Van Maldergem Syndrome

Mendelian MONDO:0017813 Pathograph 17 Show in embeddings browser hereditary disease

Van Maldergem syndrome (VMS) is a rare autosomal recessive multisystem developmental disorder caused by biallelic loss-of-function variants in either DCHS1 or FAT4, which encode a receptor-ligand pair of giant atypical (proto)cadherins. The clinical picture combines a distinctive blepharo-naso-facial gestalt (blepharophimosis, telecanthus, maxillary hypoplasia, microtia with external auditory canal atresia), intellectual disability, conductive hearing loss, digital contractures and skeletal anomalies, with neonatal hypotonia, chronic feeding difficulties and respiratory problems. The neuroanatomical signature is periventricular and subcortical nodular heterotopia, reflecting a failure of neuronal migration. Mechanistically, DCHS1 and FAT4 bind each other and operate as the vertebrate Fat-Dachsous planar cell polarity system. In the developing neuroepithelium their loss increases progenitor cell number at the expense of neuronal differentiation — an effect reversed by concurrent knockdown of the Hippo pathway effector Yap — and separately disrupts the polarity and collective migration of neurons, so that cells accumulate below their proper cortical layer. Because the same DCHS1-FAT4 pair also governs lymphatic endothelial polarity, biallelic FAT4 loss is allelic with Hennekam lymphangiectasia-lymphedema syndrome 2; the two conditions share a facial gestalt and intellectual disability but are distinguished by neonatal hypotonia, hearing loss, tracheal anomalies and osteopenia in VMS versus prominent lymphedema in Hennekam syndrome.

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1
Inheritance
7
Pathophys.
20
Phenotypes
17
Pathograph
2
Genes
2
Medical Actions
2
Subtypes
2
Differentials
5
Models
1
Deep Research
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Inheritance

1
Autosomal recessive inheritance HP:0000007
Both the DCHS1 and FAT4 forms are autosomal recessive. Sibling recurrence and parental consanguinity in reported families established the mode of inheritance before the genes were identified.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"In our cohort, we have observed one instance of sibling recurrence and parental consanguinity in three of the families, indicating that autosomal recessive inheritance is likely."
Sibling recurrence plus consanguinity across multiple families supports autosomal recessive inheritance.
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Subtypes

2
Van Maldergem syndrome 1 (DCHS1) MONDO:0011070
DCHS1 hgnc:13681 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in DCHS1 (hgnc:13681). hgnc:13681 is a gene from the HUGO Gene Nomenclature Committee.
Caused by biallelic DCHS1 variants. DCHS1 encodes Dachsous cadherin-related 1, the ligand of the pair.
Show evidence (1 reference)
PMID:24056717 SUPPORT Human Clinical
"Here we show that mutations in genes encoding the receptor-ligand cadherin pair DCHS1 and FAT4 lead to a recessive syndrome in humans that includes periventricular neuronal heterotopia."
Establishes DCHS1 as one of the two genes underlying the recessive syndrome.
Van Maldergem syndrome 2 (FAT4) MONDO:0014242
FAT4 hgnc:23109 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in FAT4 (hgnc:23109). hgnc:23109 is a gene from the HUGO Gene Nomenclature Committee.
Caused by biallelic FAT4 variants. FAT4 encodes the receptor of the pair and is allelic with Hennekam lymphangiectasia-lymphedema syndrome 2.
Show evidence (1 reference)
PMID:29681106 SUPPORT Human Clinical
"Biallelic variants in FAT4 are associated with the two disorders, Van Maldergem syndrome (VMS) (n = 11) and Hennekam syndrome (HS) (n= 40)."
Establishes the FAT4 form of VMS and quantifies the reported cohort.
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Pathophysiology

7
Loss of DCHS1-FAT4 Cadherin Pair Function
Biallelic loss-of-function variants in DCHS1 or FAT4 abolish the function of a heterophilic receptor-ligand pair of giant atypical cadherins. Because the two proteins bind each other, loss of either produces the same downstream defect, which is the mechanistic basis for curating the two numbered forms as one disease.
DCHS1 hgnc:13681 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DCHS1 (hgnc:13681). hgnc:13681 is a gene from the HUGO Gene Nomenclature Committee. FAT4 hgnc:23109 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves FAT4 (hgnc:23109). hgnc:23109 is a gene from the HUGO Gene Nomenclature Committee.
Genetic context variant_origin: GERMLINE zygosity: HOMOZYGOUS functional_impact_category: LOSS_OF_FUNCTION
Biallelic germline DCHS1 or FAT4 alleles, homozygous or compound heterozygous. Reported classes are nonsense, frameshift, canonical splice-site and missense; the disease is defined by loss of function of the pair, and no gain-of-function or dominant-negative mechanism has been described.
establishment of planar polarity GO:0001736 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased establishment of planar polarity (GO:0001736). GO:0001736 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
dchs1b zebrafish maternal-zygotic mutant Zebrafish partially recapitulates Establishes that Dchs1 regulates the actin and microtubule cytoskeleton, and that some of this is independent of Fat. That matters for this entry because it means DCHS1 loss is not wholly equivalent to loss of the pair.
Downstream
Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation Reducing Dchs1 or Fat4 in the embryonic neuroepithelium increases progenitor number and reduces differentiation into neurons.
Impaired Osteoblast Differentiation The same cadherin pair is required for osteoblast differentiation. Loss of Dchs1-Fat4 signalling increases osteoprogenitor proliferation and delays their differentiation, through the same Yap-Tead route as the neural arm.
Disrupted Planar-Polarity-Guided Neuronal Migration Fat4 and Dchs1 are expressed in complementary gradients that establish intracellular polarity across migrating neurons; disrupting the gradient alters both polarity and migration.
Show evidence (1 reference)
PMID:24998526 SUPPORT Model Organism
"Mutations in human FAT4 and DCHS1, key components of Fat-PCP signaling, cause Van Maldergem syndrome, characterized by severe neuronal abnormalities indicative of altered neuronal migration"
Identifies the two genes as components of the Fat planar cell polarity system and links their mutation to the syndrome.
Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
Loss of Dchs1-Fat4 signaling in the neuroepithelium shifts the balance from neuronal differentiation toward progenitor self-renewal. The effect is mediated through the Hippo pathway: concurrent knockdown of Yap, the pathway's transcriptional effector, rescues the phenotype, placing Dchs1 and Fat4 upstream of Yap in mammalian neurogenesis.
hippo signaling GO:0035329 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased hippo signaling (GO:0035329). GO:0035329 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Dchs1/Fat4 knockdown mouse neuroepithelium Mouse recapitulates Reproduces the progenitor expansion, reduced neuronal differentiation and subcortical heterotopic accumulation seen in patients, and identifies Yap as the mediating effector.
Dchs1 intracellular-domain deletion mouse Mouse recapitulates Reproduces the craniofacial and periventricular proliferative phenotype and measures the Hippo pathway shift directly.
Downstream
Periventricular and Subcortical Nodular Heterotopia Cells retained in the progenitor state accumulate heterotopically below the neuronal layers instead of populating the cortical plate.
Show evidence (2 references)
PMID:24056717 SUPPORT Model Organism
"These effects were countered by concurrent knockdown of Yap, a transcriptional effector of the Hippo signaling pathway."
The Yap rescue establishes Hippo signaling as the mediator of the progenitor expansion.
PMID:41972678 SUPPORT Model Organism
"Neonatal brains display reduced pYAP1: YAP1 ratios and increased Ki67+ proliferation with greater Ki67-neuronal co-localization within the periventricular zone."
Independently measures the Hippo pathway shift (reduced YAP1 phosphorylation) alongside increased periventricular proliferation, confirming the mechanism in a targeted mouse allele.
Disrupted Planar-Polarity-Guided Neuronal Migration
Fat-PCP acts as a neuronal guidance system in its own right, distinct from and orthogonal to the Frizzled-PCP axis. Loss of the Dchs1-Fat4 gradient removes the directional cue for collective tangential migration, contributing to the mislocalization of neurons independently of the progenitor imbalance.
neuron migration GO:0001764 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased neuron migration (GO:0001764). GO:0001764 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Fat4/Dchs1 mutant mouse facial branchiomotor neurons Mouse recapitulates Establishes that the Dchs1-Fat4 gradient is required for neuronal polarity and collective migration.
Neuron-specific fat knockdown Drosophila Drosophila melanogaster partially recapitulates Neuron-restricted loss of the fat homologue impairs synapse structure and axonal targeting, supporting a neuron-intrinsic requirement for the cadherin in nervous system formation.
Downstream
Periventricular and Subcortical Nodular Heterotopia Neurons that lose their directional cue fail to reach their target layer and remain in ectopic nodules.
Show evidence (2 references)
PMID:24998526 SUPPORT Model Organism
"We find that Fat4 and Dchs1 are expressed in complementary gradients and are required for the collective tangential migration of FBM neurons and for their PCP."
Establishes the requirement for the gradient in collective neuronal migration.
PMID:24998526 SUPPORT Model Organism
"Our results also identify Fat-PCP as a novel neuronal guidance system and reveal that Fat-PCP and Fz-PCP can act along orthogonal axes."
Identifies Fat-PCP as an independent guidance system, supporting a migration defect separate from the progenitor effect.
Periventricular and Subcortical Nodular Heterotopia
Nodules of neurons arrested along the ventricular wall and in the subcortical white matter. This is the imaging signature of the syndrome and the structural correlate of the intellectual disability.
cerebral cortex UBERON:0000956 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebral cortex (UBERON:0000956). UBERON:0000956 is an anatomical location from the Uberon multi-species anatomy ontology.
Show evidence (2 references)
PMID:24056717 SUPPORT Human Clinical
"Periventricular neuronal heterotopia, a specific form of mislocalization of cortical neurons, can arise from neuronal progenitors that fail to negotiate aspects of these developmental processes."
Defines the lesion and attributes it to failed progenitor development.
PMID:25930014 SUPPORT Human Clinical
"we show that when key regulators during mammalian cerebral cortical development are disrupted due to DCHS1-FAT4 mutations, functional cerebral asymmetries are stronger"
Provides a functional correlate of the disrupted cortical architecture. Graded PARTIAL because it is a single-patient dichotic-listening/EEG study, so it establishes an association rather than a population-level finding.
Impaired Osteoblast Differentiation
Loss of Dchs1-Fat4 signalling expands the osteoprogenitor pool and delays its differentiation into osteoblasts. Mechanistically this is the same Yap-Tead shift that drives the neural progenitor imbalance, which is why one molecular lesion produces both a brain and a skeletal phenotype. Yap and Taz are not interchangeable here: Yap is required for osteoprogenitor proliferation and is the arm that is deranged, while Taz-Tead activity is unaffected in mutants.
osteoblast CL:0000062 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves osteoblast (CL:0000062). CL:0000062 is a cell type from the Cell Ontology.
osteoblast differentiation GO:0001649 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased osteoblast differentiation (GO:0001649). GO:0001649 is a biological process from the Gene Ontology. ↓ DECREASED hippo signaling GO:0035329 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased hippo signaling (GO:0035329). GO:0035329 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Impaired Craniofacial and Middle Ear Morphogenesis Delayed osteoblast differentiation in the craniofacial skeleton is what produces the facial gestalt; the mouse mutants reproduce the human craniofacial phenotype.
Show evidence (2 references)
PMID:31358536 SUPPORT Model Organism
"We show that loss of Dchs1-Fat4 signalling is linked to increased Yap-Tead activity and that Yap is expressed and required for proliferation in osteoprogenitors."
Identifies increased Yap-Tead activity as the mediator, the same effector shift as in the neural arm.
PMID:31358536 SUPPORT Model Organism
"In contrast, Taz is expressed in more-committed Runx2-expressing osteoblasts, Taz does not regulate osteoblast proliferation and Taz-Tead activity is unaffected in Dchs1/Fat4 mutants."
Distinguishes the Yap arm, which is deranged, from the Taz arm, which is not - a specificity claim that matters for interpreting the node.
Impaired Craniofacial and Middle Ear Morphogenesis
The blepharo-naso-facial gestalt and the ear anomalies reflect disrupted Fat-PCP signaling in craniofacial development. Conductive hearing loss in VMS was historically attributed to microtia and external canal atresia, but middle ear ossicular malformation has since been documented directly and can be the dominant contributor.
Animal models
Dchs1 intracellular-domain deletion mouse Mouse partially recapitulates Reproduces craniofacial flattening, reduced palatine/maxillary structures and airway cartilage abnormality.
Downstream
Conductive Hearing Loss External and middle ear malformation obstructs sound conduction.
Show evidence (2 references)
PMID:31358536 SUPPORT Model Organism
"In human, mutations of the protocadherins FAT4 and DCHS1 result in Van Maldergem syndrome, which is characterised, in part, by craniofacial abnormalities."
Attributes the craniofacial abnormalities to the cadherin pair, which is the claim this node makes.
PMID:27739185 SUPPORT Human Clinical
"The main features of this syndrome comprise intellectual disability, blepharo-naso-facial malformation, and hand anomalies."
Describes the clinical craniofacial phenotype this node produces.
Conductive Hearing Loss
Bilateral conductive hearing impairment, present in nearly all reported patients.
Show evidence (1 reference)
PMID:27739185 SUPPORT Human Clinical
"Almost all nine described patients have been shown to be affected by conductive hearing impairment attributed to microtia, and atresia of the outer ear canal."
Establishes near-universal conductive hearing impairment in the reported cohort.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Van Maldergem Syndrome Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

