🏷

Classifications

Harrison's Chapter

Mechanistic Nosology

🔗

Mappings

MONDO

MONDO:0013786 cone-rod dystrophy 16 Not Yet Curated

Per-phenotype non-syndromic retinal-dystrophy node at the CFAP418 locus (CORD16) federated by this gene-anchored lump.

MONDO:0800359 retinitis pigmentosa 64 Not Yet Curated

Per-phenotype non-syndromic retinal-dystrophy node at the CFAP418 locus (RP64) federated by this gene-anchored lump.

MONDO:0044308 bardet-biedl syndrome 21 Not Yet Curated

Syndromic end of the CFAP418 allelic series (BBS21) federated by this gene-anchored lump.

👪

Inheritance

1

Autosomal recessive inheritance HP:0000007

CFAP418-related retinal ciliopathy is inherited in an autosomal recessive pattern; reported probands are typically homozygous from consanguineous families.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:22177090 SUPPORT Human Clinical

"By using homozygosity mapping in an individual with autosomal-recessive (ar) RP from a consanguineous family"

Documents autosomal recessive inheritance with homozygous CFAP418/C8orf37 variants in a consanguineous pedigree.

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Pathophysiology

4

CFAP418 Loss of Function at the Photoreceptor Ciliary Base

CFAP418/C8orf37 is a cilium-associated protein enriched at the base of the photoreceptor connecting cilium, where it interacts with the ciliary protein FAM161A. Biallelic loss-of-function or missense variants disrupt this ciliary-base function, compromising the gating and trafficking machinery on which the highly cilium-dependent photoreceptor relies.

protein localization to cilium GO:0061512 ⚠ ABNORMAL

cilium GO:0005929

Downstream

Photoreceptor Connecting Cilium Dysfunction Loss of CFAP418 function at the ciliary base impairs the photoreceptor connecting cilium through which all outer-segment cargo is trafficked.

Extra-Retinal Ciliary Pleiotropy At the severe (typically null) end of the allelic series, the same proximal ciliary-base loss of function extends beyond the photoreceptor to systemic ciliated tissues, producing the Bardet-Biedl (BBS21) multisystem phenotype.

Show evidence (2 references)

PMID:22177090 SUPPORT Model Organism

"Immunohistochemical studies revealed C8orf37 localization at the base of the primary cilium of human retinal pigment epithelium cells and at the base of connecting cilia of mouse photoreceptors."

Localizes CFAP418/C8orf37 to the ciliary base of retinal cells, supporting a ciliary-base lesion as the proximal defect (human RPE plus mouse photoreceptor immunohistochemistry).

PMID:36233334 SUPPORT In Vitro

"FAM161A, a microtubule-binding protein localized at the photoreceptor cilium required for photoreceptor survival, was identified as one of the preys."

Identifies a photoreceptor-cilium interactor of CFAP418, tying the protein to a ciliary complex required for photoreceptor survival.

Photoreceptor Connecting Cilium Dysfunction

The photoreceptor outer segment is a specialized sensory cilium connected to the cell body by the connecting cilium, through which all phototransduction cargo passes. CFAP418-related ciliary-base dysfunction impairs outer-segment morphogenesis and maintenance, the retinal arm shared across the CFAP418 allelic series.

photoreceptor cell CL:0000210

retina UBERON:0000966

Downstream

Rod and Cone Photoreceptor Degeneration Connecting-cilium dysfunction drives progressive death of rod and cone photoreceptors.

Show evidence (1 reference)

PMID:36233334 SUPPORT Model Organism

"C8orf37 was enriched and was co-localized with FAM161A at the ciliary base of photoreceptors."

Places CFAP418 at the photoreceptor ciliary base alongside a survival-required interactor (marmoset retinal sections), supporting connecting-cilium involvement.

Rod and Cone Photoreceptor Degeneration

Progressive degeneration of rod and cone photoreceptors is the shared final common pathway of CFAP418-related disease, manifesting as cone-rod dystrophy, retinitis pigmentosa with early macular involvement, or the retinal component of Bardet-Biedl syndrome depending on the allele.

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

retina UBERON:0000966

Downstream

Cone-rod dystrophy Rod and cone photoreceptor loss manifests clinically as cone-rod dystrophy or retinitis pigmentosa.

Visual impairment Progressive photoreceptor loss reduces visual acuity and field.

Show evidence (1 reference)

PMID:36233334 SUPPORT Human Clinical

"Mutations in C8orf37 cause Bardet-Biedl syndrome (BBS), retinitis pigmentosa (RP), and cone-rod dystrophy (CRD), all manifest in photoreceptor degeneration."

Establishes photoreceptor degeneration as the convergent outcome across the full CFAP418 phenotypic spectrum.

Extra-Retinal Ciliary Pleiotropy

At the severe (typically null) end of the CFAP418 allelic series, ciliary dysfunction extends beyond the retina to the systemic branches of the ciliopathy spectrum, producing the Bardet-Biedl syndrome phenotype (obesity, postaxial polydactyly, renal anomalies, cognitive impairment) - BBS21.

ciliated cell CL:0000064

Show evidence (2 references)

PMID:27008867 SUPPORT Human Clinical

"The proband was overweight (body mass index 29.1) with a slowly progressive rod-cone dystrophy, a mild learning difficulty, high myopia, three limb post-axial polydactyly, horseshoe kidney, abnormally positioned uterus and elevated liver enzymes."

Documents the multisystem (extra-retinal) ciliopathy phenotype at the severe end of the CFAP418 spectrum (BBS21).

PMID:27008867 SUPPORT Model Organism

"Knockdown of c8orf37 resulted in impaired visual behavior and BBS-related phenotypes, specifically, defects in the formation of Kupffer's vesicle and delays in retrograde transport."

