Chromosome Xq Duplication

Genetic MONDO:0017010 Pathograph 16 Show in embeddings browser Chromosomal Disorder Neurodevelopmental Disorder

Chromosome Xq duplication comprises a heterogeneous group of segmental copy-number gains involving the long arm of the X chromosome. They arise either as intrachromosomal duplications or through unbalanced X/Y or X/autosome translocations. The pathophysiological core is gene *dosage* rather than loss of function: an extra copy of one or more dosage-sensitive genes within the duplicated interval produces intellectual disability, hypotonia, and dysmorphism, and — depending on gene content — hypopituitarism, genital anomalies, and proneness to infection. Expression is governed by whether X-chromosome dosage compensation succeeds. In XY males any structural Xq disomy is necessarily functional disomy, so males are typically severely affected. In females the duplicated X is usually preferentially inactivated, and carriers are frequently asymptomatic or mildly affected; manifesting females are those in whom compensation fails — through a random rather than skewed inactivation pattern, or because an unbalanced translocation separates the duplicated segment from the X-inactivation centre in cis so that it cannot be silenced at all. Recurrent, dosage-defined intervals are modelled here as subtypes. The best characterised is Xq28 duplication encompassing MECP2, the single most important dosage-sensitive gene in distal Xq duplications; SOX3 at Xq26.3–q27.1 accounts for the hypopituitary presentations, and a 173 kb minimal region at Xq25 containing STAG2 defines a duplication cohesinopathy.

Ask OpenScientist

Ask a research question about Chromosome Xq Duplication. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

1
Mappings
1
Definitions
1
Inheritance
9
Pathophys.
32
Phenotypes
3
Gaps
16
Pathograph
6
Genes
4
Medical Actions
6
Subtypes
3
Trials
1
References
1
Deep Research
🔗

Mappings

MONDO
MONDO:0017010 partial duplication of the long arm of chromosome X
skos:exactMatch MONDO
MONDO:0017010 is the grouping term for segmental copy-number gain of the long arm of the X chromosome, carrying "partial duplication of chromosome Xq" and "partial trisomy of the long arm of chromosome X" as EXACT synonyms and an RO:0004030 (disease has location) relation to Xq. It is the exact concept this entry models.
📘

Definitions

1
Array CGH confirmation of Xq copy-number gain
Diagnosis rests on recognition of the clinical phenotype and is confirmed by demonstration of the copy-number gain. Array comparative genomic hybridization is the confirmatory test of choice, having superseded karyotyping, which detects only duplications above roughly 5-10 Mb.
DIAGNOSTIC_CRITERIA
Show evidence (2 references)
PMID:19232094 SUPPORT Human Clinical
"Diagnosis is based on clinical features and is confirmed by CGH array techniques."
States the diagnostic pathway.
PMID:20301461 SUPPORT Human Clinical
"The diagnosis of MECP2 duplication syndrome is established in an individual by identification of a heterozygous whole-gene duplication of MECP2 on molecular genetic testing."
GeneReviews Diagnosis/Testing - molecular demonstration of the whole-gene duplication is what establishes the diagnosis for the Xq28 subtype.
👪

Inheritance

1
X-linked inheritance HP:0001417
Most Xq duplications in affected males are inherited from a carrier mother who is herself unaffected or only mildly affected because of skewed X-inactivation; de novo events and unbalanced products of a parental balanced rearrangement also occur. Rearrangement architecture predicts recurrence risk: de novo events are much more common among terminal duplications than tandem duplications.
X-linked inheritance
Show evidence (2 references)
PMID:19232094 SUPPORT Human Clinical
"The recurrence risk is significant if a structural rearrangement is present in one of the parent, the most frequent situation being that of an intrachromosomal duplication inherited from the mother."
States the predominant X-linked maternal transmission pattern.
PMID:39696717 SUPPORT Human Clinical
"Notably, 65% of de novo events occurred in the Terminal duplication group in contrast with 17% observed in Tandem duplications."
Quantifies how rearrangement architecture predicts de novo versus inherited origin, which drives recurrence counselling.
◆

Subtypes

6
Xq28 duplication encompassing MECP2 MONDO:0010283
MECP2 hgnc:6990 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in MECP2 (hgnc:6990). hgnc:6990 is a gene from the HUGO Gene Nomenclature Committee. L1CAM hgnc:6470 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in L1CAM (hgnc:6470). hgnc:6470 is a gene from the HUGO Gene Nomenclature Committee.
Duplication spanning MECP2 at Xq28, consistently including L1CAM in the interstitial microduplication form. The most frequently reported and best characterised Xq duplication; increased MECP2 dosage is the principal driver of the neurodevelopmental phenotype. Rearrangement structures are heterogeneous — tandem duplications, terminal duplications (mostly translocations), inverted triplications and other complex genomic rearrangements — and this architecture modulates severity. Corresponds to the separately curated entry MECP2 Duplication Syndrome (MONDO:0010283).
Show evidence (2 references)
PMID:19232094 SUPPORT Human Clinical
"These microduplications are var- iable in size, ranging from 0.2 to 2.2 Mb, but consistently include MECP2 and L1 cell adhesion molecule (L1CAM), as well as intervening genes"
Defines the size range and obligate gene content of the Xq28 interstitial interval.
PMID:39696717 SUPPORT Human Clinical
"Duplication sizes in the cohort ranging from 64.6 kb to 16.5 Mb were classified into four categories comprising of tandem duplications (48%), terminal duplications (22%), inverted triplications (20%), and other CGRs (10%)."
Contemporary 137-individual cohort defining the size range and structural classes of MECP2-spanning gains.
Xq26–qter duplication / distal Xq functional disomy
Larger, cytogenetically visible duplications of the distal long arm, spanning Xq26–q28 (often reported as Xq27–qter). These yield the classic recognisable distal Xq disomy phenotype and overlap the Xq28/MECP2 subtype in gene content, but carry a heavier burden of growth failure, microcephaly, and craniofacial dysmorphism.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"In particular, the Xq26–q28 chromosome region yields a recognisable phenotype including distinctive facial fea- tures, major axial hypotonia, severe developmental delay, severe feeding difficulties, abnormal genitalia and prone- ness to infections"
Defines the distal Xq26-q28 interval as a recognisable clinical entity.
Xq26.3–q27.1 duplication encompassing SOX3 MONDO:0010712
SOX3 hgnc:11199 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in SOX3 (hgnc:11199). hgnc:11199 is a gene from the HUGO Gene Nomenclature Committee.
Duplication of the Xq26–q27 region containing the transcription factor SOX3. Presents with hypopituitarism, anterior pituitary hypoplasia, ectopic posterior pituitary and absent infundibulum. Notably, SOX3 over- and underdosage converge on the same pituitary phenotype, and intellectual disability is not obligate.
Show evidence (1 reference)
PMID:15800844 SUPPORT Human Clinical
"We report a submicroscopic duplication of Xq27.1, the smallest reported to date (685.6 kb), in two siblings with variable hypopituitarism, callosal abnormalities, anterior pituitary hypoplasia (APH), an ectopic posterior pituitary (EPP), and an absent infundibulum."
Defines the minimal SOX3-containing duplication and its pituitary phenotype.
Xq25 duplication encompassing STAG2 MONDO:0010507
STAG2 hgnc:11355 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in STAG2 (hgnc:11355). hgnc:11355 is a gene from the HUGO Gene Nomenclature Committee.
Xq25 microduplication with a shortest region of overlap of 173 kb containing only STAG2, a subunit of the cohesin complex. Presents with delayed milestones, speech disturbance, intellectual disability, abnormal behaviour and characteristic facial dysmorphism. Increased STAG2 dosage makes this a cohesinopathy — mechanistically distinct from the chromatin-reader (MECP2) and transcription-factor (SOX3) intervals.
Show evidence (1 reference)
PMID:25677961 SUPPORT Human Clinical
"The common duplicated interval allowed further refinement of the shortest region of overlap to 173 kb, including only one gene, STAG2, which encodes a component of the cohesin complex."
Defines the minimal Xq25 interval and identifies STAG2 as the dosage-sensitive gene.
Xq25–q26 duplication (hypopituitarism and hemihyperplasia) MONDO:0010252
Mid-Xq gains spanning Xq25–q26 associated with two further presentations: X-linked panhypopituitarism with variable intellectual disability mapping to a duplicated dosage-sensitive locus, and a 1.65 Mb critical region at Xq25 for hemihyperplasia with digital anomalies.
Show evidence (2 references)
PMID:9106538 SUPPORT Human Clinical
"An apparent extra copy of the marker DXS102, observed in the region of the disease gene in affected males and heterozygous carrier females, suggests that a segment including this marker is duplicated."
Establishes an Xq25-q26 duplication segregating with panhypopituitarism.
PMID:20101693 SUPPORT Human Clinical
"we have delineated a 1.65 Mb critical region for hemihyperplasia and digital anomalies on chromosome Xq25"
Defines the Xq25 critical region for the hemihyperplasia/digital presentation.
Proximal Xq (Xq21–q24) duplication
Proximal long-arm duplications, reported less often and more heterogeneous in breakpoint. Patients show craniofacial dysmorphism, aberrant brain myelination, hypotonia, psychomotor and growth retardation, feeding problems and hypoplastic genitalia.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Patients show craniofacial dysmorphism, brain and neurologic abnormalities such as aberrant brain myelination, hypot- onia, mental, psychomotor and growth retardation, feed- ing issues, hypoplasic genitalia."
Describes the proximal Xq duplication phenotype.
?

Discussions and Knowledge Gaps

3
Is the recurrent-infection phenotype of Xq28 functional disomy caused by increased innate-immune gene dosage (IRAK1/IKBKG), or is it secondary to aspiration from severe hypotonia and feeding difficulty?
KNOWLEDGE GAP gap_xq_dup_irak1_vs_aspiration
Attached to
pathophysiology#Increased IRAK1 Dosage
The IRAK1/IKBKG dosage hypothesis is stated only speculatively in the primary literature ("might result from"), and no study has demonstrated altered innate immune signalling in patient cells. A purely mechanical explanation is plausible given that severe axial hypotonia, dysphagia and gastroesophageal reflux are themselves near-universal in this population. The distinction matters clinically: an immune mechanism would justify immunological evaluation and possibly prophylaxis, whereas an aspiration mechanism directs management to feeding and airway protection.
Proposed experiments
Innate immune signalling assay in patient-derived cells
exp_xq_dup_irak1_signalling
Quantify IRAK1 and IKBKG transcript and protein levels and measure TLR/IL-1 pathway output in cells from individuals with Xq28 duplication, stratified by whether the duplication includes IRAK1/IKBKG.
Genotype-stratified infection burden comparison
exp_xq_dup_infection_stratified
Compare respiratory infection rates between individuals whose duplications do and do not encompass IRAK1/IKBKG, controlling for degree of hypotonia and documented aspiration.
What determines whether a female carrier of an Xq duplication is asymptomatic or manifests a male-like phenotype?
KNOWLEDGE GAP gap_xq_dup_female_manifesting_carriers
Attached to
pathophysiology#Failure of X-Chromosome Dosage Compensation
X-inactivation pattern explains most of the variance - skewing towards the duplicated X protects, random inactivation manifests, and an unbalanced translocation separating the segment from the XIC in cis produces full expression. But rare manifesting females have been described despite favourable skewing, for which local escape from inactivation, expression of recessive alleles on the active X, or gene disruption at the breakpoint have all been proposed without resolution. Predicting carrier outcome is directly actionable for genetic counselling.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"In rare cases, a favourable skewed X-inactivation is observed. For these cases, other explana- tions such as local escape from inactivation, expression of recessive genes from the active X, or disruption of a gene by the rearrangement have been suggested"
States the unresolved alternatives for manifesting females with favourable skewing.
Which cohesin-dependent transcriptional programs are dysregulated by increased STAG2 dosage, and do they explain the Xq25 duplication phenotype?
KNOWLEDGE GAP gap_xq_dup_stag2_transcriptional_mechanism
Attached to
pathophysiology#Increased STAG2 Dosage and Cohesin Dysregulation
The Xq25 interval has been mapped to a 173 kb region containing STAG2 alone, which is strong positional evidence, but the proposed mechanism - dysregulation of cohesin downstream target genes - is an inference rather than a measurement. No patient-derived transcriptomic data establishing which targets change, or in which direction, has been reported. Without it, Xq25 duplication is classified as a cohesinopathy on positional grounds alone, and the mechanistic contrast with loss-of-function STAG2 cohesinopathies remains untested.
Proposed experiments
Transcriptomic profiling of STAG2 duplication patient cells
exp_xq25_stag2_transcriptome
RNA-seq of patient-derived cells carrying the Xq25 duplication versus controls, testing whether cohesin target gene sets are differentially expressed and whether the direction of change is opposite to that seen in STAG2 loss-of-function cohesinopathy.
⚙

Pathophysiology

9
Segmental Copy Number Gain on Xq
An extra copy of a segment of the long arm of the X chromosome. In males this arises most often as an intrachromosomal duplication transmitted by a non-manifesting mother, and less often from an unbalanced X/Y or X/autosome translocation. Duplication size and gene content vary widely, from cytogenetically visible multi-megabase segments to submicroscopic gains encompassing only one or a few genes detectable by array CGH.
Downstream
Failure of X-Chromosome Dosage Compensation Whether the extra segment is phenotypically expressed depends entirely on whether X-inactivation can silence it.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Xq duplications may be caused either by an intrachromosomal duplication or an unbalanced X/Y or X/ autosome translocation."
Establishes the two structural routes to an Xq segmental gain.
Failure of X-Chromosome Dosage Compensation
X-chromosome inactivation, initiated from the X-inactivation centre (XIC) at Xq13, normally equalises X-linked gene expression between XX and XY cells. This safeguard fails in three distinguishable ways. In XY males there is no second X to inactivate, so any structural Xq disomy is obligatorily functional disomy. In females carrying an intrachromosomal duplication, inactivation is usually skewed towards the abnormal X, which rescues the phenotype; manifesting females are those with a random inactivation pattern. In females with an unbalanced X/autosome translocation, the translocated X segment is physically separated from its XIC in cis and therefore cannot be inactivated at all, so the phenotype is fully expressed and can be as severe as in males.
X-chromosome inactivation GO:0009048 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased X-chromosome inactivation, annotated with dosage compensation by inactivation of X chromosome (GO:0009048). GO:0009048 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Functional Xq Disomy and Increased Gene Dosage Uncompensated duplicated genes are expressed at double their normal level.
Show evidence (2 references)
PMID:19232094 SUPPORT Human Clinical
"In XY males, structural X disomy always results in functional disomy. In females, failure of X chromosome dosage compensation could result from a variety of mechanisms, including an unfavourable pattern of inactivation, a breakpoint separating an X segment from the X-inactivation centre in..."
States the sex-dependent mechanisms by which dosage compensation fails.
PMID:16080119 SUPPORT Human Clinical
"The duplications segregate with the disease in the families, and asymptomatic carrier females show complete skewing of X inactivation."
Demonstrates that successful skewing towards the duplicated X protects female carriers.
Functional Xq Disomy and Increased Gene Dosage
Double expression of the X-linked genes lying within the duplicated segment. Because most X-linked genes are not tolerant of a twofold expression increase, the identity of the dosage-sensitive genes captured by the duplication determines which organ systems are affected — this is why breakpoint position, not duplication size alone, drives the phenotype.
gene expression GO:0010467 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased gene expression (GO:0010467). GO:0010467 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
MECP2 Overexpression Distal Xq duplications spanning Xq28 raise MECP2 dosage.
SOX3 Overdosage Xq26.3-q27.1 duplications raise SOX3 dosage.
Increased STAG2 Dosage and Cohesin Dysregulation Xq25 duplications raise STAG2 dosage.
Increased IRAK1 Dosage IRAK1 lies immediately adjacent to MECP2 and is co-duplicated in most Xq28 gains.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Clinical manifestations widely vary depending on the gender of the patient and on the gene content of the duplicated segment."
Links phenotypic outcome to which genes the duplicated segment contains.
MECP2 Overexpression
MeCP2 is a methyl-CpG-binding chromatin protein expressed most highly in post-mitotic, post-migratory neurons. Its level must be tightly regulated in both directions: loss of function causes Rett syndrome, while a roughly twofold increase from duplication is itself pathogenic. The duplicated allele is structurally wild type, so this is a quantitative overexpression rather than a qualitative change in protein function. Copy number is transmitted through to protein: patient-derived lymphoblastoid RNA and protein levels are correlated, and triplications produce significantly more MECP2 transcript than duplications.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
methyl-CpG binding GO:0008327 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves increased methyl-CpG binding (GO:0008327). GO:0008327 is a molecular function from the Gene Ontology. ↑ INCREASED
Downstream
Impaired Neuronal Maturation and Progressive Neurological Decline Excess MeCP2 perturbs the transcriptional programs of maturing neurons.
Dosage- and Architecture-Dependent Severity Gradient The absolute level of MeCP2 reached - highest in triplications - is one of the two determinants of where an individual falls on the severity gradient.
Show evidence (3 references)
PMID:19232094 SUPPORT Human Clinical
"The MECP2 gene in Xq28 is the most important dosage-sensitive gene responsible for the abnormal phenotype in duplications of distal Xq."
Identifies MECP2 dosage as the principal driver in distal Xq duplication.
PMID:16080119 SUPPORT Human Clinical
"Our findings demonstrate that, in humans, not only impaired or abolished gene function but also increased MeCP2 dosage causes a distinct phenotype."
Establishes increased MECP2 dosage as causal in humans, distinct from loss of function.
PMID:39696717 SUPPORT Human Clinical
"demonstrating that genomic aberrations spanning MECP2 lead to altered MECP2 RNA and MECP2 protein levels."
Confirms the copy-number-to-protein-dosage step in patient-derived cells.
Impaired Neuronal Maturation and Progressive Neurological Decline
Excess MeCP2 disturbs activity-dependent transcriptional regulation in maturing neurons. In transgenic mice expressing MeCP2 at approximately twice wild-type levels the course is biphasic and delayed: an early period of enhanced hippocampal synaptic plasticity and learning is followed after 20 weeks by seizures, hypoactivity and premature death. This delayed, progressive trajectory mirrors the human course, in which early hypotonia and developmental delay give way to progressive spasticity and epilepsy.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
neuron maturation GO:0042551 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased neuron maturation (GO:0042551). GO:0042551 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Intellectual Disability Disrupted neuronal maturation underlies the cognitive impairment.
Progressive Spasticity The progressive motor component of the neurological decline.
Seizures Epilepsy emerges as part of the delayed, progressive phase.
Show evidence (2 references)
PMID:15351775 SUPPORT Model Organism
"After 20 weeks of age, however, these mice developed seizures, became hypoactive and approximately 30% of them died by 1 year of age."
Documents the delayed, progressive neurological course under MeCP2 overexpression.
PMID:16080119 SUPPORT Human Clinical
"we identified a small duplication at Xq28 in a large family with a severe form of MR associated with progressive spasticity."
Human counterpart - severe intellectual disability with progressive spasticity.
Dosage- and Architecture-Dependent Severity Gradient
Severity is graded rather than all-or-none, and is set by two partly separable variables: the absolute level of MeCP2 (triplication worse than duplication) and the structural class of the rearrangement itself. Phenotypic burden — survival, developmental level, microcephaly, epilepsy, and genitourinary/eye anomalies — worsens progressively across tandem duplications, other complex rearrangements, terminal duplications/translocations, and triplications. Rearrangement structure therefore contributes to expression variability independently of copy number alone, plausibly through position effects and disruption of regulatory architecture at the breakpoints.
Show evidence (2 references)
PMID:39696717 SUPPORT Human Clinical
"Genotype-phenotype analyses indicated a gradual worsening of phenotypic features, including overall survival, developmental levels, microcephaly, epilepsy, and genitourinary/eye abnormalities in the following order: Tandem duplications, Other complex duplications, Terminal..."
Establishes the ordered severity gradient across rearrangement classes.
PMID:39696717 SUPPORT Human Clinical
"Whereas the level of MECP2 is a key determinant of the phenotype, the DNA rearrangement structure can contribute to clinical severity and disease expression variability."
Separates the two contributions - MECP2 level and rearrangement architecture - to clinical severity.
SOX3 Overdosage
SOX3 is a developmental transcription factor at Xq27.1 expressed in the infundibulum. Both over- and underdosage impair infundibular development and produce hypopituitarism, indicating a narrow tolerated expression window rather than a simple loss-of-function relationship. This is the mechanistic basis of the hypopituitary presentations of Xq26-q27 duplication.
adenohypophysis development GO:0021984 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased adenohypophysis development (GO:0021984). GO:0021984 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Hypopituitarism Infundibular and anterior pituitary hypoplasia produce deficient anterior pituitary hormone output.
Show evidence (1 reference)
PMID:15800844 SUPPORT Human Clinical
"We conclude that both over- and underdosage of SOX3 are associated with similar phenotypes, consisting of infundibular hypoplasia and hypopituitarism but not necessarily MR."
Establishes SOX3 dosage sensitivity in both directions for the pituitary phenotype.
Increased STAG2 Dosage and Cohesin Dysregulation
STAG2 encodes a subunit of the cohesin complex, which mediates sister chromatid cohesion and, critically for this phenotype, shapes chromatin architecture and enhancer-promoter looping. Increased STAG2 copy number at Xq25 is proposed to act by dysregulating cohesin downstream target genes, placing this interval among the cohesinopathies. The transcriptional consequences are inferred from the mapping data rather than directly measured in patients.
sister chromatid cohesion GO:0007062 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased sister chromatid cohesion (GO:0007062). GO:0007062 is a biological process from the Gene Ontology. ↑ INCREASED
Show evidence (1 reference)
PMID:25677961 SUPPORT Human Clinical
"We suggest that increased STAG2 gene copy number and dysregulation of its downstream target genes may be responsible for the specific clinical findings of this syndrome."
Proposes the cohesin-dysregulation mechanism. Marked PARTIAL because the source frames it as a suggestion ("may be responsible") supported by mapping rather than direct transcriptional measurement in patients.
Increased IRAK1 Dosage
IRAK1 and IKBKG lie immediately telomeric to MECP2 and are usually contained within the duplicated Xq28 segment. Both are innate immune signalling components downstream of the Toll-like and IL-1 receptors, and their increased dosage has been proposed as the explanation for the recurrent respiratory infections that distinguish Xq28 functional disomy from other X-linked intellectual disability/hypotonia syndromes. This remains a proposed rather than demonstrated mechanism.
toll-like receptor signaling pathway GO:0002224 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased toll-like receptor signaling pathway (GO:0002224). GO:0002224 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Recurrent Respiratory Infections Proposed contribution of innate immune gene dosage to infection proneness.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"The recurrent infections might result from the increased dosage of the IRAK1 or IKBKG genes generally present in the duplicated region"
Proposes IRAK1/IKBKG dosage as the basis of recurrent infection. Marked PARTIAL because the source states this as a hypothesis ("might result from"), not a demonstrated mechanism.
⬡

Pathograph

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

Phenotypes

32
Cardiovascular 1
Mottled Skin Cutis marmorata HP:0000965 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cutis marmorata (HP:0000965). HP:0000965 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"autistic behaviors, nonspecific neuroradiologic findings on brain MRI, mottled skin, and urogenital anomalies have been observed in several affected boys."
GeneReviews lists mottled skin among the additional features.
Digestive 3
Severe Feeding Difficulties FREQUENT HP:0011968 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties (HP:0011968), qualified as severity severe. HP:0011968 is a phenotype from the Human Phenotype Ontology.
Severity: SEVERE
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Others frequent clinical manifestations: severe feeding difficulties with gastro oesophageal reflux, excessive drooling, seizures, recurrent infections."
Listed among frequent manifestations; Table 1 records severe feeding problems in 9/9, 10/14 and 15/29 patients, supporting FREQUENT.
Gastroesophageal Reflux HP:0002020 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Gastroesophageal reflux (HP:0002020). HP:0002020 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"gastrointestinal manifestations including gastroesophageal reflux and constipation"
GeneReviews lists reflux among core gastrointestinal manifestations.
Constipation HP:0002019 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Constipation (HP:0002019). HP:0002019 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"gastrointestinal manifestations including gastroesophageal reflux and constipation"
GeneReviews lists constipation among core gastrointestinal manifestations.
Ear 1
Macrotia HP:0000400 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Macrotia (HP:0000400). HP:0000400 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"epicanthal folds, large ears, small and open mouth, ear anomalies, pointed nose, abnormal palate and facial hypotonia)"
Large ears listed among the characteristic distal Xq facial features.
Endocrine 1
Anterior Pituitary Hypoplasia HP:0010627 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Anterior pituitary hypoplasia (HP:0010627). HP:0010627 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15800844 SUPPORT Human Clinical
"anterior pituitary hypoplasia (APH), an ectopic posterior pituitary (EPP), and an absent infundibulum."
Structural pituitary findings on MRI in SOX3 duplication.
Genitourinary 2
Cryptorchidism HP:0000028 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cryptorchidism (HP:0000028). HP:0000028 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"hypoplasic genitalia, hypospadias and/or cryptorchidism"
Cryptorchidism listed among the frequent genital malformations.
Gonadal Dysgenesis HP:0000133 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Gonadal dysgenesis (HP:0000133). HP:0000133 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"facial dysmorphism and gonadal dysgenesis [21,22]."
Gonadal dysgenesis among the manifestations reported in females.
Head and Neck 2
Microcephaly FREQUENT HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:19232094 SUPPORT Human Clinical
"Growth: prenatal and postnatal growth retardation, microcephaly"
Microcephaly listed among the core growth features of distal Xq duplication. Table 1 of the same review shows it is near-universal in the cytogenetically visible duplications (19/19) but uncommon in MECP2 microduplication (5/39); FREQUENT reflects the pooled spectrum.
PMID:39696717 SUPPORT Human Clinical
"Genotype-phenotype analyses indicated a gradual worsening of phenotypic features, including overall survival, developmental levels, microcephaly, epilepsy, and genitourinary/eye abnormalities"
Confirms microcephaly varies systematically with rearrangement class rather than being uniformly present.
Epicanthus HP:0000286 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Epicanthus (HP:0000286). HP:0000286 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"epicanthal folds, large ears, small and open mouth, ear anomalies, pointed nose, abnormal palate and facial hypotonia)"
Epicanthal folds listed among the characteristic facial features.
Immune 1
Recurrent Respiratory Infections FREQUENT HP:0002205 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent respiratory infections (HP:0002205), qualified as temporality recurrent. HP:0002205 is a phenotype from the Human Phenotype Ontology.
Temporal: RECURRENT
Show evidence (2 references)
PMID:20301461 SUPPORT Human Clinical
"recurrent respiratory infections (in ~75% of affected individuals)"
GeneReviews gives ~75%, mapping to FREQUENT (30-79%).
PMID:19232094 SUPPORT Human Clinical
"Recurrent respiratory infections, especially recur- rent pneumonia, help to distinguish Xq28 functional disomy (including MECP2 duplication) from other XLMR-hypotonia syndromes."
Establishes the discriminating value of recurrent pneumonia.
Musculoskeletal 2
Progressive Spasticity FREQUENT HP:0001257 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spasticity (HP:0001257), qualified as course progressive. HP:0001257 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"poor speech development, progressive spasticity, recurrent respiratory infections (in ~75% of affected individuals), and seizures (in ~50%)"
GeneReviews lists progressive spasticity as a core feature; Table 1 of PMID:19232094 records spasticity in 17/21 MECP2 duplication patients (~81%), supporting FREQUENT.
Musculoskeletal Complications FREQUENT Recurrent fractures HP:0002757 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent fractures (HP:0002757). HP:0002757 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"We obtained data on 93 subjects for their musculoskeletal problems and 49 (52.6%) reported musculoskeletal abnormalities, with the most common ones including bone fractures (26 subjects), osteopenia/osteoporosis (13 subjects including 3 requiring alendronate infusion), scoliosis (13 subjects),..."
52.6% overall musculoskeletal involvement maps to FREQUENT (30-79%); fractures were the single most common component.
Nervous System 10
Global Developmental Delay VERY_FREQUENT HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Psychomotor retardation: severe mental retardation, absence or severely retarded speech"
Reported for the distal Xq phenotype; Table 1 of the same review records developmental delay in 12/12, 19/19 and 47/47 patients across the three duplication groups, supporting VERY_FREQUENT.
Intellectual Disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:16080119 SUPPORT Human Clinical
"we identified a small duplication at Xq28 in a large family with a severe form of MR associated with progressive spasticity."
Severe intellectual disability in the Xq28 duplication family.
PMID:25677961 SUPPORT Human Clinical
"the phenotype of our patients is characterized by delayed milestones, speech disturbance, intellectual disability, abnormal behaviours and a characteristic facial dysmorphism."
Intellectual disability in the Xq25/STAG2 duplication interval.
Delayed or Absent Speech VERY_FREQUENT Delayed speech and language development HP:0000750 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Delayed speech and language development (HP:0000750). HP:0000750 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"delayed psychomotor development leading to severe intellectual disability, poor speech development"
GeneReviews lists poor speech development as a core feature; Table 1 of PMID:19232094 records absent or delayed speech in 46/47 MECP2 duplication patients, supporting VERY_FREQUENT.
Seizures FREQUENT HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"recurrent respiratory infections (in ~75% of affected individuals), and seizures (in ~50%)"
GeneReviews gives ~50% for seizures, mapping to FREQUENT (30-79%).
Autistic Behavior HP:0000729 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Autistic behavior (HP:0000729). HP:0000729 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"In addition to the core features, autistic behaviors, nonspecific neuroradiologic findings on brain MRI, mottled skin, and urogenital anomalies have been observed in several affected boys."
GeneReviews lists autistic behaviours among the additional features.
Dysautonomia VERY_FREQUENT Abnormal autonomic nervous system physiology HP:0012332 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dysautonomia, annotated with Abnormal autonomic nervous system physiology (HP:0012332). HP:0012332 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"We identified the frequency of dysautonomia in 105/121 (86.7%) of individuals."
86.7% maps to VERY_FREQUENT (80-100%).
High Pain Tolerance FREQUENT Impaired pain sensation HP:0007328 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is High pain tolerance, annotated with Impaired pain sensation (HP:0007328). HP:0007328 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"High pain tolerance was present in 85/109 (77.9%) of MRXSL individuals."
77.9% maps to FREQUENT (30-79%).
Insomnia FREQUENT HP:0100785 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Insomnia (HP:0100785). HP:0100785 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"We had information on insomnia from 118 subjects and 62 of them (52.5%) were found to have insomnia."
52.5% maps to FREQUENT (30-79%).
Obstructive Sleep Apnea FREQUENT HP:0002870 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Obstructive sleep apnea (HP:0002870). HP:0002870 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"Data on sleep apnea status were available in 114 subjects and 63 subjects (55.2%) were reported to have sleep apnea. Only two subjects were reported to have central sleep apnea and the remaining had obstructive sleep apnea."
55.2% maps to FREQUENT (30-79%), and the same sentence establishes that the apnea is predominantly obstructive.
Abnormal Behaviour Atypical behavior HP:0000708 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal behaviour, annotated with Atypical behavior (HP:0000708). HP:0000708 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25677961 SUPPORT Human Clinical
"delayed milestones, speech disturbance, intellectual disability, abnormal behaviours and a characteristic facial dysmorphism."
Abnormal behaviour among the defining features of Xq25 duplication.
Growth 2
Growth Retardation VERY_FREQUENT Short stature HP:0004322 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short stature (HP:0004322). HP:0004322 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Growth: prenatal and postnatal growth retardation, microcephaly"
Listed as a core growth feature; Table 1 records growth retardation in 9/10 and 17/19 patients in the two cytogenetically visible duplication groups, supporting VERY_FREQUENT.
Hemihyperplasia Hemihypertrophy HP:0001528 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hemihypertrophy (HP:0001528). HP:0001528 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20101693 SUPPORT Human Clinical
"We report on a 4-year-old female with hemihyperplasia, syndactyly of fingers and toes, bilateral 5th finger clinodactyly, short stature, developmental delay, and microcephaly associated with an 11.2 Mb duplication of Xq25-Xq27.1."
Hemihyperplasia with an Xq25-q27.1 duplication.
Other 7
Axial Hypotonia VERY_FREQUENT HP:0008936 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Axial hypotonia (HP:0008936), qualified as temporality chronic. HP:0008936 is a phenotype from the Human Phenotype Ontology.
Temporal: CHRONIC
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"major axial hypotonia, severe developmental delay, severe feeding difficulties, abnormal genitalia and proneness to infections."
Axial hypotonia listed as a core distal Xq feature; Table 1 records hypotonia in 11/11, 19/19 and 29/32 patients, supporting VERY_FREQUENT.
Inability to Walk or Limited Walking FREQUENT HP:0002540 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Inability to walk (HP:0002540). HP:0002540 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Never walked or limited walking nr 12/14 21/34"
Table 1 records 12/14 (86%) in Xq26.3qter and 21/34 (62%) in MECP2 duplication; the pooled range supports FREQUENT.
Bruxism FREQUENT HP:0003763 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bruxism (HP:0003763). HP:0003763 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"Bruxism was reported in 81/112 (72.3%) of subjects."
72.3% maps to FREQUENT (30-79%).
Refractive Error and Strabismus FREQUENT Abnormality of refraction HP:0000539 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormality of refraction (HP:0000539). HP:0000539 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39696717 SUPPORT Human Clinical
"Information on visual abnormalities were present in 117 subjects and 71 of them (60.6%) reported various, relatively minor visual abnormalities including refraction errors and strabismus."
60.6% maps to FREQUENT (30-79%).
Hypoplastic Genitalia FREQUENT Hypoplastic male external genitalia HP:0000050 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoplastic male external genitalia (HP:0000050). HP:0000050 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Malformations: genitalia malformations including hypoplasic genitalia, hypospadias and/or cryptorchidism are the more frequent malformations"
Named as the most frequent malformation class; Table 1 records hypoplastic genitalia/cryptorchidism in 11/11, 15/19 and 5/10 patients, supporting FREQUENT.
Hypopituitarism HP:0040075 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypopituitarism (HP:0040075). HP:0040075 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:15800844 SUPPORT Human Clinical
"in two siblings with variable hypopituitarism, callosal abnormalities, anterior pituitary hypoplasia (APH), an ectopic posterior pituitary (EPP), and an absent infundibulum."
Hypopituitarism in the minimal SOX3-containing Xq27.1 duplication.
PMID:9106538 SUPPORT Human Clinical
"Affected members exhibit variable degrees of hypopituitarism and mental retardation."
Panhypopituitarism segregating with an Xq25-q26 duplication.
Digital Anomalies Abnormal digit morphology HP:0011297 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal digit morphology (HP:0011297). HP:0011297 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:20101693 SUPPORT Human Clinical
"syndactyly of fingers and toes, bilateral 5th finger clinodactyly"
Digital anomalies co-segregating with the Xq25 critical region.
PMID:19232094 SUPPORT Human Clinical
"Abnormal fingers and toes have been reported"
Digital anomalies also reported in the general distal Xq phenotype.
🧬

Genetic Associations

6
MECP2
Gene: MECP2 hgnc:6990 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MECP2 (hgnc:6990). hgnc:6990 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (2 references)
PMID:20301461 SUPPORT Human Clinical
"MECP2 duplication syndrome is 100% penetrant in males. Occasionally females have been described with a MECP2 duplication and a range of findings from mild intellectual disability to a phenotype similar to that seen in males."
GeneReviews establishes complete penetrance in males and the variable female range.
PMID:19232094 SUPPORT Human Clinical
"The MECP2 gene in Xq28 is the most important dosage-sensitive gene responsible for the abnormal phenotype in duplications of distal Xq."
Identifies MECP2 as the key dosage-sensitive gene.
SOX3
Gene: SOX3 hgnc:11199 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SOX3 (hgnc:11199). hgnc:11199 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:15800844 SUPPORT Human Clinical
"This duplication contains SOX3 and sequences corresponding to two transcripts of unknown function; only Sox3 is expressed in the infundibulum in mice."
Localises the pituitary phenotype to SOX3 within the duplicated interval.
STAG2
Gene: STAG2 hgnc:11355 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is STAG2 (hgnc:11355). hgnc:11355 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:25677961 SUPPORT Human Clinical
"further refinement of the shortest region of overlap to 173 kb, including only one gene, STAG2, which encodes a component of the cohesin complex."
Identifies STAG2 as the sole gene in the Xq25 minimal region.
L1CAM
Gene: L1CAM hgnc:6470 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is L1CAM (hgnc:6470). hgnc:6470 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: COOPERATING
Show evidence (1 reference)
PMID:16080119 SUPPORT Human Clinical
"The duplications in the four patients vary in size from 0.4 to 0.8 Mb and harbor several genes, which, for each duplication, include the MR-related L1CAM and MECP2 genes."
L1CAM is consistently within the Xq28 duplicated segment.
IRAK1
Gene: IRAK1 hgnc:6112 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is IRAK1 (hgnc:6112). hgnc:6112 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: MODIFIER
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"The recurrent infections might result from the increased dosage of the IRAK1 or IKBKG genes generally present in the duplicated region"
Proposed modifier role. PARTIAL because the source frames this as a hypothesis rather than a demonstrated mechanism.
PLP1
Gene: PLP1 hgnc:9086 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is PLP1 (hgnc:9086). hgnc:9086 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Complete duplication of the PLP1 gene on Xq22 is the cause of 60–70% of PMD cases"
Establishes PLP1 duplication as a distinct dosage mechanism within Xq.
💊

Medical Actions

4
Symptomatic and Multidisciplinary Supportive Care
Action: Supportive CareNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. NCIT:C15747
No disease-modifying therapy exists. Management is symptomatic and multi-specialist, with particular attention to preventing malnutrition and recurrent infection. Educational and rehabilitation support should be offered to all patients.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Management is multi-specialist and only symptomatic, with special attention to prevention of malnutrition and recurrent infections."
Establishes supportive, symptomatic management as the standard of care.
Prompt Antibiotic Treatment of Respiratory Infections
Action: antibiotic therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is antibiotic therapy (NCIT:C15620). NCIT:C15620 is a clinical intervention from the NCI Thesaurus. Ontology label: Antibiotic Therapy NCIT:C15620
Respiratory infections should be treated promptly with antibiotics, all vaccines should be given, and gastrostomy should be considered where aspiration is present.
Mechanism Target:
MODULATES Recurrent Respiratory Infections — Symptomatic control of the infection burden; does not address the underlying gene dosage.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"Prompt antibiotic treatment for respiratory infections; all vaccines should be given; consider gastrostomy tube if aspiration is present."
GeneReviews management recommendation for the infection burden.
Physical Therapy
Action: Physical TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Physical Therapy (NCIT:C15302). NCIT:C15302 is a clinical intervention from the NCI Thesaurus. NCIT:C15302
Physical therapy to maintain range of motion and reduce the likelihood of contractures in the setting of progressive spasticity.
Mechanism Target:
MODULATES Progressive Spasticity — Maintains range of motion against progressive spasticity.
Show evidence (1 reference)
PMID:20301461 SUPPORT Human Clinical
"Physical therapy to maintain range of motion to reduce likelihood of contractures."
GeneReviews management recommendation.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Recurrence risk is substantial where a parent carries a structural rearrangement, most often a maternally inherited intrachromosomal duplication. Because de novo events cluster in the terminal duplication class, rearrangement architecture informs counselling. Prenatal diagnosis by cytogenetic testing including FISH and/or DNA quantification, and preimplantation genetic testing, are available.
Show evidence (2 references)
PMID:19232094 SUPPORT Human Clinical
"Prenatal diagnosis is performed by cytogenetic testing including FISH and/or DNA quantification methods."
Establishes the prenatal testing options underpinning counselling.
PMID:20301461 SUPPORT Human Clinical
"Males who inherit the MECP2 duplication will be affected; females who inherit the MECP2 duplication are typically asymptomatic but may exhibit clinical manifestations ranging from mild nonspecific intellectual disability to a severe phenotype similar to that observed in males."
GeneReviews Genetic Counseling - the sex-dependent outcome for inheriting offspring, which is the substance of the counselling discussion.
📊

Prevalence

1
Worldwide
Unknown Not yet documented
No prevalence estimate exists for Xq duplications as a class. The 2009 review counted roughly 40 reported cases of cytogenetically visible Xq28 functional disomy and about 50 cryptic MECP2-encompassing duplications; array CGH has since raised ascertainment, but no denominator-based estimate has been published for the grouping. A birth-prevalence figure exists only for the MECP2 subtype and is recorded on MECP2_Duplication_Syndrome.yaml.
Show evidence (1 reference)
PMID:19232094 SUPPORT Human Clinical
"Prevalence of Xq duplications remains unknown. About 40 cases of Xq28 functional disomy due to cytogenetically visible rearrangements, and about 50 cases of cryptic duplications encompassing the MECP2 gene have been reported."
States explicitly that prevalence is unknown, and gives the case counts that are the only quantitative anchor available.
🔬

Clinical Trials

3
NCT06430385 PHASE_I RECRUITING
ATTUNE - double-blind, sham-controlled multiple ascending dose study of intrathecally administered ION440, an antisense oligonucleotide intended to lower MECP2 expression in MECP2 duplication syndrome. Directly targets the dosage mechanism modelled in this entry rather than a downstream symptom. ClinicalTrials.gov registers this as Phase 1-2; `phase:` is recorded as PHASE_I because the enum has no combined Phase 1/2 value.
Target Phenotypes: Global developmental delay HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
clinicaltrials:NCT06430385 SUPPORT Human Clinical
"The primary purpose of this study is to evaluate the safety and tolerability of ION440."
First-in-class attempt to correct MECP2 overdosage therapeutically; still a safety/tolerability trial, so no efficacy claim is made here.
NCT06615206 NOT_APPLICABLE RECRUITING
Open-label study of HG204, a CRISPR RNA-editing therapy delivered by a single intracerebroventricular AAV injection, designed to knock down MECP2 mRNA in the brain.
Show evidence (1 reference)
clinicaltrials:NCT06615206 SUPPORT Human Clinical
"HG204 is a CRISPR RNA-editing therapy packaging novel high-fidelity Cas13Y (hfCas13Y) technology, using one single adeno-associated virus (AAV) vector to target and knock down MECP2 mRNA in the brain."
A second, mechanistically distinct attempt to reverse MECP2 overdosage, supporting the dosage model as the therapeutic target.
NCT06014541 TERMINATED
Prospective and retrospective observational natural-history study characterising CSF and blood MECP2 biomarkers, clinical scales and seizure burden over time. Terminated; no published outcome results were located.
Show evidence (1 reference)
clinicaltrials:NCT06014541 SUPPORT Human Clinical
"The purpose of the study is to prospectively assess longitudinal changes in biomarkers (MECP2, potential biomarkers of target engagement and disease activity) in cerebrospinal fluid (CSF) and blood"
Natural-history and biomarker study underpinning the interventional programmes above.
{ }

Source YAML

click to show 
name: Chromosome Xq Duplication
creation_date: '2026-08-12T00:00:00Z'
category: Genetic
parents:
- Chromosomal Disorder
- Neurodevelopmental Disorder
disease_term:
  preferred_term: chromosome Xq duplication
  term:
    id: MONDO:0017010
    label: partial duplication of the long arm of chromosome X
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0017010
      label: partial duplication of the long arm of chromosome X
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: >
      MONDO:0017010 is the grouping term for segmental copy-number gain of the
      long arm of the X chromosome, carrying "partial duplication of chromosome
      Xq" and "partial trisomy of the long arm of chromosome X" as EXACT
      synonyms and an RO:0004030 (disease has location) relation to Xq. It is
      the exact concept this entry models.
description: >
  Chromosome Xq duplication comprises a heterogeneous group of segmental
  copy-number gains involving the long arm of the X chromosome. They arise
  either as intrachromosomal duplications or through unbalanced X/Y or
  X/autosome translocations. The pathophysiological core is gene *dosage*
  rather than loss of function: an extra copy of one or more dosage-sensitive
  genes within the duplicated interval produces intellectual disability,
  hypotonia, and dysmorphism, and — depending on gene content — hypopituitarism,
  genital anomalies, and proneness to infection.

  Expression is governed by whether X-chromosome dosage compensation succeeds.
  In XY males any structural Xq disomy is necessarily functional disomy, so
  males are typically severely affected. In females the duplicated X is usually
  preferentially inactivated, and carriers are frequently asymptomatic or
  mildly affected; manifesting females are those in whom compensation fails —
  through a random rather than skewed inactivation pattern, or because an
  unbalanced translocation separates the duplicated segment from the
  X-inactivation centre in cis so that it cannot be silenced at all.

  Recurrent, dosage-defined intervals are modelled here as subtypes. The best
  characterised is Xq28 duplication encompassing MECP2, the single most
  important dosage-sensitive gene in distal Xq duplications; SOX3 at
  Xq26.3–q27.1 accounts for the hypopituitary presentations, and a 173 kb
  minimal region at Xq25 containing STAG2 defines a duplication cohesinopathy.
notes: >
  Relationship to the existing dismech entry MECP2 Duplication Syndrome: that
  entry is curated against MONDO:0010283 (syndromic X-linked intellectual
  disability Lubs type, OMIM:300260), a sibling MONDO concept scoped to the
  MECP2-containing duplication as a named Mendelian syndrome. This entry is the
  broader chromosomal grouping (MONDO:0017010) covering the full range of Xq
  segmental gains. The Xq28/MECP2 subtype below is deliberately kept to the
  dosage mechanism and the features that place it within the Xq duplication
  spectrum; the detailed MECP2-specific pathograph (neurodegeneration,
  astrocyte and microglial contributions, mouse reversal studies) is not
  re-derived here and lives in MECP2_Duplication_Syndrome.yaml. Curators editing
  either entry should check the other so the two do not silently diverge.

  Scope of the phenotype list: quantitative frequencies are drawn from the
  MECP2/Xq28 literature, because that is the only interval with cohort-scale
  phenotyping (PMID:39696717, n=137; PMID:19232094 Table 1). Frequencies should
  therefore be read as applying to MECP2-spanning duplications, not uniformly
  across every Xq interval. The non-MECP2 intervals are represented by their
  distinguishing features (hypopituitarism for SOX3, behaviour for STAG2,
  hemihyperplasia for Xq25) without frequency bands, since no denominator-based
  series exists for them.

  Not yet curated, deliberately: a CGDS ClinGen dosage-sensitivity record for
  MECP2 triplosensitivity. `just clingen-dosage-refresh` currently fails a
  checksum check because upstream ClinGen has republished gene_dosage.csv since
  data/clingen-dosage/MANIFEST.yaml was pinned, so no CGDS_* cache file could be
  generated. Dosage-sensitivity claims here rest on primary literature instead.
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >
    No prevalence estimate exists for Xq duplications as a class. The 2009
    review counted roughly 40 reported cases of cytogenetically visible Xq28
    functional disomy and about 50 cryptic MECP2-encompassing duplications;
    array CGH has since raised ascertainment, but no denominator-based
    estimate has been published for the grouping. A birth-prevalence figure
    exists only for the MECP2 subtype and is recorded on
    MECP2_Duplication_Syndrome.yaml.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prevalence of Xq duplications remains unknown. About 40 cases of Xq28 \nfunctional disomy due to cytogenetically visible rearrangements, and about 50 \ncases of cryptic duplications encompassing the MECP2 gene have been reported."
    explanation: >
      States explicitly that prevalence is unknown, and gives the case counts
      that are the only quantitative anchor available.
inheritance:
- name: X-linked inheritance
  description: >
    Most Xq duplications in affected males are inherited from a carrier mother
    who is herself unaffected or only mildly affected because of skewed
    X-inactivation; de novo events and unbalanced products of a parental
    balanced rearrangement also occur. Rearrangement architecture predicts
    recurrence risk: de novo events are much more common among terminal
    duplications than tandem duplications.
  inheritance_term:
    preferred_term: X-linked inheritance
    term:
      id: HP:0001417
      label: X-linked inheritance
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The recurrence risk is
significant if a structural rearrangement is present in one of the parent, the
most frequent situation being that of an intrachromosomal duplication inherited
from the mother."
    explanation: States the predominant X-linked maternal transmission pattern.
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Notably, 65% of de novo events \noccurred in the Terminal duplication group in contrast with 17% observed in \nTandem duplications."
    explanation: >
      Quantifies how rearrangement architecture predicts de novo versus
      inherited origin, which drives recurrence counselling.
has_subtypes:
- name: Xq28 (MECP2)
  display_name: Xq28 duplication encompassing MECP2
  subtype_term:
    preferred_term: MECP2 duplication syndrome
    term:
      id: MONDO:0010283
      label: syndromic X-linked intellectual disability Lubs type
  description: >
    Duplication spanning MECP2 at Xq28, consistently including L1CAM in the
    interstitial microduplication form. The most frequently reported and best
    characterised Xq duplication; increased MECP2 dosage is the principal
    driver of the neurodevelopmental phenotype. Rearrangement structures are
    heterogeneous — tandem duplications, terminal duplications (mostly
    translocations), inverted triplications and other complex genomic
    rearrangements — and this architecture modulates severity. Corresponds to
    the separately curated entry MECP2 Duplication Syndrome (MONDO:0010283).
  genes:
  - preferred_term: MECP2
    term:
      id: hgnc:6990
      label: MECP2
  - preferred_term: L1CAM
    term:
      id: hgnc:6470
      label: L1CAM
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These microduplications are var-\niable in size, ranging from 0.2 to 2.2 Mb, but consistently\ninclude MECP2 and L1 cell adhesion molecule (L1CAM), as\nwell as intervening genes"
    explanation: Defines the size range and obligate gene content of the Xq28 interstitial interval.
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Duplication sizes in the cohort ranging from 64.6 kb to 16.5 Mb were \nclassified into four categories comprising of tandem duplications (48%), \nterminal duplications (22%), inverted triplications (20%), and other CGRs (10%)."
    explanation: >
      Contemporary 137-individual cohort defining the size range and structural
      classes of MECP2-spanning gains.
- name: Xq26-qter
  display_name: Xq26–qter duplication / distal Xq functional disomy
  description: >
    Larger, cytogenetically visible duplications of the distal long arm,
    spanning Xq26–q28 (often reported as Xq27–qter). These yield the classic
    recognisable distal Xq disomy phenotype and overlap the Xq28/MECP2 subtype
    in gene content, but carry a heavier burden of growth failure,
    microcephaly, and craniofacial dysmorphism.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In particular, the Xq26–q28 chromosome region yields a\nrecognisable phenotype including distinctive facial fea-\ntures, major axial hypotonia, severe developmental delay,\nsevere feeding difficulties, abnormal genitalia and prone-\nness to infections"
    explanation: Defines the distal Xq26-q28 interval as a recognisable clinical entity.
- name: Xq26.3-q27.1 (SOX3)
  display_name: Xq26.3–q27.1 duplication encompassing SOX3
  subtype_term:
    preferred_term: X-linked panhypopituitarism
    term:
      id: MONDO:0010712
      label: panhypopituitarism, X-linked
  description: >
    Duplication of the Xq26–q27 region containing the transcription factor
    SOX3. Presents with hypopituitarism, anterior pituitary hypoplasia, ectopic
    posterior pituitary and absent infundibulum. Notably, SOX3 over- and
    underdosage converge on the same pituitary phenotype, and intellectual
    disability is not obligate.
  genes:
  - preferred_term: SOX3
    term:
      id: hgnc:11199
      label: SOX3
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a submicroscopic duplication of Xq27.1, the smallest reported to date (685.6 kb), in two siblings \nwith variable hypopituitarism, callosal abnormalities, anterior pituitary hypoplasia (APH), an ectopic posterior pituitary (EPP), and an absent \ninfundibulum."
    explanation: Defines the minimal SOX3-containing duplication and its pituitary phenotype.
- name: Xq25 (STAG2)
  display_name: Xq25 duplication encompassing STAG2
  subtype_term:
    preferred_term: Xq25 microduplication syndrome
    term:
      id: MONDO:0010507
      label: Xq25 microduplication syndrome
  description: >
    Xq25 microduplication with a shortest region of overlap of 173 kb
    containing only STAG2, a subunit of the cohesin complex. Presents with
    delayed milestones, speech disturbance, intellectual disability, abnormal
    behaviour and characteristic facial dysmorphism. Increased STAG2 dosage
    makes this a cohesinopathy — mechanistically distinct from the
    chromatin-reader (MECP2) and transcription-factor (SOX3) intervals.
  genes:
  - preferred_term: STAG2
    term:
      id: hgnc:11355
      label: STAG2
  evidence:
  - reference: PMID:25677961
    reference_title: "Xq25 duplication: the crucial role of the STAG2 gene in this novel human cohesinopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The common duplicated \ninterval allowed further refinement of the shortest region of overlap to 173 kb, \nincluding only one gene, STAG2, which encodes a component of the cohesin \ncomplex."
    explanation: Defines the minimal Xq25 interval and identifies STAG2 as the dosage-sensitive gene.
- name: Xq25-q26
  display_name: Xq25–q26 duplication (hypopituitarism and hemihyperplasia)
  subtype_term:
    preferred_term: X-linked intellectual disability with panhypopituitarism
    term:
      id: MONDO:0010252
      label: intellectual disability, X-linked, with panhypopituitarism
  description: >
    Mid-Xq gains spanning Xq25–q26 associated with two further presentations:
    X-linked panhypopituitarism with variable intellectual disability mapping
    to a duplicated dosage-sensitive locus, and a 1.65 Mb critical region at
    Xq25 for hemihyperplasia with digital anomalies.
  evidence:
  - reference: PMID:9106538
    reference_title: "X-linked recessive panhypopituitarism associated with a regional duplication in Xq25-q26."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "An apparent extra copy of the \nmarker DXS102, observed in the region of the disease gene in affected males and \nheterozygous carrier females, suggests that a segment including this marker is \nduplicated."
    explanation: Establishes an Xq25-q26 duplication segregating with panhypopituitarism.
  - reference: PMID:20101693
    reference_title: "Delineation of a 1.65 Mb critical region for hemihyperplasia and digital anomalies on Xq25."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we have delineated a 1.65 Mb critical region for hemihyperplasia and digital anomalies on chromosome Xq25"
    explanation: Defines the Xq25 critical region for the hemihyperplasia/digital presentation.
- name: Xq21-q24
  display_name: Proximal Xq (Xq21–q24) duplication
  description: >
    Proximal long-arm duplications, reported less often and more heterogeneous
    in breakpoint. Patients show craniofacial dysmorphism, aberrant brain
    myelination, hypotonia, psychomotor and growth retardation, feeding
    problems and hypoplastic genitalia.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients show craniofacial dysmorphism, brain and neurologic\nabnormalities such as aberrant brain myelination, hypot-\nonia, mental, psychomotor and growth retardation, feed-\ning issues, hypoplasic genitalia."
    explanation: Describes the proximal Xq duplication phenotype.
pathophysiology:
- name: Segmental Copy Number Gain on Xq
  biological_scale: MOLECULAR
  description: >
    An extra copy of a segment of the long arm of the X chromosome. In males
    this arises most often as an intrachromosomal duplication transmitted by a
    non-manifesting mother, and less often from an unbalanced X/Y or
    X/autosome translocation. Duplication size and gene content vary widely,
    from cytogenetically visible multi-megabase segments to submicroscopic
    gains encompassing only one or a few genes detectable by array CGH.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Xq duplications may be caused either by an \nintrachromosomal duplication or an unbalanced X/Y or X/\nautosome translocation."
    explanation: Establishes the two structural routes to an Xq segmental gain.
  downstream:
  - target: Failure of X-Chromosome Dosage Compensation
    causal_link_type: DIRECT
    description: >
      Whether the extra segment is phenotypically expressed depends entirely on
      whether X-inactivation can silence it.
- name: Failure of X-Chromosome Dosage Compensation
  biological_scale: CELLULAR
  description: >
    X-chromosome inactivation, initiated from the X-inactivation centre (XIC)
    at Xq13, normally equalises X-linked gene expression between XX and XY
    cells. This safeguard fails in three distinguishable ways. In XY males
    there is no second X to inactivate, so any structural Xq disomy is
    obligatorily functional disomy. In females carrying an intrachromosomal
    duplication, inactivation is usually skewed towards the abnormal X, which
    rescues the phenotype; manifesting females are those with a random
    inactivation pattern. In females with an unbalanced X/autosome
    translocation, the translocated X segment is physically separated from its
    XIC in cis and therefore cannot be inactivated at all, so the phenotype is
    fully expressed and can be as severe as in males.
  biological_processes:
  - preferred_term: X-chromosome inactivation
    term:
      id: GO:0009048
      label: dosage compensation by inactivation of X chromosome
    modifier: DECREASED
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In XY males, structural X disomy always results in functional disomy. In \nfemales, failure of X chromosome dosage compensation could result from a variety \nof mechanisms, including an unfavourable pattern of inactivation, a breakpoint \nseparating an X segment from the X-inactivation centre in cis, or a small ring \nchromosome."
    explanation: States the sex-dependent mechanisms by which dosage compensation fails.
  - reference: PMID:16080119
    reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The duplications segregate with the disease in the families, and asymptomatic \ncarrier females show complete skewing of X inactivation."
    explanation: Demonstrates that successful skewing towards the duplicated X protects female carriers.
  downstream:
  - target: Functional Xq Disomy and Increased Gene Dosage
    causal_link_type: DIRECT
    description: >
      Uncompensated duplicated genes are expressed at double their normal level.
    evidence:
    - reference: PMID:19232094
      reference_title: "Distal Xq duplication and functional Xq disomy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Functional disomy\n(FD) is the double expression of X-linked genes compared\nto their normal level."
      explanation: Defines functional disomy as the direct consequence of failed compensation.
- name: Functional Xq Disomy and Increased Gene Dosage
  biological_scale: MOLECULAR
  description: >
    Double expression of the X-linked genes lying within the duplicated
    segment. Because most X-linked genes are not tolerant of a twofold
    expression increase, the identity of the dosage-sensitive genes captured by
    the duplication determines which organ systems are affected — this is why
    breakpoint position, not duplication size alone, drives the phenotype.
  biological_processes:
  - preferred_term: gene expression
    term:
      id: GO:0010467
      label: gene expression
    modifier: INCREASED
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical manifestations widely vary \ndepending on the gender of the patient and on the gene content of the duplicated \nsegment."
    explanation: Links phenotypic outcome to which genes the duplicated segment contains.
  downstream:
  - target: MECP2 Overexpression
    causal_link_type: DIRECT
    description: Distal Xq duplications spanning Xq28 raise MECP2 dosage.
  - target: SOX3 Overdosage
    causal_link_type: DIRECT
    description: Xq26.3-q27.1 duplications raise SOX3 dosage.
  - target: Increased STAG2 Dosage and Cohesin Dysregulation
    causal_link_type: DIRECT
    description: Xq25 duplications raise STAG2 dosage.
  - target: Increased IRAK1 Dosage
    causal_link_type: DIRECT
    description: >
      IRAK1 lies immediately adjacent to MECP2 and is co-duplicated in most
      Xq28 gains.
- name: MECP2 Overexpression
  biological_scale: MOLECULAR
  description: >
    MeCP2 is a methyl-CpG-binding chromatin protein expressed most highly in
    post-mitotic, post-migratory neurons. Its level must be tightly regulated
    in both directions: loss of function causes Rett syndrome, while a roughly
    twofold increase from duplication is itself pathogenic. The duplicated
    allele is structurally wild type, so this is a quantitative overexpression
    rather than a qualitative change in protein function. Copy number is
    transmitted through to protein: patient-derived lymphoblastoid RNA and
    protein levels are correlated, and triplications produce significantly more
    MECP2 transcript than duplications.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  molecular_functions:
  - preferred_term: methyl-CpG binding
    term:
      id: GO:0008327
      label: methyl-CpG binding
    modifier: INCREASED
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The MECP2 gene in Xq28 is the most important dosage-sensitive gene
responsible for the abnormal phenotype in duplications of distal Xq."
    explanation: Identifies MECP2 dosage as the principal driver in distal Xq duplication.
  - reference: PMID:16080119
    reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings demonstrate \nthat, in humans, not only impaired or abolished gene function but also increased \nMeCP2 dosage causes a distinct phenotype."
    explanation: Establishes increased MECP2 dosage as causal in humans, distinct from loss of function.
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "demonstrating that genomic aberrations spanning MECP2 lead to altered MECP2 RNA \nand MECP2 protein levels."
    explanation: Confirms the copy-number-to-protein-dosage step in patient-derived cells.
  downstream:
  - target: Impaired Neuronal Maturation and Progressive Neurological Decline
    causal_link_type: DIRECT
    description: >
      Excess MeCP2 perturbs the transcriptional programs of maturing neurons.
    evidence:
    - reference: PMID:15351775
      reference_title: "Mild overexpression of MeCP2 causes a progressive neurological disorder in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These data demonstrate that \nMeCP2 levels must be tightly regulated in vivo, and that even mild \noverexpression of this protein is detrimental."
      explanation: Transgenic mice at ~2x wild-type MeCP2 develop a progressive neurological disorder.
  - target: Dosage- and Architecture-Dependent Severity Gradient
    causal_link_type: DIRECT
    description: >
      The absolute level of MeCP2 reached - highest in triplications - is one of
      the two determinants of where an individual falls on the severity
      gradient.
    evidence:
    - reference: PMID:39696717
      reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "RNA-seq data from lymphoblastoid cell lines indicated that \nthe MECP2 transcript quantity in MECP2 triplications is statistically different \nfrom all duplications"
      explanation: >
        Links the MECP2 dosage node to the graded severity node via measured
        transcript differences between triplications and duplications.
- name: Impaired Neuronal Maturation and Progressive Neurological Decline
  biological_scale: CELLULAR
  description: >
    Excess MeCP2 disturbs activity-dependent transcriptional regulation in
    maturing neurons. In transgenic mice expressing MeCP2 at approximately
    twice wild-type levels the course is biphasic and delayed: an early period
    of enhanced hippocampal synaptic plasticity and learning is followed after
    20 weeks by seizures, hypoactivity and premature death. This delayed,
    progressive trajectory mirrors the human course, in which early hypotonia
    and developmental delay give way to progressive spasticity and epilepsy.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: neuron maturation
    term:
      id: GO:0042551
      label: neuron maturation
    modifier: DECREASED
  evidence:
  - reference: PMID:15351775
    reference_title: "Mild overexpression of MeCP2 causes a progressive neurological disorder in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "After 20 weeks of age, however, these mice developed seizures, became hypoactive and \napproximately 30% of them died by 1 year of age."
    explanation: Documents the delayed, progressive neurological course under MeCP2 overexpression.
  - reference: PMID:16080119
    reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified a small duplication at Xq28 in a large family with a \nsevere form of MR associated with progressive spasticity."
    explanation: Human counterpart - severe intellectual disability with progressive spasticity.
  downstream:
  - target: Intellectual Disability
    causal_link_type: DIRECT
    description: >
      Disrupted neuronal maturation underlies the cognitive impairment.
    evidence:
    - reference: PMID:16080119
      reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Comparison of the \nclinical features in these patients and in a previously reported patient enables \nrefinement of the genotype-phenotype correlation and strongly suggests that \nincreased dosage of MECP2 results in the MR phenotype."
      explanation: Links increased MECP2 dosage to the intellectual disability phenotype.
  - target: Progressive Spasticity
    causal_link_type: DIRECT
    description: >
      The progressive motor component of the neurological decline.
    evidence:
    - reference: PMID:16080119
      reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "a \nsevere form of MR associated with progressive spasticity."
      explanation: Progressive spasticity accompanies the neurological decline in Xq28 duplication.
  - target: Seizures
    causal_link_type: DIRECT
    description: >
      Epilepsy emerges as part of the delayed, progressive phase.
    evidence:
    - reference: PMID:15351775
      reference_title: "Mild overexpression of MeCP2 causes a progressive neurological disorder in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "After 20 weeks of age, however, these mice developed seizures"
      explanation: >
        Seizure onset in the delayed phase of the MeCP2 overexpression mouse
        model. MODEL_ORGANISM evidence; the human seizure frequency is
        separately evidenced on the phenotype itself.
- name: Dosage- and Architecture-Dependent Severity Gradient
  biological_scale: ORGANISM
  description: >
    Severity is graded rather than all-or-none, and is set by two partly
    separable variables: the absolute level of MeCP2 (triplication worse than
    duplication) and the structural class of the rearrangement itself.
    Phenotypic burden — survival, developmental level, microcephaly, epilepsy,
    and genitourinary/eye anomalies — worsens progressively across tandem
    duplications, other complex rearrangements, terminal
    duplications/translocations, and triplications. Rearrangement structure
    therefore contributes to expression variability independently of copy
    number alone, plausibly through position effects and disruption of
    regulatory architecture at the breakpoints.
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genotype-phenotype analyses indicated a gradual \nworsening of phenotypic features, including overall survival, developmental \nlevels, microcephaly, epilepsy, and genitourinary/eye abnormalities in the \nfollowing order: Tandem duplications, Other complex duplications, Terminal \nduplications/Translocations, and Triplications encompassing MECP2."
    explanation: Establishes the ordered severity gradient across rearrangement classes.
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whereas the \nlevel of MECP2 is a key determinant of the phenotype, the DNA rearrangement \nstructure can contribute to clinical severity and disease expression \nvariability."
    explanation: >
      Separates the two contributions - MECP2 level and rearrangement
      architecture - to clinical severity.
- name: SOX3 Overdosage
  biological_scale: MOLECULAR
  description: >
    SOX3 is a developmental transcription factor at Xq27.1 expressed in the
    infundibulum. Both over- and underdosage impair infundibular development
    and produce hypopituitarism, indicating a narrow tolerated expression
    window rather than a simple loss-of-function relationship. This is the
    mechanistic basis of the hypopituitary presentations of Xq26-q27
    duplication.
  biological_processes:
  - preferred_term: adenohypophysis development
    term:
      id: GO:0021984
      label: adenohypophysis development
    modifier: DECREASED
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that both \nover- and underdosage of SOX3 are associated with similar phenotypes, consisting \nof infundibular hypoplasia and hypopituitarism but not necessarily MR."
    explanation: Establishes SOX3 dosage sensitivity in both directions for the pituitary phenotype.
  downstream:
  - target: Hypopituitarism
    causal_link_type: DIRECT
    description: >
      Infundibular and anterior pituitary hypoplasia produce deficient
      anterior pituitary hormone output.
- name: Increased STAG2 Dosage and Cohesin Dysregulation
  biological_scale: MOLECULAR
  description: >
    STAG2 encodes a subunit of the cohesin complex, which mediates sister
    chromatid cohesion and, critically for this phenotype, shapes chromatin
    architecture and enhancer-promoter looping. Increased STAG2 copy number at
    Xq25 is proposed to act by dysregulating cohesin downstream target genes,
    placing this interval among the cohesinopathies. The transcriptional
    consequences are inferred from the mapping data rather than directly
    measured in patients.
  biological_processes:
  - preferred_term: sister chromatid cohesion
    term:
      id: GO:0007062
      label: sister chromatid cohesion
    modifier: INCREASED
  evidence:
  - reference: PMID:25677961
    reference_title: "Xq25 duplication: the crucial role of the STAG2 gene in this novel human cohesinopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We suggest that increased STAG2 gene copy number and dysregulation of \nits downstream target genes may be responsible for the specific clinical \nfindings of this syndrome."
    explanation: >
      Proposes the cohesin-dysregulation mechanism. Marked PARTIAL because the
      source frames it as a suggestion ("may be responsible") supported by
      mapping rather than direct transcriptional measurement in patients.
- name: Increased IRAK1 Dosage
  biological_scale: MOLECULAR
  description: >
    IRAK1 and IKBKG lie immediately telomeric to MECP2 and are usually
    contained within the duplicated Xq28 segment. Both are innate immune
    signalling components downstream of the Toll-like and IL-1 receptors, and
    their increased dosage has been proposed as the explanation for the
    recurrent respiratory infections that distinguish Xq28 functional disomy
    from other X-linked intellectual disability/hypotonia syndromes. This
    remains a proposed rather than demonstrated mechanism.
  biological_processes:
  - preferred_term: toll-like receptor signaling pathway
    term:
      id: GO:0002224
      label: toll-like receptor signaling pathway
    modifier: INCREASED
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The recurrent infections\nmight result from the increased dosage of the IRAK1 or\nIKBKG genes generally present in the duplicated region"
    explanation: >
      Proposes IRAK1/IKBKG dosage as the basis of recurrent infection. Marked
      PARTIAL because the source states this as a hypothesis ("might result
      from"), not a demonstrated mechanism.
  downstream:
  - target: Recurrent Respiratory Infections
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - >-
      Unresolved. Dysregulated innate immune signalling is the proposed route,
      but aspiration secondary to severe hypotonia and feeding difficulty is a
      competing, non-immune explanation for the same clinical finding.
    description: >
      Proposed contribution of innate immune gene dosage to infection
      proneness.
phenotypes:
- category: Neurologic
  name: Global Developmental Delay
  description: >
    Severe developmental delay is essentially universal in affected males
    across all reported Xq duplication intervals, with absent or severely
    delayed speech.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Psychomotor retardation: severe mental retardation,\nabsence or severely retarded speech"
    explanation: >
      Reported for the distal Xq phenotype; Table 1 of the same review records
      developmental delay in 12/12, 19/19 and 47/47 patients across the three
      duplication groups, supporting VERY_FREQUENT.
- category: Neurologic
  name: Intellectual Disability
  description: >
    Usually severe in MECP2-spanning duplications; mild to moderate in the
    Xq25/STAG2 interval.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:16080119
    reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified a small duplication at Xq28 in a large family with a \nsevere form of MR associated with progressive spasticity."
    explanation: Severe intellectual disability in the Xq28 duplication family.
  - reference: PMID:25677961
    reference_title: "Xq25 duplication: the crucial role of the STAG2 gene in this novel human cohesinopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the phenotype of our patients is characterized by \ndelayed milestones, speech disturbance, intellectual disability, abnormal \nbehaviours and a characteristic facial dysmorphism."
    explanation: Intellectual disability in the Xq25/STAG2 duplication interval.
- category: Neurologic
  name: Delayed or Absent Speech
  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:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "delayed psychomotor development leading to severe intellectual \ndisability, poor speech development"
    explanation: >
      GeneReviews lists poor speech development as a core feature; Table 1 of
      PMID:19232094 records absent or delayed speech in 46/47 MECP2 duplication
      patients, supporting VERY_FREQUENT.
- category: Neurologic
  name: Axial Hypotonia
  description: >
    Major axial hypotonia is an early and near-universal finding, contributing
    to feeding difficulty and delayed motor milestones.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Axial hypotonia
    term:
      id: HP:0008936
      label: Axial hypotonia
    temporality: CHRONIC
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "major axial hypotonia, severe \ndevelopmental delay, severe feeding difficulties, abnormal genitalia and \nproneness to infections."
    explanation: >
      Axial hypotonia listed as a core distal Xq feature; Table 1 records
      hypotonia in 11/11, 19/19 and 29/32 patients, supporting VERY_FREQUENT.
- category: Neurologic
  name: Progressive Spasticity
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "poor speech development, progressive spasticity, recurrent \nrespiratory infections (in ~75% of affected individuals), and seizures (in \n~50%)"
    explanation: >
      GeneReviews lists progressive spasticity as a core feature; Table 1 of
      PMID:19232094 records spasticity in 17/21 MECP2 duplication patients
      (~81%), supporting FREQUENT.
- category: Neurologic
  name: Seizures
  description: >
    Reported in approximately half of individuals with MECP2 duplication.
    Epilepsy is a major driver of developmental regression, and onset is
    earlier in the more severe rearrangement classes.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "recurrent \nrespiratory infections (in ~75% of affected individuals), and seizures (in \n~50%)"
    explanation: >
      GeneReviews gives ~50% for seizures, mapping to FREQUENT (30-79%).
- category: Neurologic
  name: Inability to Walk or Limited Walking
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Inability to walk
    term:
      id: HP:0002540
      label: Inability to walk
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Never walked or limited walking nr 12/14 21/34"
    explanation: >
      Table 1 records 12/14 (86%) in Xq26.3qter and 21/34 (62%) in MECP2
      duplication; the pooled range supports FREQUENT.
- category: Behavioral
  name: Autistic Behavior
  description: >
    Autistic behaviours are observed in several affected boys with MECP2
    duplication, in addition to the core neurodevelopmental features.
  phenotype_term:
    preferred_term: Autistic behavior
    term:
      id: HP:0000729
      label: Autistic behavior
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition to the core features, autistic behaviors, nonspecific \nneuroradiologic findings on brain MRI, mottled skin, and urogenital anomalies \nhave been observed in several affected boys."
    explanation: GeneReviews lists autistic behaviours among the additional features.
- category: Neurologic
  name: Dysautonomia
  description: >
    Autonomic features including drooling, dysregulated blood flow to the
    extremities, and abnormal breathing (breath-holding or hyperventilation),
    shared with the allelic Rett syndrome.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Dysautonomia
    term:
      id: HP:0012332
      label: Abnormal autonomic nervous system physiology
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified the frequency of dysautonomia in 105/121 (86.7%) of individuals."
    explanation: >
      86.7% maps to VERY_FREQUENT (80-100%).
- category: Neurologic
  name: High Pain Tolerance
  frequency: FREQUENT
  phenotype_term:
    preferred_term: High pain tolerance
    term:
      id: HP:0007328
      label: Impaired pain sensation
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "High pain tolerance was present in 85/109 (77.9%) of MRXSL individuals."
    explanation: >
      77.9% maps to FREQUENT (30-79%).
- category: Neurologic
  name: Bruxism
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Bruxism
    term:
      id: HP:0003763
      label: Bruxism
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bruxism was reported in 81/112 (72.3%) of subjects."
    explanation: >
      72.3% maps to FREQUENT (30-79%).
- category: Neurologic
  name: Insomnia
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Insomnia
    term:
      id: HP:0100785
      label: Insomnia
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We had information on insomnia from 118 subjects and 62 of them (52.5%) were found to have insomnia."
    explanation: >
      52.5% maps to FREQUENT (30-79%).
- category: Respiratory
  name: Obstructive Sleep Apnea
  description: >
    Sleep apnea is predominantly obstructive; only two individuals in the
    cohort had central sleep apnea.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Obstructive sleep apnea
    term:
      id: HP:0002870
      label: Obstructive sleep apnea
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Data on sleep apnea status were available in 114 subjects and 63 subjects (55.2%) were reported to have sleep apnea. Only two subjects were reported to have central sleep apnea and the remaining had obstructive sleep apnea."
    explanation: >
      55.2% maps to FREQUENT (30-79%), and the same sentence establishes that
      the apnea is predominantly obstructive.
- category: Ophthalmologic
  name: Refractive Error and Strabismus
  description: >
    Generally minor visual abnormalities. More serious eye disease (nystagmus,
    corneal abnormality, optic nerve hypoplasia) was confined to the
    triplication group.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Abnormality of refraction
    term:
      id: HP:0000539
      label: Abnormality of refraction
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Information on visual abnormalities were present in 117 subjects and 71 of them (60.6%) reported various, relatively minor visual abnormalities including refraction errors and strabismus."
    explanation: >
      60.6% maps to FREQUENT (30-79%).
- category: Musculoskeletal
  name: Musculoskeletal Complications
  description: >
    Bone fractures, osteopenia/osteoporosis, scoliosis and joint contractures,
    attributed to deconditioning, immobility and nutritional deficiency rather
    than to a primary skeletal defect.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Recurrent fractures
    term:
      id: HP:0002757
      label: Recurrent fractures
  evidence:
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We obtained data on 93 subjects for their musculoskeletal problems and 49 (52.6%) reported musculoskeletal abnormalities, with the most common ones including bone fractures (26 subjects), osteopenia/osteoporosis (13 subjects including 3 requiring alendronate infusion), scoliosis (13 subjects), joint contractures (nine subjects)."
    explanation: >
      52.6% overall musculoskeletal involvement maps to FREQUENT (30-79%);
      fractures were the single most common component.
- category: Dermatologic
  name: Mottled Skin
  description: >
    Mottled skin is reported among the additional, non-core features of MECP2
    duplication.
  phenotype_term:
    preferred_term: Cutis marmorata
    term:
      id: HP:0000965
      label: Cutis marmorata
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "autistic behaviors, nonspecific \nneuroradiologic findings on brain MRI, mottled skin, and urogenital anomalies \nhave been observed in several affected boys."
    explanation: GeneReviews lists mottled skin among the additional features.
- category: Respiratory
  name: Recurrent Respiratory Infections
  description: >
    Recurrent pneumonia in particular helps distinguish Xq28 functional disomy
    from other X-linked intellectual disability/hypotonia syndromes, and is a
    leading cause of hospitalisation and premature mortality.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Recurrent respiratory infections
    term:
      id: HP:0002205
      label: Recurrent respiratory infections
    temporality: RECURRENT
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "recurrent \nrespiratory infections (in ~75% of affected individuals)"
    explanation: >
      GeneReviews gives ~75%, mapping to FREQUENT (30-79%).
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recurrent respiratory infections, especially recur-\nrent pneumonia, help to distinguish Xq28 functional\ndisomy (including MECP2 duplication) from other\nXLMR-hypotonia syndromes."
    explanation: Establishes the discriminating value of recurrent pneumonia.
- category: Gastrointestinal
  name: Severe Feeding Difficulties
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
    severity: SEVERE
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Others frequent clinical manifestations: severe feeding\ndifficulties with gastro oesophageal reflux, excessive\ndrooling, seizures, recurrent infections."
    explanation: >
      Listed among frequent manifestations; Table 1 records severe feeding
      problems in 9/9, 10/14 and 15/29 patients, supporting FREQUENT.
- category: Gastrointestinal
  name: Gastroesophageal Reflux
  phenotype_term:
    preferred_term: Gastroesophageal reflux
    term:
      id: HP:0002020
      label: Gastroesophageal reflux
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "gastrointestinal manifestations including gastroesophageal reflux \nand constipation"
    explanation: GeneReviews lists reflux among core gastrointestinal manifestations.
- category: Gastrointestinal
  name: Constipation
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "gastrointestinal manifestations including gastroesophageal reflux \nand constipation"
    explanation: GeneReviews lists constipation among core gastrointestinal manifestations.
- category: Growth
  name: Growth Retardation
  description: Prenatal and postnatal growth retardation in distal Xq duplication.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Growth: prenatal and postnatal growth retardation,\nmicrocephaly"
    explanation: >
      Listed as a core growth feature; Table 1 records growth retardation in
      9/10 and 17/19 patients in the two cytogenetically visible duplication
      groups, supporting VERY_FREQUENT.
- category: Craniofacial
  name: Microcephaly
  description: >
    Near-universal in the larger cytogenetically visible duplications but
    considerably less common in MECP2 microduplication, and part of the
    severity gradient across rearrangement classes.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Growth: prenatal and postnatal growth retardation,\nmicrocephaly"
    explanation: >
      Microcephaly listed among the core growth features of distal Xq
      duplication. Table 1 of the same review shows it is near-universal in the
      cytogenetically visible duplications (19/19) but uncommon in MECP2
      microduplication (5/39); FREQUENT reflects the pooled spectrum.
  - reference: PMID:39696717
    reference_title: "Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genotype-phenotype analyses indicated a gradual \nworsening of phenotypic features, including overall survival, developmental \nlevels, microcephaly, epilepsy, and genitourinary/eye abnormalities"
    explanation: >
      Confirms microcephaly varies systematically with rearrangement class
      rather than being uniformly present.
- category: Craniofacial
  name: Macrotia
  phenotype_term:
    preferred_term: Macrotia
    term:
      id: HP:0000400
      label: Macrotia
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "epicanthal folds, large ears, small and open mouth, ear anomalies, pointed nose,
abnormal palate and facial hypotonia)"
    explanation: Large ears listed among the characteristic distal Xq facial features.
- category: Craniofacial
  name: Epicanthus
  phenotype_term:
    preferred_term: Epicanthus
    term:
      id: HP:0000286
      label: Epicanthus
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "epicanthal folds, large ears, small and open mouth, ear anomalies, pointed nose,
abnormal palate and facial hypotonia)"
    explanation: Epicanthal folds listed among the characteristic facial features.
- category: Genitourinary
  name: Hypoplastic Genitalia
  description: >
    Hypoplastic genitalia, hypospadias and/or cryptorchidism are the most
    frequent malformations in affected males.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Hypoplastic male external genitalia
    term:
      id: HP:0000050
      label: Hypoplastic male external genitalia
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Malformations: genitalia malformations including\nhypoplasic genitalia, hypospadias and/or cryptorchidism\nare the more frequent malformations"
    explanation: >
      Named as the most frequent malformation class; Table 1 records
      hypoplastic genitalia/cryptorchidism in 11/11, 15/19 and 5/10 patients,
      supporting FREQUENT.
- category: Genitourinary
  name: Cryptorchidism
  phenotype_term:
    preferred_term: Cryptorchidism
    term:
      id: HP:0000028
      label: Cryptorchidism
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hypoplasic genitalia, hypospadias and/or cryptorchidism"
    explanation: Cryptorchidism listed among the frequent genital malformations.
- category: Endocrine
  name: Hypopituitarism
  description: >
    Seen with Xq25-q27 duplications involving SOX3, presenting with variable
    anterior pituitary hormone deficiency, anterior pituitary hypoplasia,
    ectopic posterior pituitary and absent infundibulum.
  subtype: Xq26.3-q27.1 (SOX3)
  phenotype_term:
    preferred_term: Hypopituitarism
    term:
      id: HP:0040075
      label: Hypopituitarism
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "in two siblings \nwith variable hypopituitarism, callosal abnormalities, anterior pituitary hypoplasia (APH), an ectopic posterior pituitary (EPP), and an absent \ninfundibulum."
    explanation: Hypopituitarism in the minimal SOX3-containing Xq27.1 duplication.
  - reference: PMID:9106538
    reference_title: "X-linked recessive panhypopituitarism associated with a regional duplication in Xq25-q26."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected members exhibit variable degrees of hypopituitarism and mental \nretardation."
    explanation: Panhypopituitarism segregating with an Xq25-q26 duplication.
- category: Endocrine
  name: Anterior Pituitary Hypoplasia
  subtype: Xq26.3-q27.1 (SOX3)
  phenotype_term:
    preferred_term: Anterior pituitary hypoplasia
    term:
      id: HP:0010627
      label: Anterior pituitary hypoplasia
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "anterior pituitary hypoplasia (APH), an ectopic posterior pituitary (EPP), and an absent \ninfundibulum."
    explanation: Structural pituitary findings on MRI in SOX3 duplication.
- category: Behavioral
  name: Abnormal Behaviour
  description: >
    Behavioural disturbance is a recognised component of the Xq25/STAG2
    duplication phenotype alongside speech disturbance and intellectual
    disability.
  subtype: Xq25 (STAG2)
  phenotype_term:
    preferred_term: Abnormal behaviour
    term:
      id: HP:0000708
      label: Atypical behavior
  evidence:
  - reference: PMID:25677961
    reference_title: "Xq25 duplication: the crucial role of the STAG2 gene in this novel human cohesinopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "delayed milestones, speech disturbance, intellectual disability, abnormal \nbehaviours and a characteristic facial dysmorphism."
    explanation: Abnormal behaviour among the defining features of Xq25 duplication.
- category: Musculoskeletal
  name: Hemihyperplasia
  description: >
    Reported with Xq25 duplications, mapping to a 1.65 Mb critical region
    distinct from the distal Xq neurodevelopmental intervals.
  subtype: Xq25-q26
  phenotype_term:
    preferred_term: Hemihypertrophy
    term:
      id: HP:0001528
      label: Hemihypertrophy
  evidence:
  - reference: PMID:20101693
    reference_title: "Delineation of a 1.65 Mb critical region for hemihyperplasia and digital anomalies on Xq25."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report on a 4-year-old female with hemihyperplasia, syndactyly of fingers and \ntoes, bilateral 5th finger clinodactyly, short stature, developmental delay, and \nmicrocephaly associated with an 11.2 Mb duplication of Xq25-Xq27.1."
    explanation: Hemihyperplasia with an Xq25-q27.1 duplication.
- category: Musculoskeletal
  name: Digital Anomalies
  description: >
    Syndactyly of fingers and toes and clinodactyly, reported with Xq25
    duplication and also as a general finding in distal Xq duplication.
  phenotype_term:
    preferred_term: Abnormal digit morphology
    term:
      id: HP:0011297
      label: Abnormal digit morphology
  evidence:
  - reference: PMID:20101693
    reference_title: "Delineation of a 1.65 Mb critical region for hemihyperplasia and digital anomalies on Xq25."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "syndactyly of fingers and \ntoes, bilateral 5th finger clinodactyly"
    explanation: Digital anomalies co-segregating with the Xq25 critical region.
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Abnormal fingers and toes have been reported"
    explanation: Digital anomalies also reported in the general distal Xq phenotype.
- category: Reproductive
  name: Gonadal Dysgenesis
  description: >
    Reported in manifesting females; a critical region for gonadal dysgenesis
    has been proposed at Xq13-q26.
  phenotype_term:
    preferred_term: Gonadal dysgenesis
    term:
      id: HP:0000133
      label: Gonadal dysgenesis
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "facial dysmorphism and gonadal dysgenesis [21,22]."
    explanation: Gonadal dysgenesis among the manifestations reported in females.
genetic:
- name: MECP2
  gene_term:
    preferred_term: MECP2
    term:
      id: hgnc:6990
      label: MECP2
  notes: >
    Methyl-CpG-binding protein 2 at Xq28. The principal dosage-sensitive gene
    of distal Xq duplication; copy-number gain (not loss of function) is the
    disease mechanism here. Duplication is 100% penetrant in males; female
    carriers range from asymptomatic to a male-like phenotype depending on
    X-inactivation.
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MECP2 duplication syndrome is 100% penetrant in males. Occasionally \nfemales have been described with a MECP2 duplication and a range of findings \nfrom mild intellectual disability to a phenotype similar to that seen in males."
    explanation: >
      GeneReviews establishes complete penetrance in males and the variable
      female range.
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The MECP2 gene in Xq28 is the most important dosage-sensitive gene
responsible for the abnormal phenotype in duplications of distal Xq."
    explanation: Identifies MECP2 as the key dosage-sensitive gene.
- name: SOX3
  gene_term:
    preferred_term: SOX3
    term:
      id: hgnc:11199
      label: SOX3
  notes: >
    SRY-box transcription factor 3 at Xq27.1. Duplication causes infundibular
    hypoplasia and hypopituitarism; deletion/loss of function produces a
    similar pituitary phenotype, indicating a narrow tolerated dosage window.
  evidence:
  - reference: PMID:15800844
    reference_title: "Over- and underdosage of SOX3 is associated with infundibular hypoplasia and hypopituitarism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This duplication contains SOX3 and sequences corresponding to two \ntranscripts of unknown function; only Sox3 is expressed in the infundibulum in \nmice."
    explanation: Localises the pituitary phenotype to SOX3 within the duplicated interval.
- name: STAG2
  gene_term:
    preferred_term: STAG2
    term:
      id: hgnc:11355
      label: STAG2
  subtype: Xq25 (STAG2)
  notes: >
    Cohesin complex subunit at Xq25. The only gene in the 173 kb shortest
    region of overlap for the Xq25 duplication cohesinopathy.
  evidence:
  - reference: PMID:25677961
    reference_title: "Xq25 duplication: the crucial role of the STAG2 gene in this novel human cohesinopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "further refinement of the shortest region of overlap to 173 kb, \nincluding only one gene, STAG2, which encodes a component of the cohesin \ncomplex."
    explanation: Identifies STAG2 as the sole gene in the Xq25 minimal region.
- name: L1CAM
  gene_term:
    preferred_term: L1CAM
    term:
      id: hgnc:6470
      label: L1CAM
  relationship_type: COOPERATING
  notes: >
    L1 cell adhesion molecule at Xq28, consistently co-duplicated with MECP2
    in the interstitial Xq28 interval.
  evidence:
  - reference: PMID:16080119
    reference_title: "Duplication of the MECP2 region is a frequent cause of severe mental retardation and progressive neurological symptoms in males."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The duplications in the four patients vary in \nsize from 0.4 to 0.8 Mb and harbor several genes, which, for each duplication, \ninclude the MR-related L1CAM and MECP2 genes."
    explanation: L1CAM is consistently within the Xq28 duplicated segment.
- name: IRAK1
  gene_term:
    preferred_term: IRAK1
    term:
      id: hgnc:6112
      label: IRAK1
  relationship_type: MODIFIER
  notes: >
    Interleukin-1 receptor-associated kinase 1 at Xq28, adjacent to MECP2 and
    usually co-duplicated. Proposed contributor to the recurrent-infection
    phenotype.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The recurrent infections\nmight result from the increased dosage of the IRAK1 or\nIKBKG genes generally present in the duplicated region"
    explanation: >
      Proposed modifier role. PARTIAL because the source frames this as a
      hypothesis rather than a demonstrated mechanism.
- name: PLP1
  gene_term:
    preferred_term: PLP1
    term:
      id: hgnc:9086
      label: PLP1
  notes: >
    Proteolipid protein 1 at Xq22. Duplication causes Pelizaeus-Merzbacher
    disease and accounts for the leukodystrophy presentation of proximal Xq
    gains; a separate dosage-sensitive locus from the distal Xq genes.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Complete duplication of the PLP1 gene on Xq22 is the cause of 60–70% of PMD\ncases"
    explanation: Establishes PLP1 duplication as a distinct dosage mechanism within Xq.
definitions:
- name: Array CGH confirmation of Xq copy-number gain
  definition_type: DIAGNOSTIC_CRITERIA
  description: >
    Diagnosis rests on recognition of the clinical phenotype and is confirmed
    by demonstration of the copy-number gain. Array comparative genomic
    hybridization is the confirmatory test of choice, having superseded
    karyotyping, which detects only duplications above roughly 5-10 Mb.
  derivation_basis: ESTABLISHED_CRITERIA
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diagnosis \nis based on clinical features and is confirmed by CGH array techniques."
    explanation: States the diagnostic pathway.
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of MECP2 duplication syndrome is established in \nan individual by identification of a heterozygous whole-gene duplication of \nMECP2 on molecular genetic testing."
    explanation: >
      GeneReviews Diagnosis/Testing - molecular demonstration of the whole-gene
      duplication is what establishes the diagnosis for the Xq28 subtype.
treatments:
- name: Symptomatic and Multidisciplinary Supportive Care
  description: >
    No disease-modifying therapy exists. Management is symptomatic and
    multi-specialist, with particular attention to preventing malnutrition and
    recurrent infection. Educational and rehabilitation support should be
    offered to all patients.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Management is multi-specialist and only symptomatic, with special attention \nto prevention of malnutrition and recurrent infections."
    explanation: Establishes supportive, symptomatic management as the standard of care.
- name: Prompt Antibiotic Treatment of Respiratory Infections
  description: >
    Respiratory infections should be treated promptly with antibiotics, all
    vaccines should be given, and gastrostomy should be considered where
    aspiration is present.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: antibiotic therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
  target_mechanisms:
  - target: Recurrent Respiratory Infections
    treatment_effect: MODULATES
    description: >
      Symptomatic control of the infection burden; does not address the
      underlying gene dosage.
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prompt antibiotic treatment for respiratory infections; all \nvaccines should be given; consider gastrostomy tube if aspiration is present."
    explanation: GeneReviews management recommendation for the infection burden.
- name: Physical Therapy
  description: >
    Physical therapy to maintain range of motion and reduce the likelihood of
    contractures in the setting of progressive spasticity.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Physical Therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  target_mechanisms:
  - target: Progressive Spasticity
    treatment_effect: MODULATES
    description: Maintains range of motion against progressive spasticity.
  evidence:
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical therapy to maintain range of motion to reduce likelihood of \ncontractures."
    explanation: GeneReviews management recommendation.
- name: Genetic Counseling
  description: >
    Recurrence risk is substantial where a parent carries a structural
    rearrangement, most often a maternally inherited intrachromosomal
    duplication. Because de novo events cluster in the terminal duplication
    class, rearrangement architecture informs counselling. Prenatal diagnosis
    by cytogenetic testing including FISH and/or DNA quantification, and
    preimplantation genetic testing, are available.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prenatal diagnosis is performed by cytogenetic testing \nincluding FISH and/or DNA quantification methods."
    explanation: Establishes the prenatal testing options underpinning counselling.
  - reference: PMID:20301461
    reference_title: "MECP2 Duplication Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Males who inherit the MECP2 duplication will be \naffected; females who inherit the MECP2 duplication are typically asymptomatic \nbut may exhibit clinical manifestations ranging from mild nonspecific \nintellectual disability to a severe phenotype similar to that observed in males."
    explanation: >
      GeneReviews Genetic Counseling - the sex-dependent outcome for inheriting
      offspring, which is the substance of the counselling discussion.
clinical_trials:
- name: NCT06430385
  phase: PHASE_I
  status: RECRUITING
  description: >
    ATTUNE - double-blind, sham-controlled multiple ascending dose study of
    intrathecally administered ION440, an antisense oligonucleotide intended to
    lower MECP2 expression in MECP2 duplication syndrome. Directly targets the
    dosage mechanism modelled in this entry rather than a downstream symptom.
    ClinicalTrials.gov registers this as Phase 1-2; `phase:` is recorded as
    PHASE_I because the enum has no combined Phase 1/2 value.
  target_phenotypes:
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: clinicaltrials:NCT06430385
    reference_title: "A Phase 1-2, Double-Blind, Sham-Controlled Multiple Ascending Dose Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Intrathecally-Administered ION440 in Patients With MECP2 Duplication Syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The primary purpose of this study is to evaluate the safety and tolerability of ION440."
    explanation: >
      First-in-class attempt to correct MECP2 overdosage therapeutically; still
      a safety/tolerability trial, so no efficacy claim is made here.
- name: NCT06615206
  phase: NOT_APPLICABLE
  status: RECRUITING
  description: >
    Open-label study of HG204, a CRISPR RNA-editing therapy delivered by a
    single intracerebroventricular AAV injection, designed to knock down MECP2
    mRNA in the brain.
  evidence:
  - reference: clinicaltrials:NCT06615206
    reference_title: "An Open-label, Multiple-dose Clinical Study to Evaluating the Safety, Tolerability and Preliminary Efficacy of a Single Intracerebroventricular Injection of HG204 for the Treatment of MECP2 Duplication Syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "HG204 is a CRISPR RNA-editing therapy packaging novel high-fidelity Cas13Y (hfCas13Y) technology, using one single adeno-associated virus (AAV) vector to target and knock down MECP2 mRNA in the brain."
    explanation: >
      A second, mechanistically distinct attempt to reverse MECP2 overdosage,
      supporting the dosage model as the therapeutic target.
- name: NCT06014541
  status: TERMINATED
  description: >
    Prospective and retrospective observational natural-history study
    characterising CSF and blood MECP2 biomarkers, clinical scales and seizure
    burden over time. Terminated; no published outcome results were located.
  evidence:
  - reference: clinicaltrials:NCT06014541
    reference_title: "A Prospective and Retrospective Observational/Non-interventional Study to Characterize Biomarkers and Disease Progression in Patients With MECP2 Duplication Syndrome"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The purpose of the study is to prospectively assess longitudinal changes in biomarkers (MECP2, potential biomarkers of target engagement and disease activity) in cerebrospinal fluid (CSF) and blood"
    explanation: >
      Natural-history and biomarker study underpinning the interventional
      programmes above.
discussions:
- discussion_id: gap_xq_dup_irak1_vs_aspiration
  kind: KNOWLEDGE_GAP
  prompt: >
    Is the recurrent-infection phenotype of Xq28 functional disomy caused by
    increased innate-immune gene dosage (IRAK1/IKBKG), or is it secondary to
    aspiration from severe hypotonia and feeding difficulty?
  attaches_to:
  - pathophysiology#Increased IRAK1 Dosage
  rationale: >
    The IRAK1/IKBKG dosage hypothesis is stated only speculatively in the
    primary literature ("might result from"), and no study has demonstrated
    altered innate immune signalling in patient cells. A purely mechanical
    explanation is plausible given that severe axial hypotonia, dysphagia and
    gastroesophageal reflux are themselves near-universal in this population.
    The distinction matters clinically: an immune mechanism would justify
    immunological evaluation and possibly prophylaxis, whereas an aspiration
    mechanism directs management to feeding and airway protection.
  proposed_experiments:
  - experiment_id: exp_xq_dup_irak1_signalling
    name: Innate immune signalling assay in patient-derived cells
    description: >
      Quantify IRAK1 and IKBKG transcript and protein levels and measure
      TLR/IL-1 pathway output in cells from individuals with Xq28 duplication,
      stratified by whether the duplication includes IRAK1/IKBKG.
  - experiment_id: exp_xq_dup_infection_stratified
    name: Genotype-stratified infection burden comparison
    description: >
      Compare respiratory infection rates between individuals whose
      duplications do and do not encompass IRAK1/IKBKG, controlling for degree
      of hypotonia and documented aspiration.
- discussion_id: gap_xq_dup_female_manifesting_carriers
  kind: KNOWLEDGE_GAP
  prompt: >
    What determines whether a female carrier of an Xq duplication is
    asymptomatic or manifests a male-like phenotype?
  attaches_to:
  - pathophysiology#Failure of X-Chromosome Dosage Compensation
  rationale: >
    X-inactivation pattern explains most of the variance - skewing towards the
    duplicated X protects, random inactivation manifests, and an unbalanced
    translocation separating the segment from the XIC in cis produces full
    expression. But rare manifesting females have been described despite
    favourable skewing, for which local escape from inactivation, expression of
    recessive alleles on the active X, or gene disruption at the breakpoint
    have all been proposed without resolution. Predicting carrier outcome is
    directly actionable for genetic counselling.
  evidence:
  - reference: PMID:19232094
    reference_title: "Distal Xq duplication and functional Xq disomy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In rare cases, a favourable skewed\nX-inactivation is observed. For these cases, other explana-\ntions such as local escape from inactivation, expression of\nrecessive genes from the active X, or disruption of a gene\nby the rearrangement have been suggested"
    explanation: States the unresolved alternatives for manifesting females with favourable skewing.
- discussion_id: gap_xq_dup_stag2_transcriptional_mechanism
  kind: KNOWLEDGE_GAP
  prompt: >
    Which cohesin-dependent transcriptional programs are dysregulated by
    increased STAG2 dosage, and do they explain the Xq25 duplication phenotype?
  attaches_to:
  - pathophysiology#Increased STAG2 Dosage and Cohesin Dysregulation
  rationale: >
    The Xq25 interval has been mapped to a 173 kb region containing STAG2
    alone, which is strong positional evidence, but the proposed mechanism -
    dysregulation of cohesin downstream target genes - is an inference rather
    than a measurement. No patient-derived transcriptomic data establishing
    which targets change, or in which direction, has been reported. Without it,
    Xq25 duplication is classified as a cohesinopathy on positional grounds
    alone, and the mechanistic contrast with loss-of-function STAG2
    cohesinopathies remains untested.
  proposed_experiments:
  - experiment_id: exp_xq25_stag2_transcriptome
    name: Transcriptomic profiling of STAG2 duplication patient cells
    description: >
      RNA-seq of patient-derived cells carrying the Xq25 duplication versus
      controls, testing whether cohesin target gene sets are differentially
      expressed and whether the direction of change is opposite to that seen in
      STAG2 loss-of-function cohesinopathy.
references:
- reference: PMID:20301461
  title: MECP2 Duplication Syndrome.
  tags:
  - GeneReviews
📚

References & Deep Research

References

1
PMID:20301461
MECP2 Duplication Syndrome.
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Chromosome Xq Duplication: Disease Characteristics Research Report
Edison Scientific Literature 25 citations 2026-08-12T10:17:56.141972

Chromosome Xq Duplication: Disease Characteristics Research Report

Evidence cutoff: Searches emphasized literature published through 2024 and ClinicalTrials.gov records current in the retrieved registry. Critical scope note: “chromosome Xq duplication” is not a single molecular disease. It is an umbrella cytogenomic finding encompassing duplications of different portions of the X-chromosome long arm. Interpretation must retain the exact interval, copy number, orientation, insertion/translocation context, sex, and X-chromosome-inactivation (XCI) pattern. The best-characterized entities are MECP2 duplication syndrome at Xq28 and STAG2 dosage-related Xq25 duplication cohesinopathy.

The following table summarizes the principal entities.

entity/interval principal dosage-sensitive genes characteristic phenotype inheritance/sex effects strongest evidence
Broad partial Xq duplication (heterogeneous larger duplications across Xq, e.g., Xq23-q26.3) Interval-dependent; reported neurodevelopmental genes in one 20 Mb Xq23-q26.3 case included ARHGEF6, PHF6, HPRT1, SLC9A6 Variable but commonly developmental delay/intellectual disability, short stature, microcephaly, and multiple congenital findings; a 2023 adult female with de novo inverted tandem Xq23-q26.3 duplication had extremely short stature and mild mental deficiency Not a single syndrome; phenotype depends on duplicated segment and X-inactivation. Females may be unaffected or variably affected with skewed/non-random X-inactivation; males are often more severely affected (pehlivan2024structuralvariantallelic pages 1-2) 2023 case report delineating de novo inverted tandem Xq23-q26.3 duplication in an adult female; review-style statements that partial Xq duplications are associated with ID/short stature and female phenotype depends on X-inactivation (pehlivan2024structuralvariantallelic pages 1-2)
Xq25 STAG2 duplication cohesinopathy STAG2 is the shortest-region-of-overlap and principal driver; neighboring duplicated genes can include XIAP, THOC2, GRIA3, SH2D1A Intellectual disability (often mild-moderate), behavioral problems, seizures in about one-third, autism in a minority, characteristic facial features; more severe disease with triplication Mainly affects males; female carriers show variable outcomes from normal to borderline or mild ID, with clinically important effects linked to skewed X-inactivation 2015 cohort of 28 affected males (15 familial, 13 singleton) identified through ~27,000 males tested for neurodevelopmental delay; duplicated intervals 202-746 kb; behavioral problems 68%, seizures 32%, short stature 21% (kumar2015increasedstag2dosagedefinesa pages 2-2, kumar2015increasedstag2dosagedefinesa pages 2-3, kumar2015increasedstag2dosagedefinesa pages 3-4)
MECP2 duplication syndrome, Xq28 (MRXSL) MECP2 is the major disease-contributing gene; nearby genes may modify severity, especially RAB39B, and sometimes IRAK1, L1CAM, GDI1 Core phenotype: infantile hypotonia, severe developmental delay/intellectual disability, poor/absent speech, progressive spasticity, recurrent respiratory infections, epilepsy, GI problems, autistic features, dysmorphism; severity worsens with triplication and more complex structures X-linked disorder affecting primarily males; estimated prevalence about 1/100,000 live male births in one 2024 paper and 1/150,000 males in a 2022 review. Female carriers often milder due to X-inactivation, but affected females occur. In the 2024 cohort, terminal duplications had more de novo events than tandem duplications 2024 deep-genomic cohort of 137 individuals: duplication sizes 64.6 kb-16.5 Mb; structural classes were tandem 48%, terminal 22%, inverted triplication 20%, other complex rearrangements 10%; genotype-phenotype analyses showed worsening of survival and neurologic severity from tandem to triplication, with MECP2 RNA-protein correlation (pehlivan2024structuralvariantallelic pages 1-2, pehlivan2024structuralvariantallelic pages 20-21). Clinical synthesis review in 2022 summarizes 20 years of phenotype and prevalence (ta2022abriefhistory pages 1-2, ta2022abriefhistory pages 16-17, ta2022abriefhistory pages 10-11)
Distal Xq28 duplications excluding MECP2 (including K/L-mediated and int22h1/int22h2-mediated regions) Does not include MECP2; likely multigenic distal Xq28 dosage effects rather than a single confirmed driver Can resemble MECP2 duplication syndrome: regressive intellectual disability, progressive neurologic disorder/spasticity, epilepsy, recurrent infections, and brain MRI abnormalities Sex/inheritance effects not established as clearly as classic MECP2 duplication syndrome; evidence is currently based on small case numbers/case reports 2023 case report of a 17-year-old boy with a 1.2 Mb distal Xq28 duplication spanning both K/L-mediated and int22h1/int22h2-mediated regions: epilepsy from age 6, progressive lower-extremity spasticity requiring surgery at 14, recurrent infection, and hypoplasia of corpus callosum/cerebellum/brain stem; authors concluded that MECP2 alone may not explain all symptoms of distal Xq28 duplication (akahoshi2023duplicationwithintwo pages 1-2)

Table: This table summarizes the main clinically relevant Xq duplication entities discussed in the evidence gathered so far. It distinguishes the broad heterogeneous category from better-defined subtypes such as Xq25/STAG2 and Xq28/MECP2 duplications, which is useful for disease-scope clarification and genotype-phenotype interpretation.

1. Disease information

Definition and identifiers

A chromosome Xq duplication is a germline copy-number gain involving part of Xq. Large duplications may encompass many genes and produce a contiguous-gene syndrome; smaller recurrent or nonrecurrent gains may define gene-dosage disorders. Clinical effects range from apparently unaffected female carriers to severe congenital or progressive neurodevelopmental disease, particularly in hemizygous males.

The most established subtype is MECP2 duplication syndrome (MDS), also called X-linked intellectual developmental disorder, Lubs type; MRXSL; Lubs X-linked mental retardation syndrome, caused by copy-number gain spanning MECP2 at Xq28. Its established identifier is OMIM/MIM 300260; MECP2 itself is OMIM 300005. The 2024 Genome Medicine paper defines MRXSL as “a neurodevelopmental disorder caused by copy number gains spanning MECP2.” (pehlivan2024structuralvariantallelic pages 1-2)

A second defined subtype is Xq25 duplication/STAG2 duplication syndrome, described as an increased-STAG2-dosage cohesinopathy. Broad synonyms include partial duplication of Xq, Xq partial trisomy, Xq microduplication syndrome, and interval-specific terms such as Xq23–q26.3 duplication or distal Xq28 duplication.

No single disease-specific ICD-10, ICD-11, or MeSH code adequately represents every Xq duplication. Coding normally uses a congenital chromosomal-abnormality/CNV code plus the clinical manifestations. A single umbrella MONDO identifier could not be verified from the retrieved primary literature; database implementation should therefore map the exact named syndrome where available rather than assign the MDS identifier to every Xq gain.

Data provenance: Published evidence is aggregated from case reports, cross-sectional case series, laboratory cohorts, and disease reviews—not population EHR surveillance. The major MDS review emphasizes that prior data were cross-sectional and incompletely longitudinal; it called for an international registry and an MDS-specific severity scale. (ta2022abriefhistory pages 16-17)

2. Etiology

Causal factors

The cause is a constitutional structural variant, usually a duplication or triplication, generated by genomic rearrangement. In MDS, gains can be tandem, terminal, insertional/translocation-associated, recombinant, inverted triplications, or other complex genomic rearrangements. In 137 affected individuals, sizes ranged from 64.6 kb to 16.5 Mb: tandem duplications 48%, terminal duplications 22%, inverted triplications 20%, and other complex rearrangements 10%. Among terminal events, 65% were translocations and 23% recombinant chromosomes. (pehlivan2024structuralvariantallelic pages 1-2)

The same cohort found de novo events disproportionately among terminal duplications—65%, compared with 17% among tandem duplications—indicating that rearrangement architecture informs recurrence counseling. (pehlivan2024structuralvariantallelic pages 1-2)

Genetic risk and modifiers

  • MECP2 copy gain is the primary causal factor for classic MDS. Triplication and higher RNA/protein dosage generally cause more severe disease. Nearby RAB39B, GDI1, IRAK1, L1CAM, and genes introduced or disrupted by translocations can modify particular manifestations.
  • STAG2 copy gain is the best-supported driver of Xq25 duplication cohesinopathy. In a 28-male cohort, the shortest overlapping gain contained STAG2 alone; some larger gains included XIAP, THOC2, GRIA3, or SH2D1A. (kumar2015increasedstag2dosagedefinesa pages 2-2, kumar2015increasedstag2dosagedefinesa pages 3-4)
  • Distal Xq28 duplications lacking MECP2 can nevertheless produce an MDS-like phenotype, indicating that MECP2 does not explain every distal-Xq28 dosage phenotype. A 2023 report described a 1.2-Mb gain spanning K/L-mediated and int22h1/int22h2-mediated regions without MECP2. (akahoshi2023duplicationwithintwo pages 1-2)
  • In females, favorable skewing that preferentially inactivates the duplicated X can be protective; unfavorable or incomplete skewing permits functional disomy and disease. Female STAG2 carriers ranged from normal cognition to borderline or mild intellectual disability. (kumar2015increasedstag2dosagedefinesa pages 2-3, kumar2015increasedstag2dosagedefinesa pages 3-4)

These CNVs are generally too rare and structurally heterogeneous for meaningful population allele frequencies. A pathogenic dosage gain should not be summarized as a conventional SNV allele frequency; classification requires ACMG/ClinGen CNV criteria, gene dosage evidence, inheritance, and phenotype concordance.

Non-genetic risk, protective factors, and gene–environment interaction

No toxin, diet, infection, lifestyle, occupation, or behavior is known to cause a constitutional Xq duplication. Maternal or paternal age effects are not established. Respiratory infections, immobility, nutrition, and antiseizure-drug adverse effects can modify morbidity or precipitate regression but do not cause the CNV. In the 2024 cohort, regression was attributed to seizure onset in 12 individuals, refractory seizures in 17, infection in six, and antiseizure-medication effects in four. (pehlivan2024structuralvariantallelic pages 13-14)

No validated environmental or genetic “protective variant” has been identified. The main established protective mechanism is favorable XCI in heterozygous females.

3. Phenotypes

Phenotype is interval-specific. The following profile applies primarily to MDS, for which the strongest quantitative data exist.

Core neurodevelopmental phenotype

  • Infantile hypotonia—congenital/early infancy, common and often later accompanied by appendicular hypertonia or progressive spasticity. Suggested HPO: Hypotonia HP:0001252, Spasticity HP:0001257.
  • Global developmental delay and intellectual disability—usually severe in MDS, mild-to-moderate more often in STAG2 duplication. Suggested HPO: HP:0001263, HP:0001249.
  • Poor or absent speech and impaired adaptive function; HPO: Absent speech HP:0001344, Delayed speech and language development HP:0000750.
  • Epilepsy—age-dependent and potentially near-universal in older MDS cohorts. Across 2024 structural groups, observed prevalence was 40–59%; mean/representative onset became earlier with increasing complexity: tandem 8.4 years, other complex 8.2 years, terminal 5.6 years, translocation 4 years 10 months, and triplication under 2 years. Epilepsy is a major cause of regression. HPO: HP:0001250. (pehlivan2024structuralvariantallelic pages 20-21, pehlivan2024structuralvariantallelic pages 13-14)
  • Autistic and behavioral features—in the 2024 cohort, 109/127 (85.8%) had at least one of repetitive movement, poor eye contact, or sensory sensitivity in addition to poor speech. A 2022 synthesis reported formal autism diagnoses in 34/50 (68%), gaze avoidance in 44/61 (72%), impaired social interaction in 38/46 (83%), stereotypies in 158/285 (55%), and bruxism in 102/156 (65%). Suggested HPO: Autistic behavior HP:0000729, Stereotypic behavior HP:0000733, Bruxism HP:0003763. (pehlivan2024structuralvariantallelic pages 13-14, ta2022abriefhistory pages 10-11)

Other frequent manifestations

  • Recurrent respiratory infections, often beginning in childhood, are a cardinal source of hospitalization and premature mortality. HPO: Recurrent respiratory infections HP:0002205.
  • Feeding, chewing, and swallowing difficulty exceeded 80% across MDS structural groups; tube-feeding need increased with genomic severity. Gastroesophageal reflux and constipation are common. Suggested HPO: Dysphagia HP:0002015, Gastroesophageal reflux HP:0002020, Constipation HP:0002019. (pehlivan2024structuralvariantallelic pages 20-21)
  • Sleep disorders: insomnia occurred in 62/118 (52.5%) and sleep apnea in 63/114 (55.2%); apnea rose from 48.2% in tandem duplications to 100% in the two triplication subjects with data. Most was obstructive. HPO: Insomnia HP:0100785, Obstructive sleep apnea HP:0002870. (pehlivan2024structuralvariantallelic pages 13-14)
  • Dysautonomia occurred in 105/121 (86.7%), bruxism in 81/112 (72.3%), and high pain tolerance in 85/109 (77.9%) in the 2024 cohort. HPO: Autonomic nervous system dysfunction HP:0002270, Reduced sensitivity to pain HP:0007328. (pehlivan2024structuralvariantallelic pages 13-14)
  • Musculoskeletal morbidity: 49/93 (52.6%) had abnormalities, including fractures (26), osteopenia/osteoporosis (13), scoliosis (13), and contractures (9). Suggested HPO: HP:0000939 osteoporosis, HP:0002650 scoliosis, HP:0001371 contracture. (pehlivan2024structuralvariantallelic pages 13-14)
  • Vision: 71/117 (60.6%) had predominantly refractive error or strabismus. The 2022 review reported strabismus in 51/73 (70%). HPO: Strabismus HP:0000486. (pehlivan2024structuralvariantallelic pages 13-14, ta2022abriefhistory pages 10-11)
  • Head growth/dysmorphism: the review reported microcephaly in 45/195 (23%), macrocephaly in 29/169 (17%), midface hypoplasia in 67/99 (68%), open-mouth appearance in 59/72 (82%), and large ears in 83/133 (62%). Dysmorphism changes with age. (ta2022abriefhistory pages 10-11)
  • Genitourinary abnormalities include hypogenitalism/micropenis, urinary retention, stones, hydronephrosis, vesicoureteral reflux, and congenital kidney/urinary-tract anomalies; severity was greater in triplication/terminal groups. (pehlivan2024structuralvariantallelic pages 13-14)

Xq25/STAG2 phenotype

Among 28 affected males, intellectual disability was usually mild-to-moderate, behavioral problems occurred in 68%, seizures in 32%, short stature in 21%, and autism was reported in four. Facial findings included malar flatness (23/27), prognathism (16/26), and full lips (15/26). MRI findings included cerebellar-vermis hypoplasia, thin corpus callosum, and prominent subarachnoid spaces. (kumar2015increasedstag2dosagedefinesa pages 2-3)

Quality of life

No robust disease-specific EQ-5D or SF-36 dataset was identified. Severe communication and mobility limitations, epilepsy, tube feeding, recurrent hospitalization, sleep disruption, and dependence in activities of daily living imply major patient and caregiver burden. A prospective Ionis natural-history study measured the Quality-of-Life Inventory–Disability alongside communication, adaptive behavior, seizure, EEG, and biomarker outcomes, but published outcome results were not available in the retrieved record. (NCT06014541 chunk 1)

4. Genetic and molecular information

Genes and variants

The causal lesion is a germline structural CNV, not typically a somatic mutation. Relevant genes include:

  • MECP2 at Xq28: dosage-sensitive nuclear methylated-DNA reader/transcriptional modulator; increased intact-gene copy number causes MDS.
  • STAG2 at Xq25: cohesin-complex component; increased dosage perturbs transcriptional networks and defines a duplication cohesinopathy. (kumar2015increasedstag2dosagedefinesa pages 2-2)
  • Interval-dependent contributors: RAB39B, GDI1, IRAK1, L1CAM, XIAP, THOC2, GRIA3, SH2D1A, ARHGEF6, PHF6, HPRT1, and SLC9A6.

Variant classes include tandem duplication, insertional duplication, terminal duplication, unbalanced translocation, recombinant X chromosome, duplication–triplication/inverted-duplication structures, and larger cytogenetically visible partial trisomies. Genome position should be stored using the tested reference build and HGVS/ISCN-compatible coordinates.

Partial duplication of only the first two MECP2 exons was found in an otherwise neurologically asymptomatic 12-year-old male, supporting the requirement for an intact dosage gain rather than any overlap with MECP2. (pehlivan2024structuralvariantallelic pages 20-21)

Expression and epigenetics

MeCP2 binds methylated cytosines, especially CG and CAC contexts, and fine-tunes thousands of neuronal genes. It can repress or activate transcription, alter chromatin, and participate in RNA processing. It is nuclear, ubiquitous, and especially abundant in postnatal neurons. (pehlivan2024structuralvariantallelic pages 1-2, ta2022abriefhistory pages 1-2)

In patient lymphoblastoid cells, duplications generally produced approximately twofold MECP2 RNA and protein, although some exceeded twofold. RNA and protein were correlated (Pearson R=0.6; p<0.05). Triplications had significantly greater MECP2 transcript abundance than duplication classes. (pehlivan2024structuralvariantallelic pages 20-21, pehlivan2024structuralvariantallelic pages 1-2)

XCI is the principal epigenetic modifier in females. Blood XCI may not perfectly represent brain XCI, so it is informative but not determinative.

5. Environmental information

No causal environmental, lifestyle, infectious, dietary, radiation, or occupational exposure is established. Infectious agents are complications rather than etiologic triggers. Standard immunization, nutrition, airway care, physical activity within ability, and avoidance of aspiration or prolonged immobility may reduce complications but do not prevent the underlying disease.

6. Mechanism and pathophysiology

MECP2 dosage causal chain

Structural gain spanning intact MECP2 → increased MECP2 RNA and protein → abnormal binding/modulation across methylated neuronal chromatin → widespread transcriptional and synaptic-network dysregulation → impaired postnatal neuronal maturation and circuit function → hypotonia, developmental impairment, epilepsy, autistic features, and progressive spasticity. Greater dosage and complex rearrangements add earlier seizures, poorer development, microcephaly, organ abnormalities, and reduced survival. The 2024 authors concluded that “MECP2 is the major disease contributing gene since its dosage and the structure of CNV drive the phenotype.” (pehlivan2024structuralvariantallelic pages 20-21)

Suggested GO terms include DNA methylation-dependent heterochromatin assembly, regulation of transcription by RNA polymerase II, chromatin organization, regulation of synaptic plasticity, neuron maturation, and nervous-system development. Relevant cellular compartments are nucleus/chromatin (GO cellular component) and synaptic neuronal networks downstream. Suggested Cell Ontology targets include neuron (CL:0000540), neural progenitor cell, excitatory neuron, inhibitory neuron, and glial cells; the exact vulnerable cell class remains incompletely resolved.

STAG2 dosage chain

Xq25 gain → increased STAG2 dosage → altered cohesin stoichiometry/chromatin-loop and transcriptional regulation → dysregulated neurodevelopmental gene networks, including increased OPHN1 expression in studied cells → intellectual disability, behavioral problems, and variably epilepsy/autism. This is a dosage-gain cohesinopathy, distinct from STAG2 loss-of-function disease. (kumar2015increasedstag2dosagedefinesa pages 2-2)

Suggested GO terms: sister chromatid cohesion, chromosome organization, chromatin organization, regulation of transcription, and nervous-system development.

Other systems and omics

Recurrent infections may reflect aspiration, impaired airway clearance, central/neuromuscular dysfunction, and possibly dosage effects of immune-related genes such as IRAK1, but no single immune mechanism explains all patients. No reproducible disease-specific metabolomic, lipidomic, or proteomic signature is established.

The major current multi-omics advance is the 2024 integration of array/short- and long-read WGS, optical mapping, RNA sequencing, protein measurement, and deep HPO phenotyping in 137 individuals. It demonstrated genome-structure-dependent severity and provides a rationale for measuring baseline MECP2 expression before dose-reduction therapy. (pehlivan2024structuralvariantallelic pages 4-5, pehlivan2024structuralvariantallelic pages 1-2)

No sufficiently replicated single-cell or spatial-transcriptomic human MDS atlas was identified.

7. Anatomical structures affected

The central nervous system is primary: cerebral cortex and distributed neuronal circuits, corticospinal pathways, white matter, corpus callosum, cerebellum, and brainstem. A distal-Xq28 case had hypoplasia of the corpus callosum, cerebellum, and brainstem plus reduced/deep-white-matter abnormalities. (akahoshi2023duplicationwithintwo pages 1-2)

Suggested UBERON concepts include brain (UBERON:0000955), cerebral cortex (UBERON:0000956), corpus callosum, cerebellum UBERON:0002037, brainstem UBERON:0002298, spinal cord, peripheral skeletal muscle, lung, gastrointestinal tract, kidney/urinary tract, eye, and skeleton.

Secondary systems include respiratory, gastrointestinal, musculoskeletal, genitourinary, ocular, sleep/upper-airway, and autonomic systems. There is no consistent lateralization. At subcellular level, MeCP2 acts primarily in the nucleus/chromatin; STAG2 acts in nuclear cohesin complexes.

8. Temporal development

The duplication is congenital and lifelong. Hypotonia and developmental delay usually appear in infancy; speech and motor delay become evident in early childhood. Spasticity, epilepsy, scoliosis, contractures, feeding impairment, and loss of skills may emerge or worsen over years. Epilepsy becomes more frequent with age, and its onset is earlier in triplication/complex rearrangements. (pehlivan2024structuralvariantallelic pages 20-21, pehlivan2024structuralvariantallelic pages 13-14)

The course is generally chronic and variably progressive rather than relapsing-remitting. Regression is often linked to epilepsy, refractory seizures, infection, or medication effects. There is no spontaneous molecular remission. Early developmental therapy, prevention of aspiration/infection, and early seizure control represent practical windows for limiting secondary disability.

9. Inheritance and population

MDS is an X-linked genomic disorder predominantly affecting males. Many tandem duplications are inherited from heterozygous mothers who are asymptomatic or mildly affected because of favorable XCI; de novo and paternal-origin events occur, especially with complex or terminal structures. A 2024 Chinese family had a 14.45-Mb Xq27.1–q28 duplication inherited by an affected boy from a mildly affected mother. (zeng2024geneticanalysisof pages 2-5, zeng2024geneticanalysisof pages 1-2)

For a carrier mother, the theoretical risk per pregnancy is 50% of transmitting the duplicated X; clinical severity is sex- and XCI-dependent. Affected males transmit their X to all daughters and no sons, although survival and reproductive fitness may limit observed transmission. Germline mosaicism is possible but not quantified. No anticipation, founder effect, consanguinity association, or population-specific enrichment is established.

For classic MDS, estimated live-birth prevalence is approximately 0.65/100,000 overall (about 1/150,000) and approximately 1/100,000 male live births in the cited Australian estimate; underdiagnosis is likely. (ta2022abriefhistory pages 1-2)

No reliable prevalence or incidence exists for the umbrella category or STAG2 duplication. The STAG2 study found 28 affected males, including 15 from six families and 13 singletons, through systematic/clinical analysis that included approximately 27,000 males with neurodevelopmental delay; this is ascertainment data, not population prevalence. (kumar2015increasedstag2dosagedefinesa pages 2-2)

10. Diagnostics

Recommended approach

  1. Clinical recognition: congenital hypotonia, severe developmental/speech delay, progressive spasticity, epilepsy, recurrent respiratory infection, GI dysfunction, autism-like behavior, or an X-linked family history.
  2. Chromosomal microarray (CMA): preferred first-line test for unexplained developmental delay, ID, autism, or congenital anomalies because it defines dosage and approximate coordinates. CMA does not reliably resolve orientation, insertion site, or all complex structures.
  3. Orthogonal confirmation: MLPA, qPCR, ddPCR, CNV-seq, or another validated dosage assay; test parents.
  4. Karyotype/FISH: important for large duplications, terminal gains, insertional rearrangements, unbalanced translocations, and reproductive-risk assessment.
  5. WGS/long-read sequencing and optical genome mapping: useful when breakpoints and structural architecture affect prognosis or trial eligibility. In 2024, apparent tandem gains on array were reclassified as inverted or insertional/complex events using WGS and optical mapping. (pehlivan2024structuralvariantallelic pages 20-21, pehlivan2024structuralvariantallelic pages 4-5)
  6. XCI testing in females: may help explain phenotype but should not be treated as a brain-specific functional assay.

WES can detect exon-level CNVs but may miss or mischaracterize structural complexity; it should not replace genome-wide CNV analysis. The 2024 pedigree diagnosis combined G-banding, WES, CNV-seq, and family validation. (zeng2024geneticanalysisof pages 1-2)

Clinical assessment and surveillance

Baseline and periodic evaluations should include developmental/adaptive and communication testing; neurological examination; EEG when seizures or regression are suspected; swallow/feeding and nutritional assessment; respiratory and aspiration history; sleep study when apnea is suspected; orthopedic assessment; vision/hearing; renal/genitourinary evaluation; and brain MRI when seizures, regression, focal signs, or trial criteria warrant it.

There is no biochemical enzyme assay or pathognomonic circulating biomarker. CSF/blood MeCP2, plasma proteomics, EEG/evoked potentials, pupillometry, and disease-severity scales are investigational biomarkers. (NCT06014541 chunk 1)

Differential diagnosis

Principal differentials include Rett syndrome/MECP2 loss of function, CDKL5 and FOXG1 disorders, Angelman syndrome, Phelan–McDermid syndrome, cerebral palsy, mitochondrial disease, other X-linked ID syndromes, and other Xq CNVs. Distinguishing evidence is an intact-gene copy-number gain spanning the relevant Xq interval. Distal Xq28 duplications lacking MECP2 and Xq25/STAG2 gains should not be mislabeled as classic MDS. (kumar2015increasedstag2dosagedefinesa pages 2-2, akahoshi2023duplicationwithintwo pages 1-2)

No population newborn screening is available. Cascade testing of relatives, prenatal diagnosis by CVS/amniocentesis, and preimplantation genetic testing for a known familial CNV are technically feasible.

11. Outcome and prognosis

Prognosis varies greatly with interval, sex, XCI, copy number, structure, epilepsy, infection burden, feeding/respiratory impairment, and associated deletion/translocation. Tandem MECP2 duplications generally had the least severe profile, followed by other complex duplications, terminal/translocation-associated duplications, and triplications. The 2024 analysis found progressively worse survival, developmental level, microcephaly, epilepsy timing, and genitourinary/ocular abnormalities along this gradient. (pehlivan2024structuralvariantallelic pages 1-2)

Classic MDS can cause premature death, often related to recurrent respiratory infection, aspiration, epilepsy, or severe neurologic impairment; historical summaries report deaths before age 25 in severe cases, but no reliable universal five- or ten-year survival percentage exists. (neri2018x‐linkedintellectualdisability pages 4-6, NCT06615206 chunk 1)

Long-term morbidity includes severe communication and adaptive disability, loss of mobility, refractory epilepsy, tube-feeding dependence, recurrent hospitalization, sleep apnea, scoliosis, contractures, osteoporosis/fractures, and caregiver burden. Recovery of the constitutional duplication does not occur; functional gains are possible with rehabilitation and complication control. Disease-specific validated prognostic biomarkers remain investigational.

12. Treatment

Current standard care

No approved curative or CNV-correcting therapy was identified. Management is multidisciplinary and symptom-directed:

  • individualized antiseizure therapy and rescue planning;
  • vaccination, prompt treatment of infection, airway-clearance support, aspiration assessment, and pulmonology input;
  • feeding therapy, reflux/constipation treatment, nutritional support, and gastrostomy when oral intake is unsafe or inadequate;
  • physical and occupational therapy, mobility/orthotic aids, and management of spasticity, contractures, scoliosis, and low bone density;
  • speech-language therapy and augmentative/alternative communication;
  • behavioral, sleep, ophthalmologic, audiologic, urologic/nephrologic, and genetic-counseling support.

A distal-Xq28 case received physical, occupational, and speech therapy; the 2024 Chinese case illustrates acute antibiotic treatment for recurrent severe infection, but neither report establishes disease-specific response rates. (zeng2024geneticanalysisof pages 2-5, akahoshi2023duplicationwithintwo pages 1-2)

Suggested NCIt intervention concepts include physical therapy, occupational therapy, speech therapy, antiepileptic therapy, gastrostomy, noninvasive ventilation, genetic counseling, antisense oligonucleotide therapy, and gene therapy.

Molecular therapies and 2024 clinical translation

  • ION440/ATTUNE, NCT06430385: recruiting phase 1/2, randomized, quadruple-blind, sham-controlled multiple-ascending-dose trial of intrathecal ION440 in 48 planned males aged 2–65, followed by open-label extension. It evaluates safety, pharmacokinetics, and pharmacodynamics. Severe terminal/translocation duplications and MECP2 triplications are excluded from Part 1. Registry first posted 28 May 2024: https://clinicaltrials.gov/study/NCT06430385. (NCT06430385 chunk 1, NCT06430385 chunk 2)
  • HG204/HERO, NCT06615206: recruiting first-in-human, open-label study of one intracerebroventricular AAV carrying high-fidelity Cas13Y RNA-editing machinery to reduce MECP2 mRNA; planned enrollment is six males aged 2–18. Preclinical registry data report reduced cortical MECP2 RNA/protein, reversal of motor/social abnormalities, and prolonged survival in MDS mice. First posted 26 September 2024: https://clinicaltrials.gov/study/NCT06615206. (NCT06615206 chunk 1)

These therapies remain experimental; no human efficacy or response-rate conclusion should be inferred from recruitment status. Because some duplication carriers express more than twofold MeCP2, individualized baseline expression and structural classification may be needed to avoid under- or over-suppression. (pehlivan2024structuralvariantallelic pages 20-21)

No established pharmacogenomic prescribing rule, stem-cell therapy, immunotherapy, or surgical cure exists.

13. Prevention

The structural event cannot usually be prevented by lifestyle or vaccination.

  • Primary prevention: genetic counseling and reproductive options for known carriers—prenatal diagnosis, preimplantation genetic testing, donor gametes, or adoption. These reduce recurrence risk but do not alter an established fetal CNV.
  • Secondary prevention: cascade testing and early molecular diagnosis; early developmental therapy and surveillance before epilepsy, aspiration, malnutrition, sleep apnea, or orthopedic complications become advanced.
  • Tertiary prevention: vaccination and infection control, aspiration precautions, seizure management, mobility/positioning, bone-health care, nutrition, and respiratory support.

No disease-specific vaccine or prophylactic medication exists. Routine immunization is particularly important because recurrent respiratory infection is a major morbidity.

14. Other species and natural disease

No established naturally occurring veterinary syndrome directly equivalent to a human partial Xq duplication was identified. Therefore, breed prevalence, VBO mapping, zoonotic transmission, and cross-species contagion are not applicable. The disease is genetic and noninfectious.

Orthologs of MECP2 and cohesin genes including STAG2 are evolutionarily conserved across vertebrates, enabling comparative mechanistic studies. Exact animal NCBI Gene identifiers should be imported directly from NCBI/Alliance rather than inferred from human records.

15. Model organisms

The principal models are transgenic mice overexpressing human or murine Mecp2, patient-derived lymphoblastoid/fibroblast cells, and potentially iPSC-derived neurons. MeCP2-overexpressing mice reproduce progressive neurologic disease, seizures, spasticity, motor/social abnormalities, and premature death; severity tracks MeCP2 abundance, supporting causal dosage rather than a coincidental neighboring-gene effect. (collins2022rettsyndromeand pages 2-4)

Mouse studies also provide proof of reversibility: reducing MECP2 expression can improve neurological phenotypes and survival, which underlies current ASO and RNA-targeting trials. HG204 preclinical studies reportedly reversed motor/social phenotypes and prolonged survival after intracerebroventricular treatment. (NCT06615206 chunk 1)

Patient lymphoblastoid cells are useful for measuring MECP2 transcript/protein dosage and rearrangement-dependent expression but cannot recapitulate mature brain circuitry. Mouse models cannot fully capture human CNV complexity, female XCI mosaicism, recurrent infection burden, or the contribution of every co-duplicated gene. There is no single model for the broad “Xq duplication” category; models must match the duplicated interval and dosage.

Evidence limitations and expert interpretation

  1. The umbrella label should never replace exact cytogenomic coordinates and gene content.
  2. Most phenotype percentages are affected by referral bias, missing data, changing age, and duplicated cases across historical reports. The 2022 review explicitly noted that no prior study supplied a complete longitudinal clinical history. (ta2022abriefhistory pages 16-17)
  3. The strongest recent evidence is the 2024 137-person structural/genomic study, but even it is not population-based and some subgroup denominators are small. (pehlivan2024structuralvariantallelic pages 1-2, pehlivan2024structuralvariantallelic pages 13-14)
  4. PMIDs were not exposed in the retrieved full-text metadata; DOI URLs and publication dates are therefore supplied rather than risking incorrect PMID assignment.

Selected primary/recent sources

  • Pehlivan D, et al. Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression. Genome Medicine. Published December 2024. https://doi.org/10.1186/s13073-024-01411-7. Abstract conclusion: “the level of MECP2 is a key determinant of the phenotype,” while rearrangement structure contributes to severity. (pehlivan2024structuralvariantallelic pages 1-2)
  • Zeng L, et al. Genetic analysis of a pedigree with MECP2 duplication syndrome in China. BMC Medical Genomics. Published February 2024. https://doi.org/10.1186/s12920-024-01831-9. (zeng2024geneticanalysisof pages 2-5, zeng2024geneticanalysisof pages 1-2)
  • Akahoshi K, et al. Duplication within two regions distal to MECP2: clinical similarity with MECP2 duplication syndrome. BMC Medical Genomics. Published March 2023. https://doi.org/10.1186/s12920-023-01465-3. The authors concluded that “MECP2 alone may not explain all symptoms” of distal Xq28 duplication. (akahoshi2023duplicationwithintwo pages 1-2)
  • Ta D, et al. A brief history of MECP2 duplication syndrome: 20-years of clinical understanding. Orphanet Journal of Rare Diseases. Published March 2022. https://doi.org/10.1186/s13023-022-02278-w. (ta2022abriefhistory pages 16-17, ta2022abriefhistory pages 1-2)
  • Kumar R, et al. Increased STAG2 dosage defines a novel cohesinopathy with intellectual disability and behavioral problems. Human Molecular Genetics. Published October 2015. https://doi.org/10.1093/hmg/ddv414. (kumar2015increasedstag2dosagedefinesa pages 2-2, kumar2015increasedstag2dosagedefinesa pages 2-3, kumar2015increasedstag2dosagedefinesa pages 3-4)

References

  1. (pehlivan2024structuralvariantallelic pages 1-2): Davut Pehlivan, Jesse D. Bengtsson, Sameer S. Bajikar, Christopher M. Grochowski, Ming Yin Lun, Mira Gandhi, Angad Jolly, Alexander J. Trostle, Holly K. Harris, Bernhard Suter, Sukru Aras, Melissa B. Ramocki, Haowei Du, Michele G. Mehaffey, KyungHee Park, Ellen Wilkey, Cemal Karakas, Jesper J. Eisfeldt, Maria Pettersson, Lynn Liu, Marwan S. Shinawi, Virginia E. Kimonis, Wojciech Wiszniewski, Kyle Mckenzie, Timo Roser, Angela M. Vianna-Morgante, Alberto S. Cornier, Ahmed Abdelmoity, James P. Hwang, Shalini N. Jhangiani, Donna M. Muzny, Tadahiro Mitani, Kazuhiro Muramatsu, Shin Nabatame, Daniel G. Glaze, Jawid M. Fatih, Richard A. Gibbs, Zhandong Liu, Anna Lindstrand, Fritz J. Sedlazeck, James R. Lupski, Huda Y. Zoghbi, and Claudia M. B. Carvalho. Structural variant allelic heterogeneity in mecp2 duplication syndrome provides insight into clinical severity and variability of disease expression. Genome Medicine, Dec 2024. URL: https://doi.org/10.1186/s13073-024-01411-7, doi:10.1186/s13073-024-01411-7. This article has 16 citations and is from a highest quality peer-reviewed journal.

  2. (kumar2015increasedstag2dosagedefinesa pages 2-2): Raman Kumar, Mark A. Corbett, Bregje W.M. Van Bon, Alison Gardner, Joshua A. Woenig, Lachlan A. Jolly, Evelyn Douglas, Kathryn Friend, Chuan Tan, Hilde Van Esch, Maureen Holvoet, Martine Raynaud, Michael Field, Melanie Leffler, Bartłomiej Budny, Marzena Wisniewska, Magdalena Badura-Stronka, Anna Latos-Bieleńska, Jacqueline Batanian, Jill A. Rosenfeld, Lina Basel-Vanagaite, Corinna Jensen, Melanie Bienek, Guy Froyen, Reinhard Ullmann, Hao Hu, Michael I. Love, Stefan A. Haas, Pawel Stankiewicz, Sau Wai Cheung, Anne Baxendale, Jillian Nicholl, Elizabeth M. Thompson, Eric Haan, Vera M. Kalscheuer, and Jozef Gecz. Increasedstag2dosage defines a novel cohesinopathy with intellectual disability and behavioral problems. Human Molecular Genetics, 24:7171-7181, Oct 2015. URL: https://doi.org/10.1093/hmg/ddv414, doi:10.1093/hmg/ddv414. This article has 44 citations and is from a domain leading peer-reviewed journal.

  3. (kumar2015increasedstag2dosagedefinesa pages 2-3): Raman Kumar, Mark A. Corbett, Bregje W.M. Van Bon, Alison Gardner, Joshua A. Woenig, Lachlan A. Jolly, Evelyn Douglas, Kathryn Friend, Chuan Tan, Hilde Van Esch, Maureen Holvoet, Martine Raynaud, Michael Field, Melanie Leffler, Bartłomiej Budny, Marzena Wisniewska, Magdalena Badura-Stronka, Anna Latos-Bieleńska, Jacqueline Batanian, Jill A. Rosenfeld, Lina Basel-Vanagaite, Corinna Jensen, Melanie Bienek, Guy Froyen, Reinhard Ullmann, Hao Hu, Michael I. Love, Stefan A. Haas, Pawel Stankiewicz, Sau Wai Cheung, Anne Baxendale, Jillian Nicholl, Elizabeth M. Thompson, Eric Haan, Vera M. Kalscheuer, and Jozef Gecz. Increasedstag2dosage defines a novel cohesinopathy with intellectual disability and behavioral problems. Human Molecular Genetics, 24:7171-7181, Oct 2015. URL: https://doi.org/10.1093/hmg/ddv414, doi:10.1093/hmg/ddv414. This article has 44 citations and is from a domain leading peer-reviewed journal.

  4. (kumar2015increasedstag2dosagedefinesa pages 3-4): Raman Kumar, Mark A. Corbett, Bregje W.M. Van Bon, Alison Gardner, Joshua A. Woenig, Lachlan A. Jolly, Evelyn Douglas, Kathryn Friend, Chuan Tan, Hilde Van Esch, Maureen Holvoet, Martine Raynaud, Michael Field, Melanie Leffler, Bartłomiej Budny, Marzena Wisniewska, Magdalena Badura-Stronka, Anna Latos-Bieleńska, Jacqueline Batanian, Jill A. Rosenfeld, Lina Basel-Vanagaite, Corinna Jensen, Melanie Bienek, Guy Froyen, Reinhard Ullmann, Hao Hu, Michael I. Love, Stefan A. Haas, Pawel Stankiewicz, Sau Wai Cheung, Anne Baxendale, Jillian Nicholl, Elizabeth M. Thompson, Eric Haan, Vera M. Kalscheuer, and Jozef Gecz. Increasedstag2dosage defines a novel cohesinopathy with intellectual disability and behavioral problems. Human Molecular Genetics, 24:7171-7181, Oct 2015. URL: https://doi.org/10.1093/hmg/ddv414, doi:10.1093/hmg/ddv414. This article has 44 citations and is from a domain leading peer-reviewed journal.

  5. (pehlivan2024structuralvariantallelic pages 20-21): Davut Pehlivan, Jesse D. Bengtsson, Sameer S. Bajikar, Christopher M. Grochowski, Ming Yin Lun, Mira Gandhi, Angad Jolly, Alexander J. Trostle, Holly K. Harris, Bernhard Suter, Sukru Aras, Melissa B. Ramocki, Haowei Du, Michele G. Mehaffey, KyungHee Park, Ellen Wilkey, Cemal Karakas, Jesper J. Eisfeldt, Maria Pettersson, Lynn Liu, Marwan S. Shinawi, Virginia E. Kimonis, Wojciech Wiszniewski, Kyle Mckenzie, Timo Roser, Angela M. Vianna-Morgante, Alberto S. Cornier, Ahmed Abdelmoity, James P. Hwang, Shalini N. Jhangiani, Donna M. Muzny, Tadahiro Mitani, Kazuhiro Muramatsu, Shin Nabatame, Daniel G. Glaze, Jawid M. Fatih, Richard A. Gibbs, Zhandong Liu, Anna Lindstrand, Fritz J. Sedlazeck, James R. Lupski, Huda Y. Zoghbi, and Claudia M. B. Carvalho. Structural variant allelic heterogeneity in mecp2 duplication syndrome provides insight into clinical severity and variability of disease expression. Genome Medicine, Dec 2024. URL: https://doi.org/10.1186/s13073-024-01411-7, doi:10.1186/s13073-024-01411-7. This article has 16 citations and is from a highest quality peer-reviewed journal.

  6. (ta2022abriefhistory pages 1-2): Daniel Ta, Jenny Downs, Gareth Baynam, Andrew Wilson, Peter Richmond, and Helen Leonard. A brief history of mecp2 duplication syndrome: 20-years of clinical understanding. Orphanet Journal of Rare Diseases, Mar 2022. URL: https://doi.org/10.1186/s13023-022-02278-w, doi:10.1186/s13023-022-02278-w. This article has 69 citations and is from a peer-reviewed journal.

  7. (ta2022abriefhistory pages 16-17): Daniel Ta, Jenny Downs, Gareth Baynam, Andrew Wilson, Peter Richmond, and Helen Leonard. A brief history of mecp2 duplication syndrome: 20-years of clinical understanding. Orphanet Journal of Rare Diseases, Mar 2022. URL: https://doi.org/10.1186/s13023-022-02278-w, doi:10.1186/s13023-022-02278-w. This article has 69 citations and is from a peer-reviewed journal.

  8. (ta2022abriefhistory pages 10-11): Daniel Ta, Jenny Downs, Gareth Baynam, Andrew Wilson, Peter Richmond, and Helen Leonard. A brief history of mecp2 duplication syndrome: 20-years of clinical understanding. Orphanet Journal of Rare Diseases, Mar 2022. URL: https://doi.org/10.1186/s13023-022-02278-w, doi:10.1186/s13023-022-02278-w. This article has 69 citations and is from a peer-reviewed journal.

  9. (akahoshi2023duplicationwithintwo pages 1-2): Keiko Akahoshi, Eiji Nakagawa, Yu-ichi Goto, and Ken Inoue. Duplication within two regions distal to mecp2: clinical similarity with mecp2 duplication syndrome. BMC Medical Genomics, Mar 2023. URL: https://doi.org/10.1186/s12920-023-01465-3, doi:10.1186/s12920-023-01465-3. This article has 0 citations and is from a peer-reviewed journal.

  10. (pehlivan2024structuralvariantallelic pages 13-14): Davut Pehlivan, Jesse D. Bengtsson, Sameer S. Bajikar, Christopher M. Grochowski, Ming Yin Lun, Mira Gandhi, Angad Jolly, Alexander J. Trostle, Holly K. Harris, Bernhard Suter, Sukru Aras, Melissa B. Ramocki, Haowei Du, Michele G. Mehaffey, KyungHee Park, Ellen Wilkey, Cemal Karakas, Jesper J. Eisfeldt, Maria Pettersson, Lynn Liu, Marwan S. Shinawi, Virginia E. Kimonis, Wojciech Wiszniewski, Kyle Mckenzie, Timo Roser, Angela M. Vianna-Morgante, Alberto S. Cornier, Ahmed Abdelmoity, James P. Hwang, Shalini N. Jhangiani, Donna M. Muzny, Tadahiro Mitani, Kazuhiro Muramatsu, Shin Nabatame, Daniel G. Glaze, Jawid M. Fatih, Richard A. Gibbs, Zhandong Liu, Anna Lindstrand, Fritz J. Sedlazeck, James R. Lupski, Huda Y. Zoghbi, and Claudia M. B. Carvalho. Structural variant allelic heterogeneity in mecp2 duplication syndrome provides insight into clinical severity and variability of disease expression. Genome Medicine, Dec 2024. URL: https://doi.org/10.1186/s13073-024-01411-7, doi:10.1186/s13073-024-01411-7. This article has 16 citations and is from a highest quality peer-reviewed journal.

  11. (NCT06014541 chunk 1): Observational Study to Characterize Biomarkers and Disease Progression in Participants With Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome. Ionis Pharmaceuticals, Inc.. 2023. ClinicalTrials.gov Identifier: NCT06014541

  12. (pehlivan2024structuralvariantallelic pages 4-5): Davut Pehlivan, Jesse D. Bengtsson, Sameer S. Bajikar, Christopher M. Grochowski, Ming Yin Lun, Mira Gandhi, Angad Jolly, Alexander J. Trostle, Holly K. Harris, Bernhard Suter, Sukru Aras, Melissa B. Ramocki, Haowei Du, Michele G. Mehaffey, KyungHee Park, Ellen Wilkey, Cemal Karakas, Jesper J. Eisfeldt, Maria Pettersson, Lynn Liu, Marwan S. Shinawi, Virginia E. Kimonis, Wojciech Wiszniewski, Kyle Mckenzie, Timo Roser, Angela M. Vianna-Morgante, Alberto S. Cornier, Ahmed Abdelmoity, James P. Hwang, Shalini N. Jhangiani, Donna M. Muzny, Tadahiro Mitani, Kazuhiro Muramatsu, Shin Nabatame, Daniel G. Glaze, Jawid M. Fatih, Richard A. Gibbs, Zhandong Liu, Anna Lindstrand, Fritz J. Sedlazeck, James R. Lupski, Huda Y. Zoghbi, and Claudia M. B. Carvalho. Structural variant allelic heterogeneity in mecp2 duplication syndrome provides insight into clinical severity and variability of disease expression. Genome Medicine, Dec 2024. URL: https://doi.org/10.1186/s13073-024-01411-7, doi:10.1186/s13073-024-01411-7. This article has 16 citations and is from a highest quality peer-reviewed journal.

  13. (zeng2024geneticanalysisof pages 2-5): Lan Zeng, Hui Zhu, Jin Wang, Qiyan Wang, Ying Pang, Zemin Luo, Ai Chen, Shengfang Qin, and Shuyao Zhu. Genetic analysis of a pedigree with mecp2 duplication syndrome in china. BMC Medical Genomics, Feb 2024. URL: https://doi.org/10.1186/s12920-024-01831-9, doi:10.1186/s12920-024-01831-9. This article has 0 citations and is from a peer-reviewed journal.

  14. (zeng2024geneticanalysisof pages 1-2): Lan Zeng, Hui Zhu, Jin Wang, Qiyan Wang, Ying Pang, Zemin Luo, Ai Chen, Shengfang Qin, and Shuyao Zhu. Genetic analysis of a pedigree with mecp2 duplication syndrome in china. BMC Medical Genomics, Feb 2024. URL: https://doi.org/10.1186/s12920-024-01831-9, doi:10.1186/s12920-024-01831-9. This article has 0 citations and is from a peer-reviewed journal.

  15. (neri2018x‐linkedintellectualdisability pages 4-6): Giovanni Neri, Charles E. Schwartz, Herbert A. Lubs, and Roger E. Stevenson. X‐linked intellectual disability update 2017. American Journal of Medical Genetics Part A, 176:1375-1388, Jun 2018. URL: https://doi.org/10.1002/ajmg.a.38710, doi:10.1002/ajmg.a.38710. This article has 154 citations.

  16. (NCT06615206 chunk 1): A First-in-Human Clinical Trial to Evaluate the Safety, Tolerability, and Efficacy of a Novel CRISPR RNA-editing Therapy in Patients with Mecp2 Duplication Syndrome, a Rare Orphan Disease (HERO). HuidaGene Therapeutics Co., Ltd.. 2024. ClinicalTrials.gov Identifier: NCT06615206

  17. (NCT06430385 chunk 1): ATTUNE: A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Intrathecally-Administered ION440 in Participants With Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome (MDS). Ionis Pharmaceuticals, Inc.. 2024. ClinicalTrials.gov Identifier: NCT06430385

  18. (NCT06430385 chunk 2): ATTUNE: A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Intrathecally-Administered ION440 in Participants With Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome (MDS). Ionis Pharmaceuticals, Inc.. 2024. ClinicalTrials.gov Identifier: NCT06430385

  19. (collins2022rettsyndromeand pages 2-4): Bridget E Collins and Jeffrey L Neul. Rett syndrome and mecp2 duplication syndrome: disorders of mecp2 dosage. Neuropsychiatric Disease and Treatment, 18:2813-2835, Nov 2022. URL: https://doi.org/10.2147/ndt.s371483, doi:10.2147/ndt.s371483. This article has 89 citations and is from a peer-reviewed journal.

Artifacts