20
Digestive 1
Feeding Difficulties FREQUENT HP:0011968 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties (HP:0011968). HP:0011968 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"Affected patients typically have neonatal hypotonia, chronic feeding difficulties and respiratory problems."
Reports chronic feeding difficulties as a typical feature.
Ear 2
External Auditory Canal Atresia VERY_FREQUENT Atresia of the external auditory canal HP:0000413 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Atresia of the external auditory canal (HP:0000413). HP:0000413 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27739185 SUPPORT Human Clinical
"Almost all nine described patients have been shown to be affected by conductive hearing impairment attributed to microtia, and atresia of the outer ear canal."
Reports external canal atresia in almost all described patients.
Conductive Hearing Impairment VERY_FREQUENT HP:0000405 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Conductive hearing impairment (HP:0000405). HP:0000405 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27739185 SUPPORT Human Clinical
"Here, we present a VMS patient with congenital malformations of the middle ear as the main reason for severe conductive bilateral hearing impairment."
Documents severe bilateral conductive hearing impairment in a VMS patient.
Endocrine 1
Hypogonadotropic Hypogonadism OCCASIONAL HP:0000044 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypogonadotropic hypogonadism (HP:0000044). HP:0000044 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:29046692 SUPPORT Human Clinical
"At age 15, she presented with no breast development and other findings consistent with hypogonadotropic hypogonadism."
Documents hypogonadotropic hypogonadism in a molecularly confirmed DCHS1 patient.
PMID:29046692 SUPPORT Human Clinical
"Based on the clinical findings reported, two previously published patients with VMS may also have been affected by hypogonadotropic hypogonadism, but endocrine abnormalities were not evaluated or mentioned."
Suggests the feature is under-ascertained rather than rare. Graded PARTIAL because the two earlier patients were never endocrinologically assessed.
Limbs 1
Short Fourth Metacarpal OCCASIONAL Short 4th metacarpal HP:0010044 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short 4th metacarpal (HP:0010044). HP:0010044 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40797481 SUPPORT Human Clinical
"A 7-year-old female Chinese patient presented with a series of developmental defects, including precocious puberty, mild intellectual disability, unusual craniofacial features, mild shortening of the fourth metacarpal bone, and clumsy movements with poor coordination."
Documents fourth metacarpal shortening in a molecularly confirmed patient.
Musculoskeletal 3
Neonatal Hypotonia FREQUENT HP:0001319 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Neonatal hypotonia (HP:0001319). HP:0001319 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"Affected patients typically have neonatal hypotonia, chronic feeding difficulties and respiratory problems."
Reports neonatal hypotonia as a typical feature.
Osteopenia FREQUENT HP:0000938 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Osteopenia (HP:0000938). HP:0000938 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:29681106 SUPPORT Human Clinical
"but differ in the occurrence of neonatal hypotonia and feeding problems, hearing loss, tracheal anomalies, and osteopenia in VMS, and lymphedema in HS"
Names osteopenia as a VMS-specific feature in the direct comparison with Hennekam syndrome.
PMID:31358536 SUPPORT Model Organism
"In Dchs1/Fat4 mutants, proliferation of osteoprogenitors is increased and osteoblast differentiation is delayed."
Supplies a mechanism for the reduced bone density. Graded PARTIAL because it is a mouse osteoblast-differentiation result rather than a measurement of bone density in patients.
Scoliosis OCCASIONAL HP:0002650 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Scoliosis (HP:0002650). HP:0002650 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28878612 SUPPORT Human Clinical
"We present the case of a patient of Macedonian origin with unilateral renal agenesis and ureterovesical junction obstruction in combination with further abnormalities including midface hypoplasia, scoliosis as well as camptodactyly of one toe."
Documents scoliosis in a molecularly confirmed FAT4 patient.
Nervous System 2
Periventricular Nodular Heterotopia VERY_FREQUENT HP:0032388 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Periventricular nodular heterotopia (HP:0032388). HP:0032388 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"digital contractures and skeletal anomalies together with subependymal and subcortical neuronal heterotopia"
Documents the heterotopia as part of the defining phenotype in the characterisation cohort.
Intellectual Disability VERY_FREQUENT HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29681106 SUPPORT Human Clinical
"Both conditions are characterized by a typical facial gestalt and mild to moderate intellectual disability"
States mild to moderate intellectual disability as a defining feature.
Other 10
Blepharophimosis VERY_FREQUENT HP:0000581 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Blepharophimosis (HP:0000581). HP:0000581 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"The phenotype comprises a distinctive facial appearance that includes blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia of the external auditory meatus, intellectual disability, digital contractures and skeletal anomalies"
Lists blepharophimosis as part of the distinctive facial appearance.
Telecanthus VERY_FREQUENT HP:0000506 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Telecanthus (HP:0000506). HP:0000506 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"The phenotype comprises a distinctive facial appearance that includes blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia of the external auditory meatus, intellectual disability, digital contractures and skeletal anomalies"
Lists telecanthus as part of the distinctive facial appearance.
Maxillary Hypoplasia VERY_FREQUENT Hypoplasia of the maxilla HP:0000327 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Maxillary hypoplasia, annotated with Hypoplasia of the maxilla (HP:0000327). HP:0000327 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"The phenotype comprises a distinctive facial appearance that includes blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia of the external auditory meatus, intellectual disability, digital contractures and skeletal anomalies"
Lists maxillary hypoplasia as part of the distinctive facial appearance.
Microtia VERY_FREQUENT HP:0008551 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microtia (HP:0008551). HP:0008551 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27739185 SUPPORT Human Clinical
"Almost all nine described patients have been shown to be affected by conductive hearing impairment attributed to microtia, and atresia of the outer ear canal."
Reports microtia in almost all described patients.
Digital Contractures FREQUENT Finger joint contracture HP:0034681 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Digital contractures, annotated with Finger joint contracture (HP:0034681). HP:0034681 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22473091 SUPPORT Human Clinical
"The phenotype comprises a distinctive facial appearance that includes blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia of the external auditory meatus, intellectual disability, digital contractures and skeletal anomalies"
Reports digital contractures alongside hand anomalies. Graded PARTIAL because the source says "digital", which also encompasses toes, while the bound HPO term is finger-specific.
Tracheal Anomalies OCCASIONAL Abnormal tracheal morphology HP:0002778 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tracheal anomalies, annotated with Abnormal tracheal morphology (HP:0002778). HP:0002778 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29681106 SUPPORT Human Clinical
"but differ in the occurrence of neonatal hypotonia and feeding problems, hearing loss, tracheal anomalies, and osteopenia in VMS, and lymphedema in HS"
Reports tracheal anomalies as VMS-specific, bound to the generic HPO tracheal morphology term that matches the source's own level of specificity.
Congenital Anomalies of the Kidney and Urinary Tract OCCASIONAL Unilateral renal agenesis HP:0000122 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Unilateral renal agenesis (HP:0000122). HP:0000122 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:28878612 SUPPORT Human Clinical
"Recessive variants in FAT4 are a known cause of van Maldergem syndrome (VMS) in which congenital anomalies of the kidney and urinary tract are a less characteristic but common feature."
States that CAKUT is a common though non-defining feature of the syndrome.
PMID:28878612 SUPPORT Human Clinical
"We present the case of a patient of Macedonian origin with unilateral renal agenesis and ureterovesical junction obstruction in combination with further abnormalities including midface hypoplasia, scoliosis as well as camptodactyly of one toe."
Documents the specific renal anomalies in a molecularly confirmed FAT4 patient.
Breast Aplasia VERY_RARE HP:0100783 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Breast aplasia (HP:0100783). HP:0100783 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29046692 SUPPORT Human Clinical
"We report a female patient with endocrine abnormalities, hypogonadotropic hypogonadism and amazia (breasts aplasia/hypoplasia but normal nipples and areolas) in a rare syndrome: Van Maldergem syndrome (VMS)."
Documents amazia in a single reported patient, hence the VERY_RARE band.
Central Precocious Puberty VERY_RARE HP:0000826 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Precocious puberty (HP:0000826). HP:0000826 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40797481 SUPPORT Human Clinical
"A 7-year-old female Chinese patient presented with a series of developmental defects, including precocious puberty, mild intellectual disability, unusual craniofacial features, mild shortening of the fourth metacarpal bone, and clumsy movements with poor coordination."
Documents central precocious puberty in a molecularly confirmed VMS-1 patient.
Poor Coordination OCCASIONAL Incoordination HP:0002311 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Incoordination (HP:0002311). HP:0002311 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40797481 SUPPORT Human Clinical
"A 7-year-old female Chinese patient presented with a series of developmental defects, including precocious puberty, mild intellectual disability, unusual craniofacial features, mild shortening of the fourth metacarpal bone, and clumsy movements with poor coordination."
Documents clumsy movements with poor coordination.
🧬

Genetic Associations

2
DCHS1
Gene: DCHS1 hgnc:13681 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is DCHS1 (hgnc:13681). hgnc:13681 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:24056717 SUPPORT Human Clinical
"Here we show that mutations in genes encoding the receptor-ligand cadherin pair DCHS1 and FAT4 lead to a recessive syndrome in humans that includes periventricular neuronal heterotopia."
Establishes DCHS1 causality for the recessive syndrome.
PMID:29046692 SUPPORT Human Clinical
"WES revealed compound heterozygous variants in DCHS1 (rs145099391:G > A, p.P197L & rs753548138:G > A, p.T2334 M)"
Documents a compound heterozygous DCHS1 genotype, confirming that biallelic loss need not be homozygous.
FAT4
Gene: FAT4 hgnc:23109 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is FAT4 (hgnc:23109). hgnc:23109 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:24913602 SUPPORT Human Clinical
"Subsequent targeted mutation analysis of FAT4 in a cohort of 24 CCBE1 mutation-negative Hennekam syndrome patients identified homozygous or compound heterozygous mutations in four additional families."
Documents the FAT4 allelism between van Maldergem and Hennekam syndromes.
PMID:30853441 SUPPORT Model Organism
"Thus, FAT4 interacts with RET to fine-tune RET signaling, establishing a juxtacrine mechanism controlling kidney development."
Identifies a second, Hippo-independent FAT4 mechanism operating in kidney development, which is the likely route to the renal anomalies in this syndrome. Recorded on the gene rather than as a pathophysiology node because it is demonstrated in mouse kidney development and has not been shown to operate in patients.
💊

Medical Actions

2
Middle Ear Implantation for Conductive Hearing Loss
Action: surgical procedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is surgical procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Platform: Device
Hearing rehabilitation is the principal intervention for the syndrome's chief morbidity. A conventional skin-drive bone-conduction device gave suboptimal restoration in a reported child, so an active middle ear implant (Vibrant Soundbridge) was placed instead, requiring an original surgical approach because of tympanic cavity hypoplasia. Craniofacial deformity also complicated intubation, which is an anaesthetic consideration in its own right.
Mechanism Target:
Conductive Hearing Loss — Bypasses the malformed external and middle ear conduction pathway by driving the ossicular chain directly.
Show evidence (1 reference)
PMID:26491591 SUPPORT Human Clinical
"The decision made was to position Vibrant Soundbridge, a middle ear implant, with an original surgical application due to hypoplasia of the tympanic cavity."
Documents the intervention placed against this node in a VMS patient.
Show evidence (2 references)
PMID:26491591 SUPPORT Human Clinical
"A five-year-old child, affected by a rare congenital disease (Van Maldergem Syndrome), suffered from conductive hearing loss."
Establishes that the treated patient had van Maldergem syndrome with conductive hearing loss.
PMID:26491591 SUPPORT Human Clinical
"Postoperative hearing rehabilitation involved a multidisciplinary team, showing improved social skills and language development."
Reports the functional outcome, which extends beyond audiometry to language and social development.
GnRH Agonist Therapy for Central Precocious Puberty
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: leuprorelin CHEBI:6427 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses leuprorelin, annotated with leuprolide (CHEBI:6427). CHEBI:6427 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Peptide
Monthly leuprorelin acetate microspheres controlled central precocious puberty over a two-year follow-up in a reported VMS-1 patient. The neurodevelopmental deficits in the same patient were managed by surveillance only, there being no established protocol.
Mechanism Target:
Central Precocious Puberty — GnRH agonist suppression of the hypothalamic-pituitary-gonadal axis halts the precocious pubertal progression.
Show evidence (1 reference)
PMID:40797481 SUPPORT Human Clinical
"Over the 2-year follow-up, the precocious pubertal development was successfully controlled, and the neurodevelopmental deficits remained stable without progression."
Reports the outcome of the intervention against this phenotype.
Show evidence (1 reference)
PMID:40797481 SUPPORT Human Clinical
"The treatment for precocious puberty involved monthly administration of leuprorelin acetate microspheres (Enantone®)."
Names the agent and schedule used.
🔬

Diagnosis

3
Brain MRI for the recognisable heterotopia pattern
Periventricular and subcortical nodular heterotopia on brain MRI, together with the facial gestalt and hearing loss, is the pattern that should prompt targeted genetic testing. Van Maldergem syndrome is one of a small set of neurogenetic disorders whose brain MRI appearance is recognisable enough to direct the molecular workup rather than follow it.
brain magnetic resonance imaging NCIT:C16809 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:39462795 SUPPORT Human Clinical
"The comprehensively reviewed conditions include DDX3X-related neurodevelopmental disorder, Van Maldergem syndrome, NMDAR-related disorders, EML1-associated disorder and ARFGEF2-related periventricular nodular heterotopia with microcephaly."
Places van Maldergem syndrome among the disorders whose brain MRI pattern is recognisable enough to guide genetic testing.
PMID:39462795 SUPPORT Human Clinical
"As these conditions can often prove challenging to diagnose, a clinical suspicion of a specific disorder may be invaluable to guide and interpret genetic testing."
States the diagnostic logic: imaging-led suspicion directs and interprets the molecular result.
Temporal bone imaging for the conductive hearing loss
High-resolution CT of the petrous temporal bone characterises the middle ear malformation. This matters because conductive loss in VMS was historically attributed to microtia and canal atresia alone, and ossicular malformation is only demonstrable on imaging and exploratory tympanotomy.
high-resolution computed tomography of the temporal bone NCIT:C17204 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:27739185 SUPPORT Human Clinical
"These malformations were seen on high resolution Computed Tomography scanning and during an exploratory tympanotomy."
Names the two modalities that demonstrated the middle ear malformation.
Molecular diagnosis by exome sequencing of DCHS1 and FAT4
Confirmation is by identifying biallelic pathogenic variants in DCHS1 or FAT4. Reported diagnoses have come from whole-exome sequencing, including in patients whose presentation was not clinically recognisable as VMS.
whole exome sequencing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:28878612 SUPPORT Human Clinical
"The initial presentation of our patient was not clinically recognizable. However, in view of the molecular findings, the most likely diagnosis is a mild manifestation of VMS."
Shows exome sequencing making a diagnosis that clinical recognition missed, which is the argument for molecular-first testing in mild presentations.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
First described in 1992; a 2018 review of all reported FAT4-variant patients counted 11 with van Maldergem syndrome, and the DCHS1 form adds a similarly small number.
Show evidence (1 reference)
PMID:29681106 SUPPORT Human Clinical
"Biallelic variants in FAT4 are associated with the two disorders, Van Maldergem syndrome (VMS) (n = 11) and Hennekam syndrome (HS) (n= 40)."
Gives the reported FAT4-related VMS case count supporting the ultra-rare band.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Van Maldergem Syndrome:

Hennekam lymphangiectasia-lymphedema syndrome 2
Overlapping Features Allelic — also caused by biallelic FAT4 variants — and shares the facial gestalt and intellectual disability. The discriminator that holds is lymphedema, a Hennekam feature, set against neonatal hypotonia, feeding problems, hearing loss, tracheal anomalies and osteopenia in van Maldergem syndrome. Intestinal lymphangiectasia is deliberately not offered as a discriminator: it has since been reported in van Maldergem syndrome as well, in a report titled as challenging exactly this distinction.
Show evidence (1 reference)
PMID:29681106 SUPPORT Human Clinical
"but differ in the occurrence of neonatal hypotonia and feeding problems, hearing loss, tracheal anomalies, and osteopenia in VMS, and lymphedema in HS"
Gives the discriminating features between the two allelic conditions.
Other periventricular nodular heterotopia syndromes
Overlapping Features FLNA-related periventricular nodular heterotopia is X-linked and lacks the blepharo-naso-facial gestalt, ear anomalies and digital contractures of van Maldergem syndrome.
🐁

