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Inheritance

1

Sporadic post-zygotic mosaicism

Usually sporadic chromosomal mosaicism arising through an early post-zygotic error, including mitotic Y-chromosome loss. Structural Y abnormalities can also contribute. This differs from Mendelian forms of 46,XY gonadal dysgenesis; counseling should use the individual cytogenetic findings rather than infer a universal parental karyotype or a precisely quantified recurrence risk.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The condition emerges from early embryonic errors in chromosomal arrangements resulting in a mixture of 45,X/46,XY cell lines"

States the post-zygotic origin that makes the condition sporadic.

PMID:34566299 SUPPORT BACKGROUND Human Clinical

"MGD arises due to late anaphase lag during mitosis in the zygote, although Y chromosomal abnormalities are sometimes seen and interchromosomal rearrangement occurs."

The article reviews post-zygotic origin and possible structural abnormalities; it does not provide a numerical recurrence estimate.

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Discussions and Knowledge Gaps

4

How does gonadal mosaic distribution shape differentiation during fetal development?

KNOWLEDGE GAP mgd_mosaic_distribution_and_development

Attached to

pathophysiology#Tissue-Specific Sex Chromosome Mosaicism pathophysiology#Abnormal Gonadal Differentiation

Human gonadal FISH already demonstrates tissue and cellular mosaicism. Two MGD cases in a five-person study had higher XY fractions in testicular than ovarian tissue. In a later case, combined FISH and lineage-marker staining demonstrated gonadal mosaicism despite a 46,XY blood karyotype, but only one gonad was examined and both FISH artifacts and cell-dependent SRY expression complicated inference. These observations do not establish the timing, spatial signal interactions or causal mosaic threshold during fetal development. A high XY fraction also occurred in an atrophic infertile testis, showing that fraction alone is insufficient to predict function.

Show evidence (2 references)

PMID:9763660 SUPPORT PRIMARY RESULT Human Clinical

"In the mixed gonadal dysgenesis cases (cases 3 and 4), the testis had a higher percentage (greater than two fold) of XY cells than the ovary had."

Demonstrates existing human gonadal measurements.

PMID:25860218 SUPPORT PRIMARY RESULT Human Clinical

"FISH analysis on paraffin sections has the inevitable problem of false negativity for the Y chromosome. Immunohistochemical study for SRY is useful in proving the presence of Y chromosome; however, not all cell types express SRY protein and the interpretation of the results is complicated."

States key measurement limitations.

How does the mouse FGF9-SOX9 and WNT4 network translate to a human mosaic gonad?

HUMAN MODEL MISMATCH mgd_sry_threshold_model_is_murine

Attached to

pathophysiology#Abnormal Gonadal Differentiation

Mouse knockout and culture experiments establish interdependent SOX9 and FGF9 expression and antagonism with WNT4. Fgf9-null XY gonads initially express SRY and SOX9 but fail to maintain SOX9 and form normal testis cords. The experimental genotypes are not 45,X/46,XY mosaic models. A requirement for a critical number of supporting cells and non-cell-autonomous recruitment is an author-proposed explanation rather than a measured human threshold. FGF9/WNT4 antagonism does not specify a direct biochemical repression step, and transient SOX9 induction in Wnt4-null XX gonads did not produce Sertoli differentiation or testis cords.

Show evidence (2 references)

PMID:16700629 SUPPORT PRIMARY RESULT Model Organism

"Whether FGF9 normally acts non-cell-autonomously in vivo to recruit XY cells to the Sertoli lineage by up-regulating SOX9 is not clear."

Explicitly identifies the remaining mechanistic uncertainty.

PMID:16700629 SUPPORT PRIMARY RESULT Model Organism

"Further experiments will be required to deﬁne the molecular mechanism of FGF9 and WNT4 action."

The antagonistic relationship is not a resolved biochemical chain.

Which patients gain adult height from growth hormone treatment?

KNOWLEDGE GAP mgd_gh_efficacy_contested

Attached to

treatments#Growth Hormone Therapy pathophysiology#SHOX Haploinsufficiency in the 45,X Lineage

The clinical review describes improvement in growth velocity and final height, while a retrospective 100-person cohort found no significant height difference between treated and untreated groups. Variation in indication, baseline height, dose, timing and residual growth may affect observational comparisons. The available evidence does not establish uniform benefit or lack of benefit. The five-person series of growth-axis testing describes heterogeneous GH deficiency or resistance patterns but does not provide treatment-effect follow-up.

Show evidence (2 references)

PMID:37882230 SUPPORT PRIMARY RESULT Human Clinical

"Growth hormone (GH) treatment did not result in a significant height increase compared to the untreated group (p = 0.5)."

Retains the nonsignificant observational comparison.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Recombinant human growth hormone (rhGH) therapy has been found to significantly improve growth velocity and final adult height in individuals with MGD, with outcomes similar to those observed in Turner syndrome"

Retains the review assessment without treating it as a randomized estimate.

How should gonadal position, histology and function inform individualized tumour-risk assessment?

KNOWLEDGE GAP mgd_gonad_position_and_tumour_risk

Attached to

pathophysiology#Germ Cell Neoplasia in Dysgenetic Gonads treatments#Individualized Gonadal Surgery treatments#Surveillance of Retained Gonads

In one 14-patient prophylactic gonadectomy series, all gonadoblastomas were in abdominal gonads. A different 21-child study found germ cell neoplasia in situ in abdominal, inguinal and scrotal dysgenetic testes. These cohorts studied different lesions and selected populations, so their counts are not directly contradictory or suitable for pooling. Scrotal position does not exclude neoplasia, and current surveillance methods have important sensitivity and sampling limitations. Reliable individual risk prediction while preserving gonadal function remains unresolved.