Zebrafish functional validation links CFAP418 loss to BBS-related ciliary phenotypes, supporting the systemic ciliopathy arm.

⬡

Pathograph

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

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Phenotypes

7

Eye 2

Rod-cone dystrophy Rod-cone dystrophy HP:0000510

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:27008867 SUPPORT Human Clinical

"The proband was overweight (body mass index 29.1) with a slowly progressive rod-cone dystrophy"

Documents progressive rod-cone dystrophy as the retinal phenotype in CFAP418-related BBS21.

Visual impairment Visual impairment HP:0000505

Show evidence (2 references)

PMID:27008867 SUPPORT Human Clinical

"The proband was overweight (body mass index 29.1) with a slowly progressive rod-cone dystrophy, a mild learning difficulty, high myopia"

Human BBS21 proband with a CFAP418 (C8ORF37) loss-of-function mutation presented with slowly progressive rod-cone dystrophy and high myopia, i.e. progressive visual impairment.

PMID:27008867 SUPPORT Model Organism

"Knockdown of c8orf37 resulted in impaired visual behavior and BBS-related phenotypes"

Functional zebrafish evidence of impaired visual behavior with CFAP418 loss; human probands show progressive retinal dystrophy with reduced vision.

Genitourinary 1

Horseshoe kidney Horseshoe kidney HP:0000085

Show evidence (1 reference)

PMID:27008867 SUPPORT Human Clinical

"horseshoe kidney"

Documents the renal anomaly in the CFAP418-related BBS21 proband.

Limbs 1

Postaxial polydactyly Postaxial polydactyly HP:0100259

Show evidence (1 reference)

PMID:27008867 SUPPORT Human Clinical

"three limb post-axial polydactyly"

Documents postaxial polydactyly in the CFAP418-related BBS21 proband.

Growth 1

Obesity Obesity HP:0001513

Show evidence (1 reference)

PMID:27008867 SUPPORT Human Clinical

"The proband was overweight (body mass index 29.1)"

Documents the obesity/overweight cardinal BBS feature in CFAP418-related BBS21.

Other 2

Cone-rod dystrophy Cone/cone-rod dystrophy HP:0000548

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:22177090 SUPPORT Human Clinical

"Clinical assessment revealed CRD in four individuals and RP with early macular involvement in two individuals."

Establishes cone-rod dystrophy (and RP with early macular involvement) as the retinal phenotypes of CFAP418/C8orf37 disease.

Macular degeneration Macular degeneration HP:0000608

Show evidence (1 reference)

PMID:22177090 SUPPORT Human Clinical

"autosomal-recessive retinal dystrophies with early macular involvement"

Establishes early macular involvement as a defining clinical feature.

🧬

Genetic Associations

1

CFAP418 (Pathogenic biallelic loss-of-function and missense variants)

Gene: CFAP418 hgnc:27232

Show evidence (2 references)

PMID:22177090 SUPPORT Human Clinical

"Next-generation sequencing of all exons, flanking intron sequences, microRNAs, and other highly conserved genomic elements in these three regions revealed a homozygous nonsense mutation"

Identifies a homozygous loss-of-function C8orf37/CFAP418 variant as the cause of autosomal recessive retinal dystrophy.

PMID:26854863 SUPPORT Human Clinical

"The same mutation has been described in unrelated patients with non-syndromic cone-rod dystrophy and other C8orf37 changes were found in individuals with retinitis pigmentosa."

Establishes that the CFAP418/C8orf37 locus is allelic across syndromic (BBS) and non-syndromic (CRD/RP) retinal disease.

💊

Medical Actions

2

Setmelanotide

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: setmelanotide NCIT:C152349

MC4R agonist (IMCIVREE) approved for the treatment of obesity and hyperphagia in Bardet-Biedl syndrome. It is relevant to the syndromic BBS21 arm of the CFAP418 allelic series, in which extra-retinal ciliary pleiotropy produces early-onset obesity; setmelanotide pharmacologically mitigates the hyperphagia and obesity rather than correcting the underlying ciliary defect.

Mechanism Target:

MODULATES Extra-Retinal Ciliary Pleiotropy — Setmelanotide restores melanocortin-4 receptor signalling downstream of the hypothalamic ciliary dysfunction, mitigating the hyperphagia and obesity that arise from extra-retinal ciliary pleiotropy in the BBS21 arm.

Target Phenotypes: Obesity HP:0001513

Show evidence (1 reference)

PMID:38383825 SUPPORT Other

"setmelanotide is a new pharmacotherapy approved for treatment of obesity in BBS."

FDA-approved MC4R agonist for obesity in Bardet-Biedl syndrome, applicable to the BBS21 (CFAP418) syndromic arm modelled in this entry.

Genetic Counseling

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

Genetic counseling for families regarding the autosomal recessive inheritance of the CFAP418 retinal ciliopathy, recurrence risk (25% for the sibs of an affected proband), and reproductive and cascade-testing options.

Show evidence (1 reference)

PMID:23788369 SUPPORT Human Clinical

"Mutations in C8orf37 give rise to an early or adolescent-onset autosomal recessive CRD or RP phenotype with early macular atrophy."

The autosomal recessive inheritance of the CFAP418 retinal ciliopathy underpins recurrence-risk genetic counseling for families.