Animal Models

5
Dchs1/Fat4 knockdown mouse neuroepithelium
Knockdown of Dchs1 or Fat4 in the embryonic mouse neuroepithelium, with a Yap co-knockdown rescue arm.
Species
Mouse
Genotype
In utero electroporation knockdown of Dchs1 or Fat4
Publication
PMID:24056717
Pathograph links
Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation recapitulates fidelity: high Reproduces the progenitor expansion, reduced neuronal differentiation and subcortical heterotopic accumulation seen in patients, and identifies Yap as the mediating effector.
Limitations: Acute knockdown in a subset of electroporated cells rather than a germline biallelic null, so it models the cell-autonomous requirement rather than the full constitutional genotype. Mouse neocortex lacks the expanded outer subventricular zone of human cortex.
Readouts
Heterotopic cell accumulation below neuronal layers
Direction: INCREASED
Interpretation: Structural correlate of the human periventricular nodular heterotopia.
Show evidence (1 reference)
PMID:24056717 SUPPORT Model Organism
"resulting in the heterotopic accumulation of cells below the neuronal layers in the neocortex, reminiscent of the human phenotype"
Reports the heterotopia measurement behind this readout.
Progenitor cell number
Direction: INCREASED
Interpretation: Quantifies the progenitor expansion that precedes the heterotopia.
Show evidence (1 reference)
PMID:24056717 SUPPORT Model Organism
"Reducing the expression of Dchs1 or Fat4 within mouse embryonic neuroepithelium increased progenitor cell numbers and reduced their differentiation into neurons"
Reports the progenitor count and differentiation measurements.
Show evidence (1 reference)
PMID:24056717 SUPPORT Model Organism
"These findings implicate Dchs1 and Fat4 upstream of Yap as key regulators of mammalian neurogenesis."
Supports treating this model as informative for the progenitor/ differentiation node.
Fat4/Dchs1 mutant mouse facial branchiomotor neurons
Murine facial branchiomotor neuron migration used as a tractable model of Fat-PCP-guided collective neuronal migration.
Species
Mouse
Genotype
Fat4 and Dchs1 loss-of-function; mosaic Dchs1 inactivation
Publication
PMID:24998526
Pathograph links
Disrupted Planar-Polarity-Guided Neuronal Migration recapitulates fidelity: moderate Establishes that the Dchs1-Fat4 gradient is required for neuronal polarity and collective migration.
Limitations: Facial branchiomotor neurons migrate tangentially in the hindbrain, which is not the cortical radial migration whose failure produces the human periventricular heterotopia, so the model demonstrates the mechanism in a different neuronal population than the one affected clinically.
Readouts
FBM neuron polarity and migration
Direction: ALTERED
Interpretation: Direct measure of the polarity-dependent migration defect.
Show evidence (1 reference)
PMID:24998526 SUPPORT Model Organism
"Disruption of the Dchs1 gradients by mosaic inactivation of Dchs1 alters FBM neuron polarity and migration."
Reports the polarity and migration measurement behind this readout.
Show evidence (1 reference)
PMID:24998526 SUPPORT Model Organism
"Fat4 and Dchs1 are required intrinsically within the FBM neurons and extrinsically within the neuroepithelium."
Supports the model as informative for cell-intrinsic and extrinsic control of migration.
Dchs1 intracellular-domain deletion mouse
Mouse in which the DCHS1 intracellular domain is replaced with a V5 epitope tag, isolating the signaling function of the ICD from the extracellular DCHS1-FAT4 binding interaction.
Species
Mouse
Genotype
Dchs1(delta-ICD-V5) homozygous
Publication
PMID:41972678
Pathograph links
Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation recapitulates fidelity: high Reproduces the craniofacial and periventricular proliferative phenotype and measures the Hippo pathway shift directly.
Limitations: A targeted domain deletion rather than a patient allele, so it models the ICD signaling requirement specifically rather than the full spectrum of human loss-of-function variants. Unlike the neonatal-lethal global Dchs1 knockout these mice are viable, which aids study but means the model is milder than complete loss.
Readouts
Periventricular Ki67+ proliferation
Direction: INCREASED
Interpretation: Direct measure of the expanded proliferative compartment.
Show evidence (1 reference)
PMID:41972678 SUPPORT Model Organism
"Neonatal brains display reduced pYAP1: YAP1 ratios and increased Ki67+ proliferation with greater Ki67-neuronal co-localization within the periventricular zone."
Reports the proliferation measurement behind this readout.
Subventricular zone cell polarization
Direction: ALTERED
Interpretation: Loss of the polarized DCHS1 localization seen in wild type.
Show evidence (1 reference)
PMID:41972678 SUPPORT Model Organism
"In periventricular regions, wild-type DCHS1 expression shows polarized localization, whereas mice with the ICD deletion exhibit altered cell polarization within the subventricular zone, concomitant with changes in neural cellular distribution."
Reports the polarization measurement behind this readout.
Show evidence (1 reference)
PMID:41972678 SUPPORT Model Organism
"Additionally, our data establish Dchs1ΔICD-V5/ΔICD-V5 mice as a model that recapitulates core features of VMS, thereby allowing new mechanistic discoveries into its pathogenesis."
The authors explicitly position the line as a VMS model, supporting its use for this node.
Impaired Craniofacial and Middle Ear Morphogenesis partially recapitulates fidelity: moderate Reproduces craniofacial flattening, reduced palatine/maxillary structures and airway cartilage abnormality.
Limitations: Mouse craniofacial morphology does not map one-to-one onto the human blepharo-naso-facial gestalt, and the model does not reproduce the microtia and external auditory canal atresia that drive the human hearing loss.
Readouts
Craniofacial and airway cartilage morphology
Direction: ALTERED
Interpretation: Structural correlate of the human craniofacial and tracheal phenotype.
Show evidence (1 reference)
PMID:41972678 SUPPORT Model Organism
"exhibit VMS-like craniofacial flattening with enlarged fontanelles and reduced palatine/maxillary structures, along with airway cartilage abnormalities including reduced mineralization and decreased tracheal circularity"
Reports the craniofacial and tracheal cartilage measurements behind this readout.
Show evidence (1 reference)
PMID:41972678 SUPPORT Model Organism
"Van Maldergem Syndrome (VMS) is a rare autosomal recessive disorder caused by pathogenic variants in the atypical cadherin genes DCHS1 or FAT4 and is marked by craniofacial, skeletal, and neurodevelopmental abnormalities."
Establishes the craniofacial domain of the syndrome that this model arm addresses.
dchs1b zebrafish maternal-zygotic mutant
Maternal-zygotic dchs1b mutant zebrafish, which reveal a cytoskeletal role for Dachsous that is separable from its Fat-binding function.
Species
Zebrafish
Genotype
maternal zygotic dchs1b mutant
Publication
PMID:26160902
Pathograph links
Loss of DCHS1-FAT4 Cadherin Pair Function partially recapitulates fidelity: low Establishes that Dchs1 regulates the actin and microtubule cytoskeleton, and that some of this is independent of Fat. That matters for this entry because it means DCHS1 loss is not wholly equivalent to loss of the pair.
Limitations: The phenotypes are in the single-celled and gastrulating embryo - egg activation, cortical granule exocytosis, dorsal organizer specification - none of which correspond to any human van Maldergem feature. It is evidence about Dchs1 protein function, not a model of the disease, and is curated at LOW fidelity for that reason.
Show evidence (1 reference)
PMID:26160902 SUPPORT Model Organism
"Moreover, the bundled microtubule phenotype was partially rescued by expressing either full-length Dchs1b or its intracellular domain, suggesting that Dchs1b affects microtubules and some developmental processes independent of its known ligand Fat."
Supports a Fat-independent DCHS1 function. Graded PARTIAL because it qualifies the receptor-ligand-pair framing of this entry without overturning it, and does so in a developmental context with no human counterpart.
Neuron-specific fat knockdown Drosophila
Knockdown of the Drosophila FAT4 homologue fat restricted to the nervous system, testing whether the neuronal phenotype of the human syndrome is cell-autonomous to neurons.
Species
Drosophila melanogaster
Genotype
neuron-specific fat RNAi knockdown
Publication
PMID:28488382
Pathograph links
Disrupted Planar-Polarity-Guided Neuronal Migration partially recapitulates fidelity: low Neuron-restricted loss of the fat homologue impairs synapse structure and axonal targeting, supporting a neuron-intrinsic requirement for the cadherin in nervous system formation.
Limitations: Drosophila fat is a homologue rather than an orthologue-matched model, the readouts are neuromuscular junction structure and photoreceptor axon targeting rather than cortical neuronal migration, and the fly has no cortex in which heterotopia could form. The authors themselves frame the link to human disease as a consideration rather than a demonstration.
Show evidence (1 reference)
PMID:28488382 SUPPORT Model Organism
"Taken together, the results indicate that Drosophila fat plays an essential role in formation and/or maintenance of neuron."
Supports a neuron-intrinsic requirement for the cadherin. Graded PARTIAL because it is an invertebrate homologue and the paper offers the human connection as a hypothesis.
{ }

Source YAML

click to show 
name: Van Maldergem Syndrome
creation_date: "2026-08-29T00:00:00Z"
description: >-
  Van Maldergem syndrome (VMS) is a rare autosomal recessive multisystem
  developmental disorder caused by biallelic loss-of-function variants in either
  DCHS1 or FAT4, which encode a receptor-ligand pair of giant atypical
  (proto)cadherins. The clinical picture combines a distinctive
  blepharo-naso-facial gestalt (blepharophimosis, telecanthus, maxillary
  hypoplasia, microtia with external auditory canal atresia), intellectual
  disability, conductive hearing loss, digital contractures and skeletal
  anomalies, with neonatal hypotonia, chronic feeding difficulties and
  respiratory problems. The
  neuroanatomical signature is periventricular and subcortical nodular
  heterotopia, reflecting a failure of neuronal migration.