Show evidence (2 references)

PMID:27052295 SUPPORT PRIMARY RESULT Human Clinical

"The exclusive presence of GB in intra-abdominal gonads is in keeping with the findings of several other series."

Describes location within this selected gonadoblastoma series.

PMID:27032613 SUPPORT PRIMARY RESULT Human Clinical

"the 4 dysgenetic testes affected by CIS in 3 patients were intraabdominal (n=1), inguinal (n=1) and scrotal (n=2) in positions."

Shows in-situ neoplasia at all three locations.

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Pathophysiology

11

Post-Zygotic Loss of the Y Chromosome

Mechanism confidence: Established

Early post-zygotic Y-chromosome loss, for example through mitotic anaphase lag, can generate a 45,X lineage alongside Y-bearing cells. Structural Y abnormalities may also be involved. The resulting mosaicism is a chromosomal event, with variable distribution among tissues.

Downstream

Tissue-Specific Sex Chromosome Mosaicism Chromosome loss produces coexisting cell lineages; their distribution can differ among tissues.

Show evidence (1 reference)

PMID:34566299 SUPPORT BACKGROUND Human Clinical

"MGD arises due to late anaphase lag during mitosis in the zygote, although Y chromosomal abnormalities are sometimes seen and interchromosomal rearrangement occurs."

Reviews the proposed chromosomal origin rather than documenting the embryonic event in the cohort.

Tissue-Specific Sex Chromosome Mosaicism

Mechanism confidence: Established

45,X and Y-bearing cell lineages vary between blood and gonadal tissue and among gonadal cell populations. Human gonadal FISH has directly measured this mosaicism. Two MGD cases in a five-person study had higher XY fractions in testicular than streak ovarian tissue; a separate case had gonadal mosaicism despite a 46,XY blood karyotype. These postnatal observations do not define the embryonic threshold for testis differentiation.

Downstream

Abnormal Gonadal Differentiation Spatial variation in sex-chromosome content is associated with different gonadal differentiation patterns, but chromosome ratios alone do not establish the developmental mechanism.

SHOX Haploinsufficiency in the 45,X Lineage Monosomy-X cells have a single copy of the pseudoautosomal SHOX locus.

Show evidence (2 references)

PMID:9763660 SUPPORT PRIMARY RESULT Human Clinical

"In the mixed gonadal dysgenesis cases (cases 3 and 4), the testis had a higher percentage (greater than two fold) of XY cells than the ovary had."

Direct human tissue evidence in two cases, not a universal ratio or developmental threshold.

PMID:25860218 SUPPORT PRIMARY RESULT Human Clinical

"The average percentages of 45,X cells of this patient's gonad and a control testis were 39.0% and 5.7%, respectively (χ2 test, P < 0.001)."

Digital FISH analysis of one resected gonad supports tissue mosaicism, with a nonzero false-negative background in the control.

Abnormal Gonadal Differentiation

Mechanism confidence: Established

Gonadal tissue may include a streak gonad, dysgenetic testis, or apparently normal testis. The characteristic contralateral streak/testis combination is not universal: a selected 34-patient biopsy/gonadectomy series also included bilateral streaks and bilateral dysgenetic testes, and some individual gonads contained both streak and testicular portions.

gonad UBERON:0000991

Experimental models

Mouse gonadal cultures testing FGF9 and WNT4 interactions OTHER Manipulates developmental signaling and measures supporting-cell markers in mouse cultures.

Animal models

Fgf9-null mouse model of gonadal differentiation Mouse partially recapitulates Provides a causal perturbation of mouse testis differentiation through loss of Fgf9.

Downstream

Reduced Sertoli Cell Anti-Mullerian Hormone Secretion Dysgenetic testicular tissue can have impaired AMH output.

Reduced Leydig Cell Testosterone Production Dysgenetic testes can have reduced steroidogenic function.

Impaired Pubertal Sertoli Cell Function Sertoli functional impairment can emerge during puberty even with mild genital findings.

Germ Cell Neoplasia in Dysgenetic Gonads Dysgenetic gonads containing Y material and immature germ cells are susceptible to germ cell neoplasia.

Impaired Spermatogenesis Disordered testicular development is associated with impaired germ-cell maturation, although individual histologic patterns and residual function vary.

Show evidence (3 references)

PMID:31883875 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Of 34 patients with 45,X/46,XY mosaicism, a unilateral dysgenetic testis and a contralateral streak gonad was detected in 20 patients (59%), bilateral streak gonads in 9 (26%), and bilateral dysgenetic testes in 5 (15%)."

Reports histologic distributions in a surgically selected cohort, not population frequencies.

PMID:31883875 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"A gonad composed of both streak and dysgenetic testicular portions was observed in 7 gonads of 6 patients."

Demonstrates intragonadal histologic heterogeneity without identifying its embryonic cause.

PMID:41208147 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"typically characterised by the presence of a dysgenetic testis at various levels of descent on one side and a streak gonad on the other"

The canonical description of the asymmetric anatomy.

Reduced Sertoli Cell Anti-Mullerian Hormone Secretion

AMH secretion by dysgenetic Sertoli-cell tissue can be reduced, with concentrations often toward the lower end of the typical male infant range. The degree of dysfunction varies; a universal reduction in Sertoli cell number has not been established by the cited clinical measurements.

Sertoli cell CL:0000216

Downstream

Incomplete Mullerian Regression Insufficient fetal AMH action can permit persistence of Müllerian derivatives.

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"AMH concentrations in individuals with MGD are typically toward the lower end of the reference range for healthy male infants with normal testicular function, reflecting relative Sertoli cell dysfunction"

Describes impaired secretion rather than a measured loss of Sertoli cell mass.