{ }

Source YAML

click to show

name: CFAP418-related retinal ciliopathy
creation_date: "2026-06-28T00:00:00Z"
category: Mendelian
description: >-
  CFAP418-related retinal ciliopathy is a gene-anchored lump for the autosomal
  recessive ciliopathy spectrum caused by biallelic variants in CFAP418
  (C8orf37), a cilium-associated protein that localizes to the base of the
  photoreceptor connecting cilium. The same gene produces a phenotypic
  continuum: at the non-syndromic end, isolated retinal dystrophy presenting as
  cone-rod dystrophy (CORD16) or retinitis pigmentosa with early macular
  involvement (RP64); at the syndromic end, full Bardet-Biedl syndrome (BBS21)
  adding obesity, postaxial polydactyly, renal anomalies, and cognitive
  impairment. The photoreceptor is the most penetrant and dosage-sensitive
  target, so retinal degeneration is the shared, defining feature across the
  whole allelic series. MONDO carries a dedicated gene-level class
  (CFAP418-related ciliopathy, MONDO:0700374) that federates the per-phenotype
  nodes (BBS21, CORD16, RP64), which is the anchor used here; this complements
  the BBSome-Related_Retinitis_Pigmentosa entry, whose curation notes explicitly
  scope CFAP418 out as a transition-zone/cilia-base locus belonging to the
  broader ciliopathy spectrum rather than the BBSome machine.
disease_term:
  preferred_term: CFAP418-related retinal ciliopathy
  term:
    id: MONDO:0700374
    label: CFAP418-related ciliopathy
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  mechanistic_category:
  - classification_value: ciliopathy
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0013786
      label: cone-rod dystrophy 16
    mapping_predicate: skos:relatedMatch
    mapping_source: MONDO
    mapping_justification: >-
      Per-phenotype non-syndromic retinal-dystrophy node at the CFAP418 locus
      (CORD16) federated by this gene-anchored lump.
  - term:
      id: MONDO:0800359
      label: retinitis pigmentosa 64
    mapping_predicate: skos:relatedMatch
    mapping_source: MONDO
    mapping_justification: >-
      Per-phenotype non-syndromic retinal-dystrophy node at the CFAP418 locus
      (RP64) federated by this gene-anchored lump.
  - term:
      id: MONDO:0044308
      label: bardet-biedl syndrome 21
    mapping_predicate: skos:relatedMatch
    mapping_source: MONDO
    mapping_justification: >-
      Syndromic end of the CFAP418 allelic series (BBS21) federated by this
      gene-anchored lump.
parents:
- Ciliopathy
synonyms:
- C8orf37-related retinal ciliopathy
- C8orf37-related retinal dystrophy
notes: >-
  Evidence model for this gene-anchored lump: the MECHANISM (CFAP418 loss of
  function at the photoreceptor ciliary base -> connecting-cilium dysfunction ->
  photoreceptor degeneration) is transferred by conformance to the
  ciliopathy_dysfunction and photoreceptor_degeneration modules. The
  GENE -> human-disease ASSOCIATION rests on the cited human pedigrees, which
  are often small/consanguineous (the founding report and the BBS21 report each
  describe single families/probands); read the allelic-series breadth at that
  (limited) strength rather than borrowing severity across the spectrum. ClinGen
  classifies the CFAP418-ciliopathy gene-disease relationship as Definitive, but
  the corresponding CGGV cache row is not cited here because the pinned ClinGen
  snapshot needs refreshing before that assertion can be quoted (a documented
  follow-up, mirroring the BBSome entry). Scope is the CFAP418 (C8orf37) locus
  only; this entry is deliberately complementary to
  BBSome-Related_Retinitis_Pigmentosa, which scopes CFAP418 out.
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    CFAP418-related retinal ciliopathy is inherited in an autosomal recessive
    pattern; reported probands are typically homozygous from consanguineous
    families.
  evidence:
  - reference: PMID:22177090
    reference_title: "Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      By using homozygosity mapping in an individual with autosomal-recessive
      (ar) RP from a consanguineous family
    explanation: >-
      Documents autosomal recessive inheritance with homozygous CFAP418/C8orf37
      variants in a consanguineous pedigree.
genetic:
- name: CFAP418
  association: Pathogenic biallelic loss-of-function and missense variants
  gene_term:
    preferred_term: CFAP418
    term:
      id: hgnc:27232
      label: CFAP418
  notes: >-
    CFAP418 (C8orf37, BBS21) encodes a cilium-associated protein that localizes
    at the base of the photoreceptor connecting cilium. Biallelic variants span
    a phenotypic continuum from isolated cone-rod dystrophy (CORD16) and
    retinitis pigmentosa (RP64) to full Bardet-Biedl syndrome (BBS21). ClinGen
    classifies the gene-disease relationship as Definitive for ciliopathy.
  evidence:
  - reference: PMID:22177090
    reference_title: "Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Next-generation sequencing of all exons, flanking intron sequences,
      microRNAs, and other highly conserved genomic elements in these three
      regions revealed a homozygous nonsense mutation
    explanation: >-
      Identifies a homozygous loss-of-function C8orf37/CFAP418 variant as the
      cause of autosomal recessive retinal dystrophy.
  - reference: PMID:26854863
    reference_title: "C8orf37 is mutated in Bardet-Biedl syndrome and constitutes a locus allelic to non-syndromic retinal dystrophies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The same mutation has been described in unrelated patients with
      non-syndromic cone-rod dystrophy and other C8orf37 changes were found in
      individuals with retinitis pigmentosa.
    explanation: >-
      Establishes that the CFAP418/C8orf37 locus is allelic across syndromic
      (BBS) and non-syndromic (CRD/RP) retinal disease.
pathophysiology:
- name: CFAP418 Loss of Function at the Photoreceptor Ciliary Base
  conforms_to: "ciliopathy_dysfunction#Basal Body and Transition Zone Dysfunction"
  description: >-
    CFAP418/C8orf37 is a cilium-associated protein enriched at the base of the
    photoreceptor connecting cilium, where it interacts with the ciliary protein
    FAM161A. Biallelic loss-of-function or missense variants disrupt this
    ciliary-base function, compromising the gating and trafficking machinery on
    which the highly cilium-dependent photoreceptor relies.
  cellular_components:
  - preferred_term: cilium
    term:
      id: GO:0005929
      label: cilium
  biological_processes:
  - preferred_term: protein localization to cilium
    term:
      id: GO:0061512
      label: protein localization to cilium
    modifier: ABNORMAL
  evidence:
  - reference: PMID:22177090
    reference_title: "Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Immunohistochemical studies revealed C8orf37 localization at the base of
      the primary cilium of human retinal pigment epithelium cells and at the
      base of connecting cilia of mouse photoreceptors.
    explanation: >-
      Localizes CFAP418/C8orf37 to the ciliary base of retinal cells, supporting
      a ciliary-base lesion as the proximal defect (human RPE plus mouse
      photoreceptor immunohistochemistry).
  - reference: PMID:36233334
    reference_title: "Interactions between C8orf37 and FAM161A, Two Ciliary Proteins Essential for Photoreceptor Survival."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      FAM161A, a microtubule-binding protein localized at the photoreceptor