  Mechanistically, DCHS1 and FAT4 bind each other and operate as the vertebrate
  Fat-Dachsous planar cell polarity system. In the developing neuroepithelium
  their loss increases progenitor cell number at the expense of neuronal
  differentiation — an effect reversed by concurrent knockdown of the Hippo
  pathway effector Yap — and separately disrupts the polarity and collective
  migration of neurons, so that cells accumulate below their proper cortical
  layer. Because the same DCHS1-FAT4 pair also governs lymphatic endothelial
  polarity, biallelic FAT4 loss is allelic with Hennekam
  lymphangiectasia-lymphedema syndrome 2; the two conditions share a facial
  gestalt and intellectual disability but are distinguished by neonatal
  hypotonia, hearing loss, tracheal anomalies and osteopenia in VMS versus
  prominent lymphedema in Hennekam syndrome.
category: Mendelian
parents:
- hereditary disease
synonyms:
- VMS
- van Maldergem syndrome
- blepharo-naso-facial malformation syndrome
disease_term:
  preferred_term: van Maldergem syndrome
  term:
    id: MONDO:0017813
    label: van Maldergem syndrome
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Both the DCHS1 and FAT4 forms are autosomal recessive. Sibling recurrence
    and parental consanguinity in reported families established the mode of
    inheritance before the genes were identified.
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In our cohort, we have observed one instance of sibling recurrence and
      parental consanguinity in three of the families, indicating that autosomal
      recessive inheritance is likely.
    explanation: >-
      Sibling recurrence plus consanguinity across multiple families supports
      autosomal recessive inheritance.
has_subtypes:
- name: VMS1
  display_name: Van Maldergem syndrome 1 (DCHS1)
  description: >-
    Caused by biallelic DCHS1 variants. DCHS1 encodes Dachsous cadherin-related
    1, the ligand of the pair.
  subtype_term:
    preferred_term: van Maldergem syndrome 1
    term:
      id: MONDO:0011070
      label: van Maldergem syndrome 1
  genes:
  - preferred_term: DCHS1
    term:
      id: hgnc:13681
      label: DCHS1
  evidence:
  - reference: PMID:24056717
    reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we show that mutations in genes encoding the receptor-ligand cadherin
      pair DCHS1 and FAT4 lead to a recessive syndrome in humans that includes
      periventricular neuronal heterotopia.
    explanation: >-
      Establishes DCHS1 as one of the two genes underlying the recessive
      syndrome.
- name: VMS2
  display_name: Van Maldergem syndrome 2 (FAT4)
  description: >-
    Caused by biallelic FAT4 variants. FAT4 encodes the receptor of the pair and
    is allelic with Hennekam lymphangiectasia-lymphedema syndrome 2.
  subtype_term:
    preferred_term: van Maldergem syndrome 2
    term:
      id: MONDO:0014242
      label: van Maldergem syndrome 2
  genes:
  - preferred_term: FAT4
    term:
      id: hgnc:23109
      label: FAT4
  evidence:
  - reference: PMID:29681106
    reference_title: "Van Maldergem syndrome and Hennekam syndrome: Further delineation of allelic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Biallelic variants in FAT4 are associated with the two disorders, Van
      Maldergem syndrome (VMS) (n = 11) and Hennekam syndrome (HS) (n= 40).
    explanation: >-
      Establishes the FAT4 form of VMS and quantifies the reported cohort.
pathophysiology:
- name: Loss of DCHS1-FAT4 Cadherin Pair Function
  biological_scale: MOLECULAR
  description: >-
    Biallelic loss-of-function variants in DCHS1 or FAT4 abolish the function of
    a heterophilic receptor-ligand pair of giant atypical cadherins. Because the
    two proteins bind each other, loss of either produces the same downstream
    defect, which is the mechanistic basis for curating the two numbered forms
    as one disease.
  genes:
  - preferred_term: DCHS1
    term:
      id: hgnc:13681
      label: DCHS1
  - preferred_term: FAT4
    term:
      id: hgnc:23109
      label: FAT4
  genetic_context:
    variant_origin: GERMLINE
    zygosity: HOMOZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Biallelic germline DCHS1 or FAT4 alleles, homozygous or compound
      heterozygous. Reported classes are nonsense, frameshift, canonical
      splice-site and missense; the disease is defined by loss of function of
      the pair, and no gain-of-function or dominant-negative mechanism has been
      described.
  biological_processes:
  - preferred_term: establishment of planar polarity
    term:
      id: GO:0001736
      label: establishment of planar polarity
    modifier: DECREASED
  evidence:
  - reference: PMID:24998526
    reference_title: Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Mutations in human FAT4 and DCHS1, key components of Fat-PCP signaling,
      cause Van Maldergem syndrome, characterized by severe neuronal
      abnormalities indicative of altered neuronal migration
    explanation: >-
      Identifies the two genes as components of the Fat planar cell polarity
      system and links their mutation to the syndrome.
  downstream:
  - target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
    causal_link_type: DIRECT
    description: >-
      Reducing Dchs1 or Fat4 in the embryonic neuroepithelium increases
      progenitor number and reduces differentiation into neurons.
    evidence:
    - reference: PMID:24056717
      reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Reducing the expression of Dchs1 or Fat4 within mouse embryonic
        neuroepithelium increased progenitor cell numbers and reduced their
        differentiation into neurons, resulting in the heterotopic accumulation
        of cells below the neuronal layers in the neocortex, reminiscent of the
        human phenotype.
      explanation: >-
        Directly demonstrates the progenitor/differentiation imbalance
        downstream of losing either gene.
  - target: Impaired Osteoblast Differentiation
    causal_link_type: DIRECT
    description: >-
      The same cadherin pair is required for osteoblast differentiation. Loss of
      Dchs1-Fat4 signalling increases osteoprogenitor proliferation and delays
      their differentiation, through the same Yap-Tead route as the neural arm.
    evidence:
    - reference: PMID:31358536
      reference_title: Dchs1-Fat4 regulation of osteogenic differentiation in mouse.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        In Dchs1/Fat4 mutants, proliferation of osteoprogenitors is increased and
        osteoblast differentiation is delayed.
      explanation: >-
        Establishes the osteoblast arm as a direct consequence of losing the
        cadherin pair.
  - target: Disrupted Planar-Polarity-Guided Neuronal Migration
    causal_link_type: DIRECT
    description: >-
      Fat4 and Dchs1 are expressed in complementary gradients that establish
      intracellular polarity across migrating neurons; disrupting the gradient
      alters both polarity and migration.
    evidence:
    - reference: PMID:24998526
      reference_title: Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Disruption of the Dchs1 gradients by mosaic inactivation of Dchs1 alters
        FBM neuron polarity and migration.
      explanation: >-
        Establishes the causal dependence of neuronal polarity and migration on
        the Dchs1 gradient.
- name: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
  biological_scale: CELLULAR
  description: >-
    Loss of Dchs1-Fat4 signaling in the neuroepithelium shifts the balance from
    neuronal differentiation toward progenitor self-renewal. The effect is
    mediated through the Hippo pathway: concurrent knockdown of Yap, the
    pathway's transcriptional effector, rescues the phenotype, placing Dchs1 and
    Fat4 upstream of Yap in mammalian neurogenesis.
  biological_processes:
  - preferred_term: hippo signaling
    term:
      id: GO:0035329
      label: hippo signaling
    modifier: DECREASED
  evidence:
  - reference: PMID:24056717
    reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These effects were countered by concurrent knockdown of Yap, a
      transcriptional effector of the Hippo signaling pathway.
    explanation: >-
      The Yap rescue establishes Hippo signaling as the mediator of the
      progenitor expansion.
  - reference: PMID:41972678
    reference_title: Loss of the DCHS1 Intracellular Domain Expands Neurogenic Proliferation and Generates Van Maldergem-like Neurodevelopmental Defects.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Neonatal brains display reduced pYAP1: YAP1 ratios and increased Ki67+
      proliferation with greater Ki67-neuronal co-localization within the
      periventricular zone.
    explanation: >-
      Independently measures the Hippo pathway shift (reduced YAP1
      phosphorylation) alongside increased periventricular proliferation,
      confirming the mechanism in a targeted mouse allele.
  downstream:
  - target: Periventricular and Subcortical Nodular Heterotopia
    causal_link_type: DIRECT
    description: >-
      Cells retained in the progenitor state accumulate heterotopically below
      the neuronal layers instead of populating the cortical plate.
    evidence:
    - reference: PMID:24056717
      reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        resulting in the heterotopic accumulation of cells below the neuronal
        layers in the neocortex, reminiscent of the human phenotype
      explanation: >-
        States the heterotopic accumulation that is the direct anatomical
        consequence.
- name: Disrupted Planar-Polarity-Guided Neuronal Migration
  biological_scale: CELLULAR
  description: >-
    Fat-PCP acts as a neuronal guidance system in its own right, distinct from
    and orthogonal to the Frizzled-PCP axis. Loss of the Dchs1-Fat4 gradient
    removes the directional cue for collective tangential migration, contributing
    to the mislocalization of neurons independently of the progenitor imbalance.
  biological_processes:
  - preferred_term: neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DECREASED
  evidence:
  - reference: PMID:24998526
    reference_title: Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We find that Fat4 and Dchs1 are expressed in complementary gradients and
      are required for the collective tangential migration of FBM neurons and
      for their PCP.
    explanation: >-
      Establishes the requirement for the gradient in collective neuronal
      migration.
  - reference: PMID:24998526
    reference_title: Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Our results also identify Fat-PCP as a novel neuronal guidance system and
      reveal that Fat-PCP and Fz-PCP can act along orthogonal axes.
    explanation: >-
      Identifies Fat-PCP as an independent guidance system, supporting a
      migration defect separate from the progenitor effect.
  downstream:
  - target: Periventricular and Subcortical Nodular Heterotopia
    causal_link_type: DIRECT
    description: >-
      Neurons that lose their directional cue fail to reach their target layer
      and remain in ectopic nodules.
    evidence:
    - reference: PMID:22473091
      reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        digital contractures and skeletal anomalies together with subependymal
        and subcortical neuronal heterotopia
      explanation: >-
        Documents the human heterotopia that the migration defect produces.
- name: Periventricular and Subcortical Nodular Heterotopia
  biological_scale: TISSUE
  description: >-
    Nodules of neurons arrested along the ventricular wall and in the subcortical
    white matter. This is the imaging signature of the syndrome and the
    structural correlate of the intellectual disability.
  locations:
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  evidence:
  - reference: PMID:24056717
    reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Periventricular neuronal heterotopia, a specific form of mislocalization
      of cortical neurons, can arise from neuronal progenitors that fail to
      negotiate aspects of these developmental processes.
    explanation: >-
      Defines the lesion and attributes it to failed progenitor development.
  - reference: PMID:25930014
    reference_title: Mammalian cadherins DCHS1-FAT4 affect functional cerebral architecture.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we show that when key regulators during mammalian cerebral cortical
      development are disrupted due to DCHS1-FAT4 mutations, functional cerebral
      asymmetries are stronger
    explanation: >-
      Provides a functional correlate of the disrupted cortical architecture.
      Graded PARTIAL because it is a single-patient dichotic-listening/EEG study,
      so it establishes an association rather than a population-level finding.
- name: Impaired Osteoblast Differentiation
  biological_scale: CELLULAR
  description: >-
    Loss of Dchs1-Fat4 signalling expands the osteoprogenitor pool and delays
    its differentiation into osteoblasts. Mechanistically this is the same
    Yap-Tead shift that drives the neural progenitor imbalance, which is why one
    molecular lesion produces both a brain and a skeletal phenotype. Yap and Taz
    are not interchangeable here: Yap is required for osteoprogenitor
    proliferation and is the arm that is deranged, while Taz-Tead activity is
    unaffected in mutants.
  cell_types:
  - preferred_term: osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: osteoblast differentiation
    term:
      id: GO:0001649
      label: osteoblast differentiation
    modifier: DECREASED
  - preferred_term: hippo signaling
    term:
      id: GO:0035329
      label: hippo signaling
    modifier: DECREASED
  evidence:
  - reference: PMID:31358536
    reference_title: Dchs1-Fat4 regulation of osteogenic differentiation in mouse.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We show that loss of Dchs1-Fat4 signalling is linked to increased Yap-Tead
      activity and that Yap is expressed and required for proliferation in
      osteoprogenitors.
    explanation: >-
      Identifies increased Yap-Tead activity as the mediator, the same effector
      shift as in the neural arm.
  - reference: PMID:31358536
    reference_title: Dchs1-Fat4 regulation of osteogenic differentiation in mouse.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In contrast, Taz is expressed in more-committed Runx2-expressing
      osteoblasts, Taz does not regulate osteoblast proliferation and Taz-Tead
      activity is unaffected in Dchs1/Fat4 mutants.
    explanation: >-
      Distinguishes the Yap arm, which is deranged, from the Taz arm, which is
      not - a specificity claim that matters for interpreting the node.
  downstream:
  - target: Impaired Craniofacial and Middle Ear Morphogenesis
    causal_link_type: DIRECT
    description: >-
      Delayed osteoblast differentiation in the craniofacial skeleton is what
      produces the facial gestalt; the mouse mutants reproduce the human
      craniofacial phenotype.
    evidence:
    - reference: PMID:31358536
      reference_title: Dchs1-Fat4 regulation of osteogenic differentiation in mouse.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We show that Fat4 and Dchs1 mutants mimic the craniofacial phenotype of
        the human syndrome and that Dchs1-Fat4 signalling is essential for
        osteoblast differentiation.
      explanation: >-
        Directly connects the osteoblast defect to the craniofacial phenotype of
        the human syndrome.
- name: Impaired Craniofacial and Middle Ear Morphogenesis
  biological_scale: TISSUE
  description: >-
    The blepharo-naso-facial gestalt and the ear anomalies reflect disrupted
    Fat-PCP signaling in craniofacial development. Conductive hearing loss in
    VMS was historically attributed to microtia and external canal atresia, but
    middle ear ossicular malformation has since been documented directly and can
    be the dominant contributor.
  evidence:
  - reference: PMID:31358536
    reference_title: Dchs1-Fat4 regulation of osteogenic differentiation in mouse.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In human, mutations of the protocadherins FAT4 and DCHS1 result in Van
      Maldergem syndrome, which is characterised, in part, by craniofacial
      abnormalities.
    explanation: >-
      Attributes the craniofacial abnormalities to the cadherin pair, which is
      the claim this node makes.
  - reference: PMID:27739185
    reference_title: Middle ear abnormalities in Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The main features of this syndrome comprise intellectual disability,
      blepharo-naso-facial malformation, and hand anomalies.
    explanation: >-
      Describes the clinical craniofacial phenotype this node produces.
  downstream:
  - target: Conductive Hearing Loss
    causal_link_type: DIRECT
    description: >-
      External and middle ear malformation obstructs sound conduction.
    evidence:
    - reference: PMID:27739185
      reference_title: Middle ear abnormalities in Van Maldergem syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Here, we present a VMS patient with congenital malformations of the
        middle ear as the main reason for severe conductive bilateral hearing
        impairment.
      explanation: >-
        Directly attributes conductive hearing loss to middle ear malformation
        in a VMS patient.
- name: Conductive Hearing Loss
  biological_scale: ORGANISM
  description: >-
    Bilateral conductive hearing impairment, present in nearly all reported
    patients.
  evidence:
  - reference: PMID:27739185
    reference_title: Middle ear abnormalities in Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Almost all nine described patients have been shown to be affected by
      conductive hearing impairment attributed to microtia, and atresia of the
      outer ear canal.
    explanation: >-
      Establishes near-universal conductive hearing impairment in the reported
      cohort.
phenotypes:
- category: Neurologic
  name: Periventricular Nodular Heterotopia
  description: >-
    Subependymal and subcortical neuronal heterotopia, the neuroradiological
    signature of the syndrome.
  phenotype_term:
    preferred_term: Periventricular nodular heterotopia
    term:
      id: HP:0032388
      label: Periventricular nodular heterotopia
  frequency: VERY_FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      digital contractures and skeletal anomalies together with subependymal
      and subcortical neuronal heterotopia