Reduced Leydig Cell Testosterone Production

Leydig-cell steroidogenic function can be reduced in dysgenetic testes. Basal and stimulated testosterone values vary with age and retained gonadal tissue. Reduced fetal androgen exposure contributes to incomplete external genital virilization; later androgen insufficiency may require replacement.

Leydig cell CL:0000178

Downstream

Undervirilization of the External Genitalia Reduced androgen exposure during fetal genital development can limit virilization.

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Due to the presence of dysgenetic testis, the plasma testosterone concentrations in MGD patients tend to be low‐normal relative to typical male infants but remain elevated compared with those typically seen in female infants."

Supports a relative and variable secretory deficit.

Impaired Pubertal Sertoli Cell Function

Low inhibin B and rising FSH indicate impaired Sertoli-cell function in some individuals during or after puberty. Spontaneous pubertal onset and Sertoli dysfunction can coexist; gonadotropin or inhibin measurements do not by themselves demonstrate universal Leydig-cell failure.

Sertoli cell CL:0000216

Downstream

Declining Testicular Function Reduced Sertoli function is reflected in low inhibin B and elevated FSH.

Show evidence (1 reference)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)"

Five individuals in the evaluated end-of-puberty subset had this biochemical pattern.

Incomplete Mullerian Regression

Mechanism confidence: Established

Incomplete fetal regression of Müllerian derivatives can leave a uterus or hemi-uterus, fallopian tube remnant, or prostatic utricle. Remnants are often ipsilateral to the streak gonad. This anatomic association is compatible with variable local AMH action but does not, by itself, prove that AMH acts exclusively locally or exclude systemic hormone effects.

Mullerian duct regression GO:0001880 ↓ DECREASED

Mullerian duct UBERON:0003890

Downstream

Persistent Mullerian Structures Incomplete duct regression produces retained Müllerian-derived anatomy.

Show evidence (1 reference)

PMID:41208147 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Many individuals have Müllerian remnants on the same side as the streak gonad, whereas the most common phenotypic finding is proximal hypospadias with perineal division of the corpus spongiosum and ventral curvature"

Reports the anatomic association, without establishing a unique mode of hormone action.

Undervirilization of the External Genitalia

Mechanism confidence: Established

Variable androgen exposure during fetal development contributes to atypical external genital anatomy, including hypospadias and ventral curvature. The wider mosaicism spectrum also includes typical external genitalia; the mechanism is not present to the same degree in every individual.

male genitalia development GO:0030539 ⚠ ABNORMAL

Downstream

Proximal Hypospadias Incomplete external genital differentiation can include proximal hypospadias.

Atypical Genitalia Variable fetal virilization contributes to atypical genital appearance.

Show evidence (1 reference)

PMID:41208147 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"The clinical spectrum of MGD to an extent is influenced by the functional capacity of the dysgenetic gonad along with the degree of androgen exposure during critical periods of foetal development"

Ties the degree of virilization to androgen exposure during the fetal window.

Germ Cell Neoplasia in Dysgenetic Gonads

Mechanism confidence: Established

Gonadoblastoma or germ cell neoplasia in situ can occur in dysgenetic gonads containing Y material, and invasive germ cell tumours are also reported. Risk estimates vary with phenotype, age, gonadal histology, ascertainment and prior gonadectomy. TSPY and DDX3Y are candidate susceptibility genes expressed in affected germ cells, but their expression also occurs in nonmalignant cells and does not establish sufficiency for transformation.

Germ cell CL:0000586

Downstream

Gonadoblastoma Gonadoblastoma is a documented neoplastic lesion in resected dysgenetic gonads.

Dysgerminoma Invasive dysgerminoma can accompany gonadoblastoma.

Show evidence (5 references)

PMID:30753444 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The GBY candidate genes DDX3Y and TSPY are expressed in the germ cells of DSD-XY patients from distinct etiologies: patients with mixed gonadal dysgenesis (MGD) and sex chromosome mosaics (45,X0/46,XY; 46,XX/46,XY)"

Patient-tissue expression supports candidate involvement, with nonmalignant expression limiting causal interpretation.

PMID:30753444 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"This suggest that GBY candidate proteins are also expressed in the non-malignant germ cells of DSD-XY individuals like in male spermatogonia."

Patient-tissue expression supports candidate involvement, with nonmalignant expression limiting causal interpretation.

PMID:41208147 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"For individuals with 45,X/46,XY mosaicism, the lifetime risk of developing gonadal tumours is estimated at 15%–25%, with this risk rising with age, although the true incidence may be confounded by the historical practice of early gonadectomy and diagnostic challenges"

The review qualifies its estimated tumour risk by prior surgery and diagnostic uncertainty.

+ 2 more references

SHOX Haploinsufficiency in the 45,X Lineage

Mechanism confidence: Established

Cells of the 45,X lineage carry one copy of the pseudoautosomal SHOX gene rather than the usual two copies. This provides a plausible contribution to impaired skeletal growth, while tissue mosaicism and other endocrine or chromosomal factors can also influence stature. SHOX dosage does not explain all Turner-associated cardiac, renal or autoimmune findings.

SHOX hgnc:10853 ↓ DECREASED

Downstream

Short Stature Reduced SHOX dosage is a recognized contributor to impaired linear growth, but is not established as the sole cause of short stature in this mosaic population.

Show evidence (1 reference)

PMID:41208147 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Short stature is a common clinical feature in individuals with MGD and is typically attributed to the 45,X cell line, and associated haploinsufficiency of the SHOX gene"

Attributes the short stature to SHOX dosage in the 45,X lineage, which is what this node asserts.

