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Inheritance

3

Autosomal Dominant

X-linked Recessive

Autosomal Recessive

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Subtypes

4

MED13-related intellectual developmental disorder (MRD61) MONDO:0032485

MED13 link {'name': 'Autosomal Dominant'}

Caused by heterozygous (usually de novo) variants in MED13, encoding a subunit of the CDK8 kinase module of the Mediator complex. Characterized by intellectual disability, expressive speech delay, behavioral abnormalities (ASD, ADHD), nonspecific dysmorphic features, obstipation, and poor overall growth. This subtype often falls at the milder end of the Mediator spectrum, but severe presentations with epilepsy, structural brain anomalies, and additional congenital complications have also been reported.

Show evidence (2 references)

PMID:41195223 SUPPORT Human Clinical

"Intellectual developmental disorder type 61 (MRD61) is an extremely rare autosomal dominant disorder caused by variants in the MED13 gene."

Directly defines MRD61 as an autosomal dominant MED13-related disorder.

PMID:29740699 SUPPORT Human Clinical

"Here we describe a GeneMatcher collaboration which led to a cohort of 13 affected individuals harboring protein-altering variants, 11 of which are de novo, in MED13; the only inherited variant was transmitted to an affected child from an affected mother."

Syndrome-defining cohort establishing recurrent, mostly de novo MED13-associated neurodevelopmental disease.

MED13L syndrome (MRFACD) MONDO:0014773

MED13L link {'name': 'Autosomal Dominant'}

Caused by heterozygous (mostly de novo) variants in MED13L, a paralog of MED13 also in the CDK8 kinase module. The most syndromic subtype, characterized by mild to profound intellectual disability, distinctive facial dysmorphism (depressed nasal bridge, bulbous nasal tip, upslanting palpebral fissures, macrostomia), congenital heart defects with variable penetrance, hypotonia, seizures, and corpus callosum anomalies. Also known as Asadollahi-Rauch syndrome.

Show evidence (2 references)

PMID:40228085 SUPPORT Human Clinical

"The diagnosis of MED13L syndrome is established in a proband with a heterozygous pathogenic variant in MED13L identified by molecular genetic testing."

Directly defines MED13L syndrome as the heterozygous MED13L-associated disorder.

PMID:28645799 SUPPORT Human Clinical

"Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."

Human review further delineating the recurrent MED13L syndrome phenotype.

MED12-related intellectual disability (FG syndrome / Opitz-Kaveggia) MONDO:0100000

MED12 link {'name': 'X-linked Recessive'}

Caused by hemizygous variants in MED12, encoding a subunit of the CDK8 kinase module. FG syndrome type 1 (Opitz-Kaveggia syndrome) is caused by the recurrent p.R961W missense variant. Characterized by moderate to severe intellectual disability, relative macrocephaly, imperforate anus or constipation, congenital hypotonia, corpus callosum agenesis or hypoplasia, broad thumbs and halluces, and characteristic facial features with tall forehead, downslanting palpebral fissures, and small ears.

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"FG syndrome is a rare X-linked multiple congenital anomaly-cognitive impairment disorder caused by the p.R961W mutation in the MED12 gene."

Establishes the best-characterized MED12-related mediatoropathy form as an X-linked MED12 disorder.

MED23-related intellectual disability (MRT18) MONDO:0013651

MED23 link {'name': 'Autosomal Recessive'}

Caused by biallelic (homozygous or compound heterozygous) variants in MED23, encoding a subunit of the tail module of the Mediator complex. Distinguished from other Mediator subtypes by prominent movement disorder features (spasticity, dystonia, choreoathetosis), autosomal recessive inheritance, and seizures with or without epilepsy. Brain imaging may show hypomyelination, pontine hypoplasia, and thin corpus callosum.

Show evidence (2 references)

PMID:36824420 SUPPORT Human Clinical

"Biallelic loss-of-function variants in MED23 cause a recessive syndromic intellectual disability condition with or without epilepsy (MRT18)."

Directly defines MED23-related MRT18 as a recessive syndromic intellectual disability disorder.

PMID:21868677 SUPPORT Human Clinical

"Here, we report a missense mutation (p. R617Q) in MED23 that cosegregates with nonsyndromic autosomal recessive intellectual disability."

Original human genetic evidence linking MED23 to recessive intellectual disability.

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Pathophysiology

7

Mediator Complex Disruption

The Mediator complex is a large multi-subunit assembly (~30 subunits in humans) that serves as a transcriptional coactivator bridging gene-specific transcription factors bound at enhancers and the RNA polymerase II general transcription machinery at promoters. Mutations in Mediator subunits disrupt this enhancer-promoter communication, leading to dysregulated expression of developmentally critical genes. The complex is organized into head, middle, tail, and CDK8 kinase modules, each with distinct interaction partners and regulatory functions.

neuron link

Transcription by RNA polymerase II link ↓ DECREASED Regulation of gene expression link ↕ DYSREGULATED

Downstream

CDK8 Kinase Module Dysfunction Variants in MED12, MED13, and MED13L perturb the dissociable CDK8 kinase module, a regulatory submodule of the Mediator complex.

Tail Module Disruption and Immediate Early Gene Dysregulation Variants in MED23 perturb a tail-module arm of Mediator-dependent transcriptional regulation.

Show evidence (2 references)

PMID:37516429 SUPPORT Other

"The Mediator complex (MED) is a large, evolutionarily conserved multiprotein that facilities the interaction between transcription factors and RNA Polymerase II in eukaryotes."

Confirms the Mediator complex's role as a bridge between transcription factors and RNA Pol II.

PMID:21868677 SUPPORT In Vitro

"MED23 is a subunit of the Mediator complex, a key regulator of protein-coding gene expression."

Establishes the Mediator complex as a key regulator of gene expression.

CDK8 Kinase Module Dysfunction

MED12, MED13, and MED13L are all components of the CDK8 kinase module, which reversibly associates with the core Mediator complex to regulate its activity. The CDK8 module has both activating and repressive roles in transcription and modulates Wnt, Notch, and other signaling pathways during development. Mutations in CDK8 module subunits preferentially affect neural crest-derived structures and brain development.

migratory neural crest cell link

MED12 link MED13 link MED13L link

Wnt signaling pathway link ↕ DYSREGULATED Notch signaling pathway link ↕ DYSREGULATED

Downstream

Neurodevelopmental Transcriptional Dysregulation CDK8 module dysfunction disrupts Wnt and Notch signaling programs critical for neuronal and neural crest cell differentiation.

Cardiac Developmental Defects CKM dysfunction is the main upstream branch for the recurrent cardiac developmental defects seen especially in MED13L and MED12, with milder involvement in some MED13 cases.

Show evidence (2 references)

PMID:29740699 SUPPORT Human Clinical

"MED13 is a component of the CDK8-kinase module that can reversibly bind Mediator, a multi-protein complex that is required for Polymerase II transcription initiation."

Confirms MED13's role in the CDK8 kinase module and its relationship to the broader Mediator complex.

PMID:37516429 SUPPORT Other

"Interestingly, most of the genomic mutations have been found in the subunits of the kinase module."

Confirms that kinase module subunits are disproportionately affected by disease-causing mutations.

Neurodevelopmental Transcriptional Dysregulation

Mediator subunit mutations lead to broad transcriptional dysregulation affecting genes required for neuronal differentiation, cortical layering, radial migration, callosal projection, dendritic arborization, and synaptogenesis. This manifests as intellectual disability and speech delay across all subtypes, with severity correlating with the degree of transcriptional disruption.

neuron link

Neuron migration link ↕ DYSREGULATED Neuron projection development link ↕ DYSREGULATED Dendrite development link ↓ DECREASED

Downstream

Cortical Neuron Migration and Projection Defects In MED13-associated disorder, dysregulated developmental transcription programs impair cortical neuron migration, callosal projection, and dendritic elaboration.

Show evidence (3 references)

PMID:21868677 SUPPORT In Vitro

"These findings highlight the crucial role of Mediator in brain development and functioning and suggest that altered IEG expression might be a common molecular hallmark of cognitive deficit."

Establishes Mediator's crucial role in brain development and links transcriptional dysregulation to cognitive deficits.

PMID:37516429 SUPPORT Other

"Mutations in MED subunits were associated with a wide range of genetic diseases for MED12, MED13, MED13L, MED20, MED23, MED25, and CDK8 genes."

Confirms disease-causation for MED12, MED13, MED13L, and MED23 genes in the mediatoropathy spectrum, supporting a shared neurodevelopmental transcriptional dysregulation mechanism.

PMID:41663567 SUPPORT Model Organism

"We found that silencing Med13 in cortical neurons impaired its radial migration and contralateral projection as well as dendritic complexity in mice."

Directly links Med13 dysfunction to neuronal migration, projection, and dendritic defects in a cortical development model.

Cortical Neuron Migration and Projection Defects

MED13 deficiency disrupts cortical neuron radial migration, contralateral projection, and dendritic complexity during corticogenesis. Experimental rescue of migration and callosal projection by PLXNA4 overexpression suggests that altered axon-guidance and projection programs are a specific downstream mechanism within the broader CKM-mediated neurodevelopmental defect.

neuron link

MED13 link

Neuron migration link ↕ DYSREGULATED Neuron projection development link ↕ DYSREGULATED Dendrite development link ↓ DECREASED

cerebral cortex link

Show evidence (2 references)

PMID:41663567 SUPPORT Model Organism

"We found that silencing Med13 in cortical neurons impaired its radial migration and contralateral projection as well as dendritic complexity in mice."

Directly supports a MED13-linked cortical migration and projection mechanism.

PMID:41663567 SUPPORT Model Organism

"Notably, the impaired radial migration and callosal projection, but not dendritic complexity, were largely restored by overexpression of PlxnA4 in Med13 knock-down neurons."

PLXNA4 rescue localizes part of the MED13 mechanism to cortical migration and callosal projection programs.

MED13 Ubiquitination Regulatory Cluster Variants

A subset of MED13 missense variants in MED13-related intellectual developmental disorder (MRD61) cluster at adjacent N-terminal residues p.Thr326 and p.Pro327, which are regulatory sites for MED13 ubiquitination and proteasomal degradation. Variants at this cluster are predicted to disrupt MED13 protein turnover, providing a stability/regulatory loss-of-function mechanism distinct from truncating alleles. In the syndrome-defining 13-patient cohort, six of seven non-truncating variants clustered at N- or C-terminal hotspots, and the four N-terminal variants involved these adjacent ubiquitination-related residues — pointing to MED13 protein-turnover dysregulation as a recurrent MRD61 mechanism rather than purely structural disruption.

MED13 link

MED13 protein ubiquitination link ↕ DYSREGULATED Proteasomal degradation of MED13 link ↕ DYSREGULATED

Downstream

CDK8 Kinase Module Dysfunction Disrupted MED13 ubiquitination/degradation regulation alters MED13 protein levels within the CDK8 kinase module, contributing to module-wide transcriptional regulatory dysfunction in MRD61.

Show evidence (2 references)

PMID:29740699 SUPPORT Human Clinical

"The four N-terminal clustering mutations affect two adjacent amino acids that are known to be involved in MED13 ubiquitination and degradation, p.Thr326 and p.Pro327."

Identifies the p.Thr326/Pro327 ubiquitination-regulatory cluster as a recurrent MED13-variant hotspot in MRD61 patients.

PMID:29740699 SUPPORT Human Clinical

"Six affected individuals had mutations that are predicted to truncate the MED13 protein, six had missense mutations, and one had an in-frame-deletion of one amino acid."

Establishes that roughly half of MED13 variants in the MRD61 cohort are missense or in-frame, motivating distinct mechanism modeling for residue-specific alleles versus truncating loss-of-function.

Cardiac Developmental Defects

Congenital heart defects are a prominent feature of MED13L syndrome and are also recurrent in MED12/FG syndrome, with milder involvement in some MED13 cases. MED13L is highly expressed in the developing heart, and Mediator dysfunction affects transcription factor programs (e.g., NKX2-5, GATA4, TBX5) required for cardiac septation, outflow tract development, and valve formation. Cardiac phenotypes range from patent foramen ovale to septal defects and transposition of the great arteries.

cardiac muscle cell link

Heart morphogenesis link ↕ DYSREGULATED

heart link

Show evidence (3 references)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

Documents congenital heart defects in 20-50% of MED13L haploinsufficiency patients with reduced penetrance.

PMID:40228085 SUPPORT Human Clinical

"Distal limb and/or digit anomalies, ocular manifestations and vision issues, and congenital heart defects have been reported."

GeneReviews confirms congenital heart defects as a reported feature of MED13L syndrome.

PMID:19938245 SUPPORT Human Clinical

"The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."

Documents congenital cardiac anomalies in the majority of MED12-confirmed FG syndrome patients.

Tail Module Disruption and Immediate Early Gene Dysregulation

MED23, a subunit of the Mediator tail module, specifically interacts with transcription factors such as ELK1 and other ETS-family activators. Loss of MED23 function disrupts the activation of immediate early genes (IEGs) including JUN and FOS, which are critical for synaptic plasticity and neuronal activity-dependent gene expression. This mechanism underlies the distinct movement disorder phenotype (spasticity, dystonia, choreoathetosis) seen in MED23-related intellectual disability.

MED23 link

Immediate-early gene transcription link ↓ DECREASED

Downstream

Neurodevelopmental Transcriptional Dysregulation Tail-module dysfunction converges on impaired neuronal gene-expression programs, including immediate-early gene responses.

Show evidence (2 references)

PMID:21868677 SUPPORT In Vitro

"This mutation specifically impaired the response of JUN and FOS immediate early genes (IEGs) to serum mitogens by altering the interaction between enhancer-bound transcription factors (TCF4 and ELK1, respectively) and Mediator."

Demonstrates that the MED23 p.R617Q mutation specifically disrupts IEG activation through altered ELK1-Mediator interaction.

PMID:21868677 SUPPORT In Vitro

"Transcriptional dysregulation of these genes was also observed in cells derived from patients presenting with other neurological disorders linked to mutations in other Mediator subunits or proteins interacting with MED."

Suggests IEG dysregulation may be a common molecular hallmark across Mediator subunit disorders.

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Pathograph

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Phenotypes

25

Cardiovascular 1

Congenital Heart Defects FREQUENT Abnormal heart morphology (HP:0001627)

Show evidence (3 references)

PMID:28645799 SUPPORT Human Clinical

"showed reduced penetrance for congenital heart defects"

Documents reduced penetrance for congenital heart defects in MED13L syndrome from genotype-phenotype review.

PMID:40228085 SUPPORT Human Clinical

"Distal limb and/or digit anomalies, ocular manifestations and vision issues, and congenital heart defects have been reported."

GeneReviews confirms congenital heart defects as a feature of MED13L syndrome.

PMID:19938245 SUPPORT Human Clinical

"The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."

Demonstrates that congenital heart defects are also a frequent feature of MED12-confirmed FG syndrome.

Context-specific annotations (4)

Genetic MED13 MED13 OCCASIONAL

Mild congenital heart abnormalities are reported in a subset of MED13 patients.

Show evidence (1 reference)

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Supports occasional congenital heart involvement in MED13.

Genetic MED13L MED13L OCCASIONAL

Variable penetrance. Ranges from patent foramen ovale to ASD, VSD, and transposition of the great arteries.

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"showed reduced penetrance for congenital heart defects"

Supports non-universal congenital heart involvement in MED13L syndrome; OCCASIONAL is used conservatively for the subtype context.

Genetic MED12 MED12 FREQUENT

Congenital cardiac anomalies are a recurrent part of the MED12/FG syndrome phenotype.

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."

Supports frequent congenital heart defects in MED12-confirmed FG syndrome.

Genetic MED23 MED23 OCCASIONAL

Congenital heart disease reported in some patients.

Show evidence (1 reference)

PMID:30847200 SUPPORT Human Clinical

"The patients had severe ID, spasticity, congenital heart diseases, brain abnormalities, and atypical electroencephalography."

Supports occasional congenital heart disease in previously reported MED23 cases.

Digestive 2

Obstipation OCCASIONAL Constipation (HP:0002019)

Show evidence (1 reference)

PMID:41195223 SUPPORT Human Clinical

"the proband presented with congenital megacolon, a previously unreported complication."

Documents congenital megacolon in a MED13 patient. Described as a previously unreported complication, suggesting this is an occasional rather than frequent feature.

Imperforate Anus and Anal Anomalies FREQUENT Anal atresia (HP:0002023)

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."

Anal anomalies (fistula, stenosis, atresia) documented in 11 of 19 MED12-confirmed FG syndrome patients, making it the second most common congenital anomaly after corpus callosum abnormalities.

Ear 1

Hearing Impairment OCCASIONAL Hearing impairment (HP:0000365)

Show evidence (2 references)

PMID:36087421 SUPPORT Human Clinical

"Microcephaly, developmental delay, hypotonia, corpus callosum abnormalities, deafness, and retinal atrophy were common features in the previously described cases."

Documents hearing involvement in the expanded MED13 phenotype.

PMID:40228085 SUPPORT Human Clinical

"Other reported features include seizures and/or hearing impairment."

Documents hearing impairment as a reported MED13L feature.

Context-specific annotations (2)

Genetic MED13 MED13 OCCASIONAL

Hearing involvement is part of the expanded MED13 phenotype but is not universal.

Show evidence (1 reference)

PMID:36087421 SUPPORT Human Clinical

"Microcephaly, developmental delay, hypotonia, corpus callosum abnormalities, deafness, and retinal atrophy were common features in the previously described cases."

Supports established hearing involvement in previously reported MED13 patients while not implying obligate occurrence across the whole subtype.

Genetic MED13L MED13L OCCASIONAL

Hearing impairment is a reported but non-core MED13L feature.

Show evidence (1 reference)

PMID:40228085 SUPPORT Human Clinical

"Other reported features include seizures and/or hearing impairment."

GeneReviews directly supports hearing impairment as part of the MED13L phenotype spectrum.

Head and Neck 5

Facial Dysmorphism (MED13) Abnormal facial shape (HP:0001999)

Show evidence (2 references)

PMID:41195223 SUPPORT Human Clinical

"The main symptoms are intellectual disability (ID) of varying degrees, developmental delay (DD), hypotonia during infancy, facial dysmorphism, language impairment, restricted growth, skeletal and limb abnormalities, and behavioral abnormalities."

2025 review of 26 MRD61 cases lists facial dysmorphism among the main symptoms of MED13-related disorder.

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Dysmorphisms are reported in two or more patients in the syndrome-defining 13-patient MED13 cohort.

Distinctive Facial Dysmorphism (MED13L) VERY_FREQUENT Abnormal facial shape (HP:0001999)

Show evidence (2 references)

PMID:28645799 SUPPORT Human Clinical

"the majority of patients were reported to show broad/prominent forehead, low set ears, bitemporal narrowing, upslanting palpebral fissures, depressed/flat nasal bridge, bulbous nose, and abnormal chin, but macroglossia and horizontal eyebrows were also observed in ∼30%."

Detailed description of the MED13L facial gestalt from a genotype-phenotype review.

PMID:40228085 SUPPORT Human Clinical

"Dysmorphic facial features, including depressed nasal bridge, bulbous nose, and hypotonic open mouth, are present in most individuals."

GeneReviews confirms distinctive facial features are present in most MED13L patients.

Relative Macrocephaly VERY_FREQUENT Macrocephaly (HP:0000256)

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"Ten had macrocephaly (five absolute, five relative)."

Quantifies macrocephaly in the MED12 p.R961W-confirmed FG syndrome cohort, with both absolute and relative forms.

Characteristic Facial Features (MED12) VERY_FREQUENT Abnormal facial shape (HP:0001999)

Show evidence (2 references)

PMID:19938245 SUPPORT Human Clinical

"These features were seen most often in affected male patients: characteristic facies (13 of 13), an affable personality (13 of 13)"

Characteristic facial features were present in all 13 MED12-confirmed FG syndrome patients, making it the most consistent feature.

PMID:19938245 SUPPORT Human Clinical

"He had hypertelorism, a high forehead, upswept frontal hair, and small cup-shaped ears (for which he has had surgery), wide mouth, full lips, broad palate, and broad neck."

Detailed description of FG syndrome facial features including tall forehead and small ears.

Microcephaly OCCASIONAL Microcephaly (HP:0000252)

Show evidence (2 references)

PMID:36824420 SUPPORT Human Clinical

"A retrospective assessment of the previously reported clinical data for these subjects confirms the occurrence of postnatal progressive microcephaly as a previously unappreciated feature of the phenotype of MED23-related disorder."

Establishes postnatal progressive microcephaly as a feature of MED23-related disorder.

PMID:30847200 SUPPORT Human Clinical

"the patient manifested clinical symptoms similar to previously described cases, including developmental delay, microcephaly, hypotonia, severe intellectual disability, and spasticity."

Confirms microcephaly as part of the MED23 clinical spectrum.

Limbs 1

Broad Thumbs and Halluces FREQUENT Broad thumb (HP:0011304)

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"His thumbs and great toes are wide and flat."

Broad thumbs and great toes documented in FG syndrome patients with confirmed MED12 p.R961W mutation.

Musculoskeletal 3

Hypotonia FREQUENT Hypotonia (HP:0001252)

Show evidence (2 references)

PMID:40228085 SUPPORT Human Clinical

"MED13L syndrome is characterized by mild-to-profound developmental delay, intellectual disability, and hypotonia."

GeneReviews confirms hypotonia as a defining feature of MED13L syndrome.

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Documents hypotonia as a recurrent feature in the MED13 cohort.

Context-specific annotations (4)

Genetic MED13 MED13 OCCASIONAL

Hypotonia is recurrent but not universal in MED13/MRD61.

Show evidence (1 reference)

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Supports hypotonia as a recurrent but non-core MED13 phenotype.

Genetic MED13L MED13L FREQUENT

Hypotonia is a common feature of MED13L syndrome.

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."

Author wording "majority" maps to FREQUENT for MED13L hypotonia.

Genetic MED12 MED12 VERY_FREQUENT

Congenital hypotonia is a cardinal feature of FG syndrome.

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"Congenital hypotonia and poor gastrointestinal function, including feeding difficulties that required medical or occupational/ physical therapy, poor oral motor function, decreased gastric motility, reflux, and chronic constipation, are characteristic of FG syndrome and were present in all..."

Supports VERY_FREQUENT hypotonia in mutation-confirmed FG syndrome.

Genetic MED23 MED23 FREQUENT

Axial hypotonia reported in MED23 patients.

Show evidence (1 reference)

PMID:30847200 SUPPORT Human Clinical

"Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."

Supports hypotonia as a recurrent feature of MED23-related disorder.

Skeletal Abnormalities Abnormality of the skeletal system (HP:0000924)

Show evidence (1 reference)

PMID:41195223 SUPPORT Human Clinical

"The main symptoms are intellectual disability (ID) of varying degrees, developmental delay (DD), hypotonia during infancy, facial dysmorphism, language impairment, restricted growth, skeletal and limb abnormalities, and behavioral abnormalities."

Review of 26 MRD61 cases supports skeletal involvement as part of the MED13 clinical spectrum.

Spasticity FREQUENT Spasticity (HP:0001257)

Show evidence (2 references)

PMID:30847200 SUPPORT Human Clinical

"Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."

Literature review of MED23 patients documents spasticity as a characteristic clinical feature.

PMID:30847200 SUPPORT Human Clinical

"the patient manifested clinical symptoms similar to previously described cases, including developmental delay, microcephaly, hypotonia, severe intellectual disability, and spasticity."

Direct clinical documentation of spasticity in a MED23 patient with confirmed homozygous variant.

Nervous System 10

Intellectual Disability VERY_FREQUENT Intellectual disability (HP:0001249)

Show evidence (3 references)

PMID:29740699 SUPPORT Human Clinical

"All patients had intellectual disability and/or developmental delays, including speech delays or disorders."

Confirms universal ID/DD in the MED13 cohort of 13 patients.

PMID:40228085 SUPPORT Human Clinical

"MED13L syndrome is characterized by mild-to-profound developmental delay, intellectual disability, and hypotonia."

GeneReviews confirms the full severity spectrum of ID in MED13L syndrome.

PMID:21868677 SUPPORT Human Clinical

"Here, we report a missense mutation (p. R617Q) in MED23 that cosegregates with nonsyndromic autosomal recessive intellectual disability."

Cosegregation in a human family establishes the causal link between MED23 mutation and intellectual disability.

Context-specific annotations (4)

Genetic MED13 MED13

Intellectual disability severity is variable in MED13-related disorder, with current reports ranging from mild to severe.

Show evidence (1 reference)

PMID:36087421 SUPPORT Human Clinical

"Mutations in the MED13 gene are reported in the literature in association with clinically variable, neurodevelopmental disorders, which are characterized by mild-to-severe intellectual disability, autism spectrum disorder, attention deficit/hyperactivity disorder, epilepsy, ocular or skeletal..."

Supports a variable MED13 intellectual disability severity spectrum rather than a single fixed severity band.

Genetic MED13L MED13L

MED13L syndrome spans a wide severity range from mild to profound developmental delay and intellectual disability.

Show evidence (1 reference)

PMID:40228085 SUPPORT Human Clinical

"MED13L syndrome is characterized by mild-to-profound developmental delay, intellectual disability, and hypotonia."

Supports the broad severity range of intellectual disability in MED13L syndrome.

Genetic MED12 MED12

FG syndrome cognitive impairment is variable from borderline to severe, although all mutation-confirmed individuals have cognitive disability.

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"The degree of intellectual disability is variable from borderline to severe."

Supports a variable but consistently abnormal intellectual phenotype in MED12-confirmed FG syndrome.

Genetic MED23 MED23

MED23-related intellectual disability is variable from mild to severe.

Show evidence (1 reference)

PMID:30847200 SUPPORT Human Clinical

"Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."

Supports a variable MED23 cognitive severity spectrum.

Speech and Language Delay VERY_FREQUENT Delayed speech and language development (HP:0000750)

Show evidence (2 references)

PMID:29740699 SUPPORT Human Clinical

"All patients had intellectual disability and/or developmental delays, including speech delays or disorders."

Confirms speech delays or disorders in all 13 MED13 patients in the cohort.

PMID:28645799 SUPPORT Human Clinical

"Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."

Documents severe speech delay in the majority of MED13L patients.

Autism Spectrum Disorder OCCASIONAL Autistic behavior (HP:0000729)

Show evidence (2 references)

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Documents ASD and ADHD as recurrent features in MED13 patients.

PMID:33258286 SUPPORT Human Clinical

"It is characterized by variable intellectual disability and/or developmental delays, especially in language. Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), eye or vision problems, hypotonia, mild congenital hearth abnormalities and dysmorphisms have been..."

Confirms ASD and ADHD as part of the MED13 phenotypic spectrum.

Context-specific annotations (2)

Genetic MED13 MED13 OCCASIONAL

ASD is a recurrent but non-universal behavioral feature in MED13 patients.

Show evidence (1 reference)

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Two or more affected individuals in the syndrome-defining MED13 cohort support ASD as an occasional feature.

Genetic MED13L MED13L FREQUENT

Autistic features are part of the MED13L neurobehavioral spectrum.

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

Supports autistic features as a recurrent MED13L finding; the reported 20-50% range overlaps the FREQUENT band and is described as a common sign.

Attention Deficit-Hyperactivity Disorder FREQUENT Attention deficit hyperactivity disorder (HP:0007018)

Show evidence (2 references)

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Documents ADHD as a recurrent feature reported in two or more MED13 patients.

PMID:33258286 SUPPORT Human Clinical

"It is characterized by variable intellectual disability and/or developmental delays, especially in language. Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), eye or vision problems, hypotonia, mild congenital hearth abnormalities and dysmorphisms have been..."

Confirms ADHD as part of the MED13 phenotypic spectrum.

Seizures FREQUENT Seizure (HP:0001250)

Show evidence (2 references)

PMID:36087421 SUPPORT Human Clinical

"Mutations in the MED13 gene are reported in the literature in association with clinically variable, neurodevelopmental disorders, which are characterized by mild-to-severe intellectual disability, autism spectrum disorder, attention deficit/hyperactivity disorder, epilepsy, ocular or skeletal..."

Documents epilepsy as part of the MED13-related neurodevelopmental phenotype spectrum.

PMID:40228085 SUPPORT Human Clinical

"Other reported features include seizures and/or hearing impairment."

GeneReviews confirms seizures as a reported feature of MED13L syndrome.

Context-specific annotations (4)

Genetic MED13 MED13 OCCASIONAL

Epilepsy appears to be an uncommon but established severe manifestation of MED13-related disorder.

Show evidence (1 reference)

PMID:36087421 SUPPORT Human Clinical

"From a literature review, it emerged that epilepsy is described in only one out of nineteen of previously reported patients with a phenotype of generalized, drug-resistant epilepsy with myoclonic-atonic seizures."

Supports epilepsy as an occasional rather than excluded MED13 phenotype.

Genetic MED13L MED13L OCCASIONAL

Seizures reported in a subset of MED13L patients.

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

The reported 20-50% range overlaps OCCASIONAL and FREQUENT; OCCASIONAL is used conservatively for subtype-specific seizure frequency.

Genetic MED12 MED12 OCCASIONAL

Seizures are not a core FG syndrome feature but are reported in some MED12-confirmed individuals.

Show evidence (2 references)

PMID:19938245 SUPPORT Human Clinical

"Febrile seizures, from the age of 3 years, were followed by afebrile seizures."

Supports seizure occurrence in at least one MED12-confirmed individual, so seizures should not be excluded from the subtype.

PMID:19938245 SUPPORT Human Clinical

"Myoclonic seizures, diagnosed at 37 years of age, are worse with stress, fatigue, or cold."

A second mutation-confirmed FG syndrome individual with seizures supports an occasional rather than excluded MED12 seizure phenotype.

Genetic MED23 MED23 OCCASIONAL

Epilepsy is a variable feature; OMIM designation includes "with or without epilepsy."

Show evidence (1 reference)

PMID:36824420 SUPPORT Human Clinical

"Besides global developmental delay, axial hypotonia and peripheral increased muscular tone, absent speech, and generalized tonic seizures, which fit well MRT18, the occurrence of postnatal progressive microcephaly has been here documented."

Supports seizure occurrence in MED23-related disorder, while the syndrome remains explicitly variable for epilepsy.

Corpus Callosum Anomalies FREQUENT Abnormal corpus callosum morphology (HP:0001273)

Show evidence (2 references)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

Documents abnormal corpus callosum as a common MRI finding in 20-50% of MED13L patients.

PMID:38745205 SUPPORT Human Clinical

"He presented with congenital heart anomalies, dysmorphic features, hydrocephalic changes, hypoplastic corpus callosum, bilateral optic nerve atrophy, optic chiasm atrophy, brain stem atrophy, and overall a more severe condition compared to previously described patients."

Reports hypoplastic corpus callosum in a MED13 patient with severe phenotype, expanding the corpus callosum anomaly finding to MED13.

Context-specific annotations (4)

Genetic MED13 MED13 OCCASIONAL

Corpus callosum anomalies are not universal in MED13 but are part of the expanded reported spectrum.

Show evidence (1 reference)

PMID:36087421 SUPPORT Human Clinical

"Microcephaly, developmental delay, hypotonia, corpus callosum abnormalities, deafness, and retinal atrophy were common features in the previously described cases."

Literature review supports corpus callosum abnormalities as a recurrent MED13 finding.

Genetic MED13L MED13L OCCASIONAL

Thin or absent corpus callosum on brain imaging.

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

The reported 20-50% range overlaps OCCASIONAL and FREQUENT; OCCASIONAL is used conservatively for subtype-specific corpus callosum anomalies.

Genetic MED12 MED12 OBLIGATE

Agenesis or hypoplasia of the corpus callosum is a cardinal feature of FG syndrome.

Show evidence (1 reference)

PMID:19938245 SUPPORT Human Clinical

"The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."

13/13 mutation-confirmed individuals places corpus callosum anomalies in the OBLIGATE band for the characterized FG syndrome cohort.

Genetic MED23 MED23 OCCASIONAL

Thin corpus callosum reported in some patients.

Show evidence (1 reference)

PMID:30847200 SUPPORT Human Clinical

"The MRI of the brain may be normal or it may show temporal lobe hypomyelination, delayed myelination, pontine hypoplasia, and thin corpus callosum."

Supports occasional corpus callosum anomalies in MED23-related disorder.

White Matter Abnormalities OCCASIONAL Abnormal cerebral white matter morphology (HP:0002500)

Show evidence (2 references)

PMID:28645799 SUPPORT Human Clinical

"abnormal MRI findings of myelination defects and abnormal corpus callosum"

Confirms myelination defects as a common MRI finding in MED13L haploinsufficiency patients.

PMID:30847200 SUPPORT Human Clinical

"The MRI of the brain may be normal or it may show temporal lobe hypomyelination, delayed myelination, pontine hypoplasia, and thin corpus callosum."

Literature review documents white matter abnormalities in MED23-related disorder.

Context-specific annotations (2)

Genetic MED13L MED13L OCCASIONAL

Delayed or absent myelination, periventricular and subcortical white matter abnormalities.

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

Supports white matter/myelination abnormalities as a recurrent but non-universal MED13L imaging finding.

Genetic MED23 MED23 OCCASIONAL

Temporal lobe hypomyelination and pontine hypoplasia.

Show evidence (1 reference)

PMID:30847200 SUPPORT Human Clinical

"The MRI of the brain may be normal or it may show temporal lobe hypomyelination, delayed myelination, pontine hypoplasia, and thin corpus callosum."

Supports occasional white matter abnormalities in MED23-related disorder.

Ataxia and Coordination Problems OCCASIONAL Ataxia (HP:0001251)

Show evidence (1 reference)

PMID:28645799 SUPPORT Human Clinical

"Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."

Supports ataxia and coordination problems as established but non-universal MED13L findings.

Absent Speech OCCASIONAL Absent speech (HP:0001344)

Show evidence (1 reference)

PMID:36824420 SUPPORT Human Clinical

"Besides global developmental delay, axial hypotonia and peripheral increased muscular tone, absent speech, and generalized tonic seizures, which fit well MRT18, the occurrence of postnatal progressive microcephaly has been here documented."

Directly supports complete absence of speech in at least a subset of MED23-related disorder.

Dystonia and Choreoathetosis FREQUENT Dystonia (HP:0001332)

Show evidence (1 reference)

PMID:30847200 SUPPORT Human Clinical

"Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."

Literature review of MED23 patients documents dystonia and choreoathetosis as characteristic movement disorder features.

Growth 1

Poor Overall Growth FREQUENT Growth delay (HP:0001510)

Show evidence (1 reference)

PMID:41195223 SUPPORT Human Clinical

"The main symptoms are intellectual disability (ID) of varying degrees, developmental delay (DD), hypotonia during infancy, facial dysmorphism, language impairment, restricted growth, skeletal and limb abnormalities, and behavioral abnormalities."

Literature review of 26 MRD61 cases explicitly lists restricted growth as a main symptom of MED13-related disorder.

Other 1

Ocular Anomalies OCCASIONAL Abnormality of the eye (HP:0000478)

Show evidence (1 reference)

PMID:29740699 SUPPORT Human Clinical

"Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."

Optic nerve abnormalities and Duane anomaly are recurrent ocular features in MED13 patients.

🧬

Genetic Associations

4

MED13 Haploinsufficiency (Causative)

Autosomal Dominant

Show evidence (2 references)

PMID:29740699 SUPPORT Human Clinical

"Here we describe a GeneMatcher collaboration which led to a cohort of 13 affected individuals harboring protein-altering variants, 11 of which are de novo, in MED13; the only inherited variant was transmitted to an affected child from an affected mother."

Landmark paper establishing MED13 as a neurodevelopmental disease gene with predominantly de novo variants.

PMID:29740699 SUPPORT Human Clinical

"Six affected individuals had mutations that are predicted to truncate the MED13 protein, six had missense mutations, and one had an in-frame-deletion of one amino acid."

Details the variant spectrum in the original MED13 cohort.

MED13L Haploinsufficiency (Causative)

Autosomal Dominant

Show evidence (4 references)

PMID:28645799 SUPPORT Human Clinical

"Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."

Comprehensive genotype-phenotype review of MED13L haploinsufficiency patients.

PMID:28645799 SUPPORT Human Clinical

"the second patient shows, for the first time, recurrence of a MED13L missense mutation (p.(Asp860Gly))."

Documents recurrent missense mutations in MED13L, supporting functional significance.

PMID:40228085 SUPPORT Human Clinical

"The majority of probands reported to date whose parents have undergone molecular genetic testing have the disorder as the result of a pathogenic variant that occurred as a de novo event in the proband."

Supports the statement that most MED13L pathogenic variants arise de novo.

+ 1 more reference

MED12 Hemizygous Variants (Causative)

X-linked Recessive

Show evidence (2 references)

PMID:19938245 SUPPORT Human Clinical

"We ascertained 23 males with the p.R961W mutation in MED12 from 9 previously reported FG syndrome families and 1 new family."

Largest clinical characterization of MED12 p.R961W-confirmed FG syndrome patients.

PMID:17369503 SUPPORT Human Clinical

"The original Lujan syndrome family has a novel missense mutation (p.N1007S) in the MED12 gene."

Directly supports the allelic MED12-Lujan syndrome relationship already noted in the variant summary.

MED23 Biallelic Variants (Causative)

Autosomal Recessive

Show evidence (3 references)

PMID:21868677 SUPPORT Human Clinical

"Here, we report a missense mutation (p. R617Q) in MED23 that cosegregates with nonsyndromic autosomal recessive intellectual disability."

Original discovery of MED23 as a cause of autosomal recessive intellectual disability via cosegregation in a human family.

PMID:21868677 SUPPORT In Vitro

"These findings highlight the crucial role of Mediator in brain development and functioning and suggest that altered IEG expression might be a common molecular hallmark of cognitive deficit."

Establishes the molecular mechanism linking MED23 to intellectual disability via IEG dysregulation.

PMID:36824420 SUPPORT Human Clinical

"Here, we report a 5-year-old girl with compound heterozygous for two additional MED23 variants."

Adds direct human evidence that MED23-related disorder can also arise through compound heterozygous biallelic variation.

📊

Related Datasets

3

MED13L knockout mouse cortical neurogenesis single-cell and bulk RNA-seq geo:GSE277054

Single-cell transcriptomics and bulk RNA-seq from Med13l knockout and heterozygous mouse embryonic cortex. Homozygous knockouts exhibit neonatal lethality with severe cortical neurogenesis deficits driven by impaired neural progenitor differentiation. Heterozygous mice show microcephaly with simplified neuronal morphology. Multi-omics analyses reveal MED13L orchestrates neurogenesis by transcriptional priming of key developmental genes (Neurod2, Sox5, Auts2, Nfib).

mouse SINGLE CELL RNA SEQ n=12

embryonic cerebral cortex

Conditions: Med13l homozygous knockout Med13l heterozygous knockout wild-type control

Findings

MED13L primes transcriptional activation of Neurod2, Sox5, Auts2, and Nfib during cortical neurogenesis

Homozygous Med13l knockout shows severe cortical neurogenesis deficits due to impaired neural progenitor differentiation

Heterozygous Med13l mice recapitulate MED13L syndrome behavioral phenotype including impaired learning and motor coordination

PMID:40775066

Show evidence (1 reference)

PMID:40775066 SUPPORT Model Organism

"Single-cell transcriptomics and immunofluorescence reveal severe cortical neurogenesis deficits in Med13l knockout embryos, driven by impaired neural progenitor differentiation."

scRNA-seq directly demonstrates cortical neurogenesis deficits in Med13l knockout providing mechanistic insight into MED13L syndrome.

Cardiomyocyte-specific Med13/Med13L double knockout RNA-seq geo:GSE298801

Bulk RNA-seq from adult murine cardiomyocytes after inducible knockout of Med13 and Med13L. Double knockout results in lethal heart failure within 6 weeks, with significant gene dysregulation of fibrotic pathways and calcium handling. Demonstrates that Med13 and Med13L function redundantly in the adult heart to maintain basal cardiac function and transcription.

mouse BULK RNA SEQ n=8

cardiomyocyte

Conditions: Med13/Med13L cardiomyocyte-specific double knockout wild-type control

Findings

Med13 and Med13L are functionally redundant in adult cardiomyocytes

Double knockout causes lethal heart failure with fibrotic and calcium handling gene dysregulation

Similar gene dysregulation patterns across Mediator cardiac knockouts (Med13/13L, Med12, Med1, Med30)

PMID:40989238

Show evidence (1 reference)

PMID:40989238 SUPPORT Model Organism

"Med13/13L knockout resulted in decreased cardiac function leading to lethal heart failure in a median timeframe of 6 weeks from the start of tamoxifen."

Mouse model demonstrates functional redundancy of Med13 and Med13L in heart and lethal consequences of combined loss.

Online Study of People Who Have Genetic Changes and Features of Autism: Simons Searchlight clinicaltrials:NCT01238250

Simons Searchlight is a large prospective observational registry enrolling individuals with rare genetic neurodevelopmental variants including MED13 and MED13L. Collects medical history, developmental milestones, behavioral assessments, and longitudinal follow-up data. As of 2024, includes approximately 15 individuals with MED13 variants and 108 with MED13L variants.

human

clinical phenotype data

Conditions: MED13 pathogenic variants MED13L pathogenic variants

Findings

Longitudinal natural history data for MED13 and MED13L syndrome available to qualified researchers

Data available to qualified researchers via SFARI Base (https://base.sfari.org). Over 7,000 total participants enrolled across all gene cohorts as of 2024.

{ }

Source YAML

click to show

name: Mediator Complex Neurodevelopmental Disorder
creation_date: "2026-04-11T00:00:00Z"
updated_date: "2026-05-02T17:00:00Z"
description: >-
  A group of neurodevelopmental disorders caused by germline mutations in genes encoding
  subunits of the Mediator complex, a multi-protein assembly required for RNA polymerase
  II-dependent transcription. The Mediator complex bridges gene-specific transcription
  factors and the general transcription machinery, and its disruption leads to dysregulated
  gene expression during neurodevelopment. Shared phenotypic features across subtypes include
  intellectual disability, speech and language delay, behavioral abnormalities, and variable
  structural brain and cardiac anomalies. The four recognized subtypes involve mutations in
  MED13 (CDK8 kinase module), MED13L (CDK8 kinase module paralog), MED12 (CDK8 kinase module),
  and MED23 (tail module), reflecting that different functional modules of the Mediator complex
  contribute to distinct but overlapping neurodevelopmental phenotypes.
category: Genetic
parents:
- Neurodevelopmental Disorder
- Transcriptional Regulation Disorder
notes: >-
  MONDO grouping class requested in monarch-initiative/mondo#10146. Pending MONDO ID assignment.
  This entry follows the precedent of RASopathy (MONDO:0021060) as a complex/pathway-based
  disease grouping.
disease_term:
  preferred_term: Mediator complex neurodevelopmental disorder
  term:
    id: MONDO:0002320
    label: congenital nervous system disorder
prevalence:
- population: Global
  percentage: Rare
  notes: >-
    Each subtype is individually ultra-rare. MED13L syndrome is the most commonly
    reported, with over 100 cases in the literature. MED13 (MRD61) had at least
    26 reported cases by 2025. MED12-related disorders, especially FG syndrome type 1,
    have several hundred reported cases. MED23-related disorder remains limited to a
    small number of reported families.

inheritance:
- name: Autosomal Dominant
- name: X-linked Recessive
- name: Autosomal Recessive

has_subtypes:
- name: MED13
  display_name: MED13-related intellectual developmental disorder (MRD61)
  classification: molecular
  description: >-
    Caused by heterozygous (usually de novo) variants in MED13, encoding a subunit of
    the CDK8 kinase module of the Mediator complex. Characterized by intellectual
    disability, expressive speech delay, behavioral abnormalities (ASD, ADHD), nonspecific
    dysmorphic features, obstipation, and poor overall growth. This subtype often falls
    at the milder end of the Mediator spectrum, but severe presentations with epilepsy,
    structural brain anomalies, and additional congenital complications have also been reported.
  subtype_term:
    preferred_term: Intellectual developmental disorder 61
    term:
      id: MONDO:0032485
      label: intellectual developmental disorder 61
  genes:
  - preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: PMID:41195223
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intellectual developmental disorder type 61 (MRD61) is an extremely rare autosomal dominant disorder caused by variants in the MED13 gene."
    explanation: Directly defines MRD61 as an autosomal dominant MED13-related disorder.
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we describe a GeneMatcher collaboration which led to a cohort of 13 affected individuals harboring protein-altering variants, 11 of which are de novo, in MED13; the only inherited variant was transmitted to an affected child from an affected mother."
    explanation: Syndrome-defining cohort establishing recurrent, mostly de novo MED13-associated neurodevelopmental disease.

- name: MED13L
  display_name: MED13L syndrome (MRFACD)
  classification: molecular
  description: >-
    Caused by heterozygous (mostly de novo) variants in MED13L, a paralog of MED13 also
    in the CDK8 kinase module. The most syndromic subtype, characterized by mild to profound
    intellectual disability, distinctive facial dysmorphism (depressed nasal bridge, bulbous
    nasal tip, upslanting palpebral fissures, macrostomia), congenital heart defects with
    variable penetrance, hypotonia, seizures, and corpus callosum anomalies. Also known as
    Asadollahi-Rauch syndrome.
  subtype_term:
    preferred_term: MED13L syndrome
    term:
      id: MONDO:0014773
      label: cardiac anomalies - developmental delay - facial dysmorphism syndrome
  genes:
  - preferred_term: MED13L
    term:
      id: hgnc:22962
      label: MED13L
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of MED13L syndrome is established in a proband with a heterozygous pathogenic variant in MED13L identified by molecular genetic testing."
    explanation: Directly defines MED13L syndrome as the heterozygous MED13L-associated disorder.
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."
    explanation: Human review further delineating the recurrent MED13L syndrome phenotype.

- name: MED12
  display_name: MED12-related intellectual disability (FG syndrome / Opitz-Kaveggia)
  classification: molecular
  description: >-
    Caused by hemizygous variants in MED12, encoding a subunit of the CDK8 kinase module.
    FG syndrome type 1 (Opitz-Kaveggia syndrome) is caused by the recurrent p.R961W
    missense variant. Characterized by moderate to severe intellectual disability,
    relative macrocephaly, imperforate anus or constipation, congenital hypotonia, corpus
    callosum agenesis or hypoplasia, broad thumbs and halluces, and characteristic facial
    features with tall forehead, downslanting palpebral fissures, and small ears.
  subtype_term:
    preferred_term: MED12-related intellectual disability syndrome
    term:
      id: MONDO:0100000
      label: MED12-related intellectual disability syndrome
  genes:
  - preferred_term: MED12
    term:
      id: hgnc:11957
      label: MED12
  inheritance:
  - name: X-linked Recessive
  evidence:
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "FG syndrome is a rare X-linked multiple congenital anomaly-cognitive impairment disorder caused by the p.R961W mutation in the MED12 gene."
    explanation: Establishes the best-characterized MED12-related mediatoropathy form as an X-linked MED12 disorder.

- name: MED23
  display_name: MED23-related intellectual disability (MRT18)
  classification: molecular
  description: >-
    Caused by biallelic (homozygous or compound heterozygous) variants in MED23, encoding
    a subunit of the tail module of the Mediator complex. Distinguished from other Mediator
    subtypes by prominent movement disorder features (spasticity, dystonia, choreoathetosis),
    autosomal recessive inheritance, and seizures with or without epilepsy. Brain imaging may
    show hypomyelination, pontine hypoplasia, and thin corpus callosum.
  subtype_term:
    preferred_term: Intellectual disability, autosomal recessive 18
    term:
      id: MONDO:0013651
      label: intellectual disability, autosomal recessive 18
  genes:
  - preferred_term: MED23
    term:
      id: hgnc:2372
      label: MED23
  inheritance:
  - name: Autosomal Recessive
  evidence:
  - reference: PMID:36824420
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biallelic loss-of-function variants in MED23 cause a recessive syndromic intellectual disability condition with or without epilepsy (MRT18)."
    explanation: Directly defines MED23-related MRT18 as a recessive syndromic intellectual disability disorder.
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report a missense mutation (p. R617Q) in MED23 that cosegregates with nonsyndromic autosomal recessive intellectual disability."
    explanation: Original human genetic evidence linking MED23 to recessive intellectual disability.

pathophysiology:
- name: Mediator Complex Disruption
  description: >-
    The Mediator complex is a large multi-subunit assembly (~30 subunits in humans) that
    serves as a transcriptional coactivator bridging gene-specific transcription factors
    bound at enhancers and the RNA polymerase II general transcription machinery at
    promoters. Mutations in Mediator subunits disrupt this enhancer-promoter communication,
    leading to dysregulated expression of developmentally critical genes. The complex is
    organized into head, middle, tail, and CDK8 kinase modules, each with distinct
    interaction partners and regulatory functions.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  subtypes:
  - MED13
  - MED13L
  - MED12
  - MED23
  biological_processes:
  - preferred_term: Transcription by RNA polymerase II
    term:
      id: GO:0006366
      label: transcription by RNA polymerase II
    modifier: DECREASED
  - preferred_term: Regulation of gene expression
    term:
      id: GO:0010468
      label: regulation of gene expression
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:37516429
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The Mediator complex (MED) is a large, evolutionarily conserved multiprotein that facilities the interaction between transcription factors and RNA Polymerase II in eukaryotes."
    explanation: Confirms the Mediator complex's role as a bridge between transcription factors and RNA Pol II.
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "MED23 is a subunit of the Mediator complex, a key regulator of protein-coding gene expression."
    explanation: Establishes the Mediator complex as a key regulator of gene expression.
  downstream:
  - target: CDK8 Kinase Module Dysfunction
    description: >-
      Variants in MED12, MED13, and MED13L perturb the dissociable CDK8 kinase
      module, a regulatory submodule of the Mediator complex.
  - target: Tail Module Disruption and Immediate Early Gene Dysregulation
    description: >-
      Variants in MED23 perturb a tail-module arm of Mediator-dependent transcriptional
      regulation.

- name: CDK8 Kinase Module Dysfunction
  description: >-
    MED12, MED13, and MED13L are all components of the CDK8 kinase module, which
    reversibly associates with the core Mediator complex to regulate its activity.
    The CDK8 module has both activating and repressive roles in transcription and
    modulates Wnt, Notch, and other signaling pathways during development. Mutations
    in CDK8 module subunits preferentially affect neural crest-derived structures
    and brain development.
  genes:
  - preferred_term: MED12
    term:
      id: hgnc:11957
      label: MED12
  - preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  - preferred_term: MED13L
    term:
      id: hgnc:22962
      label: MED13L
  subtypes:
  - MED13
  - MED13L
  - MED12
  cell_types:
  - preferred_term: migratory neural crest cell
    term:
      id: CL:0000333
      label: migratory neural crest cell
  biological_processes:
  - preferred_term: Wnt signaling pathway
    term:
      id: GO:0016055
      label: Wnt signaling pathway
    modifier: DYSREGULATED
  - preferred_term: Notch signaling pathway
    term:
      id: GO:0007219
      label: Notch signaling pathway
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MED13 is a component of the CDK8-kinase module that can reversibly bind Mediator, a multi-protein complex that is required for Polymerase II transcription initiation."
    explanation: Confirms MED13's role in the CDK8 kinase module and its relationship to the broader Mediator complex.
  - reference: PMID:37516429
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Interestingly, most of the genomic mutations have been found in the subunits of the kinase module."
    explanation: Confirms that kinase module subunits are disproportionately affected by disease-causing mutations.
  downstream:
  - target: Neurodevelopmental Transcriptional Dysregulation
    description: >-
      CDK8 module dysfunction disrupts Wnt and Notch signaling programs critical
      for neuronal and neural crest cell differentiation.
  - target: Cardiac Developmental Defects
    description: >-
      CKM dysfunction is the main upstream branch for the recurrent cardiac
      developmental defects seen especially in MED13L and MED12, with milder
      involvement in some MED13 cases.

- name: Neurodevelopmental Transcriptional Dysregulation
  description: >-
    Mediator subunit mutations lead to broad transcriptional dysregulation affecting
    genes required for neuronal differentiation, cortical layering, radial migration,
    callosal projection, dendritic arborization, and synaptogenesis. This manifests as
    intellectual disability
    and speech delay across all subtypes, with severity correlating with the degree
    of transcriptional disruption.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  subtypes:
  - MED13
  - MED13L
  - MED12
  - MED23
  biological_processes:
  - preferred_term: Neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DYSREGULATED
  - preferred_term: Neuron projection development
    term:
      id: GO:0031175
      label: neuron projection development
    modifier: DYSREGULATED
  - preferred_term: Dendrite development
    term:
      id: GO:0016358
      label: dendrite development
    modifier: DECREASED
  evidence:
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These findings highlight the crucial role of Mediator in brain development and functioning and suggest that altered IEG expression might be a common molecular hallmark of cognitive deficit."
    explanation: Establishes Mediator's crucial role in brain development and links transcriptional dysregulation to cognitive deficits.
  - reference: PMID:37516429
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Mutations in MED subunits were associated with a wide range of genetic diseases for MED12, MED13, MED13L, MED20, MED23, MED25, and CDK8 genes."
    explanation: Confirms disease-causation for MED12, MED13, MED13L, and MED23 genes in the mediatoropathy spectrum, supporting a shared neurodevelopmental transcriptional dysregulation mechanism.
  - reference: PMID:41663567
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We found that silencing Med13 in cortical neurons impaired its radial migration and contralateral projection as well as dendritic complexity in mice."
    explanation: Directly links Med13 dysfunction to neuronal migration, projection, and dendritic defects in a cortical development model.
  downstream:
  - target: Cortical Neuron Migration and Projection Defects
    description: >-
      In MED13-associated disorder, dysregulated developmental transcription
      programs impair cortical neuron migration, callosal projection, and
      dendritic elaboration.

- name: Cortical Neuron Migration and Projection Defects
  description: >-
    MED13 deficiency disrupts cortical neuron radial migration, contralateral
    projection, and dendritic complexity during corticogenesis. Experimental
    rescue of migration and callosal projection by PLXNA4 overexpression
    suggests that altered axon-guidance and projection programs are a specific
    downstream mechanism within the broader CKM-mediated neurodevelopmental defect.
  genes:
  - preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  subtypes:
  - MED13
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  biological_processes:
  - preferred_term: Neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DYSREGULATED
  - preferred_term: Neuron projection development
    term:
      id: GO:0031175
      label: neuron projection development
    modifier: DYSREGULATED
  - preferred_term: Dendrite development
    term:
      id: GO:0016358
      label: dendrite development
    modifier: DECREASED
  evidence:
  - reference: PMID:41663567
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We found that silencing Med13 in cortical neurons impaired its radial migration and contralateral projection as well as dendritic complexity in mice."
    explanation: Directly supports a MED13-linked cortical migration and projection mechanism.
  - reference: PMID:41663567
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Notably, the impaired radial migration and callosal projection, but not dendritic complexity, were largely restored by overexpression of PlxnA4 in Med13 knock-down neurons."
    explanation: PLXNA4 rescue localizes part of the MED13 mechanism to cortical migration and callosal projection programs.

- name: MED13 Ubiquitination Regulatory Cluster Variants
  description: >-
    A subset of MED13 missense variants in MED13-related intellectual developmental
    disorder (MRD61) cluster at adjacent N-terminal residues p.Thr326 and p.Pro327,
    which are regulatory sites for MED13 ubiquitination and proteasomal degradation.
    Variants at this cluster are predicted to disrupt MED13 protein turnover,
    providing a stability/regulatory loss-of-function mechanism distinct from
    truncating alleles. In the syndrome-defining 13-patient cohort, six of seven
    non-truncating variants clustered at N- or C-terminal hotspots, and the four
    N-terminal variants involved these adjacent ubiquitination-related residues —
    pointing to MED13 protein-turnover dysregulation as a recurrent MRD61 mechanism
    rather than purely structural disruption.
  genes:
  - preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  subtypes:
  - MED13
  biological_processes:
  - preferred_term: MED13 protein ubiquitination
    term:
      id: GO:0016567
      label: protein ubiquitination
    modifier: DYSREGULATED
  - preferred_term: Proteasomal degradation of MED13
    term:
      id: GO:0043161
      label: proteasome-mediated ubiquitin-dependent protein catabolic process
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The four N-terminal clustering mutations affect two adjacent amino acids that are known to be involved in MED13 ubiquitination and degradation, p.Thr326 and p.Pro327."
    explanation: Identifies the p.Thr326/Pro327 ubiquitination-regulatory cluster as a recurrent MED13-variant hotspot in MRD61 patients.
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six affected individuals had mutations that are predicted to truncate the MED13 protein, six had missense mutations, and one had an in-frame-deletion of one amino acid."
    explanation: Establishes that roughly half of MED13 variants in the MRD61 cohort are missense or in-frame, motivating distinct mechanism modeling for residue-specific alleles versus truncating loss-of-function.
  downstream:
  - target: CDK8 Kinase Module Dysfunction
    description: >-
      Disrupted MED13 ubiquitination/degradation regulation alters MED13 protein
      levels within the CDK8 kinase module, contributing to module-wide
      transcriptional regulatory dysfunction in MRD61.

- name: Cardiac Developmental Defects
  description: >-
    Congenital heart defects are a prominent feature of MED13L syndrome and are also
    recurrent in MED12/FG syndrome, with milder involvement in some MED13 cases.
    MED13L is highly expressed in the developing heart, and
    Mediator dysfunction affects transcription factor programs (e.g., NKX2-5, GATA4,
    TBX5) required for cardiac septation, outflow tract development, and valve
    formation. Cardiac phenotypes range from patent foramen ovale to septal defects
    and transposition of the great arteries.
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  subtypes:
  - MED13
  - MED13L
  - MED12
  locations:
  - preferred_term: heart
    term:
      id: UBERON:0000948
      label: heart
  biological_processes:
  - preferred_term: Heart morphogenesis
    term:
      id: GO:0003007
      label: heart morphogenesis
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
    explanation: Documents congenital heart defects in 20-50% of MED13L haploinsufficiency patients with reduced penetrance.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distal limb and/or digit anomalies, ocular manifestations and vision issues, and congenital heart defects have been reported."
    explanation: GeneReviews confirms congenital heart defects as a reported feature of MED13L syndrome.
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."
    explanation: Documents congenital cardiac anomalies in the majority of MED12-confirmed FG syndrome patients.

- name: Tail Module Disruption and Immediate Early Gene Dysregulation
  description: >-
    MED23, a subunit of the Mediator tail module, specifically interacts with
    transcription factors such as ELK1 and other ETS-family activators. Loss of MED23
    function disrupts the activation of immediate early genes (IEGs) including JUN and
    FOS, which are critical for synaptic plasticity and neuronal activity-dependent
    gene expression. This mechanism underlies the distinct movement disorder phenotype
    (spasticity, dystonia, choreoathetosis) seen in MED23-related intellectual disability.
  genes:
  - preferred_term: MED23
    term:
      id: hgnc:2372
      label: MED23
  subtypes:
  - MED23
  biological_processes:
  - preferred_term: Immediate-early gene transcription
    term:
      id: GO:0006355
      label: regulation of DNA-templated transcription
    modifier: DECREASED
  evidence:
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This mutation specifically impaired the response of JUN and FOS immediate early genes (IEGs) to serum mitogens by altering the interaction between enhancer-bound transcription factors (TCF4 and ELK1, respectively) and Mediator."
    explanation: Demonstrates that the MED23 p.R617Q mutation specifically disrupts IEG activation through altered ELK1-Mediator interaction.
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Transcriptional dysregulation of these genes was also observed in cells derived from patients presenting with other neurological disorders linked to mutations in other Mediator subunits or proteins interacting with MED."
    explanation: Suggests IEG dysregulation may be a common molecular hallmark across Mediator subunit disorders.
  downstream:
  - target: Neurodevelopmental Transcriptional Dysregulation
    description: >-
      Tail-module dysfunction converges on impaired neuronal gene-expression programs,
      including immediate-early gene responses.

phenotypes:
# === SHARED PHENOTYPES (all or most subtypes) ===
- category: Neurologic
  name: Intellectual Disability
  description: >-
    Universal across all Mediator complex subtypes but with variable severity.
    Ranges from mild (MED13) to profound (some MED13L cases), with moderate to
    severe in MED12 and variable in MED23.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had intellectual disability and/or developmental delays, including speech delays or disorders."
    explanation: Confirms universal ID/DD in the MED13 cohort of 13 patients.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MED13L syndrome is characterized by mild-to-profound developmental delay, intellectual disability, and hypotonia."
    explanation: GeneReviews confirms the full severity spectrum of ID in MED13L syndrome.
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report a missense mutation (p. R617Q) in MED23 that cosegregates with nonsyndromic autosomal recessive intellectual disability."
    explanation: Cosegregation in a human family establishes the causal link between MED23 mutation and intellectual disability.
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    notes: >-
      Intellectual disability severity is variable in MED13-related disorder,
      with current reports ranging from mild to severe.
    evidence:
    - reference: PMID:36087421
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Mutations in the MED13 gene are reported in the literature in association with clinically variable, neurodevelopmental disorders, which are characterized by mild-to-severe intellectual disability, autism spectrum disorder, attention deficit/hyperactivity disorder, epilepsy, ocular or skeletal abnormalities, congenital cardiac defects, and facial dysmorphisms."
      explanation: Supports a variable MED13 intellectual disability severity spectrum rather than a single fixed severity band.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    notes: >-
      MED13L syndrome spans a wide severity range from mild to profound
      developmental delay and intellectual disability.
    evidence:
    - reference: PMID:40228085
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "MED13L syndrome is characterized by mild-to-profound developmental delay, intellectual disability, and hypotonia."
      explanation: Supports the broad severity range of intellectual disability in MED13L syndrome.
  - subtype: MED12
    genetic_context:
      gene:
        preferred_term: MED12
        term:
          id: hgnc:11957
          label: MED12
    notes: >-
      FG syndrome cognitive impairment is variable from borderline to severe,
      although all mutation-confirmed individuals have cognitive disability.
    evidence:
    - reference: PMID:19938245
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The degree of intellectual disability is variable from borderline to severe."
      explanation: Supports a variable but consistently abnormal intellectual phenotype in MED12-confirmed FG syndrome.
  - subtype: MED23
    genetic_context:
      gene:
        preferred_term: MED23
        term:
          id: hgnc:2372
          label: MED23
    notes: >-
      MED23-related intellectual disability is variable from mild to severe.
    evidence:
    - reference: PMID:30847200
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."
      explanation: Supports a variable MED23 cognitive severity spectrum.

- category: Neurologic
  name: Speech and Language Delay
  description: >-
    Speech delay is a hallmark feature across all Mediator complex subtypes.
    Expressive language is disproportionately affected in MED13. Poor speech
    acquisition is characteristic of MED13L syndrome. Communicative deficits
    are prominent in MED12/FG syndrome.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had intellectual disability and/or developmental delays, including speech delays or disorders."
    explanation: Confirms speech delays or disorders in all 13 MED13 patients in the cohort.
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."
    explanation: Documents severe speech delay in the majority of MED13L patients.

- category: Behavioral
  name: Autism Spectrum Disorder
  description: >-
    ASD features are reported in MED13 and MED13L subtypes. Evidence is weaker
    for MED12, and ASD is not currently established as part of the MED23 core phenotype.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Autism spectrum disorder
    term:
      id: HP:0000729
      label: Autistic behavior
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
    explanation: Documents ASD and ADHD as recurrent features in MED13 patients.
  - reference: PMID:33258286
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is characterized by variable intellectual disability and/or developmental delays, especially in language. Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), eye or vision problems, hypotonia, mild congenital hearth abnormalities and dysmorphisms have been described among individuals with MED13 mutations."
    explanation: Confirms ASD and ADHD as part of the MED13 phenotypic spectrum.
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    frequency: OCCASIONAL
    notes: ASD is a recurrent but non-universal behavioral feature in MED13 patients.
    evidence:
    - reference: PMID:29740699
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
      explanation: Two or more affected individuals in the syndrome-defining MED13 cohort support ASD as an occasional feature.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: FREQUENT
    notes: Autistic features are part of the MED13L neurobehavioral spectrum.
    evidence:
    - reference: PMID:28645799
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
      explanation: Supports autistic features as a recurrent MED13L finding; the reported 20-50% range overlaps the FREQUENT band and is described as a common sign.

- category: Behavioral
  name: Attention Deficit-Hyperactivity Disorder
  description: >-
    ADHD and hyperactivity are common behavioral features in MED13 and MED12 subtypes.
    Restlessness and hyperactivity are also reported in MED13L syndrome.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Attention deficit hyperactivity disorder
    term:
      id: HP:0007018
      label: Attention deficit hyperactivity disorder
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
    explanation: Documents ADHD as a recurrent feature reported in two or more MED13 patients.
  - reference: PMID:33258286
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is characterized by variable intellectual disability and/or developmental delays, especially in language. Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), eye or vision problems, hypotonia, mild congenital hearth abnormalities and dysmorphisms have been described among individuals with MED13 mutations."
    explanation: Confirms ADHD as part of the MED13 phenotypic spectrum.

- category: Neurologic
  name: Hypotonia
  description: >-
    Muscular hypotonia is common in MED13L and MED12, reported in MED23, and can
    occur in a subset of MED13 cases. Congenital hypotonia is a hallmark of FG syndrome (MED12).
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    frequency: OCCASIONAL
    notes: Hypotonia is recurrent but not universal in MED13/MRD61.
    evidence:
    - reference: PMID:29740699
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
      explanation: Supports hypotonia as a recurrent but non-core MED13 phenotype.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: FREQUENT
    notes: Hypotonia is a common feature of MED13L syndrome.
    evidence:
    - reference: PMID:28645799
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."
      explanation: Author wording "majority" maps to FREQUENT for MED13L hypotonia.
  - subtype: MED12
    genetic_context:
      gene:
        preferred_term: MED12
        term:
          id: hgnc:11957
          label: MED12
    frequency: VERY_FREQUENT
    notes: Congenital hypotonia is a cardinal feature of FG syndrome.
    evidence:
    - reference: PMID:19938245
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Congenital hypotonia and poor gastrointestinal function, including feeding difficulties that required medical or occupational/ physical therapy, poor oral motor function, decreased gastric motility, reflux, and chronic constipation, are characteristic of FG syndrome and were present in all affected individuals."
      explanation: Supports VERY_FREQUENT hypotonia in mutation-confirmed FG syndrome.
  - subtype: MED23
    genetic_context:
      gene:
        preferred_term: MED23
        term:
          id: hgnc:2372
          label: MED23
    frequency: FREQUENT
    notes: Axial hypotonia reported in MED23 patients.
    evidence:
    - reference: PMID:30847200
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."
      explanation: Supports hypotonia as a recurrent feature of MED23-related disorder.
  evidence:
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MED13L syndrome is characterized by mild-to-profound developmental delay, intellectual disability, and hypotonia."
    explanation: GeneReviews confirms hypotonia as a defining feature of MED13L syndrome.
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
    explanation: Documents hypotonia as a recurrent feature in the MED13 cohort.

- category: Neurologic
  name: Seizures
  description: >-
    Seizures and epilepsy occur in MED13L and MED23 subtypes and can also emerge
    in more severe MED13 presentations. MED23-related intellectual disability is
    formally designated "with or without epilepsy."
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    frequency: OCCASIONAL
    notes: Epilepsy appears to be an uncommon but established severe manifestation of MED13-related disorder.
    evidence:
    - reference: PMID:36087421
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "From a literature review, it emerged that epilepsy is described in only one out of nineteen of previously reported patients with a phenotype of generalized, drug-resistant epilepsy with myoclonic-atonic seizures."
      explanation: Supports epilepsy as an occasional rather than excluded MED13 phenotype.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: OCCASIONAL
    notes: Seizures reported in a subset of MED13L patients.
    evidence:
    - reference: PMID:28645799
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
      explanation: The reported 20-50% range overlaps OCCASIONAL and FREQUENT; OCCASIONAL is used conservatively for subtype-specific seizure frequency.
  - subtype: MED12
    genetic_context:
      gene:
        preferred_term: MED12
        term:
          id: hgnc:11957
          label: MED12
    frequency: OCCASIONAL
    notes: Seizures are not a core FG syndrome feature but are reported in some MED12-confirmed individuals.
    evidence:
    - reference: PMID:19938245
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Febrile seizures, from the age of 3 years, were followed by afebrile seizures."
      explanation: Supports seizure occurrence in at least one MED12-confirmed individual, so seizures should not be excluded from the subtype.
    - reference: PMID:19938245
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Myoclonic seizures, diagnosed at 37 years of age, are worse with stress, fatigue, or cold."
      explanation: A second mutation-confirmed FG syndrome individual with seizures supports an occasional rather than excluded MED12 seizure phenotype.
  - subtype: MED23
    genetic_context:
      gene:
        preferred_term: MED23
        term:
          id: hgnc:2372
          label: MED23
    frequency: OCCASIONAL
    notes: Epilepsy is a variable feature; OMIM designation includes "with or without epilepsy."
    evidence:
    - reference: PMID:36824420
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Besides global developmental delay, axial hypotonia and peripheral increased muscular tone, absent speech, and generalized tonic seizures, which fit well MRT18, the occurrence of postnatal progressive microcephaly has been here documented."
      explanation: Supports seizure occurrence in MED23-related disorder, while the syndrome remains explicitly variable for epilepsy.
  evidence:
  - reference: PMID:36087421
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in the MED13 gene are reported in the literature in association with clinically variable, neurodevelopmental disorders, which are characterized by mild-to-severe intellectual disability, autism spectrum disorder, attention deficit/hyperactivity disorder, epilepsy, ocular or skeletal abnormalities, congenital cardiac defects, and facial dysmorphisms."
    explanation: Documents epilepsy as part of the MED13-related neurodevelopmental phenotype spectrum.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other reported features include seizures and/or hearing impairment."
    explanation: GeneReviews confirms seizures as a reported feature of MED13L syndrome.

- category: Audiologic
  name: Hearing Impairment
  description: >-
    Hearing impairment is reported in MED13L syndrome and in a subset of more
    severely affected MED13 patients.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    frequency: OCCASIONAL
    notes: Hearing involvement is part of the expanded MED13 phenotype but is not universal.
    evidence:
    - reference: PMID:36087421
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Microcephaly, developmental delay, hypotonia, corpus callosum abnormalities, deafness, and retinal atrophy were common features in the previously described cases."
      explanation: Supports established hearing involvement in previously reported MED13 patients while not implying obligate occurrence across the whole subtype.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: OCCASIONAL
    notes: Hearing impairment is a reported but non-core MED13L feature.
    evidence:
    - reference: PMID:40228085
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Other reported features include seizures and/or hearing impairment."
      explanation: GeneReviews directly supports hearing impairment as part of the MED13L phenotype spectrum.
  evidence:
  - reference: PMID:36087421
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Microcephaly, developmental delay, hypotonia, corpus callosum abnormalities, deafness, and retinal atrophy were common features in the previously described cases."
    explanation: Documents hearing involvement in the expanded MED13 phenotype.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other reported features include seizures and/or hearing impairment."
    explanation: Documents hearing impairment as a reported MED13L feature.

# === BRAIN STRUCTURAL ANOMALIES ===
- category: Neurologic
  name: Corpus Callosum Anomalies
  description: >-
    Structural anomalies of the corpus callosum (thinning, hypoplasia, or agenesis)
    are seen in MED13L, MED12, and MED23 subtypes and have also been reported in
    MED13-related disorder, reflecting the role of Mediator complex in transcriptional
    programs governing midline brain development.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Abnormality of the corpus callosum
    term:
      id: HP:0001273
      label: Abnormal corpus callosum morphology
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    frequency: OCCASIONAL
    notes: Corpus callosum anomalies are not universal in MED13 but are part of the expanded reported spectrum.
    evidence:
    - reference: PMID:36087421
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Microcephaly, developmental delay, hypotonia, corpus callosum abnormalities, deafness, and retinal atrophy were common features in the previously described cases."
      explanation: Literature review supports corpus callosum abnormalities as a recurrent MED13 finding.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: OCCASIONAL
    notes: Thin or absent corpus callosum on brain imaging.
    evidence:
    - reference: PMID:28645799
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
      explanation: The reported 20-50% range overlaps OCCASIONAL and FREQUENT; OCCASIONAL is used conservatively for subtype-specific corpus callosum anomalies.
  - subtype: MED12
    genetic_context:
      gene:
        preferred_term: MED12
        term:
          id: hgnc:11957
          label: MED12
    frequency: OBLIGATE
    notes: Agenesis or hypoplasia of the corpus callosum is a cardinal feature of FG syndrome.
    evidence:
    - reference: PMID:19938245
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."
      explanation: 13/13 mutation-confirmed individuals places corpus callosum anomalies in the OBLIGATE band for the characterized FG syndrome cohort.
  - subtype: MED23
    genetic_context:
      gene:
        preferred_term: MED23
        term:
          id: hgnc:2372
          label: MED23
    frequency: OCCASIONAL
    notes: Thin corpus callosum reported in some patients.
    evidence:
    - reference: PMID:30847200
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The MRI of the brain may be normal or it may show temporal lobe hypomyelination, delayed myelination, pontine hypoplasia, and thin corpus callosum."
      explanation: Supports occasional corpus callosum anomalies in MED23-related disorder.
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
    explanation: Documents abnormal corpus callosum as a common MRI finding in 20-50% of MED13L patients.
  - reference: PMID:38745205
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "He presented with congenital heart anomalies, dysmorphic features, hydrocephalic changes, hypoplastic corpus callosum, bilateral optic nerve atrophy, optic chiasm atrophy, brain stem atrophy, and overall a more severe condition compared to previously described patients."
    explanation: Reports hypoplastic corpus callosum in a MED13 patient with severe phenotype, expanding the corpus callosum anomaly finding to MED13.

- category: Neurologic
  name: White Matter Abnormalities
  description: >-
    Delayed myelination and white matter abnormalities on brain MRI are reported
    in MED13L and MED23 subtypes. MED23 patients may show temporal lobe
    hypomyelination and pontine hypoplasia.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Abnormality of the white matter
    term:
      id: HP:0002500
      label: Abnormal cerebral white matter morphology
  phenotype_contexts:
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: OCCASIONAL
    notes: Delayed or absent myelination, periventricular and subcortical white matter abnormalities.
    evidence:
    - reference: PMID:28645799
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
      explanation: Supports white matter/myelination abnormalities as a recurrent but non-universal MED13L imaging finding.
  - subtype: MED23
    genetic_context:
      gene:
        preferred_term: MED23
        term:
          id: hgnc:2372
          label: MED23
    frequency: OCCASIONAL
    notes: Temporal lobe hypomyelination and pontine hypoplasia.
    evidence:
    - reference: PMID:30847200
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The MRI of the brain may be normal or it may show temporal lobe hypomyelination, delayed myelination, pontine hypoplasia, and thin corpus callosum."
      explanation: Supports occasional white matter abnormalities in MED23-related disorder.
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "abnormal MRI findings of myelination defects and abnormal corpus callosum"
    explanation: Confirms myelination defects as a common MRI finding in MED13L haploinsufficiency patients.
  - reference: PMID:30847200
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The MRI of the brain may be normal or it may show temporal lobe hypomyelination, delayed myelination, pontine hypoplasia, and thin corpus callosum."
    explanation: Literature review documents white matter abnormalities in MED23-related disorder.

# === MED13-SPECIFIC PHENOTYPES ===
- category: Growth
  name: Poor Overall Growth
  description: >-
    MED13/MRD61 patients show poor overall growth, which is not a prominent
    feature of other Mediator subtypes.
  frequency: FREQUENT
  subtype: MED13
  phenotype_term:
    preferred_term: Growth delay
    term:
      id: HP:0001510
      label: Growth delay
  evidence:
  - reference: PMID:41195223
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main symptoms are intellectual disability (ID) of varying degrees, developmental delay (DD), hypotonia during infancy, facial dysmorphism, language impairment, restricted growth, skeletal and limb abnormalities, and behavioral abnormalities."
    explanation: Literature review of 26 MRD61 cases explicitly lists restricted growth as a main symptom of MED13-related disorder.

- category: Skeletal
  name: Skeletal Abnormalities
  description: >-
    Skeletal and limb abnormalities are part of the broader MED13/MRD61
    phenotype, although the exact manifestations are variable across reported cases.
  subtype: MED13
  phenotype_term:
    preferred_term: Abnormality of the skeletal system
    term:
      id: HP:0000924
      label: Abnormality of the skeletal system
  evidence:
  - reference: PMID:41195223
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main symptoms are intellectual disability (ID) of varying degrees, developmental delay (DD), hypotonia during infancy, facial dysmorphism, language impairment, restricted growth, skeletal and limb abnormalities, and behavioral abnormalities."
    explanation: Review of 26 MRD61 cases supports skeletal involvement as part of the MED13 clinical spectrum.

- category: Gastrointestinal
  name: Obstipation
  description: >-
    Chronic constipation (obstipation) is reported in MED13/MRD61 patients.
    This overlaps with the constipation and anal anomalies seen in MED12/FG syndrome.
  frequency: OCCASIONAL
  subtype: MED13
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  evidence:
  - reference: PMID:41195223
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the proband presented with congenital megacolon, a previously unreported complication."
    explanation: Documents congenital megacolon in a MED13 patient. Described as a previously unreported complication, suggesting this is an occasional rather than frequent feature.

- category: Ophthalmologic
  name: Ocular Anomalies
  description: >-
    Ocular anomalies are variably reported in MED13/MRD61 patients.
  frequency: OCCASIONAL
  subtype: MED13
  phenotype_term:
    preferred_term: Abnormality of the eye
    term:
      id: HP:0000478
      label: Abnormality of the eye
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
    explanation: Optic nerve abnormalities and Duane anomaly are recurrent ocular features in MED13 patients.

- category: Craniofacial
  name: Facial Dysmorphism (MED13)
  description: >-
    Facial dysmorphism is a recurrent feature of MED13/MRD61, listed among the
    main symptoms of the disorder in the published case-series literature. The
    pattern is generally less distinctive than the MED13L gestalt and is
    described in qualitative terms in the available abstracts.
  subtype: MED13
  phenotype_term:
    preferred_term: Abnormality of facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:41195223
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main symptoms are intellectual disability (ID) of varying degrees, developmental delay (DD), hypotonia during infancy, facial dysmorphism, language impairment, restricted growth, skeletal and limb abnormalities, and behavioral abnormalities."
    explanation: 2025 review of 26 MRD61 cases lists facial dysmorphism among the main symptoms of MED13-related disorder.
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
    explanation: Dysmorphisms are reported in two or more patients in the syndrome-defining 13-patient MED13 cohort.

# === MED13L-SPECIFIC PHENOTYPES ===
- category: Craniofacial
  name: Distinctive Facial Dysmorphism (MED13L)
  description: >-
    MED13L syndrome is characterized by a distinctive facial gestalt including
    depressed nasal bridge, bulbous nasal tip, straight eyebrows, upslanting
    palpebral fissures, full cheeks, open mouth appearance, and macrostomia.
    These features become more pronounced with age.
  frequency: VERY_FREQUENT
  subtype: MED13L
  phenotype_term:
    preferred_term: Abnormality of facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the majority of patients were reported to show broad/prominent forehead, low set ears, bitemporal narrowing, upslanting palpebral fissures, depressed/flat nasal bridge, bulbous nose, and abnormal chin, but macroglossia and horizontal eyebrows were also observed in ∼30%."
    explanation: Detailed description of the MED13L facial gestalt from a genotype-phenotype review.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dysmorphic facial features, including depressed nasal bridge, bulbous nose, and hypotonic open mouth, are present in most individuals."
    explanation: GeneReviews confirms distinctive facial features are present in most MED13L patients.

- category: Neurologic
  name: Ataxia and Coordination Problems
  description: >-
    Ataxia and impaired coordination are recurrent but non-universal neurologic
    findings in MED13L syndrome.
  frequency: OCCASIONAL
  subtype: MED13L
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients."
    explanation: Supports ataxia and coordination problems as established but non-universal MED13L findings.

- category: Cardiovascular
  name: Congenital Heart Defects
  description: >-
    Congenital heart defects with variable penetrance are characteristic of
    MED13L syndrome, ranging from patent foramen ovale to atrial and ventricular
    septal defects to transposition of the great arteries. Congenital cardiac
    anomalies are also recurrent in MED12/FG syndrome and occur occasionally in
    MED13- and MED23-related disorder.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Congenital heart defect
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  phenotype_contexts:
  - subtype: MED13
    genetic_context:
      gene:
        preferred_term: MED13
        term:
          id: hgnc:22474
          label: MED13
    frequency: OCCASIONAL
    notes: Mild congenital heart abnormalities are reported in a subset of MED13 patients.
    evidence:
    - reference: PMID:29740699
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms."
      explanation: Supports occasional congenital heart involvement in MED13.
  - subtype: MED13L
    genetic_context:
      gene:
        preferred_term: MED13L
        term:
          id: hgnc:22962
          label: MED13L
    frequency: OCCASIONAL
    notes: >-
      Variable penetrance. Ranges from patent foramen ovale to ASD, VSD,
      and transposition of the great arteries.
    evidence:
    - reference: PMID:28645799
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "showed reduced penetrance for congenital heart defects"
      explanation: Supports non-universal congenital heart involvement in MED13L syndrome; OCCASIONAL is used conservatively for the subtype context.
  - subtype: MED12
    genetic_context:
      gene:
        preferred_term: MED12
        term:
          id: hgnc:11957
          label: MED12
    frequency: FREQUENT
    notes: Congenital cardiac anomalies are a recurrent part of the MED12/FG syndrome phenotype.
    evidence:
    - reference: PMID:19938245
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."
      explanation: Supports frequent congenital heart defects in MED12-confirmed FG syndrome.
  - subtype: MED23
    genetic_context:
      gene:
        preferred_term: MED23
        term:
          id: hgnc:2372
          label: MED23
    frequency: OCCASIONAL
    notes: Congenital heart disease reported in some patients.
    evidence:
    - reference: PMID:30847200
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The patients had severe ID, spasticity, congenital heart diseases, brain abnormalities, and atypical electroencephalography."
      explanation: Supports occasional congenital heart disease in previously reported MED23 cases.
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "showed reduced penetrance for congenital heart defects"
    explanation: Documents reduced penetrance for congenital heart defects in MED13L syndrome from genotype-phenotype review.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distal limb and/or digit anomalies, ocular manifestations and vision issues, and congenital heart defects have been reported."
    explanation: GeneReviews confirms congenital heart defects as a feature of MED13L syndrome.
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."
    explanation: Demonstrates that congenital heart defects are also a frequent feature of MED12-confirmed FG syndrome.

# === MED12-SPECIFIC PHENOTYPES ===
- category: Craniofacial
  name: Relative Macrocephaly
  description: >-
    Relative or absolute macrocephaly is a characteristic feature of FG syndrome
    (MED12), distinguishing it from other Mediator subtypes. MED23 patients may
    conversely show microcephaly.
  frequency: VERY_FREQUENT
  subtype: MED12
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  evidence:
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ten had macrocephaly (five absolute, five relative)."
    explanation: Quantifies macrocephaly in the MED12 p.R961W-confirmed FG syndrome cohort, with both absolute and relative forms.

- category: Gastrointestinal
  name: Imperforate Anus and Anal Anomalies
  description: >-
    Imperforate anus or other anal anomalies are a distinctive feature of FG
    syndrome (MED12), present in the original family described by Opitz and
    Kaveggia in 1974. Constipation without structural anomaly is common.
  frequency: FREQUENT
  subtype: MED12
  phenotype_term:
    preferred_term: Imperforate anus
    term:
      id: HP:0002023
      label: Anal atresia
  evidence:
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most characteristic anomalies were agenesis or hypoplasia of the corpus callosum (13 of 13), anal fistula, stenosis and atresia (11 of 19), and congenital cardiac anomalies (11 of 18)."
    explanation: Anal anomalies (fistula, stenosis, atresia) documented in 11 of 19 MED12-confirmed FG syndrome patients, making it the second most common congenital anomaly after corpus callosum abnormalities.

- category: Skeletal
  name: Broad Thumbs and Halluces
  description: >-
    Broad thumbs and great toes are characteristic skeletal features of FG syndrome (MED12).
  frequency: FREQUENT
  subtype: MED12
  phenotype_term:
    preferred_term: Broad thumb
    term:
      id: HP:0011304
      label: Broad thumb
  evidence:
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His thumbs and great toes are wide and flat."
    explanation: Broad thumbs and great toes documented in FG syndrome patients with confirmed MED12 p.R961W mutation.

- category: Craniofacial
  name: Characteristic Facial Features (MED12)
  description: >-
    FG syndrome features include tall forehead, downslanting palpebral fissures,
    and small simple ears. These are distinct from the facial gestalt of MED13L syndrome.
  frequency: VERY_FREQUENT
  subtype: MED12
  phenotype_term:
    preferred_term: Abnormality of facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These features were seen most often in affected male patients: characteristic facies (13 of 13), an affable personality (13 of 13)"
    explanation: Characteristic facial features were present in all 13 MED12-confirmed FG syndrome patients, making it the most consistent feature.
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "He had hypertelorism, a high forehead, upswept frontal hair, and small cup-shaped ears (for which he has had surgery), wide mouth, full lips, broad palate, and broad neck."
    explanation: Detailed description of FG syndrome facial features including tall forehead and small ears.

# === MED23-SPECIFIC PHENOTYPES ===
- category: Neurologic
  name: Absent Speech
  description: >-
    Some MED23 patients have no spoken language, representing a severe end of the
    communication phenotype beyond simple speech delay.
  frequency: OCCASIONAL
  subtype: MED23
  phenotype_term:
    preferred_term: Absent speech
    term:
      id: HP:0001344
      label: Absent speech
  evidence:
  - reference: PMID:36824420
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Besides global developmental delay, axial hypotonia and peripheral increased muscular tone, absent speech, and generalized tonic seizures, which fit well MRT18, the occurrence of postnatal progressive microcephaly has been here documented."
    explanation: Directly supports complete absence of speech in at least a subset of MED23-related disorder.

- category: Neurologic
  name: Spasticity
  description: >-
    Spasticity is a distinguishing feature of MED23-related intellectual disability,
    not typically seen in other Mediator subtypes.
  frequency: FREQUENT
  subtype: MED23
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:30847200
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."
    explanation: Literature review of MED23 patients documents spasticity as a characteristic clinical feature.
  - reference: PMID:30847200
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the patient manifested clinical symptoms similar to previously described cases, including developmental delay, microcephaly, hypotonia, severe intellectual disability, and spasticity."
    explanation: Direct clinical documentation of spasticity in a MED23 patient with confirmed homozygous variant.

- category: Neurologic
  name: Dystonia and Choreoathetosis
  description: >-
    Movement disorder features including dystonia and choreoathetosis are characteristic
    of MED23-related intellectual disability, reflecting disruption of immediate early
    gene-mediated transcriptional programs in motor circuits.
  frequency: FREQUENT
  subtype: MED23
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  evidence:
  - reference: PMID:30847200
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected patients manifest with axial hypotonia, choreoathetosis, dystonia, Global Developmental Delay (GDD), mental retardation, microcephaly, mild to severe ID, spasticity, with or without seizure."
    explanation: Literature review of MED23 patients documents dystonia and choreoathetosis as characteristic movement disorder features.

- category: Craniofacial
  name: Microcephaly
  description: >-
    Microcephaly is reported in some MED23 patients, contrasting with the
    macrocephaly seen in MED12/FG syndrome.
  frequency: OCCASIONAL
  subtype: MED23
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:36824420
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A retrospective assessment of the previously reported clinical data for these subjects confirms the occurrence of postnatal progressive microcephaly as a previously unappreciated feature of the phenotype of MED23-related disorder."
    explanation: Establishes postnatal progressive microcephaly as a feature of MED23-related disorder.
  - reference: PMID:30847200
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the patient manifested clinical symptoms similar to previously described cases, including developmental delay, microcephaly, hypotonia, severe intellectual disability, and spasticity."
    explanation: Confirms microcephaly as part of the MED23 clinical spectrum.

genetic:
- name: MED13 Haploinsufficiency
  association: Causative
  gene_term:
    preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  inheritance:
  - name: Autosomal Dominant
  subtype: MED13
  features: Heterozygous loss-of-function variants (nonsense, frameshift, missense, in-frame deletion); most de novo
  notes: >-
    MED13 encodes mediator complex subunit 13, a component of the CDK8 kinase module.
    The original syndrome-defining cohort included 13 affected individuals with 3
    nonsense, 2 frameshift, 6 missense, and 1 in-frame deletion variants; by 2025,
    at least 26 MRD61 cases had been reported.
  evidence:
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we describe a GeneMatcher collaboration which led to a cohort of 13 affected individuals harboring protein-altering variants, 11 of which are de novo, in MED13; the only inherited variant was transmitted to an affected child from an affected mother."
    explanation: Landmark paper establishing MED13 as a neurodevelopmental disease gene with predominantly de novo variants.
  - reference: PMID:29740699
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six affected individuals had mutations that are predicted to truncate the MED13 protein, six had missense mutations, and one had an in-frame-deletion of one amino acid."
    explanation: Details the variant spectrum in the original MED13 cohort.

- name: MED13L Haploinsufficiency
  association: Causative
  gene_term:
    preferred_term: MED13L
    term:
      id: hgnc:22962
      label: MED13L
  inheritance:
  - name: Autosomal Dominant
  subtype: MED13L
  features: Heterozygous loss-of-function and missense variants; whole-gene deletions; most de novo
  notes: >-
    MED13L is a paralog of MED13, also in the CDK8 kinase module. Recurrent missense
    variant p.Asp860Gly has been documented, and newer functional work supports
    pathogenic missense effects through reduced protein stability and impaired
    interaction with the CDK8 kinase module. Over 100 cases reported.
  evidence:
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority."
    explanation: Comprehensive genotype-phenotype review of MED13L haploinsufficiency patients.
  - reference: PMID:28645799
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the second patient shows, for the first time, recurrence of a MED13L missense mutation (p.(Asp860Gly))."
    explanation: Documents recurrent missense mutations in MED13L, supporting functional significance.
  - reference: PMID:40228085
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The majority of probands reported to date whose parents have undergone molecular genetic testing have the disorder as the result of a pathogenic variant that occurred as a de novo event in the proband."
    explanation: Supports the statement that most MED13L pathogenic variants arise de novo.
  - reference: PMID:40500968
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "3D protein modeling suggested that these missense variants may disrupt MED13L's interaction with the CDK8 kinase module, leading to functional deficits."
    explanation: Provides gene-specific mechanistic evidence that pathogenic MED13L missense variants can perturb CKM interactions.

- name: MED12 Hemizygous Variants
  association: Causative
  gene_term:
    preferred_term: MED12
    term:
      id: hgnc:11957
      label: MED12
  inheritance:
  - name: X-linked Recessive
  subtype: MED12
  features: Hemizygous missense variants; recurrent p.R961W causes FG syndrome type 1; p.N1007S causes Lujan-Fryns syndrome
  notes: >-
    MED12 is on the X chromosome. FG syndrome type 1 (Opitz-Kaveggia syndrome) is
    caused by the recurrent p.R961W missense variant in the opa repeat domain.
    MED12 is also allelic with Lujan syndrome through p.N1007S and likely other
    X-linked intellectual disability presentations.
  evidence:
  - reference: PMID:19938245
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We ascertained 23 males with the p.R961W mutation in MED12 from 9 previously reported FG syndrome families and 1 new family."
    explanation: Largest clinical characterization of MED12 p.R961W-confirmed FG syndrome patients.
  - reference: PMID:17369503
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The original Lujan syndrome family has a novel missense mutation (p.N1007S) in the MED12 gene."
    explanation: Directly supports the allelic MED12-Lujan syndrome relationship already noted in the variant summary.

- name: MED23 Biallelic Variants
  association: Causative
  gene_term:
    preferred_term: MED23
    term:
      id: hgnc:2372
      label: MED23
  inheritance:
  - name: Autosomal Recessive
  subtype: MED23
  features: Homozygous or compound heterozygous variants; founder p.R617Q disrupts ELK1 interaction
  notes: >-
    MED23 is in the tail module of the Mediator complex. The first reported variant
    (p.R617Q) specifically disrupts interaction with the ETS-family transcription factor
    ELK1, impairing immediate early gene activation. Fewer than 20 families reported.
  evidence:
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report a missense mutation (p. R617Q) in MED23 that cosegregates with nonsyndromic autosomal recessive intellectual disability."
    explanation: Original discovery of MED23 as a cause of autosomal recessive intellectual disability via cosegregation in a human family.
  - reference: PMID:21868677
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These findings highlight the crucial role of Mediator in brain development and functioning and suggest that altered IEG expression might be a common molecular hallmark of cognitive deficit."
    explanation: Establishes the molecular mechanism linking MED23 to intellectual disability via IEG dysregulation.
  - reference: PMID:36824420
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report a 5-year-old girl with compound heterozygous for two additional MED23 variants."
    explanation: Adds direct human evidence that MED23-related disorder can also arise through compound heterozygous biallelic variation.

datasets:
- accession: "geo:GSE277054"
  title: MED13L knockout mouse cortical neurogenesis single-cell and bulk RNA-seq
  description: >-
    Single-cell transcriptomics and bulk RNA-seq from Med13l knockout and heterozygous
    mouse embryonic cortex. Homozygous knockouts exhibit neonatal lethality with severe
    cortical neurogenesis deficits driven by impaired neural progenitor differentiation.
    Heterozygous mice show microcephaly with simplified neuronal morphology. Multi-omics
    analyses reveal MED13L orchestrates neurogenesis by transcriptional priming of key
    developmental genes (Neurod2, Sox5, Auts2, Nfib).
  organism:
    preferred_term: mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  data_type: SINGLE_CELL_RNA_SEQ
  sample_count: 12
  sample_types:
  - preferred_term: embryonic cerebral cortex
    tissue_term:
      preferred_term: cerebral cortex
      term:
        id: UBERON:0000956
        label: cerebral cortex
  conditions:
  - Med13l homozygous knockout
  - Med13l heterozygous knockout
  - wild-type control
  genes:
  - preferred_term: MED13L
    term:
      id: hgnc:22962
      label: MED13L
  publication: PMID:40775066
  findings:
  - statement: MED13L primes transcriptional activation of Neurod2, Sox5, Auts2, and Nfib during cortical neurogenesis
  - statement: Homozygous Med13l knockout shows severe cortical neurogenesis deficits due to impaired neural progenitor differentiation
  - statement: Heterozygous Med13l mice recapitulate MED13L syndrome behavioral phenotype including impaired learning and motor coordination
  evidence:
  - reference: PMID:40775066
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Single-cell transcriptomics and immunofluorescence reveal severe cortical neurogenesis deficits in Med13l knockout embryos, driven by impaired neural progenitor differentiation."
    explanation: scRNA-seq directly demonstrates cortical neurogenesis deficits in Med13l knockout providing mechanistic insight into MED13L syndrome.

- accession: "geo:GSE298801"
  title: Cardiomyocyte-specific Med13/Med13L double knockout RNA-seq
  description: >-
    Bulk RNA-seq from adult murine cardiomyocytes after inducible knockout of Med13
    and Med13L. Double knockout results in lethal heart failure within 6 weeks,
    with significant gene dysregulation of fibrotic pathways and calcium handling.
    Demonstrates that Med13 and Med13L function redundantly in the adult heart to
    maintain basal cardiac function and transcription.
  organism:
    preferred_term: mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  data_type: BULK_RNA_SEQ
  sample_count: 8
  sample_types:
  - preferred_term: cardiomyocyte
    tissue_term:
      preferred_term: heart
      term:
        id: UBERON:0000948
        label: heart
  conditions:
  - Med13/Med13L cardiomyocyte-specific double knockout
  - wild-type control
  genes:
  - preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  - preferred_term: MED13L
    term:
      id: hgnc:22962
      label: MED13L
  publication: PMID:40989238
  findings:
  - statement: Med13 and Med13L are functionally redundant in adult cardiomyocytes
  - statement: Double knockout causes lethal heart failure with fibrotic and calcium handling gene dysregulation
  - statement: Similar gene dysregulation patterns across Mediator cardiac knockouts (Med13/13L, Med12, Med1, Med30)
  evidence:
  - reference: PMID:40989238
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Med13/13L knockout resulted in decreased cardiac function leading to lethal heart failure in a median timeframe of 6 weeks from the start of tamoxifen."
    explanation: Mouse model demonstrates functional redundancy of Med13 and Med13L in heart and lethal consequences of combined loss.

- accession: "clinicaltrials:NCT01238250"
  title: "Online Study of People Who Have Genetic Changes and Features of Autism: Simons Searchlight"
  description: >-
    Simons Searchlight is a large prospective observational registry enrolling
    individuals with rare genetic neurodevelopmental variants including MED13 and
    MED13L. Collects medical history, developmental milestones, behavioral assessments,
    and longitudinal follow-up data. As of 2024, includes approximately 15 individuals
    with MED13 variants and 108 with MED13L variants.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  sample_types:
  - preferred_term: clinical phenotype data
  conditions:
  - MED13 pathogenic variants
  - MED13L pathogenic variants
  genes:
  - preferred_term: MED13
    term:
      id: hgnc:22474
      label: MED13
  - preferred_term: MED13L
    term:
      id: hgnc:22962
      label: MED13L
  findings:
  - statement: Longitudinal natural history data for MED13 and MED13L syndrome available to qualified researchers
  notes: >-
    Data available to qualified researchers via SFARI Base (https://base.sfari.org).
    Over 7,000 total participants enrolled across all gene cohorts as of 2024.
references:
- reference: PMID:40228085
  title: "MED13L Syndrome."
  tags:
  - GeneReviews
  findings: []

📚

References & Deep Research

References

1

PMID:40228085

MED13L Syndrome.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Mediator Complex Neurodevelopmental Disorder (MEDopathies): Disease Characteristics Report

Edison Scientific Literature 23 citations 2026-04-11T13:34:19.575536

Mediator Complex Neurodevelopmental Disorder (MEDopathies): Disease Characteristics Report

Executive summary

“Mediator Complex Neurodevelopmental Disorder” is best understood as an umbrella of monogenic neurodevelopmental disorders caused by pathogenic variants in genes encoding subunits of the RNA polymerase II Mediator complex (often termed MEDopathies or Neuro‑MEDopathies). The most clearly identifiable disease entity in the retrieved 2023–2024 evidence is MED13L haploinsufficiency syndrome (MRFACD; OMIM/MIM #616789; ORPHA:369891). Other closely related entities in the retrieved evidence include MED13-associated intellectual developmental disorder (MRD61), recessive MED23‑related MRT18, and recessive MED27‑related ponto‑cerebello‑lental degeneration. (maroofian2023biallelicmed27variants pages 3-4, siavriene2023molecularandfunctional pages 1-2, plassche2021med12related(neuro)developmentaldisorders pages 1-3)

A high-value 2023–2024 theme is that sequence-level interpretation and functional follow-up (e.g., transcript/protein assays, cell models) are increasingly used to support pathogenicity and refine genotype–phenotype correlations, while patient-advocacy organizations are explicitly organizing trial-readiness roadmaps (e.g., MED13L Foundation 2024 strategic research plan). (siavriene2023molecularandfunctional pages 1-2, heilmann2024themed13lfoundation pages 1-1)

1. Disease information

1.1 What is the disease?

Mediator complex neurodevelopmental disorders (MEDopathies) are neurodevelopmental conditions resulting from disrupted Mediator complex function, leading to dysregulated RNA polymerase II–dependent transcription programs important for brain development. Mechanistically, Mediator is described as “a large, evolutionarily conserved multiprotein complex” that “plays a critical role in facilitating transcriptional regulation by acting as a physical and functional bridge between DNA‑binding transcription factors and the transcriptional machinery.” (maroofian2023biallelicmed27variants pages 3-4)

Because clinical usage and coding tend to be gene-centric, this umbrella is most actionable in practice as a set of gene-defined syndromes (e.g., MED13L syndrome/MRFACD; MED12 syndromes; MED27 recessive neurodegeneration/NDD). (maroofian2023biallelicmed27variants pages 3-4, plassche2021med12related(neuro)developmentaldisorders pages 1-3, siavriene2023molecularandfunctional pages 1-2)

1.2 Key identifiers (as available in retrieved sources)

MED13L haploinsufficiency syndrome / MRFACD: OMIM/MIM #616789; ORPHA:369891 (siavriene2023molecularandfunctional pages 1-2)
Representative Mediator-subunit gene MIM IDs referenced in MEDopathy literature include MED23 (MIM 605042) and MED13 (MIM 603808) and others (e.g., MED17/20/25/11). (maroofian2023biallelicmed27variants pages 3-4, salzano2023casereportnovel pages 1-2, tolmacheva2024expandingphenotypeof pages 1-2)

Not found in retrieved evidence: MONDO ID, ICD‑10/ICD‑11 code, MeSH descriptor for a single umbrella entity. (siavriene2023molecularandfunctional pages 1-2)

1.3 Common synonyms/alternative names

MEDopathies; Neuro‑MEDopathies (umbrella) (maroofian2023biallelicmed27variants pages 3-4)
MED13L haploinsufficiency syndrome, MED13L syndrome, MED13L-related intellectual disability, MRFACD (“mental retardation and distinctive facial features with or without cardiac defects”) (siavriene2023molecularandfunctional pages 1-2, bessenyei2022med13lrelatedintellectualdisability pages 1-2)

1.4 Evidence sources (individual vs aggregated)

The retrieved evidence is primarily: - Case reports/case series and genotype-first matchmaker collaborations (MED13, MED23, MED27, MED13L). (tolmacheva2024expandingphenotypeof pages 1-2, salzano2023casereportnovel pages 1-2, maroofian2023biallelicmed27variants pages 3-4) - Aggregated research programs/registries: Simons Searchlight (large prospective observational program including MED13L and MED13). (NCT01238250 chunk 1, NCT01238250 chunk 2) - Patient-advocacy strategic planning for trial readiness: MED13L Foundation SRP (2024). (heilmann2024themed13lfoundation pages 1-1)

2. Etiology

2.1 Disease causal factors

Primary causal factors are germline pathogenic variants in genes encoding Mediator complex subunits. The causal chain is typically: variant → altered Mediator subunit abundance/function/localization → altered Pol II transcriptional regulation → disrupted neurodevelopmental programs → developmental delay/ID and syndromic features. (maroofian2023biallelicmed27variants pages 3-4, plassche2021med12related(neuro)developmentaldisorders pages 1-3, hamada2023med13landits pages 2-2)

2.2 Risk factors

Genetic: pathogenic variants in Mediator genes (e.g., MED13L, MED13, MED12, MED23, MED27). (siavriene2023molecularandfunctional pages 1-2, tolmacheva2024expandingphenotypeof pages 1-2, plassche2021med12related(neuro)developmentaldisorders pages 1-3, salzano2023casereportnovel pages 1-2, maroofian2023biallelicmed27variants pages 3-4)
Familial recurrence mechanisms: parental mosaicism can confer recurrence risk even in ostensibly de novo disorders (documented for MED13L). (bessenyei2022med13lrelatedintellectualdisability pages 1-2)

2.3 Protective factors / gene–environment interactions

No protective variants or robust gene–environment interactions were identified in the retrieved evidence for these Mendelian conditions. (siavriene2023molecularandfunctional pages 1-2)

3. Phenotypes (clinical features)

3.1 Cross-MEDopathy phenotype themes

Across Mediator-subunit disorders, convergent features include global developmental delay/intellectual disability, hypotonia, epilepsy, speech disorders, and behavioral comorbidity, with additional gene-specific systemic features (e.g., cataracts in MED27; congenital anomalies in MED13 and MED13L). (maroofian2023biallelicmed27variants pages 3-4, fazio2025geneticclinicaland pages 22-24)

3.2 MED13L haploinsufficiency syndrome (MRFACD; OMIM/MIM #616789)

A 2023 MED13L paper succinctly states: “Heterozygous pathogenic variants in the MED13L gene cause impaired intellectual development and distinctive facial features with or without cardiac defects (MIM #616789).” (siavriene2023molecularandfunctional pages 1-2)

Typical features described across MED13L sources include: - Neurodevelopment: intellectual disability/developmental delay; marked speech delay/poor speech (siavriene2023molecularandfunctional pages 1-2, bessenyei2022med13lrelatedintellectualdisability pages 1-2) - Neuromuscular: hypotonia; motor delay (bessenyei2022med13lrelatedintellectualdisability pages 1-2) - Craniofacial gestalt/dysmorphism: “distinctive facial features” (siavriene2023molecularandfunctional pages 1-2) - Variable congenital anomalies: plagiocephaly, strabismus, clubfoot (siavriene2023molecularandfunctional pages 1-2) - Cardiac: variable congenital heart defects (“with or without cardiac defects”) (siavriene2023molecularandfunctional pages 1-2)

Suggested HPO terms (non-exhaustive, mapped to the described features): - Intellectual disability: HP:0001249 - Global developmental delay: HP:0001263 - Speech delay / severe expressive language impairment: HP:0000750, HP:0002463 - Hypotonia: HP:0001252 - Strabismus: HP:0000486 - Plagiocephaly: HP:0001357 - Talipes equinovarus (clubfoot): HP:0001762 - Congenital heart defect: HP:0001627

3.3 MED27-related disease: quantitative phenotype frequencies

A 2023 Brain cohort study (57 affected individuals, 30 families) reports a broad continuum from developmental epileptic-dyskinetic encephalopathy to variable NDD with movement abnormalities and provides quantitative frequencies, e.g., global developmental delay/intellectual disability (100%), bilateral cataracts (89%), infantile hypotonia (74%), microcephaly (62%), gait ataxia (63%), dystonia (61%), epilepsy (50%), limb spasticity (51%), and death before adulthood (16%); MRI features include cerebellar atrophy (100%) and white matter volume loss (76.4%). (maroofian2023biallelicmed27variants pages 3-4)

Visual evidence for these frequencies is captured from the paper’s Table/Figure. (maroofian2023biallelicmed27variants media 55f96031, maroofian2023biallelicmed27variants media 45999b07)

Suggested HPO terms: cataract (HP:0000518), cerebellar atrophy (HP:0001272), dystonia (HP:0001332), spasticity (HP:0001257), epilepsy (HP:0001250), microcephaly (HP:0000252), ataxia (HP:0001251).

3.4 MED23-related MRT18 (autosomal recessive)

A 2023 case report/review states: “Biallelic loss-of-function variants in MED23 cause a recessive syndromic intellectual disability condition with or without epilepsy (MRT18).” and highlights postnatal progressive microcephaly as an underappreciated feature. (salzano2023casereportnovel pages 1-2)

Suggested HPO terms: autosomal recessive inheritance (HP:0000007), progressive microcephaly (HP:0000253), seizures (HP:0001250), hypotonia (HP:0001252), spasticity (HP:0001257), dystonia (HP:0001332).

3.5 MED13-associated NDD (MRD61): 2024 phenotype expansion

A 2024 BMC Medical Genomics case report describes an infant with a de novo MED13 missense variant identified by trio WES and proposes expanding the MED13-associated phenotype to include severe multisystem findings and neonatal death in rare cases. (tolmacheva2024expandingphenotypeof pages 1-2)

4. Genetic / molecular information

4.1 Causal genes (representative, from retrieved evidence)

MED13L (autosomal dominant, typically de novo; haploinsufficiency) (siavriene2023molecularandfunctional pages 1-2, bessenyei2022med13lrelatedintellectualdisability pages 1-2)
MED13 (autosomal dominant; de novo and inherited variants described) (tolmacheva2024expandingphenotypeof pages 1-2, yang2025anovelframeshift pages 7-7)
MED12 (X-linked spectrum: FG syndrome, Lujan–Fryns, X-linked Ohdo; and female de novo LoF in Hardikar) (plassche2021med12related(neuro)developmentaldisorders pages 1-3)
MED23 (autosomal recessive MRT18) (salzano2023casereportnovel pages 1-2)
MED27 (autosomal recessive NDD/neurodegeneration spectrum) (maroofian2023biallelicmed27variants pages 3-4)

A compact map is provided in the table below.

Gene	Disorder name(s) / synonyms	Key identifier(s)	Inheritance pattern	Hallmark phenotypes (with frequencies if reported)	Key references
MED13L	MED13L haploinsufficiency syndrome; MED13L-related intellectual disability; MRFACD (mental retardation and distinctive facial features with or without cardiac defects)	MIM/OMIM #616789; ORPHA:369891; gene MED13L MIM 608771	Autosomal dominant, usually de novo heterozygous LoF/CNV; parental mosaicism reported	Core syndrome includes intellectual disability/developmental delay, marked speech delay/poor speech, hypotonia, motor delay, characteristic facial gestalt, with cardiac defects variably present; 2023 functional study also lists plagiocephaly, strabismus, clubfoot, macrostomia; review notes missense variants may be more severe and associated with epilepsy/absent speech/walking; one review states ~one-third of reported pathogenic events are large CNVs; no robust pooled prevalence of CHD or speech impairment was given in the gathered evidence (siavriene2023molecularandfunctional pages 1-2, tørring2019ismed13lrelatedintellectual pages 1-5, bessenyei2022med13lrelatedintellectualdisability pages 1-2, fazio2025geneticclinicaland pages 11-13)	Siavrienė et al. 2023, Medicina, doi:10.3390/medicina59071225, https://doi.org/10.3390/medicina59071225, PMID: ; Tørring et al. 2019, Eur J Med Genet, doi:10.1016/j.ejmg.2018.06.014, https://doi.org/10.1016/j.ejmg.2018.06.014, PMID: ; Bessenyei et al. 2022, Cold Spring Harb Mol Case Stud, doi:10.1101/mcs.a006124, https://doi.org/10.1101/mcs.a006124, PMID: (siavriene2023molecularandfunctional pages 1-2, tørring2019ismed13lrelatedintellectual pages 1-5, bessenyei2022med13lrelatedintellectualdisability pages 1-2, fazio2025geneticclinicaland pages 11-13)
MED13	MED13-associated neurodevelopmental disorder; intellectual developmental disorder-61 / MRD61	gene MED13 OMIM/MIM 603808; disorder termed MRD61 in later literature	Predominantly autosomal dominant, largely de novo heterozygous variants; inherited transmission from affected mother also reported	Universal DD/ID in original cohort; prominent speech/language delay, autism/ADHD in some, hypotonia, optic nerve/vision abnormalities, Duane anomaly, mild congenital heart anomalies, dysmorphism; variant types include truncating, missense, in-frame deletion; 2024 neonatal case expanded phenotype to hydrocephalic changes, hypoplastic corpus callosum, optic nerve/chiasm atrophy, brainstem atrophy, multiple organ failure/neonatal death (tolmacheva2024expandingphenotypeof pages 1-2)	Blok et al. 2018, Hum Genet, doi:10.1007/s00439-018-1887-y, https://doi.org/10.1007/s00439-018-1887-y, PMID: ; Tolmacheva et al. 2024, BMC Med Genomics, doi:10.1186/s12920-024-01857-z, https://doi.org/10.1186/s12920-024-01857-z, PMID: (tolmacheva2024expandingphenotypeof pages 1-2)
MED23	MED23-related intellectual disability; MRT18; recessive syndromic intellectual disability with/without epilepsy	MED23 MIM 605042; MRT18	Autosomal recessive, biallelic pathogenic variants	Classical phenotype includes global DD/ID, microcephaly, axial hypotonia, spasticity, choreoathetosis/dystonia, EEG abnormalities and epilepsy; 2023 report emphasized postnatal progressive microcephaly as an underappreciated feature; due to rarity, phenotype frequencies remain limited (salzano2023casereportnovel pages 1-2)	Salzano et al. 2023, Front Neurol, doi:10.3389/fneur.2023.1090082, https://doi.org/10.3389/fneur.2023.1090082, PMID: (salzano2023casereportnovel pages 1-2)
MED27	MED27-associated neurodevelopmental disorder; variable ponto-cerebello-lental degeneration with movement disorders; part of Neuro-MEDopathies	gene MED27; no OMIM/ORPHA identifier provided in gathered evidence	Autosomal recessive, biallelic pathogenic variants	Large 2023 series reported global DD/ID 100%, bilateral cataracts 89%, infantile hypotonia 74%, microcephaly 62%, gait ataxia 63%, dystonia 61%, epilepsy 50%, limb spasticity 51%, facial dysmorphism 38%, death before adulthood 16%; MRI: cerebellar atrophy 100%, white-matter volume loss 76.4%, pontine hypoplasia 47.2%, basal ganglia atrophy/signal changes 44.4% (maroofian2023biallelicmed27variants pages 3-4)	Maroofian et al. 2023, Brain, doi:10.1093/brain/awad257, https://doi.org/10.1093/brain/awad257, PMID: (maroofian2023biallelicmed27variants pages 3-4)
MED12	MED12-related disorders including FG syndrome / Opitz-Kaveggia syndrome, Lujan-Fryns syndrome, X-linked Ohdo syndrome (Maat-Kievit-Brunner type), non-syndromic X-linked intellectual disability, and Hardikar syndrome	FG syndrome MIM 305450; Lujan-Fryns syndrome MIM 309520; X-linked Ohdo syndrome MIM 300895; gene MED12 at Xq13.1	Mainly X-linked; classically hemizygous inherited missense variants in males from carrier mothers; also de novo missense or truncating variants in females; Hardikar syndrome linked to de novo nonsense/LoF in females	Shared features across classical MED12 syndromes include intellectual disability, hypotonia, macrocephaly, hyperactivity/behavioral abnormalities, corpus callosum abnormalities, and characteristic craniofacial features; Hardikar syndrome adds facial clefting, pigmentary retinopathy, biliary anomalies, intestinal malrotation; more C-terminal truncations associated with severe syndromic ID in females (plassche2021med12related(neuro)developmentaldisorders pages 1-3)	van de Plassche & de Brouwer 2021, Genes, doi:10.3390/genes12050663, https://doi.org/10.3390/genes12050663, PMID: (plassche2021med12related(neuro)developmentaldisorders pages 1-3)
Multiple Mediator subunits	MEDopathies / Neuro-MEDopathies (umbrella term for Mediator-complex neurodevelopmental disorders)	Examples listed in gathered evidence: MED11 MIM 612383, MED17 MIM 603810, MED20 MIM 612915, MED23 MIM 605042, MED25 MIM 610197, MED12L MIM 611318, MED13 MIM 603808, MED13L	Mixed: AR, AD/de novo, X-linked depending on subunit	Convergent features across the group include developmental delay/intellectual disability, hypotonia, epilepsy, speech/language disorder, autism/behavioral comorbidity, and variable structural brain/cardiac anomalies; the Mediator complex acts as a bridge between DNA-binding transcription factors and RNA polymerase II transcriptional machinery (maroofian2023biallelicmed27variants pages 3-4, fazio2025geneticclinicaland pages 24-24)	Maroofian et al. 2023, Brain, doi:10.1093/brain/awad257, https://doi.org/10.1093/brain/awad257, PMID: ; Fazio et al. 2025, Genes, doi:10.3390/genes16121444, https://doi.org/10.3390/genes16121444, PMID: (maroofian2023biallelicmed27variants pages 3-4, fazio2025geneticclinicaland pages 24-24)

Table: This table summarizes Mediator-complex neurodevelopmental disorders mentioned in the gathered evidence, highlighting identifiers, inheritance, hallmark phenotypes, and key references. It is useful as a compact disease-entity map for comparing major MEDopathy subtypes relevant to diagnosis and curation.

4.2 Variant classes and functional consequences (examples)

MED13L haploinsufficiency - 2023 intragenic deletion spanning exons 3–10 predicted truncation (frameshift) and haploinsufficiency; functional follow-up after MED13L silencing found “reduced cell viability; an accelerated aging process; and inhibition of the RB1, E2F1, and CCNC gene expression.” (siavriene2023molecularandfunctional pages 1-2)

MED13 (CDK8 module-associated) - A 2018 cohort described truncating and missense variants, with non-truncating variants clustering in regions involved in ubiquitination/degradation (p.Thr326/p.Pro327), supporting variant-class dependent mechanisms. (yang2025anovelframeshift pages 7-7)

5. Environmental information

No specific environmental/lifestyle/infectious contributors were identified in the retrieved evidence for these Mendelian disorders. (siavriene2023molecularandfunctional pages 1-2)

6. Mechanism / pathophysiology

6.1 Core concept: Mediator as transcriptional bridge

The Mediator complex functions as a transcriptional regulator, “acting as a physical and functional bridge between DNA-binding transcription factors and the transcriptional machinery.” (maroofian2023biallelicmed27variants pages 3-4)

6.2 MED13L neurodevelopmental mechanisms (model evidence)

Two lines of mechanistic evidence in the retrieved sources support neuronal roles for MED13L:

1) Developmental expression + synaptic localization (mouse) - MED13L shows developmental stage-dependent expression/localization in mouse brain and “at least partially colocalized with pre- and post-synaptic markers, synaptophysin, and PSD95,” suggesting synaptic involvement. (hamada2021expressionanalysesof pages 1-2)

2) Corticogenesis/dendrite development (in utero electroporation; 2023) - Disease-associated MED13L variants show distinct subcellular localization in cortical neurons (some nuclear accumulation; others cytoplasmic), and a truncation variant was “barely detectable,” consistent with haploinsufficiency. (hamada2023med13landits pages 2-2) - Functionally, MED13L knockdown “abrogated dendritic growth in vivo,” and dendritic growth was rescued by RNAi-resistant wild-type MED13L, but not equivalently by certain disease variants. (hamada2023med13landits pages 2-2)

Suggested GO Biological Process terms (mechanism-aligned): - Regulation of transcription by RNA polymerase II (GO:0006357) - Neuron projection development (GO:0031175) - Dendrite development (GO:0016358) - Synapse organization (GO:0050808)

Suggested Cell Ontology (CL) cell types: - Cortical pyramidal neuron (CL:0000540; used as proxy for “cortical layer II/III pyramidal neurons” described experimentally) (hamada2023med13landits pages 2-2) - Neural progenitor cell (CL:0000047; mechanistically implicated broadly in NDD studies, though not directly quantified in retrieved excerpts)

7. Anatomical structures affected

Primary involvement is the central nervous system. In MED27 disease, neuroimaging commonly shows cerebellar atrophy and additional brainstem/white matter changes. (maroofian2023biallelicmed27variants pages 3-4)

Suggested UBERON terms: - Brain (UBERON:0000955) - Cerebellum (UBERON:0002037) - Cerebral cortex (UBERON:0001851)

8. Temporal development

Most MEDopathies present as early-onset neurodevelopmental disorders (infancy/childhood), with developmental delay and evolving neurologic manifestations (e.g., epilepsy, movement disorder) depending on the gene. (maroofian2023biallelicmed27variants pages 3-4, siavriene2023molecularandfunctional pages 1-2)

9. Inheritance and population

9.1 Inheritance patterns (from retrieved evidence)

Autosomal dominant (often de novo): MED13L, MED13 (siavriene2023molecularandfunctional pages 1-2, tolmacheva2024expandingphenotypeof pages 1-2)
X-linked spectrum: MED12-related disorders (plassche2021med12related(neuro)developmentaldisorders pages 1-3)
Autosomal recessive: MED23, MED27 (salzano2023casereportnovel pages 1-2, maroofian2023biallelicmed27variants pages 3-4)

9.2 Epidemiology

The retrieved sources do not provide rigorous prevalence/incidence estimates for the umbrella “Mediator Complex Neurodevelopmental Disorder.” For MED13L syndrome, one source notes “roughly a hundred reported cases” and that it is among the more common syndromic intellectual disabilities, but this is not a population prevalence estimate. (bessenyei2022med13lrelatedintellectualdisability pages 1-2)

10. Diagnostics

10.1 Genetic testing approaches in current practice (as reflected in retrieved evidence)

Chromosomal microarray / SNP-CGH (CNV detection) is used when congenital anomalies and/or syndromic NDD is suspected (e.g., MED13L intragenic deletion characterized by SNP-CGH and breakpoint refinement). (siavriene2023molecularandfunctional pages 1-2)
Trio whole-exome sequencing (WES) is emphasized for de novo variant detection in syndromic NDD and congenital anomalies (e.g., MED13 2024 phenotype expansion). (tolmacheva2024expandingphenotypeof pages 1-2)
Confirmatory methods: qPCR, Sanger sequencing (including cDNA), Western blot. (siavriene2023molecularandfunctional pages 1-2)

10.2 Emerging/adjacent diagnostics

Functional characterization in patient-derived fibroblasts and CRISPR perturbation experiments are being used to support variant interpretation in MED13L. (siavriene2023molecularandfunctional pages 1-2)

10.3 Differential diagnosis (examples)

Given shared phenotypes (DD/ID, speech impairment, hypotonia, dysmorphism, congenital anomalies), differential diagnoses include other syndromic NDDs; Mediator-subunit disorders themselves can overlap (e.g., MED13 vs MED13L; MED12 spectrum). (maroofian2023biallelicmed27variants pages 3-4, plassche2021med12related(neuro)developmentaldisorders pages 1-3, tolmacheva2024expandingphenotypeof pages 1-2)

11. Outcome / prognosis

Robust longitudinal survival/functional outcome statistics were not available in the retrieved evidence for the umbrella entity. Notably, MED27 disease includes a reported 16% death before adulthood in a large cohort, underscoring gene-specific prognosis differences within MEDopathies. (maroofian2023biallelicmed27variants pages 3-4)

12. Treatment

12.1 Current management

No disease-modifying therapies for MED13L/MED13/MED23/MED27 disorders were identified in the retrieved sources; management is generally supportive and symptom-directed (developmental therapies; seizure management where applicable). (fazio2025geneticclinicaland pages 22-24, siavriene2023molecularandfunctional pages 1-2)

Suggested MAXO terms (supportive, typical for syndromic NDD): - Developmental therapy / early intervention (MAXO:0000942; proxy) - Speech therapy (MAXO:0000717; proxy) - Physical therapy (MAXO:0000010; proxy) - Antiseizure therapy (MAXO:0000647; proxy)

12.2 2023–2024 translational/trial-readiness developments

The MED13L Foundation strategic research plan (SRP) (published Jan 2024) frames clinical-trial readiness as an explicit goal, assessing preclinical tools “largely framed through Food and Drug Administration guidelines for the development of therapeutics from bench to bedside.” (heilmann2024themed13lfoundation pages 1-1)

13. Prevention

Primary prevention is not applicable in the usual public-health sense for de novo Mendelian disorders; prevention is chiefly via genetic counseling and reproductive options.

Genetic counseling should explicitly consider parental mosaicism as a recurrence-risk mechanism (documented in MED13L). (bessenyei2022med13lrelatedintellectualdisability pages 1-2)
Prenatal/preimplantation options are implied by standard practice but were not detailed with rates or protocols in retrieved evidence. (bessenyei2022med13lrelatedintellectualdisability pages 1-2)

14. Other species / natural disease

Not addressed in the retrieved evidence.