    explanation: >-
      Documents the heterotopia as part of the defining phenotype in the
      characterisation cohort.
- category: Neurologic
  name: Intellectual Disability
  description: Mild to moderate intellectual disability.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:29681106
    reference_title: "Van Maldergem syndrome and Hennekam syndrome: Further delineation of allelic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Both conditions are characterized by a typical facial gestalt and mild to
      moderate intellectual disability
    explanation: >-
      States mild to moderate intellectual disability as a defining feature.
- category: Craniofacial
  name: Blepharophimosis
  description: Horizontally short palpebral fissures, part of the blepharo-naso-facial gestalt.
  phenotype_term:
    preferred_term: Blepharophimosis
    term:
      id: HP:0000581
      label: Blepharophimosis
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The phenotype comprises a distinctive facial appearance that includes
      blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia
      of the external auditory meatus, intellectual disability, digital
      contractures and skeletal anomalies
    explanation: >-
      Lists blepharophimosis as part of the distinctive facial appearance.
- category: Craniofacial
  name: Telecanthus
  description: Increased distance between the inner canthi.
  phenotype_term:
    preferred_term: Telecanthus
    term:
      id: HP:0000506
      label: Telecanthus
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The phenotype comprises a distinctive facial appearance that includes
      blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia
      of the external auditory meatus, intellectual disability, digital
      contractures and skeletal anomalies
    explanation: >-
      Lists telecanthus as part of the distinctive facial appearance.
- category: Craniofacial
  name: Maxillary Hypoplasia
  description: Underdevelopment of the maxilla contributing to the facial gestalt.
  phenotype_term:
    preferred_term: Maxillary hypoplasia
    term:
      id: HP:0000327
      label: Hypoplasia of the maxilla
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The phenotype comprises a distinctive facial appearance that includes
      blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia
      of the external auditory meatus, intellectual disability, digital
      contractures and skeletal anomalies
    explanation: >-
      Lists maxillary hypoplasia as part of the distinctive facial appearance.
- category: Auditory
  name: Microtia
  description: Small, malformed external ear.
  phenotype_term:
    preferred_term: Microtia
    term:
      id: HP:0008551
      label: Microtia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:27739185
    reference_title: Middle ear abnormalities in Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Almost all nine described patients have been shown to be affected by
      conductive hearing impairment attributed to microtia, and atresia of the
      outer ear canal.
    explanation: >-
      Reports microtia in almost all described patients.
- category: Auditory
  name: External Auditory Canal Atresia
  description: Atresia of the external auditory meatus.
  phenotype_term:
    preferred_term: Atresia of the external auditory canal
    term:
      id: HP:0000413
      label: Atresia of the external auditory canal
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:27739185
    reference_title: Middle ear abnormalities in Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Almost all nine described patients have been shown to be affected by
      conductive hearing impairment attributed to microtia, and atresia of the
      outer ear canal.
    explanation: >-
      Reports external canal atresia in almost all described patients.
- category: Auditory
  name: Conductive Hearing Impairment
  description: >-
    Bilateral conductive hearing loss arising from external and middle ear
    malformation.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:27739185
    reference_title: Middle ear abnormalities in Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here, we present a VMS patient with congenital malformations of the middle
      ear as the main reason for severe conductive bilateral hearing impairment.
    explanation: >-
      Documents severe bilateral conductive hearing impairment in a VMS patient.
- category: Musculoskeletal
  name: Digital Contractures
  description: Contractures of the digits, part of the hand anomalies.
  phenotype_term:
    preferred_term: Digital contractures
    term:
      id: HP:0034681
      label: Finger joint contracture
  frequency: FREQUENT
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The phenotype comprises a distinctive facial appearance that includes
      blepharophimosis, maxillary hypoplasia, telecanthus, microtia and atresia
      of the external auditory meatus, intellectual disability, digital
      contractures and skeletal anomalies
    explanation: >-
      Reports digital contractures alongside hand anomalies. Graded PARTIAL
      because the source says "digital", which also encompasses toes, while the
      bound HPO term is finger-specific.
- category: Neurologic
  name: Neonatal Hypotonia
  description: Reduced muscle tone from the neonatal period.
  phenotype_term:
    preferred_term: Neonatal hypotonia
    term:
      id: HP:0001319
      label: Neonatal hypotonia
  frequency: FREQUENT
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected patients typically have neonatal hypotonia, chronic feeding
      difficulties and respiratory problems.
    explanation: >-
      Reports neonatal hypotonia as a typical feature.
- category: Gastrointestinal
  name: Feeding Difficulties
  description: Chronic feeding difficulties from infancy.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  frequency: FREQUENT
  evidence:
  - reference: PMID:22473091
    reference_title: "Van Maldergem syndrome: further characterisation and evidence for neuronal migration abnormalities and autosomal recessive inheritance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected patients typically have neonatal hypotonia, chronic feeding
      difficulties and respiratory problems.
    explanation: >-
      Reports chronic feeding difficulties as a typical feature.
- category: Respiratory
  name: Tracheal Anomalies
  description: >-
    Structural tracheal abnormality, contributing to the respiratory problems and
    another VMS-specific discriminator from Hennekam syndrome.
  phenotype_term:
    preferred_term: Tracheal anomalies
    term:
      id: HP:0002778
      label: Abnormal tracheal morphology
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:29681106
    reference_title: "Van Maldergem syndrome and Hennekam syndrome: Further delineation of allelic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      but differ in the occurrence of neonatal hypotonia and feeding problems,
      hearing loss, tracheal anomalies, and osteopenia in VMS, and lymphedema in
      HS
    explanation: >-
      Reports tracheal anomalies as VMS-specific, bound to the generic HPO
      tracheal morphology term that matches the source's own level of
      specificity.
- category: Musculoskeletal
  name: Osteopenia
  description: >-
    Reduced bone mineral density, one of the features that distinguishes VMS
    from the allelic Hennekam syndrome. Mechanistically it follows from the
    delayed osteoblast differentiation node rather than being an unexplained
    association.
  phenotype_term:
    preferred_term: Osteopenia
    term:
      id: HP:0000938
      label: Osteopenia
  frequency: FREQUENT
  evidence:
  - reference: PMID:29681106
    reference_title: "Van Maldergem syndrome and Hennekam syndrome: Further delineation of allelic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      but differ in the occurrence of neonatal hypotonia and feeding problems,
      hearing loss, tracheal anomalies, and osteopenia in VMS, and lymphedema in
      HS
    explanation: >-
      Names osteopenia as a VMS-specific feature in the direct comparison with
      Hennekam syndrome.
  - reference: PMID:31358536
    reference_title: Dchs1-Fat4 regulation of osteogenic differentiation in mouse.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In Dchs1/Fat4 mutants, proliferation of osteoprogenitors is increased and
      osteoblast differentiation is delayed.
    explanation: >-
      Supplies a mechanism for the reduced bone density. Graded PARTIAL because
      it is a mouse osteoblast-differentiation result rather than a measurement
      of bone density in patients.
- category: Renal
  name: Congenital Anomalies of the Kidney and Urinary Tract
  description: >-
    Renal and urinary tract malformation, including unilateral renal agenesis
    and ureterovesical junction obstruction. Described as a less characteristic
    but common feature, and it can be the presenting problem in a mild
    manifestation.
  phenotype_term:
    preferred_term: Unilateral renal agenesis
    term:
      id: HP:0000122
      label: Unilateral renal agenesis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:28878612
    reference_title: "Whole-Exome Sequencing Reveals FAT4 Mutations in a Clinically Unrecognizable Patient with Syndromic CAKUT: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Recessive variants in FAT4 are a known cause of van Maldergem syndrome
      (VMS) in which congenital anomalies of the kidney and urinary tract are a
      less characteristic but common feature.
    explanation: >-
      States that CAKUT is a common though non-defining feature of the syndrome.
  - reference: PMID:28878612
    reference_title: "Whole-Exome Sequencing Reveals FAT4 Mutations in a Clinically Unrecognizable Patient with Syndromic CAKUT: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We present the case of a patient of Macedonian origin with unilateral
      renal agenesis and ureterovesical junction obstruction in combination with
      further abnormalities including midface hypoplasia, scoliosis as well as
      camptodactyly of one toe.
    explanation: >-
      Documents the specific renal anomalies in a molecularly confirmed FAT4
      patient.
- category: Endocrine
  name: Hypogonadotropic Hypogonadism
  description: >-
    Failure of pubertal development from hypogonadotropic hypogonadism,
    documented in an adult patient and retrospectively suspected in two earlier
    reports where endocrine function was never assessed.
  phenotype_term:
    preferred_term: Hypogonadotropic hypogonadism
    term:
      id: HP:0000044
      label: Hypogonadotropic hypogonadism
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:29046692
    reference_title: A patient with van Maldergem syndrome with endocrine abnormalities, hypogonadotropic hypogonadism, and breast aplasia/hypoplasia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At age 15, she presented with no breast development and other findings
      consistent with hypogonadotropic hypogonadism.
    explanation: >-
      Documents hypogonadotropic hypogonadism in a molecularly confirmed DCHS1
      patient.
  - reference: PMID:29046692
    reference_title: A patient with van Maldergem syndrome with endocrine abnormalities, hypogonadotropic hypogonadism, and breast aplasia/hypoplasia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Based on the clinical findings reported, two previously published patients
      with VMS may also have been affected by hypogonadotropic hypogonadism, but
      endocrine abnormalities were not evaluated or mentioned.
    explanation: >-
      Suggests the feature is under-ascertained rather than rare. Graded PARTIAL
      because the two earlier patients were never endocrinologically assessed.
- category: Endocrine
  name: Breast Aplasia
  description: >-
    Absent breast development with normal nipples and areolae (amazia),
    accompanying the hypogonadotropic hypogonadism.
  phenotype_term:
    preferred_term: Breast aplasia
    term:
      id: HP:0100783
      label: Breast aplasia
  frequency: VERY_RARE
  evidence:
  - reference: PMID:29046692
    reference_title: A patient with van Maldergem syndrome with endocrine abnormalities, hypogonadotropic hypogonadism, and breast aplasia/hypoplasia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We report a female patient with endocrine abnormalities, hypogonadotropic
      hypogonadism and amazia (breasts aplasia/hypoplasia but normal nipples and
      areolas) in a rare syndrome: Van Maldergem syndrome (VMS).
    explanation: >-
      Documents amazia in a single reported patient, hence the VERY_RARE band.
- category: Endocrine
  name: Central Precocious Puberty
  description: >-
    Central precocious puberty, reported in a single patient and notable because
    it is the opposite endocrine direction from the hypogonadotropic
    hypogonadism reported elsewhere in the syndrome.
  phenotype_term:
    preferred_term: Precocious puberty
    term:
      id: HP:0000826
      label: Precocious puberty
  frequency: VERY_RARE
  evidence:
  - reference: PMID:40797481
    reference_title: "Van Maldergem syndrome-1 in a patient with central precocious puberty: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A 7-year-old female Chinese patient presented with a series of
      developmental defects, including precocious puberty, mild intellectual
      disability, unusual craniofacial features, mild shortening of the fourth
      metacarpal bone, and clumsy movements with poor coordination.
    explanation: >-
      Documents central precocious puberty in a molecularly confirmed VMS-1
      patient.
- category: Musculoskeletal
  name: Scoliosis
  description: Lateral curvature of the spine.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:28878612
    reference_title: "Whole-Exome Sequencing Reveals FAT4 Mutations in a Clinically Unrecognizable Patient with Syndromic CAKUT: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We present the case of a patient of Macedonian origin with unilateral
      renal agenesis and ureterovesical junction obstruction in combination with
      further abnormalities including midface hypoplasia, scoliosis as well as
      camptodactyly of one toe.
    explanation: >-
      Documents scoliosis in a molecularly confirmed FAT4 patient.
- category: Musculoskeletal
  name: Short Fourth Metacarpal
  description: Shortening of the fourth metacarpal, part of the hand anomalies.
  phenotype_term:
    preferred_term: Short 4th metacarpal
    term:
      id: HP:0010044
      label: Short 4th metacarpal
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:40797481
    reference_title: "Van Maldergem syndrome-1 in a patient with central precocious puberty: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A 7-year-old female Chinese patient presented with a series of
      developmental defects, including precocious puberty, mild intellectual
      disability, unusual craniofacial features, mild shortening of the fourth
      metacarpal bone, and clumsy movements with poor coordination.
    explanation: >-
      Documents fourth metacarpal shortening in a molecularly confirmed patient.
- category: Neurologic
  name: Poor Coordination
  description: >-
    Clumsy movements with poor motor coordination, plausibly a functional
    correlate of the cortical heterotopia.
  phenotype_term:
    preferred_term: Incoordination
    term:
      id: HP:0002311
      label: Incoordination
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:40797481
    reference_title: "Van Maldergem syndrome-1 in a patient with central precocious puberty: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A 7-year-old female Chinese patient presented with a series of
      developmental defects, including precocious puberty, mild intellectual
      disability, unusual craniofacial features, mild shortening of the fourth
      metacarpal bone, and clumsy movements with poor coordination.
    explanation: >-
      Documents clumsy movements with poor coordination.
genetic:
- name: DCHS1
  gene_term:
    preferred_term: DCHS1
    term:
      id: hgnc:13681
      label: DCHS1
  relationship_type: CAUSATIVE
  notes: >-
    Biallelic DCHS1 variants cause van Maldergem syndrome 1. DCHS1 encodes the
    ligand half of the Dachsous-Fat atypical cadherin pair.
  evidence:
  - reference: PMID:24056717
    reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we show that mutations in genes encoding the receptor-ligand cadherin
      pair DCHS1 and FAT4 lead to a recessive syndrome in humans that includes
      periventricular neuronal heterotopia.
    explanation: >-
      Establishes DCHS1 causality for the recessive syndrome.
  - reference: PMID:29046692
    reference_title: A patient with van Maldergem syndrome with endocrine abnormalities, hypogonadotropic hypogonadism, and breast aplasia/hypoplasia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      WES revealed compound heterozygous variants in DCHS1 (rs145099391:G > A,
      p.P197L & rs753548138:G > A, p.T2334 M)
    explanation: >-
      Documents a compound heterozygous DCHS1 genotype, confirming that
      biallelic loss need not be homozygous.
- name: FAT4
  gene_term:
    preferred_term: FAT4
    term:
      id: hgnc:23109
      label: FAT4
  relationship_type: CAUSATIVE
  notes: >-
    Biallelic FAT4 variants cause van Maldergem syndrome 2, and are separately
    responsible for Hennekam lymphangiectasia-lymphedema syndrome 2. The two
    conditions are allelic; which phenotype results is not fully explained by
    genotype.
  evidence:
  - reference: PMID:24913602
    reference_title: Hennekam syndrome can be caused by FAT4 mutations and be allelic to Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Subsequent targeted mutation analysis of FAT4 in a cohort of 24 CCBE1
      mutation-negative Hennekam syndrome patients identified homozygous or
      compound heterozygous mutations in four additional families.
    explanation: >-
      Documents the FAT4 allelism between van Maldergem and Hennekam syndromes.
  - reference: PMID:30853441
    reference_title: FAT4 Fine-Tunes Kidney Development by Regulating RET Signaling.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Thus, FAT4 interacts with RET to fine-tune RET signaling, establishing a
      juxtacrine mechanism controlling kidney development.
    explanation: >-
      Identifies a second, Hippo-independent FAT4 mechanism operating in kidney
      development, which is the likely route to the renal anomalies in this
      syndrome. Recorded on the gene rather than as a pathophysiology node
      because it is demonstrated in mouse kidney development and has not been
      shown to operate in patients.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    First described in 1992; a 2018 review of all reported FAT4-variant patients
    counted 11 with van Maldergem syndrome, and the DCHS1 form adds a similarly
    small number.
  evidence:
  - reference: PMID:29681106
    reference_title: "Van Maldergem syndrome and Hennekam syndrome: Further delineation of allelic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Biallelic variants in FAT4 are associated with the two disorders, Van
      Maldergem syndrome (VMS) (n = 11) and Hennekam syndrome (HS) (n= 40).
    explanation: >-
      Gives the reported FAT4-related VMS case count supporting the ultra-rare
      band.
treatments:
- name: Middle Ear Implantation for Conductive Hearing Loss
  description: >-
    Hearing rehabilitation is the principal intervention for the syndrome's
    chief morbidity. A conventional skin-drive bone-conduction device gave
    suboptimal restoration in a reported child, so an active middle ear implant
    (Vibrant Soundbridge) was placed instead, requiring an original surgical
    approach because of tympanic cavity hypoplasia. Craniofacial deformity also
    complicated intubation, which is an anaesthetic consideration in its own
    right.
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  therapeutic_modality: DEVICE
  target_mechanisms:
  - target: Conductive Hearing Loss
    description: >-
      Bypasses the malformed external and middle ear conduction pathway by
      driving the ossicular chain directly.
    evidence:
    - reference: PMID:26491591
      reference_title: Original Solution for Middle Ear Implant and Anesthetic/Surgical Management in a Child with Severe Craniofacial Dysmorphism.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The decision made was to position Vibrant Soundbridge, a middle ear
        implant, with an original surgical application due to hypoplasia of the
        tympanic cavity.
      explanation: >-
        Documents the intervention placed against this node in a VMS patient.
  evidence:
  - reference: PMID:26491591
    reference_title: Original Solution for Middle Ear Implant and Anesthetic/Surgical Management in a Child with Severe Craniofacial Dysmorphism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A five-year-old child, affected by a rare congenital disease (Van
      Maldergem Syndrome), suffered from conductive hearing loss.
    explanation: >-
      Establishes that the treated patient had van Maldergem syndrome with
      conductive hearing loss.
  - reference: PMID:26491591
    reference_title: Original Solution for Middle Ear Implant and Anesthetic/Surgical Management in a Child with Severe Craniofacial Dysmorphism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Postoperative hearing rehabilitation involved a multidisciplinary team,
      showing improved social skills and language development.
    explanation: >-
      Reports the functional outcome, which extends beyond audiometry to
      language and social development.
- name: GnRH Agonist Therapy for Central Precocious Puberty
  description: >-
    Monthly leuprorelin acetate microspheres controlled central precocious
    puberty over a two-year follow-up in a reported VMS-1 patient. The
    neurodevelopmental deficits in the same patient were managed by surveillance
    only, there being no established protocol.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: leuprorelin
      term:
        id: CHEBI:6427
        label: leuprolide
  therapeutic_modality: PEPTIDE
  target_mechanisms:
  - target: Central Precocious Puberty
    description: >-
      GnRH agonist suppression of the hypothalamic-pituitary-gonadal axis halts
      the precocious pubertal progression.
    evidence:
    - reference: PMID:40797481
      reference_title: "Van Maldergem syndrome-1 in a patient with central precocious puberty: A case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Over the 2-year follow-up, the precocious pubertal development was
        successfully controlled, and the neurodevelopmental deficits remained
        stable without progression.
      explanation: >-
        Reports the outcome of the intervention against this phenotype.
  evidence:
  - reference: PMID:40797481
    reference_title: "Van Maldergem syndrome-1 in a patient with central precocious puberty: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The treatment for precocious puberty involved monthly administration of
      leuprorelin acetate microspheres (Enantone®).
    explanation: >-
      Names the agent and schedule used.
  notes: >-
    There is no disease-modifying therapy for van Maldergem syndrome, and no
    established protocol for the neurodevelopmental deficits - the reported
    approach is surveillance. Management is otherwise symptomatic: hearing
    rehabilitation, feeding and respiratory support in infancy, and treatment of
    the individual malformations as they present. Only interventions with a
    citable VMS-specific report are curated here.
diagnosis:
- name: Brain MRI for the recognisable heterotopia pattern
  diagnosis_term:
    preferred_term: brain magnetic resonance imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  description: >-
    Periventricular and subcortical nodular heterotopia on brain MRI, together
    with the facial gestalt and hearing loss, is the pattern that should prompt
    targeted genetic testing. Van Maldergem syndrome is one of a small set of
    neurogenetic disorders whose brain MRI appearance is recognisable enough to
    direct the molecular workup rather than follow it.
  evidence:
  - reference: PMID:39462795
    reference_title: Recognisable Neuroradiological Findings in Five Neurogenetic Disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The comprehensively reviewed conditions include DDX3X-related
      neurodevelopmental disorder, Van Maldergem syndrome, NMDAR-related
      disorders, EML1-associated disorder and ARFGEF2-related periventricular
      nodular heterotopia with microcephaly.
    explanation: >-
      Places van Maldergem syndrome among the disorders whose brain MRI pattern
      is recognisable enough to guide genetic testing.
  - reference: PMID:39462795
    reference_title: Recognisable Neuroradiological Findings in Five Neurogenetic Disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As these conditions can often prove challenging to diagnose, a clinical
      suspicion of a specific disorder may be invaluable to guide and interpret
      genetic testing.
    explanation: >-
      States the diagnostic logic: imaging-led suspicion directs and interprets
      the molecular result.
- name: Temporal bone imaging for the conductive hearing loss
  diagnosis_term:
    preferred_term: high-resolution computed tomography of the temporal bone
    term:
      id: NCIT:C17204
      label: Computed Tomography
  description: >-
    High-resolution CT of the petrous temporal bone characterises the middle ear
    malformation. This matters because conductive loss in VMS was historically
    attributed to microtia and canal atresia alone, and ossicular malformation is
    only demonstrable on imaging and exploratory tympanotomy.
  evidence:
  - reference: PMID:27739185
    reference_title: Middle ear abnormalities in Van Maldergem syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These malformations were seen on high resolution Computed Tomography
      scanning and during an exploratory tympanotomy.
    explanation: >-
      Names the two modalities that demonstrated the middle ear malformation.
- name: Molecular diagnosis by exome sequencing of DCHS1 and FAT4
  diagnosis_term:
    preferred_term: whole exome sequencing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  description: >-
    Confirmation is by identifying biallelic pathogenic variants in DCHS1 or
    FAT4. Reported diagnoses have come from whole-exome sequencing, including in
    patients whose presentation was not clinically recognisable as VMS.
  evidence:
  - reference: PMID:28878612
    reference_title: "Whole-Exome Sequencing Reveals FAT4 Mutations in a Clinically Unrecognizable Patient with Syndromic CAKUT: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The initial presentation of our patient was not clinically recognizable.
      However, in view of the molecular findings, the most likely diagnosis is a
      mild manifestation of VMS.
    explanation: >-
      Shows exome sequencing making a diagnosis that clinical recognition
      missed, which is the argument for molecular-first testing in mild
      presentations.
animal_models:
- name: Dchs1/Fat4 knockdown mouse neuroepithelium
  species: Mouse
  genotype: In utero electroporation knockdown of Dchs1 or Fat4
  publication: PMID:24056717
  description: >-
    Knockdown of Dchs1 or Fat4 in the embryonic mouse neuroepithelium, with a
    Yap co-knockdown rescue arm.
  modeled_mechanisms:
  - target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Reproduces the progenitor expansion, reduced neuronal differentiation and
      subcortical heterotopic accumulation seen in patients, and identifies Yap
      as the mediating effector.
    limitations: >-
      Acute knockdown in a subset of electroporated cells rather than a
      germline biallelic null, so it models the cell-autonomous requirement
      rather than the full constitutional genotype. Mouse neocortex lacks the
      expanded outer subventricular zone of human cortex.
    readouts:
    - name: Heterotopic cell accumulation below neuronal layers
      target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
      direction: INCREASED
      interpretation: >-
        Structural correlate of the human periventricular nodular heterotopia.
      evidence:
      - reference: PMID:24056717
        reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          resulting in the heterotopic accumulation of cells below the neuronal
          layers in the neocortex, reminiscent of the human phenotype
        explanation: >-
          Reports the heterotopia measurement behind this readout.
    - name: Progenitor cell number
      target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
      direction: INCREASED
      interpretation: >-
        Quantifies the progenitor expansion that precedes the heterotopia.
      evidence:
      - reference: PMID:24056717
        reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Reducing the expression of Dchs1 or Fat4 within mouse embryonic
          neuroepithelium increased progenitor cell numbers and reduced their
          differentiation into neurons
        explanation: >-
          Reports the progenitor count and differentiation measurements.
    evidence:
    - reference: PMID:24056717
      reference_title: Mutations in genes encoding the cadherin receptor-ligand pair DCHS1 and FAT4 disrupt cerebral cortical development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        These findings implicate Dchs1 and Fat4 upstream of Yap as key
        regulators of mammalian neurogenesis.
      explanation: >-
        Supports treating this model as informative for the progenitor/
        differentiation node.
- name: Fat4/Dchs1 mutant mouse facial branchiomotor neurons
  species: Mouse
  genotype: Fat4 and Dchs1 loss-of-function; mosaic Dchs1 inactivation
  publication: PMID:24998526
  description: >-
    Murine facial branchiomotor neuron migration used as a tractable model of
    Fat-PCP-guided collective neuronal migration.
  modeled_mechanisms:
  - target: Disrupted Planar-Polarity-Guided Neuronal Migration
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Establishes that the Dchs1-Fat4 gradient is required for neuronal polarity
      and collective migration.
    limitations: >-
      Facial branchiomotor neurons migrate tangentially in the hindbrain, which
      is not the cortical radial migration whose failure produces the human
      periventricular heterotopia, so the model demonstrates the mechanism in a
      different neuronal population than the one affected clinically.
    readouts:
    - name: FBM neuron polarity and migration
      target: Disrupted Planar-Polarity-Guided Neuronal Migration
      direction: ALTERED
      interpretation: >-
        Direct measure of the polarity-dependent migration defect.
      evidence:
      - reference: PMID:24998526
        reference_title: Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Disruption of the Dchs1 gradients by mosaic inactivation of Dchs1
          alters FBM neuron polarity and migration.
        explanation: >-
          Reports the polarity and migration measurement behind this readout.
    evidence:
    - reference: PMID:24998526
      reference_title: Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Fat4 and Dchs1 are required intrinsically within the FBM neurons and
        extrinsically within the neuroepithelium.
      explanation: >-
        Supports the model as informative for cell-intrinsic and extrinsic
        control of migration.
- name: Dchs1 intracellular-domain deletion mouse
  species: Mouse
  genotype: Dchs1(delta-ICD-V5) homozygous
  publication: PMID:41972678
  description: >-
    Mouse in which the DCHS1 intracellular domain is replaced with a V5 epitope
    tag, isolating the signaling function of the ICD from the extracellular
    DCHS1-FAT4 binding interaction.
  modeled_mechanisms:
  - target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Reproduces the craniofacial and periventricular proliferative phenotype
      and measures the Hippo pathway shift directly.
    limitations: >-
      A targeted domain deletion rather than a patient allele, so it models the
      ICD signaling requirement specifically rather than the full spectrum of
      human loss-of-function variants. Unlike the neonatal-lethal global Dchs1
      knockout these mice are viable, which aids study but means the model is
      milder than complete loss.
    readouts:
    - name: Periventricular Ki67+ proliferation
      target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
      direction: INCREASED
      interpretation: >-
        Direct measure of the expanded proliferative compartment.
      evidence:
      - reference: PMID:41972678
        reference_title: Loss of the DCHS1 Intracellular Domain Expands Neurogenic Proliferation and Generates Van Maldergem-like Neurodevelopmental Defects.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Neonatal brains display reduced pYAP1: YAP1 ratios and increased Ki67+
          proliferation with greater Ki67-neuronal co-localization within the
          periventricular zone.
        explanation: >-
          Reports the proliferation measurement behind this readout.
    - name: Subventricular zone cell polarization
      target: Expanded Neural Progenitor Pool with Reduced Neuronal Differentiation
      direction: ALTERED
      interpretation: >-
        Loss of the polarized DCHS1 localization seen in wild type.
      evidence:
      - reference: PMID:41972678
        reference_title: Loss of the DCHS1 Intracellular Domain Expands Neurogenic Proliferation and Generates Van Maldergem-like Neurodevelopmental Defects.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          In periventricular regions, wild-type DCHS1 expression shows polarized
          localization, whereas mice with the ICD deletion exhibit altered cell
          polarization within the subventricular zone, concomitant with changes
          in neural cellular distribution.
        explanation: >-
          Reports the polarization measurement behind this readout.
    evidence:
    - reference: PMID:41972678
      reference_title: Loss of the DCHS1 Intracellular Domain Expands Neurogenic Proliferation and Generates Van Maldergem-like Neurodevelopmental Defects.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Additionally, our data establish Dchs1ΔICD-V5/ΔICD-V5 mice as a model
        that recapitulates core features of VMS, thereby allowing new mechanistic
        discoveries into its pathogenesis.
      explanation: >-
        The authors explicitly position the line as a VMS model, supporting its
        use for this node.
  - target: Impaired Craniofacial and Middle Ear Morphogenesis
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces craniofacial flattening, reduced palatine/maxillary structures
      and airway cartilage abnormality.
    limitations: >-
      Mouse craniofacial morphology does not map one-to-one onto the human
      blepharo-naso-facial gestalt, and the model does not reproduce the microtia
      and external auditory canal atresia that drive the human hearing loss.
    readouts:
    - name: Craniofacial and airway cartilage morphology
      target: Impaired Craniofacial and Middle Ear Morphogenesis
      direction: ALTERED
      interpretation: >-
        Structural correlate of the human craniofacial and tracheal phenotype.
      evidence:
      - reference: PMID:41972678
        reference_title: Loss of the DCHS1 Intracellular Domain Expands Neurogenic Proliferation and Generates Van Maldergem-like Neurodevelopmental Defects.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          exhibit VMS-like craniofacial flattening with enlarged fontanelles and
          reduced palatine/maxillary structures, along with airway cartilage
          abnormalities including reduced mineralization and decreased tracheal
          circularity
        explanation: >-
          Reports the craniofacial and tracheal cartilage measurements behind
          this readout.
    evidence:
    - reference: PMID:41972678
      reference_title: Loss of the DCHS1 Intracellular Domain Expands Neurogenic Proliferation and Generates Van Maldergem-like Neurodevelopmental Defects.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Van Maldergem Syndrome (VMS) is a rare autosomal recessive disorder
        caused by pathogenic variants in the atypical cadherin genes DCHS1 or
        FAT4 and is marked by craniofacial, skeletal, and neurodevelopmental
        abnormalities.
      explanation: >-
        Establishes the craniofacial domain of the syndrome that this model arm
        addresses.
- name: dchs1b zebrafish maternal-zygotic mutant
  species: Zebrafish
  genotype: maternal zygotic dchs1b mutant
  publication: PMID:26160902
  description: >-
    Maternal-zygotic dchs1b mutant zebrafish, which reveal a cytoskeletal role
    for Dachsous that is separable from its Fat-binding function.
  modeled_mechanisms:
  - target: Loss of DCHS1-FAT4 Cadherin Pair Function
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Establishes that Dchs1 regulates the actin and microtubule cytoskeleton,
      and that some of this is independent of Fat. That matters for this entry
      because it means DCHS1 loss is not wholly equivalent to loss of the pair.
    limitations: >-
      The phenotypes are in the single-celled and gastrulating embryo - egg
      activation, cortical granule exocytosis, dorsal organizer specification -
      none of which correspond to any human van Maldergem feature. It is
      evidence about Dchs1 protein function, not a model of the disease, and is
      curated at LOW fidelity for that reason.
    evidence:
    - reference: PMID:26160902
      reference_title: Dachsous1b cadherin regulates actin and microtubule cytoskeleton during early zebrafish embryogenesis.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Moreover, the bundled microtubule phenotype was partially rescued by
        expressing either full-length Dchs1b or its intracellular domain,
        suggesting that Dchs1b affects microtubules and some developmental
        processes independent of its known ligand Fat.
      explanation: >-
        Supports a Fat-independent DCHS1 function. Graded PARTIAL because it
        qualifies the receptor-ligand-pair framing of this entry without
        overturning it, and does so in a developmental context with no human
        counterpart.
- name: Neuron-specific fat knockdown Drosophila
  species: Drosophila melanogaster
  genotype: neuron-specific fat RNAi knockdown
  publication: PMID:28488382
  description: >-
    Knockdown of the Drosophila FAT4 homologue fat restricted to the nervous
    system, testing whether the neuronal phenotype of the human syndrome is
    cell-autonomous to neurons.
  modeled_mechanisms:
  - target: Disrupted Planar-Polarity-Guided Neuronal Migration
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Neuron-restricted loss of the fat homologue impairs synapse structure and
      axonal targeting, supporting a neuron-intrinsic requirement for the
      cadherin in nervous system formation.
    limitations: >-
      Drosophila fat is a homologue rather than an orthologue-matched model, the
      readouts are neuromuscular junction structure and photoreceptor axon
      targeting rather than cortical neuronal migration, and the fly has no
      cortex in which heterotopia could form. The authors themselves frame the
      link to human disease as a consideration rather than a demonstration.
    evidence:
    - reference: PMID:28488382
      reference_title: Neuron-specific knockdown of the Drosophila fat induces reduction of life span, deficient locomotive ability, shortening of motoneuron terminal branches and defects in axonal targeting.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Taken together, the results indicate that Drosophila fat plays an
        essential role in formation and/or maintenance of neuron.
      explanation: >-
        Supports a neuron-intrinsic requirement for the cadherin. Graded PARTIAL
        because it is an invertebrate homologue and the paper offers the human
        connection as a hypothesis.
differential_diagnoses:
- name: Hennekam lymphangiectasia-lymphedema syndrome 2
  description: >-
    Allelic — also caused by biallelic FAT4 variants — and shares the facial
    gestalt and intellectual disability. The discriminator that holds is
    lymphedema, a Hennekam feature, set against neonatal hypotonia, feeding
    problems, hearing loss, tracheal anomalies and osteopenia in van Maldergem
    syndrome. Intestinal lymphangiectasia is deliberately not offered as a
    discriminator: it has since been reported in van Maldergem syndrome as well,
    in a report titled as challenging exactly this distinction.
  evidence:
  - reference: PMID:29681106
    reference_title: "Van Maldergem syndrome and Hennekam syndrome: Further delineation of allelic phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      but differ in the occurrence of neonatal hypotonia and feeding problems,
      hearing loss, tracheal anomalies, and osteopenia in VMS, and lymphedema in
      HS
    explanation: >-
      Gives the discriminating features between the two allelic conditions.
- name: Other periventricular nodular heterotopia syndromes
  description: >-
    FLNA-related periventricular nodular heterotopia is X-linked and lacks the
    blepharo-naso-facial gestalt, ear anomalies and digital contractures of van
    Maldergem syndrome.
notes: >-
  Curated as a single Disease entry covering both numbered forms. DCHS1 and FAT4
  encode a heterophilic receptor-ligand pair that binds each other and acts in
  one planar cell polarity system, so the two forms share a pathograph rather
  than merely a phenotype.