Impaired Spermatogenesis

Germ-cell maturation is impaired in some dysgenetic testes. A multicenter male cohort found both focal and arrested spermatogenesis, while some men retained motile sperm. Histologic observations and semen results came from different assessed subsets; neither establishes complete absence of fertility potential throughout the mosaic population.

spermatogenesis GO:0007283 ↓ DECREASED

Downstream

Azoospermia Impaired sperm production can contribute to absence of sperm in the ejaculate; the cohort did not establish an exclusive mechanism for every azoospermic patient.

Infertility Reduced spermatogenic capacity contributes to reduced reproductive potential.

Show evidence (1 reference)

PMID:31127831 SUPPORT PRIMARY RESULT Human Clinical

"Twenty-five percent had focal spermatogenesis, and another 25.0% had arrested spermatogenesis."

Histologic observations in the assessed subset of a 63-person multicenter male cohort; the abstract does not fully resolve the denominator for each histologic percentage.

✶

Histopathology

3

Mixed Seminiferous and Undifferentiated Gonadal Architecture

A resected gonad from one infant contained normal-appearing and abnormally shaped seminiferous tubules, undifferentiated gonadal tissue and gonadoblastoma nests. This demonstrates intragonadal heterogeneity, not a universal histologic pattern.

Show evidence (1 reference)

PMID:25860218 SUPPORT PRIMARY RESULT Human Clinical

"Histology of the gonad showed a streak testis consisting predominantly of differentiated normal-appearing seminiferous tubules with an area of undifferentiated gonadal tissue (UGT) and abnormally shaped seminiferous tubules at the periphery of the gonad"

Describes the actual tissue architecture in one resected right gonad.

Mixed Supporting-cell Lineage-marker Expression

SOX9-only Sertoli cells, FOXL2-only precursor granulosa cells and cells expressing both markers occurred in distinct areas of the same infant gonad. Coexpression indicates mixed lineage-marker expression; SRY immunostaining alone cannot assign a karyotype to every cell type.

Show evidence (1 reference)

PMID:25860218 SUPPORT PRIMARY RESULT Human Clinical

"Unexpectedly, our case showed co-expression of SOX9 and FOXL2 in abnormally shaped seminiferous tubules and gonadoblastomas."

Single-case supporting-cell immunophenotype, not a universal diagnostic biomarker.

Arrested Spermatogenesis

Arrested spermatogenesis was among the histologic patterns in a multicenter male cohort; focal spermatogenesis was also present in some samples. The cohort included genital and nongenital routes of ascertainment.

Show evidence (1 reference)

PMID:31127831 SUPPORT PRIMARY RESULT Human Clinical

"Twenty-five percent had focal spermatogenesis, and another 25.0% had arrested spermatogenesis."

Histologic observations in the assessed subset of a 63-person multicenter male cohort; the abstract does not fully resolve the denominator for each histologic percentage.

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Pathograph

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Phenotypes

35

Cardiovascular 3

Congenital Heart Defect Abnormal heart morphology HP:0001627

Coarse binding: source unspecified

Show evidence (1 reference)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"Turner-like syndrome features including cardiac (6/23 patients investigated) and renal malformations (3/19 patients investigated)"

6 of 23 investigated, 26%. No frequency band is given here because the denominator counts only patients who underwent cardiac investigation.

Bicuspid Aortic Valve HP:0001647

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"cardiac anomalies such as bicuspid aortic valve and coarctation of aorta"

The narrative review describes this feature; no disease-wide percentage is assigned.

Coarctation of the Aorta Coarctation of aorta HP:0001680

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"cardiac anomalies such as bicuspid aortic valve and coarctation of aorta"

The narrative review describes this feature; no disease-wide percentage is assigned.

Ear 1

Sensorineural Hearing Impairment HP:0000407

Show evidence (1 reference)

PMID:34566299 SUPPORT PRIMARY RESULT Human Clinical

"Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry)."

Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.

Endocrine 4

Declining Testicular Function Elevated circulating follicle stimulating hormone level HP:0008232

Show evidence (1 reference)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)"

The biochemical pattern was observed in five patients among the small subgroup evaluated at the end of puberty.

Delayed or Absent Spontaneous Puberty Delayed puberty HP:0000823

Show evidence (2 references)

PMID:37882230 SUPPORT PRIMARY RESULT Human Clinical

"All females required puberty induction in contrast to majority of males."

States the categorical split. No frequency band on the whole disease, because the figure applies to the female-raised subgroup only.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Individuals with MGD assigned female at birth almost always require pubertal induction and hormone replacement therapy as prophylactic gonadectomy is performed in most, and spontaneous breast development is extremely rare"

Identifies the contribution of prior gonadectomy.

Autoimmune Hypothyroidism HP:0000821

Show evidence (1 reference)

PMID:34566299 SUPPORT PRIMARY RESULT Human Clinical

"Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry)."

Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.

Graves Disease HP:0100647

Show evidence (1 reference)

PMID:34566299 SUPPORT PRIMARY RESULT Human Clinical

"Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry)."

Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.

Genitourinary 18

Atypical Genitalia Ambiguous genitalia HP:0000062

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The phenotypic presentation of MGD varies from atypical genitalia to typical male or female appearances often associated with Turner stigmata."

Describes the full external phenotypic range. No frequency band: the cohort denominators available count patients ascertained in different ways, and the mildest presentations are by definition under-ascertained.

Proximal Hypospadias HP:0000047

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"the most common phenotypic finding is proximal hypospadias with perineal division of the corpus spongiosum and ventral curvature"

Names it as the commonest external genital finding.

Streak Gonad HP:0025733

Show evidence (1 reference)

PMID:31883875 SUPPORT PRIMARY RESULT Human Clinical

"a unilateral dysgenetic testis and a contralateral streak gonad was detected in 20 patients (59%), bilateral streak gonads in 9 (26%)"

The surgically selected series includes at least one streak gonad in 29 of 34 patients; this is not a population frequency.

