👪

Inheritance

1

Autosomal Dominant HP:0000006

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:11471164 SUPPORT Human Clinical

"It has been reported in holoprosencephaly (HPE) cases with severe facial anomalies or as a microform in autosomal dominant HPE (ADHPE)."

Establishes autosomal dominant inheritance pattern for SHH-related HPE including microform presentations.

◆

Subtypes

4

Alobar Holoprosencephaly

Most severe form with complete failure of forebrain division, single ventricle, fused thalami, and severe midline facial defects including cyclopia or proboscis.

Semilobar Holoprosencephaly

Partial hemispheric separation posteriorly with fused frontal lobes and variable facial dysmorphism.

Lobar Holoprosencephaly

Mildest intracranial form with near-complete hemispheric separation but residual midline fusion, often with milder craniofacial features.

Microform Holoprosencephaly (SMMCI, microphthalmia)

Subclinical midline defects without overt holoprosencephaly. Includes solitary median maxillary central incisor (SMMCI), microphthalmia with coloboma, hypotelorism, and single central incisor as isolated findings. Often identified in mutation-positive relatives of HPE probands.

Show evidence (1 reference)

PMID:11471164 SUPPORT Human Clinical

"It has been reported in holoprosencephaly (HPE) cases with severe facial anomalies or as a microform in autosomal dominant HPE (ADHPE)."

Establishes SMMCI and related findings as recognized HPE microforms in autosomal dominant HPE families.

⚙

Pathophysiology

6

Reduced SHH Signaling in Forebrain Patterning

Heterozygous loss-of-function variants in SHH reduce the morphogen gradient required for ventral forebrain specification and midline patterning. SHH protein acts as a morphogen secreted from the prechordal plate and ventral midline, directing dorsoventral patterning of the prosencephalon and separation of the cerebral hemispheres.

neural progenitor cell link

Smoothened signaling pathway link ↓ DECREASED Forebrain dorsal/ventral pattern formation link ↓ DECREASED

forebrain link

Downstream

Impaired Forebrain Midline Separation

Craniofacial Midline Deficiency

Show evidence (2 references)

PMID:20850526 SUPPORT Model Organism

"It is clear that Sonic hedgehog (Shh) signaling regulates both forebrain and eye development, with defects in Shh, or components of the Shh signaling cascade leading to the generation of both birth defects."

Directly establishes SHH as the morphogen governing forebrain patterning, with signaling defects causing HPE.

PMID:20850526 SUPPORT Model Organism

"Holoprosencephaly, the most common forebrain defect, occurs when the cerebral hemispheres fail to separate and is typically associated with mispatterning of embryonic midline tissue."

Links midline tissue mispatterning to hemispheric non-separation via disrupted SHH signaling.

Impaired Forebrain Midline Separation

Insufficient SHH signaling causes failure of the prosencephalon to cleave into distinct cerebral hemispheres, resulting in the characteristic alobar through lobar HPE continuum.

forebrain link

Downstream

Neurological Impairment More severe forebrain non-separation is associated with more severe neurologic dysfunction.

Craniofacial Midline Deficiency

Reduced SHH morphogen from the prechordal plate impairs midline facial development, producing a spectrum from cyclopia and proboscis in severe cases to hypotelorism, SMMCI, and cleft lip/palate in milder forms. The principle that "the face predicts the brain" reflects the shared embryological origin.

Downstream

Pituitary Dysfunction Midline defects disrupt pituitary gland formation, causing endocrine insufficiency.

Show evidence (1 reference)

PMID:29761634 SUPPORT Human Clinical

"Nonchromosomal, nonsyndromic holoprosencephaly (NCNS-HPE) has traditionally been considered as a condition of brain and craniofacial maldevelopment."

Confirms that HPE is fundamentally a disorder of both brain and craniofacial midline development.

Neurological Impairment

Neurologic dysfunction in HPE worsens as hemispheric non-separation becomes more severe.

Show evidence (1 reference)

PMID:12370462 SUPPORT Human Clinical

"In general, the severity of clinical problems and neurologic dysfunctions correlated with the degree of hemispheric nonseparation (grade of HPE)."

Prospective human cohort data directly support that neurologic dysfunction severity tracks the degree of hemispheric non-separation in HPE.

Pituitary Dysfunction

Disrupted midline morphogenesis impairs anterior pituitary development, resulting in growth hormone deficiency, central hypothyroidism, and other endocrinopathies.

Show evidence (1 reference)

PMID:29761634 SUPPORT Human Clinical

"In addition to the systemic consequences of pituitary dysfunction (as a direct result of brain midline defects), here we describe a number of extracephalic findings of NCNS-HPE affecting various organ systems."

Pituitary dysfunction in HPE is a direct consequence of brain midline structural defects.

Modifier-Dependent Variable Expressivity

SHH HPE follows a multi-hit model in which the primary heterozygous SHH variant interacts with additional genetic modifiers and environmental factors to determine the position on the severity spectrum from microform to alobar HPE.

Show evidence (2 references)

PMID:29992659 SUPPORT Human Clinical

"we demonstrate that variation of modest intrinsic effect can synergize with these driver mutations as gene modifiers."

Large targeted sequencing study in 333 HPE probands demonstrates oligogenic inheritance with gene modifiers.

PMID:34576017 SUPPORT Human Clinical

"In these syndromes, there is wide variability in phenotype even with the same genetic mutation, so that other factors must influence the outcome."

Confirms variable expressivity is a hallmark of SHH-related HPE.

⬡

Pathograph

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

●

Phenotypes

11

Endocrine 1

Pituitary Dysfunction Anterior pituitary hypoplasia (HP:0010627)

Show evidence (1 reference)

PMID:29761634 SUPPORT Human Clinical

"In addition to the systemic consequences of pituitary dysfunction (as a direct result of brain midline defects), here we describe a number of extracephalic findings of NCNS-HPE affecting various organ systems."

Pituitary dysfunction is directly linked to brain midline defects in nonsyndromic HPE.

Eye 3

Hypotelorism Hypotelorism (HP:0000601)

Microphthalmia Microphthalmia (HP:0000568)

Show evidence (1 reference)

PMID:20850526 SUPPORT Model Organism

"we propose that holoprosencephaly and coloboma can represent mild and severe aspects of single phenotypic spectrum resulting from aberrant forebrain development."

Establishes coloboma/microphthalmia as part of the HPE spectrum via shared SHH signaling mechanisms.

Coloboma Coloboma (HP:0000589)

Show evidence (1 reference)

PMID:20850526 SUPPORT Model Organism

"we propose that holoprosencephaly and coloboma can represent mild and severe aspects of single phenotypic spectrum resulting from aberrant forebrain development."

Links coloboma to SHH signaling defects as part of the HPE phenotypic spectrum, shared embryologic origin with forebrain malformations.

Head and Neck 4

Microcephaly Microcephaly (HP:0000252)

Show evidence (1 reference)

PMID:11471164 SUPPORT Human Clinical

"These anomalies include short stature, pituitary insufficiency, microcephaly, choanal atresia, midnasal stenosis, and congenital nasal pyriform aperture stenosis."

Documents microcephaly as a recognized associated feature in SHH-related HPE spectrum including SMMCI patients.

Solitary Median Maxillary Central Incisor Solitary median maxillary central incisor (HP:0006315)

Show evidence (2 references)

PMID:11471164 SUPPORT Human Clinical

"A new missense mutation in SHH (I111F), segregating in one SMMCI family, was identified."

Identifies an SHH mutation specific to the SMMCI phenotype, establishing SMMCI as part of the HPE spectrum.

PMID:15103725 SUPPORT Human Clinical

"Solitary median maxillary central incisor (SMMCI) is a rare dental anomaly. It is usually considered as a minor manifestation of holoprosencephaly (HPE)."

Confirms SMMCI as a microform of HPE with novel SHH mutation.

Orofacial Cleft Orofacial cleft (HP:0000202)

Choanal Atresia Choanal atresia (HP:0000453)

Show evidence (1 reference)

PMID:11471164 SUPPORT Human Clinical

"These anomalies include short stature, pituitary insufficiency, microcephaly, choanal atresia, midnasal stenosis, and congenital nasal pyriform aperture stenosis."