  Two mechanistic routes to the heterotopia are curated separately and
  deliberately: a Hippo/Yap-mediated progenitor-differentiation imbalance
  (PMID:24056717) and a loss of Fat-PCP directional guidance for migrating
  neurons (PMID:24998526). Both are supported, they are not alternatives, and
  collapsing them into one node would lose the distinction.

  The FAT4 allelism with Hennekam lymphangiectasia-lymphedema syndrome 2 is
  recorded as a differential diagnosis rather than re-curated here; that entry
  already exists as kb/disorders/Hennekam_Lymphangiectasia-Lymphedema_Syndrome_2.yaml.

  Intestinal lymphangiectasia has been reported in van Maldergem syndrome
  (PMID:31063239), which erodes the lymphatic boundary between it and Hennekam
  syndrome. That report is a Letter with no abstract in the reference cache, so
  it cannot carry a verified snippet and is not cited as evidence anywhere in
  this entry; it is recorded here so the differential is not read as a firmer
  separation than the literature supports.

  FAT4 has a second, Hippo-independent mechanism - juxtacrine tuning of RET
  signalling during kidney development (PMID:30853441) - which is the likely
  route to the renal anomalies. It is recorded on the FAT4 genetic entry rather
  than as a pathophysiology node, because it is a mouse kidney-development
  result that has not been demonstrated in patients.
📚

References & Deep Research

Deep Research

1
OpenScientist ▸
Van Maldergem Syndrome — Comprehensive Disease Characteristics Report
openscientist-autonomous 2026-08-29T10:18:17.366698

Van Maldergem Syndrome — Comprehensive Disease Characteristics Report

Disease: Van Maldergem Syndrome (VMS) Category: Mendelian (rare autosomal recessive multisystem congenital disorder) Suggested MONDO: MONDO:0018852 (Van Maldergem syndrome). Subtypes: VMLDS1 (MONDO:0010875-class, DCHS1), VMLDS2 (FAT4).

Evidence source note: VMS is an ultra-rare disorder. Essentially all knowledge is derived from individual patient case reports and small case series (aggregated disease-level resources such as OMIM/Orphanet compile these), supplemented by model-organism (mouse, zebrafish, Drosophila) and in vitro mechanistic studies. There are no EHR-scale cohorts, registries, clinical trials, GWAS, or population omics datasets for this disease. Frequencies below are therefore qualitative/small-denominator estimates, not population statistics.