Dysgenetic Testis Dysplastic testis HP:0008733

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"the presence of a dysgenetic testis at various levels of descent on one side and a streak gonad on the other"

Describes the dysgenetic testis and its variable position.

Persistent Mullerian Structures Presence of uterus in 46,XY individual HP:0034546

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Many individuals have Müllerian remnants on the same side as the streak gonad"

Reports the finding and its characteristic laterality.

Undescended Gonad Cryptorchidism HP:0000028

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"undescended or partially descended gonads with varying degrees of labioscrotal fusion"

Reports incomplete gonadal descent as part of the genital phenotype.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"the presence of a dysgenetic testis at various levels of descent on one side"

States that the dysgenetic testis is found at variable levels of descent.

Infertility HP:0000789

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Testicular insufficiency develops in 60%–70% of individuals raised as males by the third decade, and infertility is the most commonly reported outcome."

Names infertility as the commonest outcome. No frequency band: "most commonly reported outcome" ranks it against other outcomes rather than giving a proportion of patients.

PMID:31127831 SUPPORT PRIMARY RESULT Human Clinical

"Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm."

The tested subgroup supports severe but not universal spermatogenic impairment.

Gonadoblastoma HP:0000150

Show evidence (2 references)

PMID:31883875 SUPPORT PRIMARY RESULT Human Clinical

"Pathologic examination revealed gonadal tumors in 6 of the 34 (18%) patients, including a gonadoblastoma in 7 gonads among 5 patients and an association of dysgerminoma with gonadoblastoma in 1 gonad."

Reports gonadoblastoma in a selected surgical series, including one specimen with associated dysgerminoma.

PMID:27052295 SUPPORT PRIMARY RESULT Human Clinical

"This sub-group of patients with GB were aged 5 months, 48 months, 71 months, and 13 years."

Supports occurrence in infancy within a prophylactic gonadectomy series.

Dysgerminoma HP:0100621

Show evidence (1 reference)

PMID:31883875 SUPPORT PRIMARY RESULT Human Clinical

"an association of dysgerminoma with gonadoblastoma in 1 gonad"

Documents co-occurrence in a single gonad, not directly observed progression.

Renal Malformation Abnormal renal morphology HP:0012210

Coarse binding: source unspecified

Show evidence (1 reference)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"Turner-like syndrome features including cardiac (6/23 patients investigated) and renal malformations (3/19 patients investigated)"

3 of 19 investigated. As with the cardiac record, the denominator is patients investigated, so no band is asserted.

Bifid Scrotum HP:0000048

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"undescended or partially descended gonads with varying degrees of labioscrotal fusion giving the appearance of a bifid scrotum"

The narrative review describes this feature; no disease-wide percentage is assigned.

Ventral Penile Curvature Chordee HP:0000041

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"severe hypospadias with a perineal or scrotal meatus, significant ventral curvature of the phallus, penoscrotal transposition"

The narrative review describes this feature; no disease-wide percentage is assigned.

Penoscrotal Transposition HP:0100600

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"severe hypospadias with a perineal or scrotal meatus, significant ventral curvature of the phallus, penoscrotal transposition"

The narrative review describes this feature; no disease-wide percentage is assigned.

Primary Amenorrhea HP:0000786

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"These patients often remain unidentified until later in childhood or adolescence, when they present with short stature, primary amenorrhea or absent secondary sexual characteristics"

The narrative review describes this feature; no disease-wide percentage is assigned.

Clitoral Enlargement Clitoral hypertrophy HP:0008665

Show evidence (1 reference)

PMID:34566299 SUPPORT PRIMARY RESULT Human Clinical

"The commonest initial clinical presentation was for the appearance of clitoromegaly (n = 8, 80%) followed by two cases presented as delayed puberty (n = 2, 20%)."

The count applies to this selected ten-person cohort.

Unilateral Renal Agenesis HP:0000122

Show evidence (1 reference)

PMID:34566299 SUPPORT PRIMARY RESULT Human Clinical

"Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry)."

Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.

Horseshoe Kidney HP:0000085

Show evidence (1 reference)

PMID:34566299 SUPPORT PRIMARY RESULT Human Clinical

"Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry)."

Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.

Azoospermia HP:0000027

Show evidence (1 reference)

PMID:31127831 SUPPORT PRIMARY RESULT Human Clinical

"Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm."

The tested subgroup is selected and no population frequency is inferred.

Head and Neck 2

Webbed Neck HP:0000465

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The other features include webbed neck, shield chest, cubitus valgus"

Lists webbed neck among the Turner-spectrum somatic features.

High Palate HP:0000218

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The other features include webbed neck, shield chest, cubitus valgus, high‐arched palate"

The narrative review describes this feature; no disease-wide percentage is assigned.

Limbs 4

Cubitus Valgus HP:0002967

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"webbed neck, shield chest, cubitus valgus, high‐arched palate"

Lists cubitus valgus among the Turner-spectrum somatic features.

Short Fourth Metacarpal Short 4th metacarpal HP:0010044

Show evidence (1 reference)

PMID:34539919 SUPPORT PRIMARY RESULT Human Clinical

"At presentation he had a short neck, widely spaced nipples, pectus excavatum, short 4thmetacarpal, wide carrying angle, short stature with mesomelia"

A single described patient supports occurrence, not a general frequency or a sole SHOX mechanism.

Mesomelia HP:0003027

Show evidence (1 reference)

PMID:34539919 SUPPORT PRIMARY RESULT Human Clinical

"At presentation he had a short neck, widely spaced nipples, pectus excavatum, short 4thmetacarpal, wide carrying angle, short stature with mesomelia"

A single described patient supports occurrence, not a general frequency or a sole SHOX mechanism.