Choanal atresia is documented as an associated anomaly in SMMCI patients.

Nervous System 3

Holoprosencephaly Holoprosencephaly (HP:0001360)

Show evidence (1 reference)

PMID:34576017 SUPPORT Human Clinical

"SHH mutations were the first identified genetic causes of holoprosencephaly, but many other genes and environmental factors can cause malformations in the holoprosencephaly spectrum."

Establishes holoprosencephaly as the cardinal feature of SHH mutations.

Intellectual Disability Intellectual disability (HP:0001249)

Seizures Seizure (HP:0001250)

🧬

Genetic Associations

1

SHH loss-of-function variants (Causative)

Show evidence (2 references)

PMID:32939873 SUPPORT Model Organism

"Genetic variation in the highly conserved Sonic Hedgehog (SHH) gene is one of the most common genetic causes for the malformations of the brain and face in humans described as the holoprosencephaly clinical spectrum."

Zebrafish functional analysis of 104 SHH variants establishes loss-of-function as the disease mechanism for HPE spectrum.

PMID:34576017 SUPPORT Human Clinical

"SHH mutations were the first identified genetic causes of holoprosencephaly, but many other genes and environmental factors can cause malformations in the holoprosencephaly spectrum."

Establishes SHH as the first known genetic cause of HPE and notes the wide variability in phenotype even with the same mutation.