1. Disease Information

Overview. Van Maldergem syndrome is a rare autosomal recessive multiple-congenital-anomaly/intellectual-disability syndrome first described by Van Maldergem and colleagues in 1992. Its cardinal features are a distinctive craniofacial (blepharo-naso-facial) gestalt, intellectual disability, auditory (external/middle ear) malformations with conductive hearing loss, hand/digit anomalies and skeletal abnormalities, and — characteristically — periventricular and subcortical neuronal heterotopia on brain imaging (PMID 22473091, 27739185). It is caused by biallelic loss-of-function variants in one of two atypical cadherin genes, DCHS1 (type 1) or FAT4 (type 2), which act as a receptor–ligand pair in Fat–Dachsous planar cell polarity (PCP)/Hippo signaling (PMID 24056717).

Key identifiers. - OMIM: #601390 — Van Maldergem syndrome 1 (VMLDS1; DCHS1); #615546 — Van Maldergem syndrome 2 (VMLDS2; FAT4). MIM#601390 explicitly cited in PMID 25930014 and PMID 40797481. - Orphanet: ORPHA:314679 (Van Maldergem syndrome). - ICD-10: Q87.8 (other specified congenital malformation syndromes, not elsewhere classified); ICD-11: LD2F.1Y / LD2F.0Y class (multiple developmental anomalies). No VMS-specific ICD code. - MeSH: No dedicated MeSH heading; indexed under "Abnormalities, Multiple" / "Intellectual Disability" and gene terms DCHS1, FAT4. - MONDO: MONDO:0018852 (parent), with type-1/type-2 children.

Synonyms / alternative names. Van Maldergem syndrome 1 and 2 (VMLDS1/VMLDS2); "blepharo-naso-facial malformation with intellectual disability" (descriptive); historically overlapping with, and now recognized as allelic to, Hennekam lymphangiectasia–lymphedema syndrome when caused by FAT4 (PMID 24913602, 29681106).

2. Etiology

Primary cause — genetic. VMS is monogenic and recessive. It is caused by biallelic (homozygous or compound heterozygous) pathogenic variants in: - DCHS1 (Dachsous cadherin-related 1; HGNC:13681; NCBI Gene 8642; chromosome 11p15.4; OMIM 603057) → VMLDS1. - FAT4 (FAT atypical cadherin 4; HGNC:23109; NCBI Gene 79633; chromosome 4q28.1; OMIM 612411) → VMLDS2.

"Here we show that mutations in genes encoding the receptor-ligand cadherin pair DCHS1 and FAT4 lead to a recessive syndrome in humans that includes periventricular neuronal heterotopia." (PMID 24056717)

Risk factors. - Genetic: The two causal genes are the only established risk determinants. Consanguinity is a major risk amplifier — parental consanguinity was present in 3/5 families in the defining cohort, and homozygous variants predominate in consanguineous pedigrees (PMID 22473091). No susceptibility loci or GWAS signals exist (disease is monogenic). Potential modifier effects (e.g., FAT4 vs DCHS1 genotype, allelic CCBE1/ADAMTS3 interactions in the lymphatic-overlap phenotype) are hypothesized but unproven. - Environmental / lifestyle / infectious: None identified. VMS is fully genetically determined; no toxin, teratogen, dietary, occupational, or infectious contributor is known or expected. (Not applicable.)

Protective factors. None described. In principle, inheriting only one variant allele (heterozygous carrier) is "protective" in the Mendelian sense — carriers are unaffected — but no protective modifier alleles are known.

Gene–environment interactions. Not applicable/none reported; the phenotype is determined by biallelic genotype independent of environment.

3. Phenotypes

VMS is a congenital, multisystem, generally non-progressive disorder; most features are present at birth or emerge in infancy, with intellectual disability apparent in childhood. Severity is variable (mild-to-moderate ID is typical). Frequencies are qualitative given the tiny reported population (~dozens of patients worldwide).

Craniofacial (physical manifestations — near-universal / "typical facial gestalt"): - Blepharophimosis (HP:0000581); telecanthus (HP:0000506); maxillary/midface hypoplasia (HP:0000327/HP:0011800); microtia (HP:0008551); atresia of external auditory canal (HP:0000413); blepharo-naso-facial malformation. (PMID 22473091, 27739185)

Auditory (clinical sign — near-universal): - Conductive hearing impairment (HP:0000405), bilateral, from microtia + aural atresia ± middle-ear/ossicular and tympanic-cavity malformations. "Almost all nine described patients have been shown to be affected by conductive hearing impairment attributed to microtia, and atresia of the outer ear canal." (PMID 27739185)

Neurological / neurodevelopmental (near-universal): - Intellectual disability, mild-to-moderate (HP:0001249); neonatal hypotonia (HP:0001319); periventricular nodular heterotopia (HP:0032388) and subcortical/subependymal neuronal heterotopia (HP:0002518); altered functional cerebral asymmetry (PMID 25930014); poor coordination/clumsiness (HP:0002317). (PMID 22473091, 24056717)

Skeletal / limb (common): - Digital contractures/camptodactyly (HP:0100490/HP:0012385); brachydactyly / short 4th metacarpal (HP:0001156); scoliosis (HP:0002650); osteopenia (HP:0000938); general skeletal anomalies. (PMID 22473091, 28878612, 40797481, 29681106)

Neonatal / feeding / respiratory (common): - Feeding difficulties (HP:0011968); respiratory problems and tracheal anomalies (HP:0002778); failure to thrive (HP:0001508). (PMID 22473091, 29681106)

Endocrine (rare/variable): - Hypogonadotropic hypogonadism (HP:0000044); breast aplasia/hypoplasia/amazia with normal nipples (HP:0100783/HP:0003187) (PMID 29046692); central precocious puberty (HP:0000826) (PMID 40797481).

Genitourinary (rare/variable): - Unilateral renal agenesis (HP:0000122/HP:0000104); ureterovesical junction obstruction/urinary tract obstruction (HP:0000073); duplex/duplicated collecting system (HP:0000081). (PMID 28878612, 30853441)

Gastrointestinal / lymphatic (rare): - Intestinal lymphangiectasia (HP:0002593) — reported in VMS and blurring the boundary with Hennekam syndrome (PMID 31063239).

Quality-of-life impact. No formal EQ-5D/SF-36/PROMIS data exist. Inferred burden: lifelong intellectual disability and hearing loss impair communication, learning, and independence; feeding/respiratory issues and multiple surgeries burden infancy; craniofacial differences carry psychosocial impact. Hearing rehabilitation measurably improves social skills and language (PMID 26491591).

4. Genetic / Molecular Information

Causal genes. | Gene | Locus | OMIM | Protein | Disease | |---|---|---|---|---| | DCHS1 (HGNC:13681, Gene 8642) | 11p15.4 | 603057 | Dachsous 1 (protocadherin, PCP ligand) | VMLDS1 (#601390) | | FAT4 (HGNC:23109, Gene 79633) | 4q28.1 | 612411 | FAT4 (protocadherin, PCP receptor) | VMLDS2 (#615546) |

DCHS1 and FAT4 form a receptor–ligand pair; FAT4 is a very large single-pass transmembrane protein with 34 extracellular cadherin repeats, EGF-like domains, and laminin-G–like domains; DCHS1 is its Dachsous-family cadherin ligand (PMID 28488382).

Pathogenic variants. - Type/class: predominantly loss-of-function — nonsense, frameshift, and canonical splice-site variants (e.g., FAT4 NM_024582.6:c.7018+1G>A, loss of the intron-6 donor site, ACMG pathogenic; PMID 37551355), as well as missense variants. Compound heterozygous and homozygous configurations both occur (PMID 29046692, 28878612). - Classification: Reported variants are curated as pathogenic / likely pathogenic by ACMG/AMP criteria; novel variants continue to be reported, some initially VUS pending segregation/functional data (PMID 31384091, 40797481). - Allele frequency: Individually rare/private; consistent with a recessive ultra-rare disease, biallelic pathogenic genotypes are essentially absent from gnomAD, though single heterozygous LoF alleles exist at very low frequency. - Origin: Germline, biallelic. (Somatically, FAT4 is a tumor-suppressor mutated in cancers, but that is unrelated to the germline VMS phenotype; PMID 28488382 notes FAT4's tumor-suppressor role.) - Functional consequence: Loss of function of the Dchs1–Fat4 PCP/Hippo module. A 2026 study shows the DCHS1 intracellular domain is functionally critical — its loss expands neurogenic proliferation and generates VMS-like defects (PMID 41972678).

Modifier genes. None validated. Phenotype-modifying candidates include the specific gene affected (FAT4 vs DCHS1) and, for the lymphatic-overlap phenotype, the allelic lymphangiogenesis genes CCBE1 and ADAMTS3 (which also cause Hennekam syndrome) (PMID 29681106).

Epigenetics. No DNA-methylation, histone-modification, or episignature data specific to VMS are available (not applicable at present).

Chromosomal abnormalities. VMS is a single-gene disorder; no recurrent aneuploidy, translocation, or copy-number syndrome. Chromosomal microarray is typically normal (useful mainly to exclude CNV mimics).

5. Environmental Information

  • Environmental factors: None. No toxin, radiation, pollutant, or occupational exposure is implicated.
  • Lifestyle factors: None (congenital genetic disease).
  • Infectious agents: None. VMS is not infectious or triggered by pathogens.

(All "Not applicable" — VMS is entirely genetically determined.)

6. Mechanism / Pathophysiology

Core molecular pathway — Fat–Dachsous PCP and Hippo/YAP signaling. DCHS1 (Dachsous) and FAT4 are the vertebrate orthologs of the Drosophila Dachsous–Fat PCP system. They bind heterophilically across cell membranes and are expressed in complementary gradients that provide directional (planar polarity) information to tissues, feeding into the Hippo kinase cascade to restrain the transcriptional co-activator YAP (PMID 24056717, 24998526). GO/pathway terms: planar cell polarity pathway (GO:0090175), Hippo signaling (GO:0035329), homophilic cell–cell adhesion via plasma-membrane adhesion molecules (GO:0007156), Reactome "Signaling by Hippo."

Causal chain (neurodevelopment — best-characterized): 1. Trigger (upstream): Biallelic LoF of DCHS1 or FAT4 → loss of Fat–Dachsous PCP signaling in the embryonic neuroepithelium. 2. De-repression of YAP: Hippo signaling is disrupted → YAP (Hippo effector) is inappropriately active.

"These effects were countered by concurrent knockdown of Yap, a transcriptional effector of the Hippo signaling pathway. These findings implicate Dchs1 and Fat4 upstream of Yap as key regulators of mammalian neurogenesis." (PMID 24056717) 3. Cellular consequence: Expanded neural progenitor proliferation with reduced neuronal differentiation → excess progenitors. Confirmed by DCHS1-intracellular-domain loss expanding neurogenic proliferation (PMID 41972678). 4. Migration failure: Loss of Dchs1/Fat4 expression gradients disrupts collective tangential neuronal migration and planar polarity (PMID 24998526). 5. Clinical manifestation (downstream): Neurons fail to reach the cortical plate → periventricular/subcortical neuronal heterotopia, intellectual disability, and altered functional cerebral asymmetry (PMID 24056717, 25930014).

Parallel causal chains in other organs (same module, tissue-specific outputs): - Bone/craniofacial: Dchs1–Fat4 regulates osteoblast differentiation; its disruption produces the craniofacial abnormalities of VMS (PMID 31358536). → maxillary hypoplasia, skeletal anomalies, osteopenia. - Kidney: FAT4 fine-tunes kidney development by regulating RET receptor-tyrosine-kinase signaling; Fat4 deletion causes duplex-kidney phenotypes (PMID 30853441). → renal agenesis/duplex kidney/urinary obstruction. - Cytoskeleton (early embryo): Dchs1 influences actin and microtubule organization, partly independent of Fat, via its intracellular domain (zebrafish; PMID 26160902). - Neuronal maintenance: Drosophila fat loss in neurons impairs neuromuscular-junction structure and axonal targeting (PMID 28488382).

Cellular processes: cell proliferation/cell-cycle control (GO:0008283), neuron differentiation (GO:0030182), neuron migration (GO:0001764), osteoblast differentiation (GO:0001649), establishment of planar polarity (GO:0001736). Cell types (CL): radial glial/neural progenitor cells (CL:0000047 / CL:0000031), migrating neurons (CL:0000540), osteoblasts (CL:0000062), ureteric-bud/renal epithelial cells (CL:1000454). Subcellular (GO CC): plasma membrane (GO:0005886), cell–cell junction (GO:0005911), actin cytoskeleton (GO:0015629), microtubule (GO:0005874); YAP acts in the nucleus (GO:0005634).

Protein dysfunction: loss of function of large transmembrane protocadherins (adhesion/signaling), not misfolding/aggregation. Metabolic changes: none characteristic. Immune involvement: none (not an immune disease). Tissue-damage mechanism: developmental malformation/dysplasia (failed morphogenesis) rather than degeneration, ischemia, or fibrosis. Molecular profiling (transcriptomics/proteomics/metabolomics/lipidomics): no patient-derived omics datasets available. Functional genomics: mechanistic knockdown/knockout screens in mouse/zebrafish/fly and YAP-epistasis (above) constitute the functional evidence.

7. Anatomical Structures Affected

Organ / system level (primary): - Nervous system (UBERON:0001016): cerebral cortex (UBERON:0000956), periventricular white matter/lateral ventricle margins (UBERON:0002289) — heterotopia; brainstem branchiomotor nuclei (migration). Body system: nervous. - Ear (UBERON:0001690): external ear/auricle (UBERON:0001757) — microtia; external auditory canal (UBERON:0001352) — atresia; middle ear / ossicles / tympanic cavity (UBERON:0001756) — malformation (PMID 27739185). Body system: special sensory/auditory. - Craniofacial skeleton & face (UBERON:0001456 face; UBERON:0001684 mandible/maxilla UBERON:0002397): midface/maxillary hypoplasia. - Skeleton / limbs (UBERON:0002091): hands/digits (UBERON:0002389), vertebral column (UBERON:0002415) — contractures, brachydactyly, scoliosis, osteopenia.

Secondary / variable organ involvement: - Kidney/urinary tract (UBERON:0002113 kidney; UBERON:0000056 ureter): agenesis, duplex kidney, ureterovesical obstruction (PMID 28878612, 30853441). - Endocrine/reproductive (UBERON:0000990 reproductive system; hypothalamic–pituitary–gonadal axis): hypogonadotropic hypogonadism, precocious puberty; breast (UBERON:0000310) aplasia (PMID 29046692, 40797481). - Respiratory tract / trachea (UBERON:0003126): tracheal anomalies, respiratory problems (PMID 29681106). - Gastrointestinal/lymphatic (UBERON:0002108 small intestine; lymphatic vessels UBERON:0001473): intestinal lymphangiectasia (PMID 31063239).

Tissue level: neuroepithelium/neural tissue, connective/skeletal tissue (bone), epithelial tissues (renal, otic). Cell level (CL): neural progenitors/radial glia, migrating neurons, osteoblasts, renal epithelial cells (see §6). Subcellular (GO CC): plasma membrane, cell–cell junctions, cytoskeleton; nuclear YAP.

Localization / lateralization: brain heterotopia typically bilateral; ear/hearing involvement bilateral; renal malformations may be unilateral (e.g., unilateral renal agenesis, PMID 28878612). Notably, functional cerebral asymmetry is increased (PMID 25930014).