Madelung Deformity HP:0003067

Show evidence (1 reference)

PMID:34539919 SUPPORT PRIMARY RESULT Human Clinical

"Turner`s stigmata in the form of wide carrying angle, multiple nevi, webbing necking and madelung deformity was found."

A single patient supports this skeletal finding.

Musculoskeletal 2

Shield Chest HP:0000914

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The other features include webbed neck, shield chest, cubitus valgus, high‐arched palate"

The narrative review describes this feature; no disease-wide percentage is assigned.

Pectus Excavatum HP:0000767

Show evidence (1 reference)

PMID:34539919 SUPPORT PRIMARY RESULT Human Clinical

"At presentation he had a short neck, widely spaced nipples, pectus excavatum, short 4thmetacarpal, wide carrying angle, short stature with mesomelia"

A single described patient supports occurrence, not a general frequency or a sole SHOX mechanism.

Growth 1

Short Stature FREQUENT HP:0004322

Show evidence (3 references)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"Most patients had stunted growth, with abnormal growth spurt during puberty and a mean adult height of 158 ± 7.6 cm, i.e. -2.3 DS with correction for target height."

Gives the adult height and its standard-deviation deficit against target height.

PMID:37882230 SUPPORT PRIMARY RESULT Human Clinical

"height Z-score was significantly decreased with age for both genders (p = 0.02)"

Confirms the progressive nature of the height deficit in an independent cohort.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Short stature is common in individuals regardless of their phenotypic sex."

States that short stature is common and independent of phenotypic sex.

💊

Medical Actions

10

Individualized Gonadal Surgery

Action: Surgical Procedure NCIT:C15329

Platform: Surgery

Removal of a nonfunctional streak or dysgenetic gonad can reduce the risk arising from that tissue. Whether and when to remove each gonad is decided individually, considering histology, position, hormone function, fertility potential, surveillance limits and the informed preferences of the patient and family. Removal may create a need for long-term hormone replacement.

Mechanism Target:

Germ Cell Neoplasia in Dysgenetic Gonads — Removes the tissue at risk; the decision balances neoplasia prevention against loss of gonadal function.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"a shared decision‐making approach, inclusive of the risks and benefits of both options, should be used to make these decisions in an individualised manner."

The review does not establish universal removal or universal retention.

PMID:38748847 SUPPORT REVIEW SYNTHESIS Human Clinical

"We recommend individualized decision-making about gonadectomy/salpingo-oophrectomy in girls and women with TS and Y chromosome material identified on standard karyotyping or FISH analysis."

The guideline supports individualization in girls and women with Turner syndrome and Y material; its precise population is retained.

Surveillance of Retained Gonads

Action: Supportive Care NCIT:C15747

Platform: Other

If gonads are retained, specialist follow-up includes examination and individualized imaging or tissue assessment. Scrotal position does not eliminate risk. Imaging can miss early lesions, biopsy can miss focal disease, and serum tumour markers are often uninformative; surveillance therefore cannot guarantee exclusion of neoplasia.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Imaging modalities for intra‐abdominal gonads often lack sufficient sensitivity to reliably detect early malignant changes"

Identifies an imaging limitation.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"However, biopsy may not reliably represent the entire gonad, and blood tumour markers are not elevated in most DSD‐ associated germ cell tumours."

Qualifies the limits of tissue sampling and blood markers.

Orchiopexy When Gonadal Preservation Is Chosen

Action: Orchiopexy NCIT:C111066

Platform: Surgery

Relocating an appropriate retained gonad can facilitate examination and surveillance. It does not abolish the neoplastic risk of dysgenetic tissue.

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The alternative option is relocating the gonads into the labioscrotal folds to facilitate easier examination, imaging, and biopsy."

Supports relocation as an option in the context of retention.

Hypospadias Repair

Action: Surgical Procedure NCIT:C15329

Platform: Surgery

Reconstruction may be considered for functional and anatomical concerns, sometimes using a staged approach. Timing and extent are individualized within multidisciplinary care and shared decision-making, with attention to patient autonomy and the irreversibility of surgery.

Mechanism Target:

Undervirilization of the External Genitalia — Addresses selected anatomic consequences through reconstruction.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The core components of care include sex assignment, excisional biopsy of the dysgenetic or streak gonads to decrease tumour risk, hypospadias repair usually in a staged approach, hormone replacement therapy for initiation and maintenance of puberty, and growth‐promoting strategies for managing..."

Names staged repair among management options, without establishing a universal indication.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The modern clinical practice focuses on patient‐centred care and advocates for the deferral of any irreversible interventions unless they are deemed clinically essential."

Provides the decision-making context.

Growth Hormone Therapy

Action: Pharmacotherapy NCIT:C15986

Agent: somatropin CHEBI:749556

Platform: Protein replacement

Recombinant growth hormone may be considered for impaired growth after endocrine evaluation. Observational evidence for adult-height benefit in the mosaic population is inconsistent; treatment decisions account for growth trajectory, remaining growth potential and gonadal follow-up. SHOX dosage is one possible contributor to short stature, and treatment does not correct the chromosomal mosaicism.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Recombinant human growth hormone (rhGH) therapy has been found to significantly improve growth velocity and final adult height in individuals with MGD, with outcomes similar to those observed in Turner syndrome"

The narrative review gives a favorable synthesis.

PMID:37882230 SUPPORT PRIMARY RESULT Human Clinical

"Growth hormone (GH) treatment did not result in a significant height increase compared to the untreated group (p = 0.5)."

The retrospective 100-patient cohort did not find a significant treated-versus-untreated difference; it is not a randomized efficacy trial.