15. Model organisms

Mouse neurodevelopmental models: MED13L expression/localization during mouse brain development (ventricular zone, cortical plate, hippocampus/cerebellum; synaptic colocalization) and in utero electroporation experiments showing dendritic-development phenotypes. (hamada2021expressionanalysesof pages 1-2, hamada2023med13landits pages 2-2)
Cell models: primary cultured hippocampal neurons (localization), fibroblast CRISPR silencing (functional consequences for MED13L). (hamada2021expressionanalysesof pages 1-2, siavriene2023molecularandfunctional pages 1-2)

Real-world implementations and applications (2023–2024 emphasis)

1) Clinical sequencing workflows: integration of CNV arrays + WES (often trio) to identify Mediator-subunit etiologies in syndromic NDD/congenital anomalies (demonstrated in MED13L 2023 functional CNV paper and MED13 2024 case). (siavriene2023molecularandfunctional pages 1-2, tolmacheva2024expandingphenotypeof pages 1-2) 2) Research registries: Simons Searchlight is a large, remote, prospective observational program enrolling individuals with gene variants including MED13L and MED13, collecting medical/behavioral/developmental data longitudinally; it reports ~7,000 participants already enrolled and plans up to 100,000. URL: https://simonssearchlight.org/ (trial record first posted 2010-11-10; last update posted 2025-06-06). (NCT01238250 chunk 1, NCT01238250 chunk 2) 3) Trial readiness infrastructure: MED13L Foundation SRP (Jan 2024; Therapeutic Advances in Rare Disease; https://doi.org/10.1177/26330040241290252). (heilmann2024themed13lfoundation pages 1-1)

Notable statistics (from recent studies)

MED27 cohort (Brain 2023): DD/ID 100%, bilateral cataracts 89%, hypotonia 74%, microcephaly 62%, gait ataxia 63%, dystonia 61%, epilepsy 50%, death before adulthood 16%; MRI cerebellar atrophy 100%. (maroofian2023biallelicmed27variants pages 3-4, maroofian2023biallelicmed27variants media 55f96031, maroofian2023biallelicmed27variants media 45999b07)
MED23 rarity: literature still small; 2023 report notes limited number of reported individuals and variants and highlights postnatal progressive microcephaly. (salzano2023casereportnovel pages 1-2)

Limitations of this report (evidence availability)

The retrieved sources did not provide MONDO/ICD/MeSH identifiers for the umbrella “Mediator Complex Neurodevelopmental Disorder.” (siavriene2023molecularandfunctional pages 1-2)
Many claims requested by the template (population prevalence/incidence, standardized clinical diagnostic criteria, treatment response rates) were not available in the retrieved evidence and would require targeted retrieval from OMIM/Orphanet pages and additional natural history cohorts beyond the currently retrieved texts. (siavriene2023molecularandfunctional pages 1-2)

References

(maroofian2023biallelicmed27variants pages 3-4): R. Maroofian, R. Kaiyrzhanov, E. Calì, M. Zamani, M. Zaki, Matteo P. Ferla, D. Tortora, Saeid Sadeghian, Saadia Maryam Saadi, Uzma Abdullah, Ehsan Ghayoor Karimiani, S. Efthymiou, G. Yeşil, Shahryar Alavi, Aisha Al Shamsi, H. Tajsharghi, M. Abdel-Hamid, N. Saadi, F. Al Mutairi, Lama Alabdi, C. Beetz, Zafar Ali, M. B. Toosi, S. Rudnik-Schöneborn, Meisam Babaei, P. Isohanni, Jameel Muhammad, Khan Sheraz, Maha Al Shalan, S. Hickey, Daphna Marom, E. Elhanan, M. Kurian, Dana Marafi, A. Saberi, M. Hamid, R. Spaull, Linyan Meng, S. Lalani, S. Maqbool, F. Rahman, J. Seeger, T. Palculict, Tracy Lau, D. Murphy, N. Mencacci, K. Steindl, A. Begemann, A. Rauch, Sinan Akbaş, Aslanger Ayça Dilruba, V. Salpietro, Hammad Yousaf, S. Ben-Shachar, K. Ejeskär, A. A. Al Aqeel, F. High, Amy Armstrong-Javors, Seyed Mohammadsaleh Zahraei, Tahereh Seifi, Jawaher Zeighami, G. Shariati, A. Sedaghat, S. N. Asl, Mohmmad Shahrooei, G. Zifarelli, L. Burglen, C. Ravelli, J. Zschocke, Ulrich A. Schatz, Maryam Ghavideldarestani, W. Kamel, H. Van Esch, A. Hackenberg, Jenny C. Taylor, L. Al-Gazali, P. Bauer, Joseph J Gleeson, F. Alkuraya, J. Lupski, H. Galehdari, Reza Azizimalamiri, Wendy K. Chung, S. Baig, H. Houlden, and M. Severino. Biallelic med27 variants lead to variable ponto-cerebello-lental degeneration with movement disorders. Brain, 146:5031-5043, Jul 2023. URL: https://doi.org/10.1093/brain/awad257, doi:10.1093/brain/awad257. This article has 19 citations and is from a highest quality peer-reviewed journal.
(siavriene2023molecularandfunctional pages 1-2): Evelina Siavrienė, Gunda Petraitytė, Violeta Mikštienė, Živilė Maldžienė, Aušra Sasnauskienė, Vilmantė Žitkutė, Laima Ambrozaitytė, Tautvydas Rančelis, Algirdas Utkus, Vaidutis Kučinskas, and Eglė Preikšaitienė. Molecular and functional characterisation of a novel intragenic 12q24.21 deletion resulting in med13l haploinsufficiency syndrome. Medicina, 59:1225, Jun 2023. URL: https://doi.org/10.3390/medicina59071225, doi:10.3390/medicina59071225. This article has 9 citations.
(plassche2021med12related(neuro)developmentaldisorders pages 1-3): Stijn R. van de Plassche and Arjan P. M. de Brouwer. Med12-related (neuro)developmental disorders: a question of causality. Genes, 12 5:663, Apr 2021. URL: https://doi.org/10.3390/genes12050663, doi:10.3390/genes12050663. This article has 26 citations.
(heilmann2024themed13lfoundation pages 1-1): Rachel Heilmann, Anna Pfalzer, Terry Jo Bichell, Ananya Terala, Alicia Campbell, Dylan Taatjes, Jamal Ghoumid, Chad Grueter, Jennifer Bain, Randy Strich, Vanessa Dias, Kimberly Sokorai, Nicholas Seaver, Kelly Sexton, and Kathleen Boychuck. The med13l foundation strategic research plan: a roadmap to the future. Therapeutic Advances in Rare Disease, Jan 2024. URL: https://doi.org/10.1177/26330040241290252, doi:10.1177/26330040241290252. This article has 9 citations.
(salzano2023casereportnovel pages 1-2): Emanuela Salzano, Marcello Niceta, Simone Pizzi, Francesca Clementina Radio, Martina Busè, Francesca Mercadante, Sabina Barresi, Arturo Ferrara, Cecilia Mancini, Marco Tartaglia, and Maria Piccione. Case report: novel compound heterozygosity for pathogenic variants in med23 in a syndromic patient with postnatal microcephaly. Frontiers in Neurology, Feb 2023. URL: https://doi.org/10.3389/fneur.2023.1090082, doi:10.3389/fneur.2023.1090082. This article has 4 citations and is from a peer-reviewed journal.
(tolmacheva2024expandingphenotypeof pages 1-2): Ekaterina Tolmacheva, Anna S. Bolshakova, Jekaterina Shubina, Margarita S. Rogacheva, Alexey N. Ekimov, Julia L. Podurovskaya, Artem A. Burov, Denis V. Rebrikov, Vladimir G. Bychenko, Dmitry Yu. Trofimov, and Gennady T. Sukhikh. Expanding phenotype of med13-associated syndrome presenting novel de novo missense variant in a patient with multiple congenital anomalies. BMC Medical Genomics, May 2024. URL: https://doi.org/10.1186/s12920-024-01857-z, doi:10.1186/s12920-024-01857-z. This article has 8 citations and is from a peer-reviewed journal.
(bessenyei2022med13lrelatedintellectualdisability pages 1-2): Beáta Bessenyei, István Balogh, Attila Mokánszki, Anikó Ujfalusi, Rolph Pfundt, and Katalin Szakszon. Med13l-related intellectual disability due to paternal germinal mosaicism. Cold Spring Harbor Molecular Case Studies, 8:a006124, Oct 2022. URL: https://doi.org/10.1101/mcs.a006124, doi:10.1101/mcs.a006124. This article has 16 citations and is from a peer-reviewed journal.
(NCT01238250 chunk 1): Online Study of People Who Have Genetic Changes and Features of Autism: Simons Searchlight. Simons Searchlight. 2010. ClinicalTrials.gov Identifier: NCT01238250
(NCT01238250 chunk 2): Online Study of People Who Have Genetic Changes and Features of Autism: Simons Searchlight. Simons Searchlight. 2010. ClinicalTrials.gov Identifier: NCT01238250
(hamada2023med13landits pages 2-2): Nanako Hamada, Ikuko Iwamoto, and Koh‐ichi Nagata. med13l and its disease‐associated variants influence the dendritic development of cerebral cortical neurons in the mammalian brain. Journal of Neurochemistry, 165:334-347, Feb 2023. URL: https://doi.org/10.1111/jnc.15783, doi:10.1111/jnc.15783. This article has 15 citations and is from a domain leading peer-reviewed journal.
(fazio2025geneticclinicaland pages 22-24): Alessandro Fazio, Roberta Leonardi, Lorenzo Aliotta, Manuela Lo Bianco, Gennaro Anastasio, Giuseppe Messina, Corrado Spatola, Pietro Valerio Foti, Stefano Palmucci, Antonio Basile, Martino Ruggieri, and Emanuele David. Genetic, clinical and neuroradiological spectrum of med-related disorders: an updated review. Genes, 16:1444, Dec 2025. URL: https://doi.org/10.3390/genes16121444, doi:10.3390/genes16121444. This article has 1 citations.
(maroofian2023biallelicmed27variants media 55f96031): R. Maroofian, R. Kaiyrzhanov, E. Calì, M. Zamani, M. Zaki, Matteo P. Ferla, D. Tortora, Saeid Sadeghian, Saadia Maryam Saadi, Uzma Abdullah, Ehsan Ghayoor Karimiani, S. Efthymiou, G. Yeşil, Shahryar Alavi, Aisha Al Shamsi, H. Tajsharghi, M. Abdel-Hamid, N. Saadi, F. Al Mutairi, Lama Alabdi, C. Beetz, Zafar Ali, M. B. Toosi, S. Rudnik-Schöneborn, Meisam Babaei, P. Isohanni, Jameel Muhammad, Khan Sheraz, Maha Al Shalan, S. Hickey, Daphna Marom, E. Elhanan, M. Kurian, Dana Marafi, A. Saberi, M. Hamid, R. Spaull, Linyan Meng, S. Lalani, S. Maqbool, F. Rahman, J. Seeger, T. Palculict, Tracy Lau, D. Murphy, N. Mencacci, K. Steindl, A. Begemann, A. Rauch, Sinan Akbaş, Aslanger Ayça Dilruba, V. Salpietro, Hammad Yousaf, S. Ben-Shachar, K. Ejeskär, A. A. Al Aqeel, F. High, Amy Armstrong-Javors, Seyed Mohammadsaleh Zahraei, Tahereh Seifi, Jawaher Zeighami, G. Shariati, A. Sedaghat, S. N. Asl, Mohmmad Shahrooei, G. Zifarelli, L. Burglen, C. Ravelli, J. Zschocke, Ulrich A. Schatz, Maryam Ghavideldarestani, W. Kamel, H. Van Esch, A. Hackenberg, Jenny C. Taylor, L. Al-Gazali, P. Bauer, Joseph J Gleeson, F. Alkuraya, J. Lupski, H. Galehdari, Reza Azizimalamiri, Wendy K. Chung, S. Baig, H. Houlden, and M. Severino. Biallelic med27 variants lead to variable ponto-cerebello-lental degeneration with movement disorders. Brain, 146:5031-5043, Jul 2023. URL: https://doi.org/10.1093/brain/awad257, doi:10.1093/brain/awad257. This article has 19 citations and is from a highest quality peer-reviewed journal.
(maroofian2023biallelicmed27variants media 45999b07): R. Maroofian, R. Kaiyrzhanov, E. Calì, M. Zamani, M. Zaki, Matteo P. Ferla, D. Tortora, Saeid Sadeghian, Saadia Maryam Saadi, Uzma Abdullah, Ehsan Ghayoor Karimiani, S. Efthymiou, G. Yeşil, Shahryar Alavi, Aisha Al Shamsi, H. Tajsharghi, M. Abdel-Hamid, N. Saadi, F. Al Mutairi, Lama Alabdi, C. Beetz, Zafar Ali, M. B. Toosi, S. Rudnik-Schöneborn, Meisam Babaei, P. Isohanni, Jameel Muhammad, Khan Sheraz, Maha Al Shalan, S. Hickey, Daphna Marom, E. Elhanan, M. Kurian, Dana Marafi, A. Saberi, M. Hamid, R. Spaull, Linyan Meng, S. Lalani, S. Maqbool, F. Rahman, J. Seeger, T. Palculict, Tracy Lau, D. Murphy, N. Mencacci, K. Steindl, A. Begemann, A. Rauch, Sinan Akbaş, Aslanger Ayça Dilruba, V. Salpietro, Hammad Yousaf, S. Ben-Shachar, K. Ejeskär, A. A. Al Aqeel, F. High, Amy Armstrong-Javors, Seyed Mohammadsaleh Zahraei, Tahereh Seifi, Jawaher Zeighami, G. Shariati, A. Sedaghat, S. N. Asl, Mohmmad Shahrooei, G. Zifarelli, L. Burglen, C. Ravelli, J. Zschocke, Ulrich A. Schatz, Maryam Ghavideldarestani, W. Kamel, H. Van Esch, A. Hackenberg, Jenny C. Taylor, L. Al-Gazali, P. Bauer, Joseph J Gleeson, F. Alkuraya, J. Lupski, H. Galehdari, Reza Azizimalamiri, Wendy K. Chung, S. Baig, H. Houlden, and M. Severino. Biallelic med27 variants lead to variable ponto-cerebello-lental degeneration with movement disorders. Brain, 146:5031-5043, Jul 2023. URL: https://doi.org/10.1093/brain/awad257, doi:10.1093/brain/awad257. This article has 19 citations and is from a highest quality peer-reviewed journal.
(yang2025anovelframeshift pages 7-7): Qi Yang, Qiang Zhang, Sheng Yi, Gaojie Huang, Xunzhao Zhou, Shang Yi, and Jingsi Luo. A novel frameshift variant in the med13 gene causing intellectual developmental disorder-61 in a chinese family. Frontiers in Pediatrics, Oct 2025. URL: https://doi.org/10.3389/fped.2025.1699544, doi:10.3389/fped.2025.1699544. This article has 1 citations.
(tørring2019ismed13lrelatedintellectual pages 1-5): Pernille Mathiesen Tørring, Martin Jakob Larsen, Charlotte Brasch-Andersen, Lotte Nylandsted Krogh, Maria Kibæk, Lone Laulund, Niels Illum, Ulrike Dunkhase-Heinl, Antje Wiesener, Bernt Popp, Giuseppe Marangi, Tina Duelund Hjortshøj, Jakob Ek, Ida Vogel, Naja Becher, Laura Roos, Marcella Zollino, and Christina Ringmann Fagerberg. Is med13l-related intellectual disability a recognizable syndrome? European journal of medical genetics, 62 2:129-136, Feb 2019. URL: https://doi.org/10.1016/j.ejmg.2018.06.014, doi:10.1016/j.ejmg.2018.06.014. This article has 46 citations and is from a peer-reviewed journal.
(fazio2025geneticclinicaland pages 11-13): Alessandro Fazio, Roberta Leonardi, Lorenzo Aliotta, Manuela Lo Bianco, Gennaro Anastasio, Giuseppe Messina, Corrado Spatola, Pietro Valerio Foti, Stefano Palmucci, Antonio Basile, Martino Ruggieri, and Emanuele David. Genetic, clinical and neuroradiological spectrum of med-related disorders: an updated review. Genes, 16:1444, Dec 2025. URL: https://doi.org/10.3390/genes16121444, doi:10.3390/genes16121444. This article has 1 citations.
(fazio2025geneticclinicaland pages 24-24): Alessandro Fazio, Roberta Leonardi, Lorenzo Aliotta, Manuela Lo Bianco, Gennaro Anastasio, Giuseppe Messina, Corrado Spatola, Pietro Valerio Foti, Stefano Palmucci, Antonio Basile, Martino Ruggieri, and Emanuele David. Genetic, clinical and neuroradiological spectrum of med-related disorders: an updated review. Genes, 16:1444, Dec 2025. URL: https://doi.org/10.3390/genes16121444, doi:10.3390/genes16121444. This article has 1 citations.
(hamada2021expressionanalysesof pages 1-2): Nanako Hamada, Ikuko Iwamoto, Masashi Nishikawa, and Koh-ichi Nagata. Expression analyses of mediator complex subunit 13-like: a responsible gene for neurodevelopmental disorders during mouse brain development. Developmental Neuroscience, 43:43-52, Apr 2021. URL: https://doi.org/10.1159/000515188, doi:10.1159/000515188. This article has 11 citations and is from a peer-reviewed journal.

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Mediator Complex Neurodevelopmental Disorder (MEDopathies): Disease Characteristics Report

Executive summary

1. Disease information

1.1 What is the disease?

1.2 Key identifiers (as available in retrieved sources)

1.3 Common synonyms/alternative names

1.4 Evidence sources (individual vs aggregated)

2. Etiology

2.1 Disease causal factors

2.2 Risk factors

2.3 Protective factors / gene–environment interactions

3. Phenotypes (clinical features)

3.1 Cross-MEDopathy phenotype themes

3.2 MED13L haploinsufficiency syndrome (MRFACD; OMIM/MIM #616789)

3.3 MED27-related disease: quantitative phenotype frequencies

3.4 MED23-related MRT18 (autosomal recessive)

3.5 MED13-associated NDD (MRD61): 2024 phenotype expansion

4. Genetic / molecular information

4.1 Causal genes (representative, from retrieved evidence)

4.2 Variant classes and functional consequences (examples)

5. Environmental information

6. Mechanism / pathophysiology

6.1 Core concept: Mediator as transcriptional bridge

6.2 MED13L neurodevelopmental mechanisms (model evidence)

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

9.1 Inheritance patterns (from retrieved evidence)

9.2 Epidemiology

10. Diagnostics

10.1 Genetic testing approaches in current practice (as reflected in retrieved evidence)

10.2 Emerging/adjacent diagnostics

10.3 Differential diagnosis (examples)

11. Outcome / prognosis

12. Treatment

12.1 Current management

12.2 2023–2024 translational/trial-readiness developments

13. Prevention

14. Other species / natural disease

15. Model organisms

Real-world implementations and applications (2023–2024 emphasis)

Notable statistics (from recent studies)

Limitations of this report (evidence availability)