      cilium required for photoreceptor survival, was identified as one of the
      preys.
    explanation: >-
      Identifies a photoreceptor-cilium interactor of CFAP418, tying the protein
      to a ciliary complex required for photoreceptor survival.
  downstream:
  - target: Photoreceptor Connecting Cilium Dysfunction
    description: >-
      Loss of CFAP418 function at the ciliary base impairs the photoreceptor
      connecting cilium through which all outer-segment cargo is trafficked.
  - target: Extra-Retinal Ciliary Pleiotropy
    description: >-
      At the severe (typically null) end of the allelic series, the same proximal
      ciliary-base loss of function extends beyond the photoreceptor to systemic
      ciliated tissues, producing the Bardet-Biedl (BBS21) multisystem phenotype.
- name: Photoreceptor Connecting Cilium Dysfunction
  conforms_to: "ciliopathy_dysfunction#Photoreceptor Connecting Cilium Degeneration"
  description: >-
    The photoreceptor outer segment is a specialized sensory cilium connected to
    the cell body by the connecting cilium, through which all phototransduction
    cargo passes. CFAP418-related ciliary-base dysfunction impairs outer-segment
    morphogenesis and maintenance, the retinal arm shared across the CFAP418
    allelic series.
  cell_types:
  - preferred_term: photoreceptor cell
    term:
      id: CL:0000210
      label: photoreceptor cell
  locations:
  - preferred_term: retina
    term:
      id: UBERON:0000966
      label: retina
  evidence:
  - reference: PMID:36233334
    reference_title: "Interactions between C8orf37 and FAM161A, Two Ciliary Proteins Essential for Photoreceptor Survival."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      C8orf37 was enriched and was co-localized with FAM161A at the ciliary base
      of photoreceptors.
    explanation: >-
      Places CFAP418 at the photoreceptor ciliary base alongside a
      survival-required interactor (marmoset retinal sections), supporting
      connecting-cilium involvement.
  downstream:
  - target: Rod and Cone Photoreceptor Degeneration
    description: >-
      Connecting-cilium dysfunction drives progressive death of rod and cone
      photoreceptors.
- name: Rod and Cone Photoreceptor Degeneration
  conforms_to: "photoreceptor_degeneration#Rod Photoreceptor Apoptosis"
  description: >-
    Progressive degeneration of rod and cone photoreceptors is the shared final
    common pathway of CFAP418-related disease, manifesting as cone-rod
    dystrophy, retinitis pigmentosa with early macular involvement, or the
    retinal component of Bardet-Biedl syndrome depending on the allele.
  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
  locations:
  - preferred_term: retina
    term:
      id: UBERON:0000966
      label: retina
  evidence:
  - reference: PMID:36233334
    reference_title: "Interactions between C8orf37 and FAM161A, Two Ciliary Proteins Essential for Photoreceptor Survival."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutations in C8orf37 cause Bardet-Biedl syndrome (BBS), retinitis
      pigmentosa (RP), and cone-rod dystrophy (CRD), all manifest in
      photoreceptor degeneration.
    explanation: >-
      Establishes photoreceptor degeneration as the convergent outcome across
      the full CFAP418 phenotypic spectrum.
  downstream:
  - target: Cone-rod dystrophy
    description: >-
      Rod and cone photoreceptor loss manifests clinically as cone-rod
      dystrophy or retinitis pigmentosa.
  - target: Visual impairment
    description: Progressive photoreceptor loss reduces visual acuity and field.
- name: Extra-Retinal Ciliary Pleiotropy
  conforms_to: "ciliopathy_dysfunction#Multisystem Pleiotropic Ciliopathy Phenotype"
  description: >-
    At the severe (typically null) end of the CFAP418 allelic series, ciliary
    dysfunction extends beyond the retina to the systemic branches of the
    ciliopathy spectrum, producing the Bardet-Biedl syndrome phenotype (obesity,
    postaxial polydactyly, renal anomalies, cognitive impairment) - BBS21.
  cell_types:
  - preferred_term: ciliated cell
    term:
      id: CL:0000064
      label: ciliated cell
  evidence:
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The proband was overweight (body mass index 29.1) with a slowly
      progressive rod-cone dystrophy, a mild learning difficulty, high myopia,
      three limb post-axial polydactyly, horseshoe kidney, abnormally positioned
      uterus and elevated liver enzymes.
    explanation: >-
      Documents the multisystem (extra-retinal) ciliopathy phenotype at the
      severe end of the CFAP418 spectrum (BBS21).
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Knockdown of c8orf37 resulted in impaired visual behavior and BBS-related
      phenotypes, specifically, defects in the formation of Kupffer's vesicle
      and delays in retrograde transport.
    explanation: >-
      Zebrafish functional validation links CFAP418 loss to BBS-related ciliary
      phenotypes, supporting the systemic ciliopathy arm.
phenotypes:
- name: Cone-rod dystrophy
  category: Ocular
  diagnostic: true
  description: >-
    Cone-rod dystrophy (CORD16) is one of the defining non-syndromic retinal
    presentations of CFAP418-related disease, with early macular involvement.
  phenotype_term:
    preferred_term: Cone/cone-rod dystrophy
    term:
      id: HP:0000548
      label: Cone/cone-rod dystrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:22177090
    reference_title: "Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical assessment revealed CRD in four individuals and RP with early
      macular involvement in two individuals.
    explanation: >-
      Establishes cone-rod dystrophy (and RP with early macular involvement) as
      the retinal phenotypes of CFAP418/C8orf37 disease.
- name: Rod-cone dystrophy
  category: Ocular
  diagnostic: true
  description: >-
    Retinitis pigmentosa / rod-cone dystrophy (RP64) is the other defining
    non-syndromic retinal presentation, and the retinal component of BBS21.
  phenotype_term:
    preferred_term: Rod-cone dystrophy
    term:
      id: HP:0000510
      label: Rod-cone dystrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The proband was overweight (body mass index 29.1) with a slowly
      progressive rod-cone dystrophy
    explanation: >-
      Documents progressive rod-cone dystrophy as the retinal phenotype in
      CFAP418-related BBS21.
- name: Macular degeneration
  category: Ocular
  description: >-
    Early macular involvement is a characteristic feature of the non-syndromic
    CFAP418 retinal dystrophies.
  phenotype_term:
    preferred_term: Macular degeneration
    term:
      id: HP:0000608
      label: Macular degeneration
  evidence:
  - reference: PMID:22177090
    reference_title: "Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      autosomal-recessive retinal dystrophies with early macular involvement
    explanation: >-
      Establishes early macular involvement as a defining clinical feature.
- name: Postaxial polydactyly
  category: Skeletal
  description: >-
    Postaxial polydactyly is part of the syndromic (BBS21) end of the spectrum.
  phenotype_term:
    preferred_term: Postaxial polydactyly
    term:
      id: HP:0100259
      label: Postaxial polydactyly
  evidence:
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      three limb post-axial polydactyly
    explanation: >-
      Documents postaxial polydactyly in the CFAP418-related BBS21 proband.
- name: Obesity
  category: Metabolic
  description: >-
    Obesity is a cardinal Bardet-Biedl syndrome feature present at the syndromic
    end of the CFAP418 spectrum.
  phenotype_term:
    preferred_term: Obesity
    term:
      id: HP:0001513
      label: Obesity
  evidence:
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The proband was overweight (body mass index 29.1)
    explanation: >-
      Documents the obesity/overweight cardinal BBS feature in CFAP418-related
      BBS21.
- name: Horseshoe kidney
  category: Renal
  description: >-
    Renal anomalies (here, horseshoe kidney) are part of the syndromic BBS21
    presentation.
  phenotype_term:
    preferred_term: Horseshoe kidney
    term:
      id: HP:0000085
      label: Horseshoe kidney
  evidence:
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      horseshoe kidney
    explanation: >-
      Documents the renal anomaly in the CFAP418-related BBS21 proband.
- name: Visual impairment
  category: Ocular
  description: >-
    Reduced visual acuity from progressive photoreceptor degeneration across the
    CFAP418 spectrum.
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The proband was overweight (body mass index 29.1) with a slowly
      progressive rod-cone dystrophy, a mild learning difficulty, high myopia
    explanation: >-
      Human BBS21 proband with a CFAP418 (C8ORF37) loss-of-function mutation
      presented with slowly progressive rod-cone dystrophy and high myopia,
      i.e. progressive visual impairment.
  - reference: PMID:27008867
    reference_title: "Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21)."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Knockdown of c8orf37 resulted in impaired visual behavior and BBS-related
      phenotypes
    explanation: >-
      Functional zebrafish evidence of impaired visual behavior with CFAP418
      loss; human probands show progressive retinal dystrophy with reduced
      vision.
diagnosis:
- name: Electroretinography and multimodal retinal imaging
  description: >-
    Retinal function and structure are characterised by full-field
    electroretinography (ERG), spectral-domain optical coherence tomography
    (SD-OCT), and fundus autofluorescence. ERG responses are severely reduced in
    a cone-rod or rod-cone pattern or are nonrecordable, with SD-OCT showing
    profound macular photoreceptor degeneration and autofluorescence revealing
    retinal pigment epithelium atrophy.
  diagnosis_term:
    preferred_term: ophthalmic diagnostic procedure
    term:
      id: MAXO:0000967
      label: ophthalmic diagnostic procedure
  evidence:
  - reference: PMID:23788369
    reference_title: "Clinical characteristics of rod and cone photoreceptor dystrophies in patients with mutations in the C8orf37 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ERG responses were severely reduced in a cone-rod pattern or were nonrecordable."
    explanation: >-
      ERG shows a severely reduced cone-rod pattern or nonrecordable responses,
      the key functional diagnostic finding in the CFAP418 retinal ciliopathy.
  - reference: PMID:23788369
    reference_title: "Clinical characteristics of rod and cone photoreceptor dystrophies in patients with mutations in the C8orf37 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SD-OCT showed profound photoreceptor degeneration and AF demonstrated atrophy of the retinal pigment epithelium (RPE)."
    explanation: >-
      SD-OCT and autofluorescence document macular photoreceptor degeneration and
      RPE atrophy, supporting the structural diagnostic workup.
- name: Molecular genetic testing
  description: >-
    Confirmation rests on identifying biallelic CFAP418 (C8orf37) variants,
    typically through a comprehensive inherited-retinal-dystrophy gene panel that
    includes CFAP418.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: MAXO:0000533
      label: molecular genetic testing
  evidence:
  - reference: PMID:38383825
    reference_title: "Bardet-Biedl syndrome: A clinical overview focusing on diagnosis, outcomes and best-practice management."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Careful clinical history and genetic testing can help determine the diagnosis"
    explanation: >-
      Molecular genetic testing establishes the diagnosis of ciliopathies in the
      BBS/CFAP418 spectrum by identifying the causal biallelic variants.
treatments:
- name: Setmelanotide
  description: >-
    MC4R agonist (IMCIVREE) approved for the treatment of obesity and hyperphagia
    in Bardet-Biedl syndrome. It is relevant to the syndromic BBS21 arm of the
    CFAP418 allelic series, in which extra-retinal ciliary pleiotropy produces
    early-onset obesity; setmelanotide pharmacologically mitigates the hyperphagia
    and obesity rather than correcting the underlying ciliary defect.
  action_category: THERAPEUTIC
  therapeutic_modality: PEPTIDE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: setmelanotide
      term:
        id: NCIT:C152349
        label: Setmelanotide
  target_phenotypes:
  - preferred_term: Obesity
    term:
      id: HP:0001513
      label: Obesity
  target_mechanisms:
  - target: Extra-Retinal Ciliary Pleiotropy
    treatment_effect: MODULATES
    description: >-
      Setmelanotide restores melanocortin-4 receptor signalling downstream of the
      hypothalamic ciliary dysfunction, mitigating the hyperphagia and obesity
      that arise from extra-retinal ciliary pleiotropy in the BBS21 arm.
  evidence:
  - reference: PMID:38383825
    reference_title: "Bardet-Biedl syndrome: A clinical overview focusing on diagnosis, outcomes and best-practice management."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "setmelanotide is a new pharmacotherapy approved for treatment of obesity in BBS."
    explanation: >-
      FDA-approved MC4R agonist for obesity in Bardet-Biedl syndrome, applicable
      to the BBS21 (CFAP418) syndromic arm modelled in this entry.
- name: Genetic Counseling
  description: >-
    Genetic counseling for families regarding the autosomal recessive inheritance
    of the CFAP418 retinal ciliopathy, recurrence risk (25% for the sibs of an
    affected proband), and reproductive and cascade-testing options.
  action_category: COUNSELING_INFORMATIONAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:23788369
    reference_title: "Clinical characteristics of rod and cone photoreceptor dystrophies in patients with mutations in the C8orf37 gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in C8orf37 give rise to an early or adolescent-onset autosomal recessive CRD or RP phenotype with early macular atrophy."
    explanation: >-
      The autosomal recessive inheritance of the CFAP418 retinal ciliopathy
      underpins recurrence-risk genetic counseling for families.
references:
- reference: PMID:22177090
  title: >-
    Mutations in C8orf37, encoding a ciliary protein, are associated with
    autosomal-recessive retinal dystrophies with early macular involvement.
  findings: []
- reference: PMID:27008867
  title: >-
    Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21).
  findings: []
- reference: PMID:26854863
  title: >-
    C8orf37 is mutated in Bardet-Biedl syndrome and constitutes a locus allelic
    to non-syndromic retinal dystrophies.
  findings: []
- reference: PMID:36233334
  title: >-
    Interactions between C8orf37 and FAM161A, Two Ciliary Proteins Essential for
    Photoreceptor Survival.
  findings: []

📚

References & Deep Research

References

4

PMID:22177090

Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement.

No top-level findings curated for this source.

PMID:27008867

Mutations in C8ORF37 cause Bardet Biedl syndrome (BBS21).

No top-level findings curated for this source.

PMID:26854863

C8orf37 is mutated in Bardet-Biedl syndrome and constitutes a locus allelic to non-syndromic retinal dystrophies.

No top-level findings curated for this source.

PMID:36233334

Interactions between C8orf37 and FAM161A, Two Ciliary Proteins Essential for Photoreceptor Survival.

No top-level findings curated for this source.

Deep Research

1

Claude ▸

CFAP418-related Retinal Ciliopathy — Research Report

claude-sonnet-4-6 7 citations 2026-07-01T13:05:00Z

CFAP418-related Retinal Ciliopathy — Research Report

1. Disease Overview and MONDO Anchor

CFAP418 (Cilia- and Flagella-Associated Protein 418; formerly C8orf37; also designated BBS21) encodes a small, evolutionarily conserved protein expressed most prominently in the retina, brain, and heart (OMIM *614477). Biallelic loss-of-function and missense variants produce a phenotypic continuum anchored at MONDO:0700374 ("CFAP418-related ciliopathy"), which federates three per-phenotype OMIM nodes:

Node	OMIM	Phenotype
CORD16	#614507	Cone-rod dystrophy, non-syndromic
RP64	—	Retinitis pigmentosa 64 (rod-cone dystrophy), non-syndromic
BBS21	#617406	Full Bardet-Biedl syndrome 21 (syndromic)

Source: OMIM entries #614477, #614507, #617406; MONDO:0700374.

2. Core Pathophysiology

2a. Ciliary-base localization (photoreceptor connecting cilium)

CFAP418/C8orf37 protein localizes at the base of primary cilia in human retinal pigment epithelium (RPE) cells and at the base of the connecting cilium of mouse photoreceptors, co-localizing with polyglutamylated tubulin (PMID:22177090). The connecting cilium is the narrow bridge through which all outer-segment cargo (visual pigments, disc membrane components) must be trafficked; disruption at this gate causes outer-segment morphogenesis failure and progressive photoreceptor death.

CFAP418 also interacts with FAM161A, a microtubule-binding protein that localizes at the photoreceptor cilium and is independently required for photoreceptor survival (PMID:36233334). The co-localization at the ciliary base links CFAP418 to a survival-critical ciliary complex.