Sex Steroid Replacement

Action: Hormone Replacement Therapy NCIT:C15599

Platform: Small molecule

Testosterone or estradiol can induce and maintain puberty when gonadal hormone production is insufficient or after gonadectomy. Treatment follows individual clinical goals, pubertal stage and residual function. A progestogen is added to an estrogen regimen when endometrial protection is needed in a person with a uterus. Spontaneous pubertal onset is common in some male cohorts, so replacement is not inevitable for every individual.

Mechanism Target:

Reduced Leydig Cell Testosterone Production — Testosterone replacement compensates for inadequate androgen production when present; estrogen-based treatment addresses other individualized pubertal goals.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Induction of puberty with either testosterone or oestrogen is essential for individuals with MGD who either have undergone gonadectomy or who do not experience spontaneous puberty."

Defines the indication rather than inferring universal natural gonadal failure.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"With the onset of breakthrough bleeding, a progestogen is added to protect the endometrial lining if a uterus is present"

Explains the anatomy-dependent regimen.

Multidisciplinary Shared Decision-Making and Psychological Support

Action: Psychosocial Care NCIT:C126880

Platform: Behavioral / lifestyle

Endocrinology, urology, gynecology, genetics and psychology coordinate care with the patient and family. Support addresses diagnostic uncertainty, body image, disclosure, relationships and fertility across childhood and adulthood. Gender identity cannot be reliably predicted from a blood mosaic ratio, genital anatomy or a single cohort percentage.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The delivery of optimal care requires a close collaboration among paediatric endocrinologists, urologists, geneticists, gynaecologists, and psychologists"

Identifies the clinical team.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Psychosocial support is equally crucial from the time of diagnosis and throughout life to help families and individuals address questions and challenges related to potential gender identity, self‐image, disclosure, and fertility"

Supports continuing psychosocial care.

Lifelong Multisystem Surveillance

Action: Supportive Care NCIT:C15747

Platform: Other

Follow-up assesses growth, puberty, bone health, hearing, thyroid function, cardiovascular and renal findings, and metabolic health. The international Turner guideline explicitly extends its surveillance recommendations to 45,X/46,XY individuals with atypical or male external genitalia regardless of sex of rearing. Surveillance is not contingent on assigning a Turner diagnosis to every individual.

Show evidence (2 references)

PMID:38748847 SUPPORT REVIEW SYNTHESIS Human Clinical

"We recommend that the surveillance guidelines also apply to individuals with 45,X/46,XY mosaicism with either ambiguous or male external genitalia, regardless of sex of rearing"

Provides direct guideline scope for the mosaic population.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Long‐term follow‐up for individuals with MGD should include regular monitoring of growth, pubertal development, monitoring for bone mineral density, sensorineural hearing loss, and screening for associated health conditions linked to the 45,X cell line, such as cardiovascular or renal anomalies,..."

Specifies the clinical domains.

Fertility Counseling

Action: Fertility and Reproductive Counseling NCIT:C171451

Platform: Other

Discuss variable germ-cell function and future reproductive options before gonadal surgery when feasible. Semen assessment and assisted reproduction may be relevant to selected individuals with retained testes. Prepubertal gonadal tissue cryopreservation and future maturation of that tissue remain investigational rather than established fertility-restoring treatments.

Mechanism Target:

Impaired Spermatogenesis — Counseling and individualized reproductive assessment address reduced spermatogenic capacity; they do not reverse the cellular defect.

Show evidence (2 references)

PMID:31127831 SUPPORT PRIMARY RESULT Human Clinical

"Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm."

Documents heterogeneity in a selected tested subset.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"gonadal tissue cryopreservation during gonadectomy or gonadal biopsy, when the germ cell numbers are high, and the use of the tissue for future fertility when technological advancement potentially allows for in vitro maturation are being explored as options"

Identifies the experimental scope of tissue preservation.

Planned Transition to Adult Care

Action: Supportive Care NCIT:C15747

Platform: Other

A structured transition between pediatric and adult specialists helps maintain endocrine treatment, gonadal follow-up and multisystem surveillance. Readiness discussions include understanding the diagnosis, self-management, fertility and mental-health support.

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Planning for transition should ideally begin as early as 12–13 years of age, and the European DSD consensus statement highlights early, staged hand‐over as the single most effective safeguard against loss to follow‐up"

The review supports staged transition planning.

🔬

Biochemical Markers

4

Inhibin B

Show evidence (2 references)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)"

Establishes the low-inhibin-B, high-FSH pattern as the marker of Sertoli decline.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"inhibin B concentrations during early puberty may serve as a reliable predictor of testicular function and the need for testosterone replacement in the future"

Reports the prognostic use of early-pubertal inhibin B.

Follicle-stimulating hormone

Show evidence (1 reference)

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)"

Establishes the low-inhibin-B, high-FSH pattern as the marker of Sertoli decline.

Anti-Mullerian hormone

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"AMH concentrations in individuals with MGD are typically toward the lower end of the reference range for healthy male infants with normal testicular function, reflecting relative Sertoli cell dysfunction"

Describes impaired secretion rather than a measured loss of Sertoli cell mass.

Testosterone

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Due to the presence of dysgenetic testis, the plasma testosterone concentrations in MGD patients tend to be low‐normal relative to typical male infants but remain elevated compared with those typically seen in female infants."

Supports a relative and variable secretory deficit.

🔬

Diagnosis

7

Chromosome analysis with adequate cell count

Peripheral-blood karyotyping identifies mosaic sex-chromosome lineages and structural abnormalities. The international Turner guideline recommends counting at least 30 metaphases, which detects approximately 10% mosaicism with 95% confidence; lower-level or tissue-restricted mosaicism may be missed. A blood mosaic ratio does not reliably predict gonadal composition or genital phenotype.