{ }

Source YAML

click to show

name: SHH_Holoprosencephaly_Spectrum
creation_date: '2026-04-04T00:00:00Z'
updated_date: '2026-04-21T03:28:11Z'
description: >-
  SHH-related holoprosencephaly spectrum encompasses a continuum of forebrain
  and craniofacial midline defects caused by heterozygous loss-of-function
  variants in the Sonic Hedgehog (SHH) gene. The phenotypic spectrum ranges
  from severe alobar holoprosencephaly with cyclopia to mild microforms such
  as solitary median maxillary central incisor (SMMCI) or microphthalmia with
  coloboma. SHH mutations were the first identified genetic cause of
  holoprosencephaly. Inheritance is autosomal dominant with highly variable
  expressivity and incomplete penetrance, consistent with a multi-hit model
  in which genetic modifiers and environmental factors influence severity.
category: Genetic
parents:
- Congenital Disorder
- Neurodevelopmental Disorder
disease_term:
  preferred_term: holoprosencephaly 3
  term:
    id: MONDO:0007733
    label: holoprosencephaly 3
prevalence:
- population: Global
  percentage: Rare
inheritance:
- name: Autosomal Dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:11471164
    reference_title: "SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It has been reported in holoprosencephaly (HPE) cases with severe facial
      anomalies or as a microform in autosomal dominant HPE (ADHPE).
    explanation: >-
      Establishes autosomal dominant inheritance pattern for SHH-related HPE
      including microform presentations.
genetic:
- name: SHH loss-of-function variants
  gene_term:
    preferred_term: SHH
    term:
      id: hgnc:10848
      label: SHH
  association: Causative
  features: >-
    Heterozygous loss-of-function and missense variants in SHH. Functional
    studies in zebrafish classify 104 clinically reported SHH variants into
    loss of function (31), hypomorphic (33), and nonpathogenic (40) categories.
    Incomplete penetrance and variable expressivity are hallmarks, consistent
    with oligogenic and environmental modifier effects.
  evidence:
  - reference: PMID:32939873
    reference_title: "Functional analysis of Sonic Hedgehog variants associated with holoprosencephaly in humans using a CRISPR/Cas9 zebrafish model."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Genetic variation in the highly conserved Sonic Hedgehog (SHH) gene is
      one of the most common genetic causes for the malformations of the brain
      and face in humans described as the holoprosencephaly clinical spectrum.
    explanation: >-
      Zebrafish functional analysis of 104 SHH variants establishes
      loss-of-function as the disease mechanism for HPE spectrum.
  - reference: PMID:34576017
    reference_title: "The Role of Sonic Hedgehog in Human Holoprosencephaly and Short-Rib Polydactyly Syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SHH mutations were the first identified genetic causes of
      holoprosencephaly, but many other genes and environmental factors can
      cause malformations in the holoprosencephaly spectrum.
    explanation: >-
      Establishes SHH as the first known genetic cause of HPE and notes the
      wide variability in phenotype even with the same mutation.
has_subtypes:
- name: Alobar HPE
  display_name: Alobar Holoprosencephaly
  description: >-
    Most severe form with complete failure of forebrain division, single
    ventricle, fused thalami, and severe midline facial defects including
    cyclopia or proboscis.
- name: Semilobar HPE
  display_name: Semilobar Holoprosencephaly
  description: >-
    Partial hemispheric separation posteriorly with fused frontal lobes
    and variable facial dysmorphism.
- name: Lobar HPE
  display_name: Lobar Holoprosencephaly
  description: >-
    Mildest intracranial form with near-complete hemispheric separation
    but residual midline fusion, often with milder craniofacial features.
- name: Microform HPE
  display_name: Microform Holoprosencephaly (SMMCI, microphthalmia)
  description: >-
    Subclinical midline defects without overt holoprosencephaly. Includes
    solitary median maxillary central incisor (SMMCI), microphthalmia with
    coloboma, hypotelorism, and single central incisor as isolated findings.
    Often identified in mutation-positive relatives of HPE probands.
  evidence:
  - reference: PMID:11471164
    reference_title: "SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It has been reported in holoprosencephaly (HPE) cases with severe facial
      anomalies or as a microform in autosomal dominant HPE (ADHPE).
    explanation: >-
      Establishes SMMCI and related findings as recognized HPE microforms in
      autosomal dominant HPE families.
phenotypes:
- category: Neurological
  name: Holoprosencephaly
  description: >-
    Failure of the prosencephalon to divide into two cerebral hemispheres,
    ranging from alobar (complete non-division) through semilobar and lobar
    forms.
  phenotype_term:
    preferred_term: Holoprosencephaly
    term:
      id: HP:0001360
      label: Holoprosencephaly
  evidence:
  - reference: PMID:34576017
    reference_title: "The Role of Sonic Hedgehog in Human Holoprosencephaly and Short-Rib Polydactyly Syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SHH mutations were the first identified genetic causes of
      holoprosencephaly, but many other genes and environmental factors can
      cause malformations in the holoprosencephaly spectrum.
    explanation: >-
      Establishes holoprosencephaly as the cardinal feature of SHH mutations.
- category: Neurological
  name: Intellectual Disability
  description: >-
    Variable cognitive impairment, more severe in alobar and semilobar forms.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
- category: Neurological
  name: Seizures
  description: >-
    Epileptic seizures occurring in patients with structural brain malformation.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
- category: Craniofacial
  name: Microcephaly
  description: >-
    Reduced head circumference reflecting reduced forebrain volume.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:11471164
    reference_title: "SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These anomalies include short stature, pituitary insufficiency,
      microcephaly, choanal atresia, midnasal stenosis, and congenital nasal
      pyriform aperture stenosis.
    explanation: >-
      Documents microcephaly as a recognized associated feature in SHH-related
      HPE spectrum including SMMCI patients.
- category: Craniofacial
  name: Hypotelorism
  description: >-
    Decreased distance between the eyes, reflecting midline developmental
    field deficiency. A hallmark of the HPE facial spectrum.
  phenotype_term:
    preferred_term: Hypotelorism
    term:
      id: HP:0000601
      label: Hypotelorism
- category: Craniofacial
  name: Solitary Median Maxillary Central Incisor
  subtype: Microform HPE
  description: >-
    A single centrally positioned maxillary incisor considered a microform
    of HPE. May occur as an isolated finding in SHH mutation carriers.
  phenotype_term:
    preferred_term: Solitary median maxillary central incisor
    term:
      id: HP:0006315
      label: Solitary median maxillary central incisor
  evidence:
  - reference: PMID:11471164
    reference_title: "SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A new missense mutation in SHH (I111F), segregating in one SMMCI
      family, was identified.
    explanation: >-
      Identifies an SHH mutation specific to the SMMCI phenotype,
      establishing SMMCI as part of the HPE spectrum.
  - reference: PMID:15103725
    reference_title: "Solitary median maxillary central incisor syndrome: clinical case with a novel mutation of sonic hedgehog."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Solitary median maxillary central incisor (SMMCI) is a rare dental
      anomaly. It is usually considered as a minor manifestation of
      holoprosencephaly (HPE).
    explanation: >-
      Confirms SMMCI as a microform of HPE with novel SHH mutation.
- category: Craniofacial
  name: Orofacial Cleft
  description: >-
    Cleft lip and/or palate resulting from impaired midline fusion.
  phenotype_term:
    preferred_term: Orofacial cleft
    term:
      id: HP:0000202
      label: Orofacial cleft
- category: Ophthalmologic
  name: Microphthalmia
  subtype: Microform HPE
  description: >-
    Abnormally small eye(s), representing deficient SHH signaling in eye
    development. Microphthalmia with coloboma is considered part of the
    HPE continuum.
  phenotype_term:
    preferred_term: Microphthalmia
    term:
      id: HP:0000568
      label: Microphthalmia
  evidence:
  - reference: PMID:20850526
    reference_title: "Aberrant forebrain signaling during early development underlies the generation of holoprosencephaly and coloboma."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      we propose that holoprosencephaly and coloboma can represent mild and
      severe aspects of single phenotypic spectrum resulting from aberrant
      forebrain development.
    explanation: >-
      Establishes coloboma/microphthalmia as part of the HPE spectrum
      via shared SHH signaling mechanisms.
- category: Ophthalmologic
  name: Coloboma
  subtype: Microform HPE
  description: >-
    Iris or retinal coloboma from incomplete choroid fissure closure.
  phenotype_term:
    preferred_term: Coloboma
    term:
      id: HP:0000589
      label: Coloboma
  evidence:
  - reference: PMID:20850526
    reference_title: "Aberrant forebrain signaling during early development underlies the generation of holoprosencephaly and coloboma."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      we propose that holoprosencephaly and coloboma can represent mild and
      severe aspects of single phenotypic spectrum resulting from aberrant
      forebrain development.
    explanation: >-
      Links coloboma to SHH signaling defects as part of the HPE phenotypic
      spectrum, shared embryologic origin with forebrain malformations.
- category: Endocrine
  name: Pituitary Dysfunction
  description: >-
    Anterior pituitary hypoplasia or dysfunction secondary to midline
    brain defects. May manifest as growth hormone deficiency, central
    hypothyroidism, or diabetes insipidus.
  phenotype_term:
    preferred_term: Anterior pituitary hypoplasia
    term:
      id: HP:0010627
      label: Anterior pituitary hypoplasia
  evidence:
  - reference: PMID:29761634
    reference_title: "Extracephalic manifestations of nonchromosomal, nonsyndromic holoprosencephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In addition to the systemic consequences of pituitary dysfunction (as
      a direct result of brain midline defects), here we describe a number
      of extracephalic findings of NCNS-HPE affecting various organ systems.
    explanation: >-
      Pituitary dysfunction is directly linked to brain midline defects in
      nonsyndromic HPE.
- category: Craniofacial
  name: Choanal Atresia
  description: >-
    Congenital narrowing or obstruction of the nasal passages, reported in
    SMMCI and HPE microform patients.
  phenotype_term:
    preferred_term: Choanal atresia
    term:
      id: HP:0000453
      label: Choanal atresia
  evidence:
  - reference: PMID:11471164
    reference_title: "SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These anomalies include short stature, pituitary insufficiency,
      microcephaly, choanal atresia, midnasal stenosis, and congenital nasal
      pyriform aperture stenosis.
    explanation: >-
      Choanal atresia is documented as an associated anomaly in SMMCI
      patients.
pathophysiology:
- name: Reduced SHH Signaling in Forebrain Patterning
  description: >-
    Heterozygous loss-of-function variants in SHH reduce the morphogen
    gradient required for ventral forebrain specification and midline
    patterning. SHH protein acts as a morphogen secreted from the
    prechordal plate and ventral midline, directing dorsoventral patterning
    of the prosencephalon and separation of the cerebral hemispheres.
  cell_types:
  - preferred_term: neural progenitor cell
    term:
      id: CL:0000047
      label: neural stem cell
  biological_processes:
  - preferred_term: Smoothened signaling pathway
    term:
      id: GO:0007224
      label: smoothened signaling pathway
    modifier: DECREASED
  - preferred_term: Forebrain dorsal/ventral pattern formation
    term:
      id: GO:0021798
      label: forebrain dorsal/ventral pattern formation
    modifier: DECREASED
  locations:
  - preferred_term: forebrain
    term:
      id: UBERON:0001890
      label: forebrain
  evidence:
  - reference: PMID:20850526
    reference_title: "Aberrant forebrain signaling during early development underlies the generation of holoprosencephaly and coloboma."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      It is clear that Sonic hedgehog (Shh) signaling regulates both
      forebrain and eye development, with defects in Shh, or components of
      the Shh signaling cascade leading to the generation of both birth
      defects.
    explanation: >-
      Directly establishes SHH as the morphogen governing forebrain
      patterning, with signaling defects causing HPE.
  - reference: PMID:20850526
    reference_title: "Aberrant forebrain signaling during early development underlies the generation of holoprosencephaly and coloboma."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Holoprosencephaly, the most common forebrain defect, occurs when the
      cerebral hemispheres fail to separate and is typically associated with
      mispatterning of embryonic midline tissue.
    explanation: >-
      Links midline tissue mispatterning to hemispheric non-separation
      via disrupted SHH signaling.
  downstream:
  - target: Impaired Forebrain Midline Separation
  - target: Craniofacial Midline Deficiency
- name: Impaired Forebrain Midline Separation
  description: >-
    Insufficient SHH signaling causes failure of the prosencephalon to
    cleave into distinct cerebral hemispheres, resulting in the
    characteristic alobar through lobar HPE continuum.
  locations:
  - preferred_term: forebrain
    term:
      id: UBERON:0001890
      label: forebrain
  downstream:
  - target: Neurological Impairment
    description: >-
      More severe forebrain non-separation is associated with more severe
      neurologic dysfunction.
- name: Craniofacial Midline Deficiency
  description: >-
    Reduced SHH morphogen from the prechordal plate impairs midline
    facial development, producing a spectrum from cyclopia and proboscis
    in severe cases to hypotelorism, SMMCI, and cleft lip/palate in milder
    forms. The principle that "the face predicts the brain" reflects the
    shared embryological origin.
  evidence:
  - reference: PMID:29761634
    reference_title: "Extracephalic manifestations of nonchromosomal, nonsyndromic holoprosencephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Nonchromosomal, nonsyndromic holoprosencephaly (NCNS-HPE) has
      traditionally been considered as a condition of brain and craniofacial
      maldevelopment.
    explanation: >-
      Confirms that HPE is fundamentally a disorder of both brain and
      craniofacial midline development.
  downstream:
  - target: Pituitary Dysfunction
    description: >-
      Midline defects disrupt pituitary gland formation, causing
      endocrine insufficiency.
- name: Neurological Impairment
  description: >-
    Neurologic dysfunction in HPE worsens as hemispheric non-separation
    becomes more severe.
  evidence:
  - reference: PMID:12370462
    reference_title: "Neuroanatomy of holoprosencephaly as predictor of function: beyond the face predicting the brain."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In general, the severity of clinical problems and neurologic
      dysfunctions correlated with the degree of hemispheric nonseparation
      (grade of HPE).
    explanation: >-
      Prospective human cohort data directly support that neurologic
      dysfunction severity tracks the degree of hemispheric non-separation
      in HPE.
- name: Pituitary Dysfunction
  description: >-
    Disrupted midline morphogenesis impairs anterior pituitary
    development, resulting in growth hormone deficiency, central
    hypothyroidism, and other endocrinopathies.
  evidence:
  - reference: PMID:29761634
    reference_title: "Extracephalic manifestations of nonchromosomal, nonsyndromic holoprosencephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In addition to the systemic consequences of pituitary dysfunction (as
      a direct result of brain midline defects), here we describe a number
      of extracephalic findings of NCNS-HPE affecting various organ systems.
    explanation: >-
      Pituitary dysfunction in HPE is a direct consequence of brain midline
      structural defects.
- name: Modifier-Dependent Variable Expressivity
  description: >-
    SHH HPE follows a multi-hit model in which the primary heterozygous
    SHH variant interacts with additional genetic modifiers and
    environmental factors to determine the position on the severity
    spectrum from microform to alobar HPE.
  evidence:
  - reference: PMID:29992659
    reference_title: "Common genetic causes of holoprosencephaly are limited to a small set of evolutionarily conserved driver genes of midline development coordinated by TGF-β, hedgehog, and FGF signaling."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we demonstrate that variation of modest intrinsic effect can synergize
      with these driver mutations as gene modifiers.
    explanation: >-
      Large targeted sequencing study in 333 HPE probands demonstrates
      oligogenic inheritance with gene modifiers.
  - reference: PMID:34576017
    reference_title: "The Role of Sonic Hedgehog in Human Holoprosencephaly and Short-Rib Polydactyly Syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In these syndromes, there is wide variability in phenotype even with
      the same genetic mutation, so that other factors must influence the
      outcome.
    explanation: >-
      Confirms variable expressivity is a hallmark of SHH-related HPE.
notes: >-
  This entry absorbs three MONDO entities: holoprosencephaly 3 (MONDO:0007733),
  microphthalmia isolated with coloboma 5 (MONDO:0012709), and solitary median
  maxillary central incisor syndrome (MONDO:0007819), reflecting the clinical
  understanding that these are part of a single SHH loss-of-function phenotypic
  continuum.

📚

References & Deep Research

Deep Research

1

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 29 citations 2026-04-04T12:31:28.559228

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: SHH Holoprosencephaly Spectrum
MONDO ID: (if available)
Category: Genetic

Research Objectives

Please provide a comprehensive research report on SHH Holoprosencephaly Spectrum covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, MAXO, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Comprehensive Research Report: SHH Holoprosencephaly Spectrum (HPE3)

Target disease

Disease name: SHH Holoprosencephaly Spectrum (SHH-related holoprosencephaly; HPE3)
Category: Genetic congenital malformation / neurodevelopmental disorder
MONDO ID: Not retrieved in the available evidence (not inferable from the current tool context).

1. Disease information

Overview (what is the disease?)

Holoprosencephaly (HPE) is a congenital forebrain malformation caused by inadequate or absent midline division of the prosencephalon/forebrain into cerebral hemispheres, frequently accompanied by midline craniofacial defects. SHH holoprosencephaly spectrum refers to the subset of HPE attributable to pathogenic variation affecting Sonic hedgehog (SHH) signaling and its dosage. (petryk2015holoprosencephalysignalinginteractions pages 1-3, lavillaureix2023aspectsgénétiquesdu pages 167-172)

Developmentally, HPE arises early in embryogenesis; one review places the critical window for failed cleavage at roughly gestational days 18–28. (lavillaureix2023aspectsgénétiquesdu pages 167-172)

Key identifiers and controlled vocabularies

HPE locus name: HPE3, corresponding to the SHH gene (singh2009sonichedgehogmutations pages 1-2)
Causal gene: SHH; location 7q36 (castro2021newshhand pages 1-2, singh2009sonichedgehogmutations pages 1-2)
MeSH term (clinicaltrials.gov browse): Holoprosencephaly (MeSH D016142) (NCT04691414 chunk 1)

Synonyms / alternative names

SHH-related holoprosencephaly
Sonic hedgehog-related holoprosencephaly
Holoprosencephaly 3 (HPE3)
SHH-deficiency (SHH-D) spectrum / SHH-dosage disorders (used in some research contexts) (NCT04691414 chunk 1, lavillaureix2023aspectsgénétiquesdu pages 167-172)

Evidence source type

This entry is derived from aggregated disease-level resources (reviews) plus primary research (human genetics papers, mouse model studies) and clinicaltrials.gov registry descriptions (observational genetics studies). (petryk2015holoprosencephalysignalinginteractions pages 1-3, malta2023holoprosencephalyreviewof pages 9-11, kim2019integratedclinicaland pages 1-2, NCT04691414 chunk 1)

A compact scaffold of the key identifiers, definition, inheritance, and epidemiology is provided in the artifact table below.

Disease / synonyms	Key identifiers	Brief definition / overview	Inheritance / penetrance / expressivity	Epidemiology
SHH-related holoprosencephaly spectrum; holoprosencephaly 3 (HPE3); Sonic hedgehog-related holoprosencephaly; SHH-associated holoprosencephaly	Locus: HPE3; gene: SHH; chromosomal location: 7q36; SHH was identified as the gene corresponding to the HPE3 locus (singh2009sonichedgehogmutations pages 1-2, castro2021newshhand pages 1-2)	Congenital forebrain malformation caused by incomplete midline division of the prosencephalon, typically arising between gestational days 18–28; part of a broad spectrum from severe alobar forms with major craniofacial anomalies to mild microforms (lavillaureix2023aspectsgénétiquesdu pages 167-172, petryk2015holoprosencephalysignalinginteractions pages 1-3, chafiq2024alobarholoprosencephalyin pages 1-3)	Usually autosomal dominant for SHH pathogenic variants, but with incomplete penetrance and variable expressivity; some cases are sporadic, and oligogenic/modifier effects are increasingly recognized. One review notes that only about 37% of human carriers of SHH mutations develop HPE (petryk2015holoprosencephalysignalinginteractions pages 1-3, roessler2018commongeneticcauses pages 1-5, kim2019integratedclinicaland pages 1-2)	HPE overall occurs in about 1 in 250 conceptuses/fetuses and about 1 in 10,000 live births/live-born infants (petryk2015holoprosencephalysignalinginteractions pages 1-3, roessler2018commongeneticcauses pages 1-5, lavillaureix2023aspectsgénétiquesdu pages 175-177)

Table: This table summarizes core disease-level facts for SHH-related holoprosencephaly spectrum, including naming, identifiers, overview, inheritance, and headline epidemiology. It is useful as a compact knowledge-base entry scaffold grounded only in the cited evidence contexts.

2. Etiology

Disease causal factors

Primary cause (genetic): Pathogenic variants affecting SHH and SHH-pathway genes reduce effective SHH signaling, producing a midline patterning defect of brain and face. SHH is repeatedly described as a major and historically first-identified gene in non-chromosomal HPE, with HPE3 mapping to SHH. (castro2021newshhand pages 1-2, singh2009sonichedgehogmutations pages 1-2, lavillaureix2023aspectsgénétiquesdu pages 167-172)

Mechanistic framing: Disruption of SHH signaling is described as a central pathophysiologic mechanism underlying HPE. (malta2023holoprosencephalyreviewof pages 9-11)

Risk factors

Genetic risk factors (driver and modifier genes): - Reviews emphasize that HPE commonly shows incomplete penetrance and variable expressivity, and that modifier effects/oligogenic inheritance contribute to phenotypic variability and diagnostic complexity. (petryk2015holoprosencephalysignalinginteractions pages 1-3, kim2019integratedclinicaland pages 1-2, lavillaureix2023aspectsgénétiquesdu pages 175-177) - In a large NGS study, Roessler et al. propose a “simple autosomal dominant with modifier pattern accounting for 25% of the molecular pathology” of HPE, while noting persistent unexplained incomplete penetrance/variable expressivity. (roessler2018commongeneticcauses pages 1-5) - In an integrative omics analysis under an oligogenic model, Kim et al. report variants of clinical interest across many genes enriched for pathways including SHH and primary cilia, and oligogenic events enriched in cases vs controls (P=10^-9). (kim2019integratedclinicaland pages 1-2)

Environmental/teratogenic risk factors (gene–environment interaction context): HPE has both genetic and environmental etiologies, and developmental biology reviews explicitly list examples such as maternal diabetes, ethanol, and retinoic acid as environmental causes/risks, with HPE often used as a model for multifactorial etiology. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Protective factors

Evidence for protective factors in the retrieved corpus is limited. One 2023 clinical review reports an association suggesting folic acid may be protective, citing a 73% risk reduction when taken in the first month in one study (details of the underlying study are not provided in the extracted text). (malta2023holoprosencephalyreviewof pages 9-11)

Gene–environment interactions

Direct experimental evidence that genetic lesions in the Hedgehog pathway can sensitize embryos to environmental teratogens is provided by mouse work in which heterozygous Gli2 variants increased penetrance/severity of HPE after low-dose exposure, supporting a mechanistic model where “normally silent genetic and environmental factors can interact to produce severe outcomes.” (petryk2015holoprosencephalysignalinginteractions pages 1-3)

3. Phenotypes

Conceptualization: “HPE spectrum” and SHH-specific variability

HPE is widely described as a nearly continuous spectrum, from severe malformations (e.g., alobar HPE with cyclopia) to mild microforms (e.g., solitary median maxillary central incisor, hypotelorism) that may occur with subtle or absent classic brain non-separation on imaging. (petryk2015holoprosencephalysignalinginteractions pages 1-3, lavillaureix2023aspectsgénétiquesdu pages 167-172, malta2023holoprosencephalyreviewof pages 2-4)

A key clinical point relevant for SHH-related disease is that facial severity often correlates with brain malformation severity, although exceptions exist by gene and mechanism. (lavillaureix2023aspectsgénétiquesdu pages 167-172, malta2023holoprosencephalyreviewof pages 2-4)

Radiologic/clinical subtypes (and a visual summary)

The 2023 clinical review provides a structured classification of HPE including alobar, semilobar, lobar, middle interhemispheric variant (MIH/syntelencephaly), and microforms/minimal forms. (malta2023holoprosencephalyreviewof pages 2-4)

The same review includes a classification table summarizing major radiologic and clinical features across the spectrum (Table 1 shown in the retrieved image). (malta2023holoprosencephalyreviewof media b1f62008)

Common clinical features and complications (selected)

From the 2023 review and a 2024 case review: - Hydrocephalus: reported frequency 16–40%; may require shunting. (malta2023holoprosencephalyreviewof pages 4-6) - Seizures/epilepsy: approximately ~50%. (malta2023holoprosencephalyreviewof pages 4-6) - Feeding/oromotor difficulties: common, including issues related to midline clefting. (malta2023holoprosencephalyreviewof pages 4-6) - Endocrine/hypothalamic–pituitary dysfunction: diabetes insipidus, adrenal hypoplasia, hypogonadism, thyroid hypoplasia, growth hormone deficiency are noted as common in some clinical summaries of HPE. (chafiq2024alobarholoprosencephalyin pages 1-3)

Suggested HPO terms (non-exhaustive; for knowledge base mapping)

The following HPO mappings are consistent with phenotypes described in the retrieved evidence: - Holoprosencephaly: HP:0001360 - Alobar holoprosencephaly: HP:0002506 - Semilobar holoprosencephaly: HP:0002510 - Lobar holoprosencephaly: HP:0002508 - Hypotelorism: HP:0000601 (petryk2015holoprosencephalysignalinginteractions pages 1-3, lavillaureix2023aspectsgénétiquesdu pages 167-172) - Cleft lip and/or palate: HP:0000204 / HP:0000175 (lavillaureix2023aspectsgénétiquesdu pages 167-172, malta2023holoprosencephalyreviewof pages 4-6) - Solitary median maxillary central incisor (SMMCI): HP:0006313 (petryk2015holoprosencephalysignalinginteractions pages 1-3, galeotti2024useofan pages 1-2) - Congenital nasal pyriform aperture stenosis (CNPAS): HP:0012722 (galeotti2024useofan pages 1-2) - Seizures: HP:0001250 (malta2023holoprosencephalyreviewof pages 4-6) - Hydrocephalus: HP:0000238 (malta2023holoprosencephalyreviewof pages 4-6)

Note: HPO IDs are provided for ontology mapping convenience; the underlying phenotype assertions are supported by the cited sources.

4. Genetic / molecular information

Causal gene

SHH (Sonic Hedgehog) is the defining causal gene for HPE3/SHH-related holoprosencephaly spectrum. (castro2021newshhand pages 1-2, singh2009sonichedgehogmutations pages 1-2)

Pathogenic variant concepts

The retrieved evidence supports a range of mechanistic classes for reduced SHH signaling in HPE: - Haploinsufficiency / reduced effective dosage with incomplete penetrance and variable expressivity is emphasized in human families with heterozygous variants. (petryk2015holoprosencephalysignalinginteractions pages 1-3, castro2021newshhand pages 1-2) - Functional molecular work indicates SHH variants can disrupt distinct steps of SHH biogenesis to attenuate activity to different levels, and can also act in dominant-negative ways in some contexts (mechanistic summary in review-level extract). (singh2009sonichedgehogmutations pages 1-2)

Penetrance and expressivity (quantitative)

A developmental biology review reports that “Only about 37% of human carriers of SHH mutations develop HPE”, emphasizing incomplete penetrance. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Modifier genes / oligogenic inheritance

Multiple sources describe oligogenic inheritance and modifier effects: - An integrative clinical/omics approach found enrichment of variants across genes linked to forebrain development pathways including SHH and primary cilia, consistent with complex inheritance. (kim2019integratedclinicaland pages 1-2) - A 2023 genetics thesis-style review notes that many SHH-dosage cases remain genetically unsolved and highlights oligogenic inheritance and modifiers as contributors to variability. (lavillaureix2023aspectsgénétiquesdu pages 175-177)

Epigenetic information

No SHH-HPE-specific epigenetic (methylation/histone/chromatin) mechanisms were directly extracted in the retrieved evidence.

Chromosomal abnormalities

Although SHH-HPE is monogenic, HPE overall frequently includes chromosomal etiologies; recent case-based and review evidence notes that 25–50% of HPE may have chromosomal abnormalities (commonly trisomy 13). (galeotti2024useofan pages 1-2)

5. Environmental information

HPE etiology includes environmental/teratogenic contributors; reviews list maternal diabetes, ethanol, and retinoic acid among examples discussed in the context of multifactorial causation and gene–environment interactions. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

The retrieved evidence did not provide quantified attributable risk fractions for specific exposures in SHH-variant carriers.

6. Mechanism / pathophysiology

Key pathway (current understanding)

The canonical SHH pathway (ligand processing and downstream transduction via PTCH/SMO/GLI) is central to ventral midline patterning of the forebrain and craniofacial development; impaired activity is repeatedly described as causal for HPE phenotypes. (singh2009sonichedgehogmutations pages 1-2, malta2023holoprosencephalyreviewof pages 9-11)

Molecular causal chain (from trigger to phenotype)

Trigger: Germline pathogenic variation affecting SHH dosage/activity (or combined variants in SHH-pathway/modifier genes), sometimes combined with environmental exposures. (petryk2015holoprosencephalysignalinginteractions pages 1-3, kim2019integratedclinicaland pages 1-2)
Molecular consequence: Reduced effective SHH ligand activity. Mechanistically, SHH is produced as a preprotein that is cleaved into N- and C-terminal domains; the C-terminal domain mediates cholesterol modification of the N-terminal ligand, and the ligand is further palmitoylated, affecting secretion and signaling potency. (singh2009sonichedgehogmutations pages 1-2)
Signal transduction disruption: Altered activation of the Hedgehog signaling cascade involving PTCH/SMO and GLI transcription factors, reducing downstream transcriptional programs needed for ventral forebrain specification and midline craniofacial morphogenesis. (singh2009sonichedgehogmutations pages 1-2)
Developmental outcome: Failed or incomplete midline cleavage of the forebrain with a correlated craniofacial midline defect spectrum, yielding alobar/semilobar/lobar HPE and microforms. (malta2023holoprosencephalyreviewof pages 2-4, lavillaureix2023aspectsgénétiquesdu pages 167-172)

Upstream vs downstream

Upstream: SHH ligand biogenesis (cleavage, lipid modification), secretion and dosage regulation; modifier genes that tune pathway strength; environmental factors that reduce pathway signaling below developmental thresholds. (singh2009sonichedgehogmutations pages 1-2, petryk2015holoprosencephalysignalinginteractions pages 1-3)
Downstream: Reduced pathway-driven transcriptional patterning programs (GLI-dependent) leading to morphogenetic defects in brain and face. (singh2009sonichedgehogmutations pages 1-2, lavillaureix2023aspectsgénétiquesdu pages 167-172)

Gene–environment mechanism (example)

A mouse model demonstrates that Gli2 dosage-dependent attenuation of Hedgehog responsiveness can convert a “normally silent” predisposition into severe HPE outcomes when combined with a low-dose teratogen exposure, supporting a threshold model for pathway failure. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Suggested ontology terms

GO biological process (examples): - Hedgehog signaling pathway: GO:0007224 - Forebrain development: GO:0030900 - Craniofacial development: GO:0060322

Cell types (CL; examples likely involved): - Neuroepithelial cell / neural progenitor (ventral forebrain progenitors) - Cranial neural crest cell (relevant to craniofacial midline development)

Pathway resources: Mechanistic details align with canonical Hedgehog signaling represented in major pathway databases; however, pathway-database URLs were not retrieved in the current tool context.

7. Anatomical structures affected

Primary affected structures: - Forebrain/prosencephalon and midline brain structures (petryk2015holoprosencephalysignalinginteractions pages 1-3, malta2023holoprosencephalyreviewof pages 2-4) - Craniofacial midline (including nasal and oral structures) (lavillaureix2023aspectsgénétiquesdu pages 167-172, galeotti2024useofan pages 1-2)

Representative UBERON suggestions: - Forebrain: UBERON:0001890 - Prosencephalon: UBERON:0001891 - Face: UBERON:0001456 - Maxilla: UBERON:0002397

8. Temporal development

Onset: Congenital; critical early embryonic window for prosencephalon cleavage is during early gestation (days ~18–28 in one summary). (lavillaureix2023aspectsgénétiquesdu pages 167-172)
Progression/course: Structural malformation is non-progressive, but clinical course depends on severity and complications (hydrocephalus, seizures, endocrine dysfunction, feeding impairment), requiring long-term multidisciplinary care in survivors. (malta2023holoprosencephalyreviewof pages 4-6)

9. Inheritance and population

Epidemiology

HPE overall is commonly reported as occurring in approximately 1:250 conceptuses/fetuses and ~1:10,000 live births/live-born infants. (petryk2015holoprosencephalysignalinginteractions pages 1-3, roessler2018commongeneticcauses pages 1-5, lavillaureix2023aspectsgénétiquesdu pages 175-177)

Inheritance (SHH-related)

Typically autosomal dominant with incomplete penetrance and variable expressivity. (petryk2015holoprosencephalysignalinginteractions pages 1-3, castro2021newshhand pages 1-2)
Penetrance estimate reported in a review: ~37% of SHH mutation carriers develop HPE. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Genetic counseling implications

Because penetrance is incomplete and expressivity is variable, recurrence risk may be substantial when a pathogenic variant is present in a parent; one 2023 clinical review provides a general example of up to 50% recurrence risk when a parent carries a mutation with incomplete penetrance (not SHH-specific but relevant to autosomal-dominant HPE genes including SHH). (malta2023holoprosencephalyreviewof pages 9-11)

10. Diagnostics

Imaging

Prenatal ultrasound: Severe forms can be detected in the first trimester; milder forms can be missed. (malta2023holoprosencephalyreviewof pages 9-11)
Fetal MRI: recommended as a second-line prenatal study. (malta2023holoprosencephalyreviewof pages 9-11)
Postnatal MRI: described as the imaging modality of choice for HPE diagnosis. (malta2023holoprosencephalyreviewof pages 9-11)

The 2024 case report/review also illustrates real-world practice: prenatal ultrasound diagnosis followed by postnatal brain MRI confirmation. (chafiq2024alobarholoprosencephalyin pages 1-3)

Genetic testing strategy (real-world implementation)

A 2023 clinical review proposes a stepwise approach: 1. Start with chromosomal analysis; if aneuploidy suspected use karyotype, otherwise chromosomal microarray (CMA) as first-line. (malta2023holoprosencephalyreviewof pages 9-11) 2. If unrevealing and/or syndromic, proceed to targeted gene panels or exome sequencing; the review reports ~22% yield for exome in a mixed cohort. (malta2023holoprosencephalyreviewof pages 9-11)

Clinical research implementations (NGS to improve counseling)

NCT04691414 (EXOMEDIANE; Rennes University Hospital): retrospective NGS on biobanked DNA to improve genetic counseling for craniofacial midline defects/HPE, noting that “70% of cases … do not have a molecular diagnosis” in their summary rationale. Posted 2020-12-31; completed 2021-12-06. URL: https://clinicaltrials.gov/study/NCT04691414 (NCT04691414 chunk 1)
NCT00645645 (NIH NHGRI): long-running observational cohort emphasizing mutational analysis of HPE genes; the registry summary states: “Mutations in one such gene, Sonic Hedgehog, have been shown by us to be responsible for approximately one quarter of familial cases of HPE.” First posted 2008-03-28; updated 2021-12-14. URL: https://clinicaltrials.gov/study/NCT00645645 (NCT00645645 chunk 1)

Differential diagnosis

The retrieved evidence emphasizes that HPE has heterogeneous etiologies including chromosomal anomalies and other monogenic syndromes; a structured differential diagnosis list was not directly extracted in the available snippets. (malta2023holoprosencephalyreviewof pages 9-11, galeotti2024useofan pages 1-2)

11. Outcome / prognosis

Survival and mortality (statistics)

A 2024 case review and the 2023 clinical review provide quantitative survival statistics for severe HPE (particularly alobar): - ~33% die within the first 24 hours - ~58% die within the first month - ~29% survive to 1 year (chafiq2024alobarholoprosencephalyin pages 4-5, malta2023holoprosencephalyreviewof pages 4-6)

Morbidity

Survivors frequently require long-term multidisciplinary care due to neurologic disability, seizures, feeding difficulties, endocrine dysfunction, and complications such as hydrocephalus. (chafiq2024alobarholoprosencephalyin pages 1-3, malta2023holoprosencephalyreviewof pages 4-6)

12. Treatment

Disease-modifying therapy

No disease-modifying pharmacotherapy for congenital SHH-related HPE was identified in the retrieved evidence. Management is described as supportive and multidisciplinary. (petryk2015holoprosencephalysignalinginteractions pages 1-3, malta2023holoprosencephalyreviewof pages 4-6)

Supportive and interventional care (real-world implementations)

Hydrocephalus management: shunt placement when needed (hydrocephalus frequency 16–40%). (malta2023holoprosencephalyreviewof pages 4-6)
Seizure management: antiepileptic treatment guided by clinical neurology (seizures ~50%). (malta2023holoprosencephalyreviewof pages 4-6)
Feeding support: addressing feeding difficulties, sometimes related to clefts. (malta2023holoprosencephalyreviewof pages 4-6)
Endocrine management: addressing diabetes insipidus and pituitary hormone deficiencies in affected individuals. (chafiq2024alobarholoprosencephalyin pages 1-3)

Example of implemented craniofacial/airway management in mild-spectrum HPE: - In an infant with mild HPE features (SMMCI) and congenital nasal pyriform aperture stenosis (CNPAS), a combined ENT–orthodontic approach used balloon dilation and a neonatal palatal expander plate to improve airway patency and sucking/swallowing. (May 2024; https://doi.org/10.3390/children11050554) (galeotti2024useofan pages 1-2)

Suggested MAXO terms (examples)

Genetic counseling: MAXO:0000077 (term label may vary across MAXO versions)
Magnetic resonance imaging: MAXO:0000715 (imaging procedure term; label may vary)
Ventriculoperitoneal shunt placement / CSF shunting: surgical intervention term
Feeding support / enteral feeding: supportive care term

(MAXO IDs are suggested for mapping; specific MAXO identifiers should be validated against the version used in your KB.)

13. Prevention

Primary prevention

No specific primary prevention is established for SHH-variant carriers in the retrieved evidence. One review states “Currently, there are no effective preventive methods for HPE,” emphasizing the need for deeper mechanistic understanding for prevention. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Secondary prevention / early detection

Prenatal screening/diagnosis via ultrasound and fetal MRI facilitates counseling and perinatal planning. (malta2023holoprosencephalyreviewof pages 9-11, chafiq2024alobarholoprosencephalyin pages 1-3)

Counseling and reproductive options

The 2023 clinical review emphasizes balanced prognostic counseling and involving genetics professionals for recurrence estimation; prenatal genetic testing via amniotic fluid is possible. (malta2023holoprosencephalyreviewof pages 9-11)

14. Other species / natural disease

The retrieved evidence did not provide naturally occurring veterinary cases for SHH-related HPE. However, experimental developmental biology literature highlights conserved SHH function across vertebrates, and the phenotype is commonly modeled in mice. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

15. Model organisms

Key models and what they show

Shh-null mouse embryos: described as having fully penetrant severe HPE, supporting a strong causal role for SHH in midline development and providing a baseline for understanding incomplete penetrance in humans. (petryk2015holoprosencephalysignalinginteractions pages 1-3)
Gli2 gene–environment interaction mouse model: heterozygous Gli2 variants increase penetrance/severity after low-dose teratogen exposure, demonstrating a mechanistic basis for variable expressivity and prevention-focused research framing. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Model limitations

Mouse Shh-null is fully penetrant and typically much more severe than the human heterozygous state, limiting direct translation to human incomplete penetrance scenarios but enabling mechanistic dissection of pathway thresholds and modifier effects. (petryk2015holoprosencephalysignalinginteractions pages 1-3)

Recent developments and latest research emphasis (2023–2024)

Updated, clinically oriented synthesis (2023): Malta et al. (Mar 2023; https://doi.org/10.3390/children10040647) consolidates classification, imaging-based diagnosis, genetic testing strategy (CMA→panel/exome), complication rates (e.g., hydrocephalus 16–40%, seizures ~50%), and survival statistics, reflecting current clinical workflows. (malta2023holoprosencephalyreviewof pages 4-6, malta2023holoprosencephalyreviewof pages 9-11)
Implementation-level multidisciplinary care reports (2024): case reports describe integrated surgical/orthodontic airway management for CNPAS in mild-spectrum HPE, demonstrating real-world interventions for survivable sub-phenotypes. (May 2024; https://doi.org/10.3390/children11050554) (galeotti2024useofan pages 1-2)
Improving diagnostic yield and counseling via NGS (ongoing/registry evidence): EXOMEDIANE (NCT04691414) and NIH cohort protocols (NCT00645645) indicate continuing efforts to use sequencing to improve gene discovery and counseling, reflecting the recognized gap that many cases remain molecularly unsolved. (NCT04691414 chunk 1, NCT00645645 chunk 1)

Expert opinion / analysis (from authoritative sources in the retrieved evidence)

Incomplete penetrance and variable expressivity are fundamental to SHH-related HPE and remain partially unexplained despite large-scale sequencing, supporting continued work on modifier genes and gene–environment interactions. (roessler2018commongeneticcauses pages 1-5, petryk2015holoprosencephalysignalinginteractions pages 1-3)
The current best-supported clinical approach prioritizes imaging for diagnosis/severity stratification and uses a tiered genetic testing strategy (chromosomal analysis → sequencing), aligning with the heterogeneity of causes. (malta2023holoprosencephalyreviewof pages 9-11)

Notes on gaps / limitations of this report

Formal mapping to MONDO, Orphanet, ICD-10/ICD-11 identifiers and SHH OMIM IDs was not retrievable from the current tool evidence; these should be added from OMIM/Orphanet in a subsequent pass.
Variant-level details (HGVS, ClinVar frequencies, gnomAD allele frequencies) were not directly accessible in the retrieved text snippets; therefore, variant cataloging is limited to conceptual classes rather than enumerated variants.

Key citations (URLs and dates where available)

Malta M, et al. Children. 2023-03. “Holoprosencephaly: Review of Embryology, Clinical Phenotypes, Etiology and Management.” https://doi.org/10.3390/children10040647 (malta2023holoprosencephalyreviewof pages 4-6, malta2023holoprosencephalyreviewof pages 9-11)
Chafiq K, et al. Cureus. 2024-11. “Alobar Holoprosencephaly in a Newborn: A Case Report…” https://doi.org/10.7759/cureus.74462 (chafiq2024alobarholoprosencephalyin pages 4-5, chafiq2024alobarholoprosencephalyin pages 1-3)
Petryk A, et al. WIREs Dev Biol. 2015-10. https://doi.org/10.1002/wdev.161 (petryk2015holoprosencephalysignalinginteractions pages 1-3)
Roessler E, et al. Hum Mutat. 2018-07. https://doi.org/10.1002/humu.23590 (roessler2018commongeneticcauses pages 1-5)
Kim A, et al. Brain. 2019-11. https://doi.org/10.1093/brain/awy290 (kim2019integratedclinicaland pages 1-2)
de Castro VF, et al. Molecular Syndromology. 2021-06. https://doi.org/10.1159/000515044 (castro2021newshhand pages 1-2)
Singh S, et al. Hum Genet. 2009-12. https://doi.org/10.1007/s00439-008-0599-0 (singh2009sonichedgehogmutations pages 1-2)
ClinicalTrials.gov NCT04691414 (EXOMEDIANE). First posted 2020-12-31; completed 2021-12-06. https://clinicaltrials.gov/study/NCT04691414 (NCT04691414 chunk 1)
ClinicalTrials.gov NCT00645645. First posted 2008-03-28; updated 2021-12-14. https://clinicaltrials.gov/study/NCT00645645 (NCT00645645 chunk 1)

References

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(singh2009sonichedgehogmutations pages 1-2): Samer Singh, Robert Tokhunts, Valerie Baubet, John A. Goetz, Zhen Jane Huang, Neal S. Schilling, Kendall E. Black, Todd A. MacKenzie, Nadia Dahmane, and David J. Robbins. Sonic hedgehog mutations identified in holoprosencephaly patients can act in a dominant negative manner. Human Genetics, 125:95-103, Dec 2009. URL: https://doi.org/10.1007/s00439-008-0599-0, doi:10.1007/s00439-008-0599-0. This article has 44 citations and is from a peer-reviewed journal.
(castro2021newshhand pages 1-2): Viviane Freitas de Castro, Daniel Mattos, Flavia Martinez de Carvalho, Denise Pontes Cavalcanti, Milagros M. Duenas-Roque, Juan Llerena Jr, Viviana Raquel Cosentino, Rachel Sayuri Honjo, Julio Cesar Loguercio Leite, Maria Teresa Sanseverino, Márcia Pereira Alves de Souza, Pricila Bernardi, Ana Maria Bolognese, Luiz Carlos Santana da Silva, Pablo Barbero, Patricia Santana Correia, Larissa Souza Mario Bueno, Clarice Pagani Savastano, and Iêda Maria Orioli. New shh and known six3 variants in a series of latin american patients with holoprosencephaly. Molecular Syndromology, 12:219-233, Jun 2021. URL: https://doi.org/10.1159/000515044, doi:10.1159/000515044. This article has 3 citations and is from a peer-reviewed journal.
(NCT04691414 chunk 1): Retrospective Study Using Next Generation Sequencing (NGS) on Biological Samples to Improve Genetic Counseling for Patients With Previously Explored Craniofacial Midline Defects.. Rennes University Hospital. 2021. ClinicalTrials.gov Identifier: NCT04691414
(malta2023holoprosencephalyreviewof pages 9-11): Maísa Malta, Rowim AlMutiri, Christine Saint Martin, and Myriam Srour. Holoprosencephaly: review of embryology, clinical phenotypes, etiology and management. Children, 10:647, Mar 2023. URL: https://doi.org/10.3390/children10040647, doi:10.3390/children10040647. This article has 37 citations.
(kim2019integratedclinicaland pages 1-2): Artem Kim, Clara Savary, Christèle Dubourg, Wilfrid Carré, Charlotte Mouden, Houda Hamdi-Rozé, Hélène Guyodo, Jerome Le Douce, Emmanuelle Génin, Dominique Campion, Jean-François Dartigues, Jean-François Deleuze, Jean-Charles Lambert, Richard Redon, Thomas Ludwig, Benjamin Grenier-Boley, Sébastien Letort, Pierre Lindenbaum, Vincent Meyer, Olivier Quenez, Christian Dina, Céline Bellenguez, Camille Charbonnier-Le Clézio, Joanna Giemza, Stéphanie Chatel, Claude Férec, Hervé Le Marec, Luc Letenneur, Gaël Nicolas, Karen Rouault, Delphine Bacq, Anne Boland, Doris Lechner, Cisca Wijmenga, Morris A Swertz, P Eline Slagboom, Gert-Jan B van Ommen, Cornelia M van Duijn, Dorret I Boomsma, Paul I W de Bakker, Jasper A Bovenberg, P Eline Slagboom, Anton J M de Craen, Marian Beekman, Albert Hofman, Dorret I Boomsma, Gonneke Willemsen, Bruce Wolffenbuttel, Mathieu Platteel, Yuanping Du, Ruoyan Chen, Hongzhi Cao, Rui Cao, Yushen Sun, Jeremy Sujie Cao, Morris A Swertz, Freerk van Dijk, Pieter B T Neerincx, Patrick Deelen, Martijn Dijkstra, George Byelas, Alexandros Kanterakis, Jan Bot, Kai Ye, Eric-Wubbo Lameijer, Martijn Vermaat, Jeroen F J Laros, Johan T den Dunnen, Peter de Knijff, Lennart C Karssen, Elisa M van Leeuwen, Najaf Amin, Vyacheslav Koval, Fernando Rivadeneira, Karol Estrada, Jayne Y Hehir-Kwa, Joep de Ligt, Abdel Abdellaoui, Jouke-Jan Hottenga, V Mathijs Kattenberg, David van Enckevort, Hailiang Mei, Mark Santcroos, Barbera D C van Schaik, Robert E Handsaker, Steven A McCarroll, Evan E Eichler, Arthur Ko, Peter Sudmant, Laurent C Francioli, Wigard P Kloosterman, Isaac J Nijman, Victor Guryev, Paul I W de Bakker, Laurent Pasquier, Elisabeth Flori, Marie Gonzales, Claire Bénéteau, Odile Boute, Tania Attié-Bitach, Joelle Roume, Louise Goujon, Linda Akloul, Sylvie Odent, Erwan Watrin, Valérie Dupé, Marie de Tayrac, and Véronique David. Integrated clinical and omics approach to rare diseases: novel genes and oligogenic inheritance in holoprosencephaly. Brain, 142:35-49, Nov 2019. URL: https://doi.org/10.1093/brain/awy290, doi:10.1093/brain/awy290. This article has 60 citations and is from a highest quality peer-reviewed journal.
(chafiq2024alobarholoprosencephalyin pages 1-3): Kamal Chafiq, Khalil Toumi, Fatima Ezzahra Khayi, and Abdellatif Daoudi. Alobar holoprosencephaly in a newborn: a case report of prenatal diagnosis and a review of the literature. Cureus, Nov 2024. URL: https://doi.org/10.7759/cureus.74462, doi:10.7759/cureus.74462. This article has 4 citations.
(roessler2018commongeneticcauses pages 1-5): E. Roessler, P. Hu, Juliana Marino, Sungkook Hong, R. Hart, Seth I. Berger, Ariel F. Martinez, Yu Abe, P. Kruszka, James W. Thomas, J. Mullikin, Nisc Comparative Sequencing Program, Yupeng Wang, Wendy S. W. Wong, J. Niederhuber, Benjamin D. Solomon, Benjamin D. Solomon, A. Richieri‐Costa, L. Ribeiro-Bicudo, and M. Muenke. Common genetic causes of holoprosencephaly are limited to a small set of evolutionarily conserved driver genes of midline development coordinated by tgf‐β, hedgehog, and fgf signaling. Human Mutation, 39:1416-1427, Jul 2018. URL: https://doi.org/10.1002/humu.23590, doi:10.1002/humu.23590. This article has 31 citations and is from a domain leading peer-reviewed journal.
(lavillaureix2023aspectsgénétiquesdu pages 175-177): A Lavillaureix. Aspects génétiques du développement cérébral, holoprosencéphalie et élargissement du spectre phénotypique aux pathologies liées à la voie de signalisation shh. Unknown journal, 2023.
(malta2023holoprosencephalyreviewof pages 2-4): Maísa Malta, Rowim AlMutiri, Christine Saint Martin, and Myriam Srour. Holoprosencephaly: review of embryology, clinical phenotypes, etiology and management. Children, 10:647, Mar 2023. URL: https://doi.org/10.3390/children10040647, doi:10.3390/children10040647. This article has 37 citations.
(malta2023holoprosencephalyreviewof media b1f62008): Maísa Malta, Rowim AlMutiri, Christine Saint Martin, and Myriam Srour. Holoprosencephaly: review of embryology, clinical phenotypes, etiology and management. Children, 10:647, Mar 2023. URL: https://doi.org/10.3390/children10040647, doi:10.3390/children10040647. This article has 37 citations.
(malta2023holoprosencephalyreviewof pages 4-6): Maísa Malta, Rowim AlMutiri, Christine Saint Martin, and Myriam Srour. Holoprosencephaly: review of embryology, clinical phenotypes, etiology and management. Children, 10:647, Mar 2023. URL: https://doi.org/10.3390/children10040647, doi:10.3390/children10040647. This article has 37 citations.
(galeotti2024useofan pages 1-2): Angela Galeotti, Giovanni Carlo De Vincentiis, Emanuela Sitzia, Giuseppe Marzo, Wanda Maldonato, Gaia Bompiani, Maria Beatrice Chiarini Testa, Alessandra Putrino, Andrea Bartuli, and Paola Festa. Use of an orthodontic and otolaryngological approach in an infant with holoprosencephaly. Children, 11:554, May 2024. URL: https://doi.org/10.3390/children11050554, doi:10.3390/children11050554. This article has 6 citations.
(NCT00645645 chunk 1): A Study of the Genetic Analysis of Brain Disorders. National Human Genome Research Institute (NHGRI). 2008. ClinicalTrials.gov Identifier: NCT00645645
(chafiq2024alobarholoprosencephalyin pages 4-5): Kamal Chafiq, Khalil Toumi, Fatima Ezzahra Khayi, and Abdellatif Daoudi. Alobar holoprosencephaly in a newborn: a case report of prenatal diagnosis and a review of the literature. Cureus, Nov 2024. URL: https://doi.org/10.7759/cureus.74462, doi:10.7759/cureus.74462. This article has 4 citations.

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Source YAML

References & Deep Research

Deep Research

Disease Characteristics Research Template

Target Disease

Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Citation Requirements

Output Format

Comprehensive Research Report: SHH Holoprosencephaly Spectrum (HPE3)

Target disease

1. Disease information

Overview (what is the disease?)

Key identifiers and controlled vocabularies

Synonyms / alternative names

Evidence source type

2. Etiology

Disease causal factors

Risk factors

Protective factors

Gene–environment interactions

3. Phenotypes

Conceptualization: “HPE spectrum” and SHH-specific variability

Radiologic/clinical subtypes (and a visual summary)

Common clinical features and complications (selected)

Suggested HPO terms (non-exhaustive; for knowledge base mapping)

4. Genetic / molecular information

Causal gene

Pathogenic variant concepts

Penetrance and expressivity (quantitative)

Modifier genes / oligogenic inheritance

Epigenetic information

Chromosomal abnormalities

5. Environmental information

6. Mechanism / pathophysiology

Key pathway (current understanding)

Molecular causal chain (from trigger to phenotype)

Upstream vs downstream

Gene–environment mechanism (example)

Suggested ontology terms

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

Epidemiology

Inheritance (SHH-related)

Genetic counseling implications

10. Diagnostics

Imaging

Genetic testing strategy (real-world implementation)

Clinical research implementations (NGS to improve counseling)

Differential diagnosis

11. Outcome / prognosis

Survival and mortality (statistics)

Morbidity

12. Treatment

Disease-modifying therapy

Supportive and interventional care (real-world implementations)

Suggested MAXO terms (examples)