8. Temporal Development

  • Onset: Congenital / prenatal–neonatal. Craniofacial, ear, and brain malformations are established in utero; neonatal hypotonia, feeding, and respiratory problems present at birth (PMID 22473091). Intellectual disability manifests through infancy/childhood. Endocrine features (precocious or hypogonadotropic puberty) emerge in childhood/adolescence (PMID 40797481, 29046692).
  • Onset pattern: Chronic/static (congenital malformation) rather than acute.
  • Progression: Generally non-progressive/stable — the structural malformations are fixed; neurodevelopmental deficits remain stable rather than degenerating. In the 2025 case, "the neurodevelopmental deficits remained stable without progression" over 2-year follow-up (PMID 40797481). No defined disease "stages."
  • Progression rate / course: Static congenital course; lifelong (chronic). Not episodic or relapsing–remitting.
  • Remission: Not applicable (structural congenital disorder; no spontaneous remission). Specific manifestations are treatment-modifiable (e.g., precocious puberty controlled with GnRH analog; hearing improved with implants).
  • Critical periods: Embryonic corticogenesis and organogenesis are the windows during which the pathology is set; there is no post-natal window to reverse the heterotopia. Intervention windows exist for managing sequelae (early hearing amplification for language development; timely endocrine therapy).

9. Inheritance and Population

Epidemiology. Ultra-rare. Orphanet prevalence class <1/1,000,000; fewer than ~50 patients reported worldwide since 1992 (only ~9 described by 2016–2017; PMID 27739185). Incidence not quantifiable. No registry/GBD data.

Inheritance & genetics. - Pattern: Autosomal recessive for both DCHS1 and FAT4 forms (PMID 22473091, 24056717). - Penetrance: Essentially complete in biallelic individuals (all reported biallelic patients are affected), though expressivity is variable (organ involvement and severity differ between patients, even within the same gene). - Anticipation: None (not a repeat-expansion disorder). - Germline mosaicism: Not specifically reported. - Consanguinity: Important risk factor — parental consanguinity in 3/5 defining families; homozygous variants common in consanguineous unions (PMID 22473091). - Founder effects: None established; variants are largely private. - Carrier frequency: Not formally estimated; expected very low. Heterozygous carriers are asymptomatic.

Population demographics. - Affected populations: Reported across diverse ancestries (European, Middle Eastern, Chinese, Macedonian, etc.; PMIDs 22473091, 40797481, 28878612) — no ethnic predilection beyond enrichment where consanguinity is common. - Geographic distribution: Worldwide, non-endemic. - Sex ratio: No clear sex bias; both sexes affected (autosomal). Some sex-specific manifestations reported (breast aplasia/hypogonadism in a female, PMID 29046692). - Age distribution: Diagnosed from newborn period (PMID 29505454) through adulthood (retrospective WES at age 37, PMID 29046692).

10. Diagnostics

Genetic testing (definitive). - Approach: Molecular confirmation of biallelic pathogenic variants in DCHS1 or FAT4. Whole-exome sequencing (WES) is the principal diagnostic modality and has repeatedly established the diagnosis, including via reverse phenotyping and expanded carrier screening of parents (PMID 37551355, 29046692, 28878612, 31384091). WGS is an alternative that also detects deep-intronic/structural variants. Multigene panels for intellectual disability / periventricular heterotopia / malformation syndromes should include DCHS1, FAT4, and — given phenotypic overlap — CCBE1 and ADAMTS3 (Hennekam). Single-gene testing is reasonable when the gestalt is classic. Chromosomal microarray/karyotype/FISH are typically normal and serve to exclude CNV/aneuploidy mimics. Mitochondrial and repeat-expansion testing are not indicated.

Imaging & clinical tests. - Brain MRI: periventricular nodular and subcortical heterotopia — a recognizable pattern that, in the right clinical context, should prompt targeted testing (PMID 39462795, 24056717). - Temporal-bone high-resolution CT: external/middle-ear and tympanic-cavity malformations (PMID 27739185). - Audiology: confirms conductive hearing loss; EEG documented altered functional cerebral asymmetry in a research setting (PMID 25930014). - Renal ultrasound/urography: for renal agenesis/duplex kidney/obstruction (PMID 28878612). - Endocrine labs: gonadotropins/sex steroids for hypogonadotropic hypogonadism or precocious puberty (PMID 29046692, 40797481).

Biomarkers / omics diagnostics: No specific biochemical biomarker; DNA sequence variants are the diagnostic marker. No validated RNA/proteomic/metabolomic/epigenomic test; no liquid biopsy role.

Clinical criteria & differential diagnosis. No formal consensus criteria; diagnosis rests on the characteristic facial gestalt + hearing loss + intellectual disability + neuronal heterotopia, confirmed genetically. Differential diagnoses: Hennekam syndrome (allelic FAT4; distinguished classically by lymphedema — though intestinal lymphangiectasia can overlap; PMID 31063239, 29681106); other periventricular-heterotopia disorders (FLNA-related; ARFGEF2-related; EML1-associated) (PMID 39462795); blepharophimosis-ptosis-epicanthus-inversus syndrome (BPES, FOXL2); other multiple-congenital-anomaly/ID syndromes.

Screening. Not part of newborn screening. Cascade/carrier screening of relatives once the familial variants are known; expanded carrier screening can identify at-risk couples (PMID 37551355). Prenatal/preimplantation testing feasible for known familial variants.

11. Outcome / Prognosis

  • Survival/mortality: No formal survival statistics. Prognosis ranges from early death in severely affected infants (two siblings died undiagnosed with multiple congenital anomalies; PMID 37551355) to survival into adulthood with stable disability (diagnosis at age 37; PMID 29046692). Mortality is driven by severe neonatal respiratory/feeding complications and major malformations rather than by a degenerative process.
  • Morbidity/function: Chief long-term morbidities are intellectual disability and conductive hearing loss, with variable skeletal, renal, endocrine, and respiratory contributions. Disability is lifelong but non-progressive.
  • Quality-of-life measures: No EQ-5D/SF-36/PROMIS data; hearing rehabilitation improves communication/social outcomes (PMID 26491591).
  • Complications: recurrent respiratory issues (tracheal anomalies), feeding failure/failure-to-thrive, hearing-loss–related language delay, urinary-tract obstruction/renal impairment, endocrine dysfunction; psychosocial impact of craniofacial differences.
  • Recovery potential: Structural malformations do not resolve, but sequelae are manageable (hearing devices, hormone therapy, surgery). Neurodevelopmental deficits are stable.
  • Prognostic factors: severity/extent of neonatal respiratory and feeding compromise and of CNS involvement predict early outcome; no molecular prognostic biomarker validated (possible gene-specific/genotype effects unproven).

12. Treatment

No disease-modifying or curative therapy exists. Management is multidisciplinary, supportive, and symptom-directed (NCIT: Supportive Care, C15277).

  • Pharmacotherapy (symptom-specific):
  • GnRH analog (leuprorelin/leuprolide acetate, e.g., Enantone®) for central precocious puberty — successfully controlled pubertal progression over 2 years (PMID 40797481). NCIT: Leuprolide (C1300); ATC L02AE02.
  • Endocrine replacement/management for hypogonadotropic hypogonadism as clinically indicated (PMID 29046692).
  • No pharmacogenomic considerations specific to VMS.
  • Surgical / interventional:
  • Hearing rehabilitation: bone-conduction hearing device (bone-anchored), or, when tympanic-cavity hypoplasia precludes ossiculoplasty, an active middle-ear implant (Vibrant Soundbridge) — improved hearing, social skills, and language (PMID 27739185, 26491591). NCIT: Cochlear/Middle Ear Implant; Hearing Aid.
  • Orthopedic/craniofacial and urological surgery as needed (e.g., for obstruction, scoliosis).
  • Supportive & rehabilitative: nutritional support/feeding management for infantile feeding difficulties; respiratory care for tracheal anomalies; physical, occupational, and speech therapy; special education for intellectual disability. (NCIT: Physical Therapy C15327; Occupational Therapy; Speech Therapy.)
  • Advanced therapeutics (gene/cell/RNA/targeted/immunotherapy): None developed or in trials; not applicable.
  • Experimental treatments / clinical trials: None registered for VMS (no NCT identifiers).
  • Treatment strategy: individualized, organ-system–based (audiology, neurodevelopment, endocrinology, nephrology, orthopedics, genetics). No standardized algorithm exists; "Neurodevelopmental deficits were managed with regular follow-ups due to the lack of established therapeutic protocols" (PMID 40797481).

13. Prevention

  • Primary prevention: Not preventable at the individual level (congenital genetic disease). Genetic counseling is the cornerstone: for consanguineous couples and families with an affected child, recurrence risk is 25% per pregnancy (autosomal recessive).
  • Secondary prevention (early detection): early brain MRI/audiology/renal imaging in suspected cases; early hearing amplification to protect language development; endocrine surveillance.
  • Tertiary prevention: manage complications (hearing devices, hormone therapy, respiratory/feeding support, surgery) to limit disability.
  • Genetic/reproductive prevention: carrier/cascade screening, expanded carrier screening for at-risk couples (PMID 37551355), and prenatal or preimplantation genetic diagnosis for known familial DCHS1/FAT4 variants.
  • Immunization / behavioral / public-health / environmental / prophylaxis: Not applicable (no infectious or environmental component).

14. Other Species / Natural Disease

  • Taxonomy of orthologs studied: Mus musculus (NCBI Taxon 10090), Danio rerio (7955), Drosophila melanogaster (7227).
  • Orthologous genes: mouse Dchs1 (Gene 94176) / Fat4 (Gene 329628); zebrafish dchs1b, dchs2, fat orthologs; Drosophila ds (dachsous) and ft (fat). The pathway is deeply evolutionarily conserved (Fat–Dachsous PCP originally defined in Drosophila; PMID 24998526, 28488382).
  • Natural disease in animals: No naturally occurring VMS-equivalent is documented in companion animals or wildlife (OMIA: none specific). Veterinary relevance is limited to experimental models, not spontaneous disease.
  • Comparative biology / conservation: The neuronal, PCP, cytoskeletal, and growth-control functions of Fat–Dachsous are conserved from flies to mammals; loss produces analogous polarity/migration/proliferation defects across species (PMID 24998526, 26160902, 28488382).
  • Transmission / zoonosis: Not applicable (non-infectious genetic disorder).

15. Model Organisms

VMS mechanism has been dissected chiefly in animal models (mammalian and invertebrate); no established patient-derived organoid/iPSC model is prominent in the literature to date.

  • Mouse (mammalian):
  • Dchs1 and Fat4 knockdown/knockout/conditional models. Phenotype recapitulation: periventricular/subcortical heterotopia with expanded progenitors and reduced differentiation, reversed by Yap knockdown (PMID 24056717); disrupted facial branchiomotor neuron migration/PCP (PMID 24998526); osteoblast-differentiation and craniofacial defects (PMID 31358536); duplex-kidney/RET phenotypes (PMID 30853441). Genetic model types: knockout, conditional/tissue-specific knockdown. Limitation: individual studies capture single organ systems; no single mouse fully reproduces the whole human syndrome. Resource: MGI.
  • A 2026 model targeting the DCHS1 intracellular domain reproduced expanded neurogenic proliferation and VMS-like neurodevelopmental defects (PMID 41972678), dissecting domain-specific function.
  • Zebrafish (Danio rerio): maternal-zygotic dchs1b (and dchs2) mutants — egg-activation, cortical-granule-exocytosis, gastrulation, dorsal-organizer, and actin/microtubule cytoskeleton defects; the Dchs1b intracellular domain rescues microtubule bundling, revealing Fat-independent roles (PMID 26160902). Resource: ZFIN. Use: early morphogenesis, cytoskeletal biology, PCP.
  • Drosophila melanogaster: neuron-specific knockdown of fat — shortened lifespan, impaired locomotion, neuromuscular-junction and axonal-targeting defects, supporting a neuronal-autonomous contribution of FAT4 loss to the human neuronal phenotype (PMID 28488382). Resource: FlyBase. Use: conserved Fat/Dachsous PCP, neuronal function.

Applications: these models establish the Dchs1–Fat4 → Hippo/YAP axis in neurogenesis, PCP-driven neuronal migration, osteogenesis, and nephrogenesis, and provide platforms for testing pathway-directed interventions (e.g., YAP modulation). Limitations: partial phenotype coverage per model; species differences in ear/craniofacial anatomy; absence of a comprehensive humanized model.

Summary of Supported vs. Refuted Hypotheses

Supported (evidence-based): - VMS is autosomal recessive, caused by biallelic DCHS1 (VMLDS1) or FAT4 (VMLDS2) LoF variants (PMID 24056717, 22473091). - Periventricular heterotopia arises from loss of Dchs1/Fat4 → YAP de-repression → excess progenitor proliferation/failed differentiation and migration (PMID 24056717, 24998526, 41972678). - The same module drives craniofacial/skeletal (osteoblast) and renal (FAT4–RET) phenotypes (PMID 31358536, 30853441). - VMS and Hennekam syndrome are allelic FAT4 disorders on a phenotypic spectrum (PMID 24913602, 29681106, 31063239). - Conductive hearing loss from ear malformation is near-constant and implant-treatable (PMID 27739185, 26491591).

Refuted / not supported: No environmental, infectious, or lifestyle etiology; no anticipation; no evidence for a progressive/degenerative course (features are static, PMID 40797481).

Limitations & Future Directions

  • Evidence rests on case reports/series (n in the dozens) → frequencies and prognosis are imprecise; no registries, trials, or patient omics.
  • Genotype–phenotype correlations (DCHS1 vs FAT4; specific domains) and modifiers need larger cohorts.
  • No targeted therapy; the well-defined Hippo/YAP axis is a rational (untested) therapeutic target.
  • Patient-derived iPSC/organoid models and standardized natural-history studies are priorities.

Key References (PMID)

41972678, 40797481, 39462795, 37551355, 31384091, 31358536, 31063239, 30853441, 29681106, 29505454, 29046692, 28878612, 28488382, 27739185, 26491591, 26160902, 25930014, 24998526, 24913602, 24056717, 22473091.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 21
Resolved 21
Unresolved (possible confabulation) 0
Unverifiable 0
Quoted claims checked 4
Quoted claims found in source 4
Quoted claims not found in source 0
References weighed for topical relevance 21
On topic 10
Off topic 0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome Count
Terms checked 72
Resolved 69
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 3
Terms whose name was checked 14
Terms named correctly 8
Terms named as a different term 2
Terms whose name is worth a second look 4

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

  • MONDO:0018852 (2 mentions) - the report calls it "Van Maldergem syndrome", "parent"; MONDO calls it achromatopsia
  • UBERON:0001756 (1 mention) - the report calls it "middle ear / ossicles / tympanic cavity"; UBERON calls it middle ear

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

  • HP:0001249 (1 mention) - the report calls it "Intellectual disability, mild-to-moderate"; HP calls it Intellectual disability
  • HP:0002778 (1 mention) - the report calls it "tracheal anomalies"; HP calls it Abnormal tracheal morphology, and lists "Tracheal disease" among its other names
  • UBERON:0002091 (1 mention) - the report calls it "Skeleton / limbs"; UBERON calls it appendicular skeleton, and lists "skeleton appendiculare" among its other names
  • UBERON:0003126 (1 mention) - the report calls it "Respiratory tract / trachea"; UBERON calls it trachea, and lists "vertebrate trachea" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

  • MONDO:0018852 - called "Van Maldergem syndrome", "parent"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA.