinal degeneration. Constitutive
    rhodopsin activation generates dark continuous noise that saturates rod
    phototransduction in the absence of light. The absence of degeneration is
    definitional for CSNBAD1 as an entity rather than a prediction for every
    carrier of the variants named: in the largest p.G90D cohort characterized to
    date only 20% were classified as CSNB while 53.3% had classic retinitis
    pigmentosa, so p.G90D carriers specifically may progress and be reclassified
    (see the evidence below and the caveat on the Congenital night blindness
    phenotype). T94I, A292E, and A295V have not been associated with
    degeneration.
  evidence:
  - reference: PMID:38743626
    reference_title: "Dark continuous noise from mutant G90D-rhodopsin predominantly underlies congenital stationary night blindness."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization."
    explanation: >
      Knock-in mouse study mechanistically demonstrates that constitutive
      G90D-rhodopsin activity in darkness is the proximal cause of the
      stationary night-blindness phenotype.
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP)."
    explanation: >
      This review explicitly places CSNBAD1 within the RHO mutation spectrum
      as a distinct gain-of-function subtype.
  - reference: PMID:33669941
    reference_title: "Stationary and Progressive Phenotypes Caused by the p.G90D Mutation in Rhodopsin Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nevertheless, the high occurrence of degeneration in our p.G90D cohort warrants caution in diagnosing p.G90D patients with CSNB without a longer follow up into adulthood."
    explanation: >
      Qualifies the "without retinal degeneration" clause of this description at
      the genotype level rather than supporting it. In this cohort of 15 p.G90D
      carriers only 20% were classified as CSNB while 53.3% had classic RP, so
      the authors advise against a CSNB diagnosis in p.G90D without long
      follow-up. Graded PARTIAL because CSNBAD1 as an entity remains defined as
      non-progressive (the same paper states "CSNB is considered a
      non-progressive rod dysfunction without retinal degeneration" and notes
      that other RHO-CSNB variants have not been associated with degeneration) —
      progressors are reclassified as RP rather than counted as degenerating
      CSNBAD1. The tension is between the nosological category and the
      genotype's real range, and both halves are recorded here rather than one
      being dropped.
  - reference: PMID:9888392
    reference_title: "A novel mutation within the rhodopsin gene (Thr-94-Ile) causing autosomal dominant congenital stationary night blindness."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report the results of molecular genetic analysis of an Irish family segregating an autosomal dominant form of CSNB in which a previously unreported threonine-to-isoleucine substitution at codon 94 in the rhodopsin gene was found to segregate with the disease."
    explanation: >
      Human genetic source for the T94I half of this subtype description:
      T94I segregates with autosomal dominant CSNB in an Irish family. The
      quoted segregation finding is a clinical/molecular observation, which is
      what this item is graded on; the paper's proposed mechanism of
      constitutive transducin activation — consistent with the gain-of-function
      model of this branch — comes from computer modelling rather than from
      observation, and is not part of what this snippet establishes.
inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >
    Most RHO-related disease is autosomal dominant; gain-of-function and dominant
    negative mechanisms underlie both the RP4 and CSNBAD1 branches.
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity."
    explanation: >
      This review directly supports autosomal dominant inheritance as the
      principal mode across both the degenerative and stationary RHO branches.
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    Rare null or severe hypomorphic RHO alleles can produce autosomal recessive
    RP through loss of rhodopsin function.
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity."
    explanation: >
      This review identifies loss-of-function as the mechanism underlying the
      rare recessive RP branch within the RHO family.
prevalence:
- population: >-
    IRD clinical genetics cohort (Foundation Fighting Blindness Consortium,
    41 international centers, 33,834 patients)
  percentage: 4%
  notes: >-
    RHO was the fifth most common solved gene in a large multinational IRD cohort,
    accounting for 4% of all genetically solved cases. This ranks behind ABCA4,
    USH2A, RPGR, and PRPH2.
  evidence:
  - reference: PMID:39908130
    reference_title: "Characterizing the Genetic Basis for Inherited Retinal Disease: Lessons Learned From the Foundation Fighting Blindness Clinical Consortium's Gene Poll"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common genetic etiologies were ABCA4 (17%), USH2A (9%), RPGR (6%), PRPH2 (5%), and RHO (4%)."
    explanation: >
      The FFB Consortium gene poll provides the most current large-scale
      estimate of RHO burden across all inherited retinal disease.
- population: Autosomal dominant RP (adRP) cohorts, Western populations
  notes: >-
    RHO mutations are the single most frequent cause of adRP, accounting for
    approximately 20–26% of adRP cases in North American and European cohorts.
    The P23H variant (c.68C>A) alone accounts for approximately 2,000–3,000
    clinically affected patients in the United States.
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."
    explanation: >
      This comprehensive review establishes RHO as the leading single-gene
      cause of adRP across Western populations.
  - reference: PMID:39278389
    reference_title: "Prevalence Estimates and Genetic Diversity for Autosomal Dominant Retinitis Pigmentosa Due to RHO, c.68C>A (p.P23H) Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The estimated clinical prevalence of adRP due to RHO P23H based on literature review was approximately 2000-3000 patients."
    explanation: >
      Meta-analysis and population genetics modeling provide an independent
      US-specific estimate for the P23H variant alone.
pathophysiology:
- name: Rhodopsin Misfolding and ER Stress
  description: >
    The majority of pathogenic RHO variants, most prominently P23H, produce
    misfolded rhodopsin that is retained in the endoplasmic reticulum rather
    than delivered to photoreceptor outer segments. Accumulation of misfolded
    rhodopsin triggers the unfolded protein response and proteotoxic stress.
    A second group of variants (e.g., P347L) produce correctly folded but
    mistrafficked rhodopsin that fails to reach the outer segment due to
    disrupted C-terminal sorting signals. Both mechanisms impair rod
    photoreceptor homeostasis and converge on rod apoptosis.
  gene:
    preferred_term: RHO
    modifier: DECREASED
    term:
      id: hgnc:10012
      label: RHO
  cell_types:
  - preferred_term: retinal rod cell
    term:
      id: CL:0000604
      label: retinal rod cell
  biological_processes:
  - preferred_term: protein folding
    modifier: DECREASED
    term:
      id: GO:0006457
      label: protein folding
  - preferred_term: response to endoplasmic reticulum stress
    modifier: INCREASED
    term:
      id: GO:0034976
      label: response to endoplasmic reticulum stress
  - preferred_term: photoreceptor cell maintenance
    modifier: DECREASED
    term:
      id: GO:0045494
      label: photoreceptor cell maintenance
  downstream:
  - target: Rod Photoreceptor Apoptosis
    description: >
      Persistent ER stress and proteotoxicity from misfolded or mistrafficked
      rhodopsin overwhelm the adaptive unfolded protein response and trigger
      programmed rod cell death.
    evidence:
    - reference: PMID:29042326
      reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Here we categorise rhodopsin mutations into seven discrete classes; with defects ranging from misfolding and disruption of proteostasis, through mislocalisation and disrupted intracellular traffic to instability and altered function."
      explanation: >
        The seven-class mutation framework links diverse RP4-causing rhodopsin
        defects to shared downstream rod photoreceptor dysfunction and death.
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."
    explanation: >
      This review supports the breadth of RHO missense variation underlying
      the RP4 pathophysiology trunk.
- name: Rod Photoreceptor Apoptosis
  conforms_to: "photoreceptor_degeneration#Rod Photoreceptor Apoptosis"
  description: >
    Proteotoxic or homeostatic failure in rod photoreceptors, driven by
    misfolded or mistrafficked rhodopsin, leads to rod-selective apoptotic
    cell death. This node is the shared convergence point for all RP4-causing
    RHO variants regardless of upstream mechanism class.
  cell_types:
  - preferred_term: retinal rod cell
    term:
      id: CL:0000604
      label: retinal rod cell
  biological_processes:
  - preferred_term: neuron apoptotic process
    modifier: INCREASED
    term:
      id: GO:0051402
      label: neuron apoptotic process
  - preferred_term: photoreceptor cell maintenance
    modifier: DECREASED
    term:
      id: GO:0045494
      label: photoreceptor cell maintenance
  downstream:
  - target: Night blindness
    description: >
      Primary rod photoreceptor loss from apoptosis produces nyctalopia, the
      earliest and most consistent presenting symptom of RP4, reflecting direct
      rod-mediated scotopic dysfunction.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:29042326
      reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."
      explanation: >
        Regraded to PARTIAL: the quoted sentence establishes only that RHO
        mutations cause RP. It does not mention nyctalopia, so the step from
        "RHO causes RP" to "rod loss produces night blindness as the earliest
        symptom" is curator inference from the classical definition of RP
        rather than something this snippet states. It is a generic definitional
        sentence attached to a specific downstream claim — the anti-pattern
        recommendation 3 of the accompanying review report says should default
        to PARTIAL. A source reporting nyctalopia in RHO-RP patients directly
        would restore SUPPORT.
  - target: Secondary Cone Degeneration and Progressive Vision Loss
    description: >
      Primary rod loss deprives cones of rod-derived trophic support and
      disrupts the retinal environment, driving secondary cone degeneration
      and loss of central vision.
    evidence:
    - reference: PMID:32301896
      reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Based on central visual fields, the optimal window of intervention for RHO-associated RP is before the 5th decade of life."
      explanation: >
        Natural-history data showing late central visual field loss support
        secondary cone involvement downstream of primary rod degeneration.
  evidence:
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"
    explanation: >
      This natural-history cohort supports progressive rod-driven degeneration
      as the central RP4 pathological process.
- name: Secondary Cone Degeneration and Progressive Vision Loss
  description: >
    Following primary rod loss, photoreceptor degeneration extends to involve
    cones, producing progressive central visual field constriction and eventual
    loss of visual acuity. Retinal remodeling with pigment migration produces
    characteristic bone-spicule pigmentation on fundus examination.
  cell_types:
  - preferred_term: retinal rod cell
    term:
      id: CL:0000604
      label: retinal rod cell
  - preferred_term: retinal cone cell
    term:
      id: CL:0000573
      label: retinal cone cell
  biological_processes:
  - preferred_term: photoreceptor cell maintenance
    modifier: DECREASED
    term:
      id: GO:0045494
      label: photoreceptor cell maintenance
  downstream:
  - target: Progressive peripheral visual field loss
    description: >
      Advancing rod-cone degeneration constricts peripheral visual fields
      progressively, with median age for low vision (central visual field <20°)
      of 52 years in the generalized phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32301896
      reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"
      explanation: Faster field loss in the generalized phenotype supports progressive peripheral degeneration as the primary visual morbidity driver.
  - target: Reduced visual acuity
    description: >
      Late cone involvement and macular degeneration produce central visual
      acuity loss. Median age to mild visual acuity impairment is 72 years.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32301896
      reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "For the best-corrected visual acuity (BCVA), the median age to reach mild impairment (20/67 ≤ BCVA < 20/40) was 72 years, whereas this could not be computed for lower acuities."
      explanation: >
        Quantifies the 72-year median age to mild acuity impairment asserted in this
        edge's description, placing late central acuity loss downstream of primary
        peripheral rod-cone degeneration. Replaces a truncated fragment of this same
        sentence that carried no figure.
  evidence:
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%), in terms of decline rates of the BCVA (P < 0.001) and V4e retinal seeing areas (P < 0.005)."
    explanation: >
      Structural OCT data link photoreceptor-RPE complex thinning to visual
      acuity loss, supporting progressive cone involvement in the late stage.
- name: Constitutive Rhodopsin Activation in Darkness
  conforms_to: "phototransduction_cascade_dysfunction#Phototransduction Cascade Component Defect"
  description: >
    Gain-of-function RHO variants (G90D, T94I) shift the receptor toward an
    active conformation in the absence of photon absorption. This generates dark
    continuous phototransduction noise that saturates the rod signaling cascade,
    mimicking constant low-level illumination and abolishing the rod's capacity
    for dark-adapted detection of dim light. Unlike RP4, this branch does not
    cause photoreceptor degeneration.
  gene:
    preferred_term: RHO gain-of-function variant
    modifier: DYSREGULATED
    term:
      id: hgnc:10012
      label: RHO
  cell_types:
  - preferred_term: retinal rod cell
    term:
      id: CL:0000604
      label: retinal rod cell
  biological_processes:
  - preferred_term: G protein-coupled opsin signaling pathway
    modifier: DYSREGULATED
    term:
      id: GO:0016056
      label: G protein-coupled opsin signaling pathway
  - preferred_term: phototransduction
    modifier: DYSREGULATED
    term:
      id: GO:0007602
      label: phototransduction
  downstream:
  - target: Congenital night blindness
    description: >
      Persistent constitutive rhodopsin activation desensitizes rods in
      darkness, causing non-progressive congenital night blindness without
      retinal structural degeneration.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38743626
      reference_title: "Dark continuous noise from mutant G90D-rhodopsin predominantly underlies congenital stationary night blindness."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization."
      explanation: Knock-in mouse data directly link gain-of-function G90D rhodopsin activity to the rod-desensitization mechanism of CSNB.
  evidence:
  - reference: PMID:38743626
    reference_title: "Dark continuous noise from mutant G90D-rhodopsin predominantly underlies congenital stationary night blindness."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "dark continuous noise comprising low-amplitude unitary events occurring at a very high molecular rate equivalent in effect to ~40,000-fold of R* s-1 from WT-Rho."
    explanation: >
      Quantitative mouse data establish that the extraordinary magnitude of
      constitutive G90D noise explains profound rod desensitization in CSNB.
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP). Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity."
    explanation: >
      This review places gain-of-function constitutive activation as the
      mechanistic basis distinguishing CSNBAD1 from the RP4 branch.
phenotypes:
- category: Ophthalmic
  name: Night blindness
  subtype: RP4
  frequency: VERY_FREQUENT
  description: >
    Rod photoreceptor dysfunction produces nyctalopia, the earliest and most
    consistent presenting symptom in the RP4 branch.
  phenotype_term:
    preferred_term: Night blindness
    term:
      id: HP:0000662
      label: Nyctalopia
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."
    explanation: >
      Regraded to PARTIAL: the sentence links RHO mutations to RP but says
      nothing about nyctalopia. Treating it as SUPPORT for night blindness
      relies on the classical definition of RP supplying the missing step,
      which is reasoning rather than evidence. Same generic-definitional-snippet
      pattern as the companion item on the Night blindness causal edge.
- category: Ophthalmic
  name: Progressive peripheral visual field loss
  subtype: RP4
  frequency: VERY_FREQUENT
  description: >
    Advancing rod-cone degeneration progressively constricts the visual field,
    more rapidly in the generalized phenotype than in sector RP.
  phenotype_term:
    preferred_term: Peripheral visual field constriction
    term:
      id: HP:0001133
      label: Constriction of peripheral visual field
  evidence:
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%)"
    explanation: >
      The multicenter cohort confirms progressive peripheral field loss as the
      dominant early functional deficit in RP4, with rate varying by phenotype class.
- category: Ophthalmic
  name: Rod-cone dystrophy
  subtype: RP4
  frequency: VERY_FREQUENT
  description: >
    RP4 is clinically classified as a rod-cone dystrophy: rod dysfunction and
    loss predominate first, followed by secondary cone involvement.
  phenotype_term:
    preferred_term: Rod-cone dystrophy
    term:
      id: HP:0000510
      label: Rod-cone dystrophy
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."
    explanation: >
      Regraded to PARTIAL: the sentence establishes that RHO mutations cause a
      degenerative retinal condition, but says nothing about the rod-first
      sequence with secondary cone involvement that defines a rod-cone
      dystrophy. It supports the classification only via the general meaning of
      "retinitis pigmentosa", not by stating the ordering this node asserts.
- category: Ophthalmic
  name: Reduced visual acuity
  subtype: RP4
  frequency: FREQUENT
  description: >
    Central visual acuity is preserved for several decades before cone and
    macular involvement produces visual acuity loss; median age to mild
    impairment is approximately 72 years.
  phenotype_term:
    preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For the best-corrected visual acuity (BCVA), the median age to reach mild impairment (20/67 ≤ BCVA < 20/40) was 72 years, whereas this could not be computed for lower acuities."
    explanation: >
      Natural-history data directly quantify the late onset of central acuity
      loss (median 72 years to mild impairment), supporting a predominantly
      rod-first degenerative trajectory with late cone and macular involvement.
- category: Ophthalmic
  name: Spicular retinal pigmentation
  subtype: RP4
  frequency: FREQUENT
  description: >
    Bone-spicule-like pigment deposits in the mid-peripheral fundus are a
    classic hallmark of RP4-type retinal remodeling as rod photoreceptors
    degenerate and retinal pigment epithelium migrates.
  phenotype_term:
    preferred_term: Spicular pigmentation of the retina
    term:
      id: HP:0007737
      label: Spicular pigmentation of the retina
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP)."
    explanation: >
      Regraded to PARTIAL: this sentence never mentions pigmentation. Its only
      link to the claim is that the disease it names is "retinitis pigmentosa",
      so it supports the finding indirectly, through the disease definition,
      rather than reporting the fundus appearance. The companion PMID:33669941
      item below carries the direct observation.
  - reference: PMID:33669941
    reference_title: "Stationary and Progressive Phenotypes Caused by the p.G90D Mutation in Rhodopsin Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bone spicule pigmentation was seen in all individuals with RP, localized in different areas depending on the pattern of retinal degeneration"
    explanation: >
      Direct human RHO source for this fundus finding: in the p.G90D cohort,
      bone-spicule pigmentation was present in every patient with an RP
      phenotype and in none of those diagnosed with CSNB. That observation
      both sources the finding for the RP4 branch and corroborates its absence
      from the CSNBAD1 branch, which is why the phenotype is scoped to RP4.
- category: Ophthalmic
  name: Reduced rod electroretinogram
  subtype: RP4
  frequency: VERY_FREQUENT
  description: >
    In RP4, the dark-adapted (scotopic) rod ERG is severely reduced or
    extinguished proportional to rod photoreceptor loss; cone responses decline
    later as secondary cone degeneration progresses.
  phenotype_term:
    preferred_term: Abnormal electroretinogram
    term:
      id: HP:0000512
      label: Abnormal electroretinogram
  reports_on:
  - target: Rod Photoreceptor Apoptosis
    relationship: READOUT_OF
    endpoint_context: DIAGNOSTIC
    interpretation: The reduced scotopic rod ERG measures rod photoreceptor loss from apoptotic degeneration.
  evidence:
  - reference: PMID:33669941
    reference_title: "Stationary and Progressive Phenotypes Caused by the p.G90D Mutation in Rhodopsin Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The function of the rod system, as revealed by dark-adapted (DA) full-field ERG (ffERG), was highly dysfunctional in all patients."
    explanation: >
      Direct human RHO source for this node: dark-adapted full-field ERG was
      highly dysfunctional in every patient tested in this p.G90D cohort, and
      the patients with classic RP specifically showed undetectable rod-specific
      (DA 0.01) responses. That is the scotopic rod ERG reduction this phenotype
      asserts, observed rather than inferred.
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Disease progression was significantly faster in patients with a generalized RP phenotype (n = 75; 75%) than that in patients with a sector RP phenotype (n = 25; 25%), in terms of decline rates of the BCVA (P < 0.001) and V4e retinal seeing areas (P < 0.005)."
    explanation: >
      Regraded to PARTIAL: this natural-history cohort quantifies decline in
      BCVA and V4e visual-field area, not electroretinography — the cached
      record contains no ERG content beyond a MeSH keyword. It corroborates
      progressive rod-cone functional loss in RP4, which is what the ERG is a
      readout of, but it does not itself evidence a reduced rod ERG. The
      PMID:33669941 item above carries that observation.
- category: Ophthalmic
  name: Riggs-type electroretinogram
  subtype: CSNBAD1
  frequency: VERY_FREQUENT
  description: >
    CSNBAD1 is a phototransduction-level (Riggs-type) CSNB: constitutive
    rhodopsin activation desensitizes the rods themselves, so the scotopic
    ERG shows loss of the rod a-wave as well as the b-wave. This is
    distinct from the "negative" Schubert-Bornschein ERG (large a-wave with
    minimal b-wave) seen in the signal-transmission forms of CSNB
    (e.g. NYX/CACNA1F), where photoreceptor-to-bipolar-cell transmission,
    not phototransduction, is the defective step.
  phenotype_term:
    preferred_term: Abnormal electroretinogram
    term:
      id: HP:0000512
      label: Abnormal electroretinogram
  reports_on:
  - target: Constitutive Rhodopsin Activation in Darkness
    relationship: READOUT_OF
    endpoint_context: DIAGNOSTIC
    interpretation: The Riggs-type loss of the rod a-wave measures photoreceptor-level rod desensitization from constitutive rhodopsin activation, rather than an inner-retinal transmission defect.
  evidence:
  - reference: PMID:30051303
    reference_title: "Riggs-type dominant congenital stationary night blindness: ERG findings, a new GNAT1 mutation and a systemic association."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "CSNB from abnormalities in phototransduction can be recessive or dominant and is much less common. This produces a Riggs type of ERG with loss of the rod a-wave as well as the b-wave."
    explanation: >
      Establishes the electrophysiological dichotomy in CSNB: phototransduction
      defects (the class to which gain-of-function RHO CSNBAD1 belongs) produce
      a Riggs-type ERG with loss of the rod a-wave, whereas the "negative"
      Schubert-Bornschein ERG with a preserved large a-wave arises from
      photoreceptor-to-bipolar-cell transmission defects.
  - reference: PMID:38743626
    reference_title: "Dark continuous noise from mutant G90D-rhodopsin predominantly underlies congenital stationary night blindness."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "One well-studied rhodopsin point mutant, G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization."
    explanation: >
      Sources the disease-level step directly for RHO rather than by inference
      from the CSNB class: a rhodopsin point mutant causes CSNB through
      constitutive activity in darkness that desensitizes rods. That is a
      phototransduction-level lesion, which is what produces the Riggs-type
      ERG pattern rather than an inner-retinal transmission defect. The
      companion PMID:30051303 item carries only the class-level ERG dichotomy.
  - reference: PMID:33669941
    reference_title: "Stationary and Progressive Phenotypes Caused by the p.G90D Mutation in Rhodopsin Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "CSNB caused by RHO mutations is of the Riggs type, electroretinographically characterized by the complete loss of rod-specific ERG activity. DA bright flash (3.0) ERG typically exhibits a reduced DA a-wave and low b-wave, while the LA cone-specific responses are largely normal, reflecting preserved cone function"
    explanation: >
      Human RHO-specific source for this node: a clinical cohort of p.G90D
      patients states directly that RHO-related CSNB is of the Riggs type,
      with loss of rod-specific ERG activity and a reduced dark-adapted
      a-wave together with a low b-wave, while cone responses are largely
      preserved. This supplies the human counterpart to the G90D knock-in
      mouse item above, which CLAUDE.md requires for a human phenotype.
  - reference: PMID:33669941
    reference_title: "Stationary and Progressive Phenotypes Caused by the p.G90D Mutation in Rhodopsin Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All three of our patients diagnosed with CSNB had typical electrophysiological features."
    explanation: >
      Sources the VERY_FREQUENT band: every CSNB-phenotype patient in this
      p.G90D cohort (3/3) showed the typical Riggs-type electrophysiology
      described above.
- category: Ophthalmic
  name: Congenital night blindness
  subtype: CSNBAD1
  frequency: VERY_FREQUENT
  description: >
    In the CSNBAD1 branch, night blindness is congenital and does not worsen
    with age. Rod sensitivity is profoundly reduced by constitutive signaling
    noise from the gain-of-function rhodopsin variant. The "stationary" label
    applies to the rod dysfunction itself; see notes on the degeneration
    caveat in p.G90D carriers.
  notes: >
    The largest p.G90D cohort characterized to date (PMID:33669941, 15
    patients from three families) classified only 20% as CSNB, with 53.3%
    developing classic retinitis pigmentosa, and cautioned against diagnosing
    p.G90D patients with CSNB without long follow-up into adulthood. Other
    RHO-CSNB variants (T94I, A292E, A295V) have not been associated with
    progressive disease.
  phenotype_term:
    preferred_term: Congenital night blindness
    term:
      id: HP:0000662
      label: Nyctalopia
  evidence:
  - reference: PMID:33669941
    reference_title: "Stationary and Progressive Phenotypes Caused by the p.G90D Mutation in Rhodopsin Gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had night vision problems for as long as they could remember, which did not worsen with age."
    explanation: >
      Human RHO-specific source for congenital, non-worsening night blindness
      in a p.G90D cohort, and the basis for the VERY_FREQUENT band. The quoted
      sentence covers all 15 characterized p.G90D carriers, which is a wider
      denominator than this node's CSNBAD1 scope; within that scope the band
      rests on the 3/3 patients classified as CSNB, and it holds on either
      denominator. Replaces reliance on model-organism evidence alone for this
      human phenotype.
  - reference: PMID:38743626
    reference_title: "Dark continuous noise from mutant G90D-rhodopsin predominantly underlies congenital stationary night blindness."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Congenital stationary night blindness (CSNB) is an inherited retinal disease that causes a profound loss of rod sensitivity without severe retinal degeneration."
    explanation: >
      Regraded to PARTIAL: this is a class-level definitional statement about
      CSNB in general, not a RHO-specific or patient-level observation, so it
      frames the phenotype rather than establishing it for this subtype. The
      RHO-specific human step is carried by the PMID:33669941 item above.
genetic:
- name: RHO pathogenic variants
  gene_term:
    preferred_term: RHO
    term:
      id: hgnc:10012
      label: RHO
  association: Causative
  notes: >
    Over 150 pathogenic RHO variants have been identified. They are classified
    into mechanistic classes ranging from misfolding (class II, e.g., P23H) and
    trafficking failure (class I, e.g., P347L) to gain-of-function constitutive
    activation (class III, e.g., G90D, T94I). The P23H variant (c.68C>A) is the
    most common single cause of adRP in North America.
  inheritance:
  - name: Autosomal dominant
    evidence:
    - reference: PMID:29042326
      reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity."
      explanation: This review identifies gain-of-function and dominant negative mechanisms as the basis for autosomal dominant RHO disease.
  evidence:
  - reference: PMID:29042326
    reference_title: "The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP)."
    explanation: >
      This review is the primary reference establishing RHO as the most
      common single adRP gene with a large pathogenic variant spectrum.
  - reference: CGGV:assertion_29542633-051c-4b06-af52-d2c5a2a8ee90-2025-02-20T170000.000Z
    reference_title: "RHO / inherited retinal dystrophy (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "RHO | HGNC:10012 | inherited retinal dystrophy | MONDO:0019118 | SD | Definitive"
    explanation: >
      ClinGen classifies the RHO–inherited retinal dystrophy gene-disease
      relationship as Definitive with semidominant inheritance, reflecting
      the predominance of AD disease alongside rare AR null-allele cases.
treatments:
- name: QR-1123
  description: >
    QR-1123 is an investigational allele-selective RNase H-mediated gapmer ASO
    that targets and degrades the P23H mutant RHO mRNA while sparing wild-type
    RHO transcripts. It was administered as a single intravitreal injection.
    ProQR suspended the development program in April 2022 following a strategic
    restructuring after the ILLUMINATE trial failure for sepofarsen.
  therapeutic_modality: ANTISENSE_OLIGONUCLEOTIDE
  aso_details:
    aso_mechanism: RNASE_H_KNOCKDOWN
    target_gene:
      preferred_term: RHO
      term:
        id: hgnc:10012
        label: RHO
    target_transcript: P23H mutant RHO mRNA (allele-selective)
    aso_chemistry: TWO_PRIME_O_METHOXYETHYL
    conjugation: UNCONJUGATED
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: clinicaltrials:NCT04123626
    reference_title: "A Prospective First-In-Human Study to Evaluate the Safety and Tolerability of QR-1123 in Subjects With Autosomal Dominant Retinitis Pigmentosa (adRP) Due to the P23H Mutation in the RHO Gene"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study evaluates the safety, tolerability and efficacy of QR-1123 injection in the eye (intravitreal; IVT) injections (one eye/unilateral) in subjects receiving a single dose or repeat doses."
    explanation: >
      AURORA Phase 1/2 first-in-human study confirms QR-1123 was clinically
      evaluated as an intravitreal ASO for adRP due to the P23H RHO mutation.
- name: Low vision rehabilitation and supportive care
  description: >
    Low vision aids, orientation and mobility training, and genetic counseling
    form the current standard of care for RP4. No approved pharmacotherapy exists.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:32301896
    reference_title: "CLINICAL CHARACTERISTICS AND NATURAL HISTORY OF RHO-ASSOCIATED RETINITIS PIGMENTOSA: A Long-Term Follow-Up Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Based on central visual fields, the optimal window of intervention for RHO-associated RP is before the 5th decade of life."
    explanation: >
      Natural-history data highlighting the optimal intervention window
      underscore the role of supportive care in managing this progressive
      disease pending disease-modifying therapies.
clinical_trials:
- name: NCT04123626
  phase: PHASE_I
  status: SUSPENDED
  notes: >-
    NCT04123626 is registered on ClinicalTrials.gov as a Phase 1/2 study.
    Mapped to PHASE_I per schema granularity; the Phase 2 component consisted
    of dose-escalation cohorts with primary safety and tolerability endpoints,
    consistent with PHASE_I scope as used in other entries (e.g.,
    Angelman_Syndrome, Canavan_Disease).
  description: >
    AURORA: first-in-human Phase 1/2 study of intravitreal QR-1123 (single and
    repeat doses) in adults with adRP due to the P23H RHO mutation. Open-label
    single-dose cohorts and double-masked repeat-dose cohorts. Program suspended
    by ProQR in April 2022.
  target_phenotypes:
  - preferred_term: Rod-cone dystrophy
    term:
      id: HP:0000510
      label: Rod-cone dystrophy
  - preferred_term: Night blindness
    term:
      id: HP:0000662
      label: Nyctalopia
  evidence:
  - reference: clinicaltrials:NCT04123626
    reference_title: "A Prospective First-In-Human Study to Evaluate the Safety and Tolerability of QR-1123 in Subjects With Autosomal Dominant Retinitis Pigmentosa (adRP) Due to the P23H Mutation in the RHO Gene"
    supports: SUPPORT
    snippet: "This study evaluates the safety, tolerability and efficacy of QR-1123 injection in the eye (intravitreal; IVT) injections (one eye/unilateral) in subjects receiving a single dose or repeat doses."
    explanation: >-
      AURORA (NCT04123626) was the sole clinical trial of QR-1123 and the
      most advanced ASO program for RHO-related RP to date.

RHO-Related Retinopathy

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