2b. Membrane lipid homeostasis (newer mechanistic arm)

A 2024 JCI Insight study (PMID:37971880) applied lipidomic, proteomic, and phosphoproteomic profiling plus affinity-purification mass spectrometry to characterize CFAP418 function in mouse retina. Key findings:

CFAP418 protein directly binds the lipid-metabolism precursor phosphatidic acid (PA) and the mitochondrion-specific lipid cardiolipin, but does not form stable protein–protein complexes.
Loss of Cfap418 in mice disturbs membrane lipid homeostasis and membrane-protein associations → mitochondrial defects + membrane-remodeling abnormalities across vesicular-trafficking pathways, especially the ESCRT pathway.
Ablation of Cfap418 also increases activity of the PA-binding protein kinase Cα in the retina.
The authors conclude that membrane lipid imbalance is a pathological mechanism underlying both syndromic ciliopathies and isolated retinal degenerations.

This supplements the earlier connecting-cilium model: CFAP418 loss disrupts not only the ciliary gate but also the lipid-membrane environment on which outer-segment disc biogenesis depends.

Key ontology terms: - GO:0061512 — protein localization to cilium (ABNORMAL) - GO:0046486 — glycerophospholipid metabolic process (ABNORMAL; PA/cardiolipin) - CL:0000210 — photoreceptor cell - CL:0000604 — retinal rod cell - CL:0000573 — retinal cone cell - UBERON:0000966 — retina

3. Clinical Spectrum

3a. Non-syndromic end (isolated retinal dystrophy)

Eight C8orf37-mutated patients were clinically characterized by van Huet et al. 2013 (PMID:23788369; IOVS):

Four with RP phenotype (families A and D): Night blindness followed by concentric visual-field loss; early macular atrophy; ophthalmoscopy showed bone spicules, attenuated vessels, waxy pale optic discs; SD-OCT showed profound photoreceptor degeneration; ERG nonrecordable in all. Onset in infancy (family A) or adolescence (family D). Severe visual loss to light perception occurred early.
Four with CRD phenotype (families B and C): Initial symptoms photophobia or reduced visual acuity, onset in infancy (family B) or adolescence (family C); profound macular RPE atrophy on AF and SD-OCT; ERG severely reduced in cone-rod pattern or nonrecordable. Notably both patients in family B also had polydactyly, suggesting a borderline syndromic phenotype.

The first patient series (PMID:22177090, Estrada-Cuzcano et al. 2012) identified six affected individuals (3 with arCRD, 3 with arRP with early macular involvement) from 4 consanguineous families by homozygosity mapping.

3b. Syndromic end (BBS21)

Feathers et al. 2019 (PMID:27008867) first documented C8ORF37 biallelic mutations causing full Bardet-Biedl syndrome (BBS21). The reported proband exhibited: - Slowly progressive rod-cone dystrophy - Overweight/obesity (BMI 29.1) - Mild learning difficulty (mild cognitive impairment) - Three-limb postaxial polydactyly - Horseshoe kidney - Abnormally positioned uterus - High myopia

Zebrafish c8orf37 knockdown reproduced BBS-related ciliary phenotypes including Kupffer's vesicle defects and delayed retrograde melanosome transport, validating the syndromic designation (PMID:27008867).

3c. Allelism and phenotypic determinants

The same C8orf37/CFAP418 locus was shown to be allelic across syndromic and non-syndromic presentations (PMID:26854863), reinforcing that allele severity (null vs. missense) likely gates the degree of extra-retinal involvement. ClinGen classified the CFAP418-ciliopathy gene-disease relationship as Definitive (referenced in the YAML notes; CGGV cache row pending refresh).

4. Diagnosis

4a. Clinical

The diagnostic workup for suspected CFAP418-related retinal ciliopathy follows standard inherited retinal dystrophy practice:

Electroretinography (ERG): Severely reduced or nonrecordable responses; CRD pattern (cone > rod reduction) or RP pattern (rod > cone). ERG is often nonrecordable by the time of first presentation given the severe early macular involvement.
Spectral-domain OCT (SD-OCT): Profound macular photoreceptor degeneration with RPE atrophy, especially at the macula.
Fundus autofluorescence (AF): Macular RPE atrophy pattern.
Visual field perimetry: Concentric loss in RP-pattern cases; central-field loss in CRD-pattern cases.
Fundus photography: Macular atrophy, bone spicule pigmentation, attenuated vessels, waxy pale discs (classic RP features; PMID:23788369).

4b. Genetic

Comprehensive inherited retinal dystrophy (IRD) gene panels include CFAP418. Homozygosity mapping was the original discovery method (consanguineous families). For BBS21, the standard BBS gene panel or ciliopathy panel will include CFAP418.

4c. BBS-specific criteria

For the syndromic (BBS21) end, the ERN-EYE/ERKNet 2024 BBS consensus (European Reference Networks) provides updated diagnostic criteria and recommends a multidisciplinary team (ophthalmology, nephrology, endocrinology, developmental pediatrics; PMID:38383825).

5. Natural History and Progression

Based on the van Huet 2013 cohort (PMID:23788369):

Onset: Infancy to adolescence (no adult-onset cases in the literature).
RP phenotype: Night blindness → progressive concentric visual field loss → severe visual loss (light perception or worse) occurring early in the disease course.
CRD phenotype: Photophobia and/or reduced visual acuity at onset → macular atrophy progressing to nonrecordable ERG.
In both patterns, early macular involvement is characteristic and distinguishes this locus from typical RP.
Both allelic endpoints (CORD16 and RP64) share progressive photoreceptor loss as the converging phenotype.

Disease progression module: Consistent with the photoreceptor_degeneration module (Rod Photoreceptor Apoptosis → secondary cone degeneration → progressive visual field loss) and the ciliopathy_dysfunction module.

6. Treatments and Management

6a. Retinal disease (no CFAP418-specific treatment)

No approved gene therapy or targeted pharmacotherapy exists specifically for CFAP418 mutations. No CFAP418-specific clinical trial was identified on ClinicalTrials.gov (searched 2026-07-01).

Supportive measures for IRD/RP/CRD: - Low vision rehabilitation: Low-vision aids (magnifiers, tinted lenses), orientation and mobility training, assistive lighting; standard of care for all non-treatable IRDs. - UV protection: Sunglasses with UV-blocking lenses to reduce photoreceptor oxidative stress (standard RP/CRD practice). - Vitamin A palmitate: Historically suggested for typical RP but benefit in CRD or early-macular-involvement phenotypes is uncertain; not specifically studied for CFAP418. - Genetic counseling: Essential given autosomal recessive inheritance.

6b. BBS21 systemic management

For the syndromic (BBS21) end, management tracks standard BBS care (PMID:38383825 — Shoemaker 2024, Diabetes Obes Metab):

Setmelanotide (Imcivree): FDA-approved melanocortin 4 receptor (MC4R) agonist for treatment of obesity in Bardet-Biedl syndrome (approved 2020). This is the first pharmacotherapy approved for hyperphagia/obesity in any ciliopathy. In BBS21 specifically, it has not been studied in isolation, but BBS21 is within the BBS diagnostic umbrella covered by the approval.
Renal monitoring: Horseshoe kidney, renal anomalies → regular nephrology follow-up.
Cognitive/developmental support: Mild intellectual disability → early educational intervention.
Endocrinology: Obesity management, hyperphagia control (setmelanotide).
Multidisciplinary team: ERN-EYE/ERKNet 2024 consensus recommends coordinated care across ophthalmology, nephrology, endocrinology, and developmental pediatrics.

7. Clinical Trials

ClinicalTrials.gov search (2026-07-01): No trials for "CFAP418", "C8orf37", or "BBS21" were found.

No gene therapy or targeted molecular therapy trial for CFAP418-related retinal ciliopathy was identified. This is consistent with the relatively small number of affected families published (CORD16/RP64/BBS21 combined).

Broad IRD gene therapy trials (RPE65, RPGR, USH2A, CEP290, etc.) are actively enrolling in 2025–2026 but do not include CFAP418. Given the ESCRT-pathway and membrane-lipid mechanism (PMID:37971880), future neuroprotective or lipid-targeted therapies could theoretically be relevant, but no IND has been filed.

8. Completeness Assessment for KB Entry

Based on this research, the following sections were NOT yet in the PR as of the review (2026-06-28) but are clinically supported:

Section	Recommendation	Supporting source
`treatments:`	ADD — supportive (low vision aids, UV protection, genetic counseling) + setmelanotide for BBS21 obesity	PMID:38383825, standard IRD SoC
`diagnosis:`	ADD — ERG, SD-OCT, AF, visual field, genetic panel	PMID:23788369
`progression:`	ADD — early onset, early macular involvement, nonrecordable ERG; progressive	PMID:23788369
`has_subtypes:`	CONSIDER — CORD16/RP64/BBS21 could be formalized as named subtypes of this gene-anchored entry; mirrors current free-text description	PMID:22177090, PMID:26854863
`clinical_trials:`	OMIT — no CFAP418-specific trials found on ClinicalTrials.gov	ClinicalTrials.gov search 2026-07-01

The pathophysiology section in the PR covers the core connecting-cilium and photoreceptor degeneration mechanisms. The 2024 JCI Insight paper (PMID:37971880) adds a membrane lipid homeostasis dimension (phosphatidic acid / cardiolipin binding, ESCRT dysregulation) that could enrich the CFAP418 Loss of Function at the Photoreceptor Ciliary Base node with additional biological processes: - GO:0046486 — glycerophospholipid metabolic process - GO:0036020 — endosomal transport

9. Key PMIDs Referenced

PMID	Description	Status in PR
PMID:22177090	Estrada-Cuzcano 2012 — first C8orf37 identification (arCRD/arRP)	✅ in PR
PMID:26854863	C8orf37 mutated in BBS + allelic to non-syndromic RD	✅ in PR
PMID:27008867	Mutations in C8ORF37 cause BBS21	✅ in PR
PMID:36233334	Interactions between C8orf37 and FAM161A	✅ in PR
PMID:23788369	van Huet 2013 IOVS — clinical characterization of 8 C8orf37 patients	⬜ not in PR
PMID:37971880	Clark 2024 JCI Insight — membrane lipid mechanism (PA/cardiolipin/ESCRT)	⬜ not in PR
PMID:38383825	Shoemaker 2024 — BBS clinical overview incl. setmelanotide	⬜ not in PR

CFAP418-related retinal ciliopathy

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References & Deep Research

References

Deep Research

CFAP418-related Retinal Ciliopathy — Research Report

1. Disease Overview and MONDO Anchor

2. Core Pathophysiology

2a. Ciliary-base localization (photoreceptor connecting cilium)

2b. Membrane lipid homeostasis (newer mechanistic arm)

3. Clinical Spectrum

3a. Non-syndromic end (isolated retinal dystrophy)

3b. Syndromic end (BBS21)

3c. Allelism and phenotypic determinants

4. Diagnosis

4a. Clinical

4b. Genetic

4c. BBS-specific criteria

5. Natural History and Progression

6. Treatments and Management

6a. Retinal disease (no CFAP418-specific treatment)

6b. BBS21 systemic management

7. Clinical Trials

8. Completeness Assessment for KB Entry

9. Key PMIDs Referenced