Show evidence (2 references)

PMID:38748847 SUPPORT REVIEW SYNTHESIS Human Clinical

"We recommend that a minimum of 30 metaphases be counted on a chromosome analysis as the first-line test which can detect approximately 10% mosaicism with 95% confidence limits"

Defines the cytogenetic sampling recommendation and its detection limit.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Since mosaicism can vary between tissues, the karyotype in the blood might not accurately reflect the gonadal karyotype."

Explains the tissue limitation.

Additional tissue and molecular cytogenetic testing

When clinical suspicion persists, targeted karyotype or FISH can assess buccal cells, skin fibroblasts or gonadal tissue obtained for clinical reasons. Microarray can characterize copy-number changes but is not uniformly more sensitive for low-level mosaicism and does not identify balanced rearrangements. Test choice depends on the suspected abnormality and laboratory method.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Targeted karyotype or Fluorescent in situ hybridisation (FISH) analysis of buccal epithelia cells obtained via swab, skin fibroblasts or gonadal tissue (if having gonadectomy for clinical reasons) may be required when clinical suspicion persists after normal karyotype results."

Supports additional-tissue assessment without recommending gonadal surgery solely to measure mosaicism.

PMID:38748847 SUPPORT REVIEW SYNTHESIS Human Clinical

"Microarray can provide better resolution compared to karyotyping, but has limitations in detecting low level 45,X mosaicism (<10%, though studies show detection as low as 5%)"

Distinguishes resolution from reliable low-level mosaic detection.

Confirmation after prenatal detection

Prenatal screening or cytogenetic findings require appropriate confirmatory testing and counseling about uncertain phenotype prediction. NIPT is a screening test, not a definitive fetal karyotype. Postnatal cytogenetic confirmation is recommended after prenatal identification of the mosaic karyotype.

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"When a 45,X/46,XY karyotype is identified prenatally by amniocentesis or chorionic villus sampling testing, postnatal confirmation by cytogenetic testing is essential to guide clinical management"

Specifies confirmation after prenatal diagnosis.

Endocrine assessment

Age-appropriate testosterone, AMH and gonadotropins assess testicular tissue and function. During the early infant mini-puberty window, basal testosterone may be informative; hCG stimulation can assess steroidogenic reserve when basal values are low or the window has passed. Electrolytes, cortisol and 17-hydroxyprogesterone help exclude adrenal causes of atypical genitalia and salt-wasting emergencies.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"If baseline testosterone concentration is low or if being evaluated outside the mini‐puberty window, a human chorionic gonadotropin (hCG) stimulation test can be useful to assess if the testicular tissue can mount an adequate testosterone response."

Specifies the functional test and timing context.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The key investigations include: plasma electrolytes, cortisol and 17‐hydroxyprogesterone (17‐OHP) concentrations"

Names the initial adrenal differential work-up.

Imaging and anatomical evaluation

Pelvic ultrasound is the initial investigation for gonadal location and Müllerian anatomy; abdominal ultrasound also evaluates the kidneys. MRI, examination under anesthesia, endoscopy or laparoscopy may be appropriate when the anatomy remains unclear or an intervention is planned. Negative imaging does not exclude small remnants or gonadal tissue. The quoted ultrasound miss rate comes from a complex-DSD series rather than an MGD-only accuracy study.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Pelvic ultrasound is typically the first‐line for localisation of gonads and identification of Müllerian structures. MRI is reserved for cases where ultrasound findings are inconclusive"

Describes the imaging sequence.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"ultrasound failed to visualise Müllerian duct remnants in approximately 40% of cases, whereas laparoscopy achieved optimal visualization in all patients"

Supports a limitation of ultrasound within the cited complex-DSD population.

Gonadal histology when clinically indicated

Biopsy or resection can characterize streak and testicular tissue, germ-cell maturation and neoplastic lesions. Gonads may be heterogeneous, so a limited biopsy cannot reliably exclude a focal lesion elsewhere. Histology is interpreted with the cytogenetic, endocrine and anatomic findings.

Show evidence (2 references)

PMID:31883875 SUPPORT PRIMARY RESULT Human Clinical

"A gonad composed of both streak and dysgenetic testicular portions was observed in 7 gonads of 6 patients."

Shows why a single sample can incompletely represent a gonad.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"However, biopsy may not reliably represent the entire gonad, and blood tumour markers are not elevated in most DSD‐ associated germ cell tumours."

States sampling and biomarker limitations.

Baseline Cardiac and Renal Assessment

Children with a 45,X/46,XY karyotype warrant renal ultrasonography and cardiac evaluation with echocardiography to detect associated anomalies. Subsequent follow-up is guided by the findings and broader surveillance recommendations.

Show evidence (1 reference)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"Given these associations, it is recommended that a comprehensive evaluation including renal ultrasonography, together with a complete cardiac evaluation with echocardiographic assessment should be performed in all children with 45,X/46,XY karyotype to facilitate early detection and management of..."

The review recommends cardiac and renal evaluation for children with the mosaic karyotype regardless of their external genital presentation.

📈

Progression

3

Childhood growth decline

Height standard-deviation scores decreased with age in a retrospective 100-patient mosaicism cohort. Individual growth trajectories vary and warrant serial measurement.

Show evidence (1 reference)

PMID:37882230 SUPPORT PRIMARY RESULT Human Clinical

"height Z-score was significantly decreased with age for both genders (p = 0.02)"

Documents the progressive height deficit.

Pubertal and post-pubertal gonadal decline

Spontaneous pubertal onset is common in individuals raised male who retain functioning testes, but later Sertoli or Leydig dysfunction can occur. In a 63-person multicenter male cohort, 80% entered puberty spontaneously; a separate mild-genital-phenotype series found impaired Sertoli markers in five of seven evaluated at the end of puberty. These selected cohorts do not imply inevitable pubertal arrest.

Show evidence (2 references)

PMID:31127831 SUPPORT PRIMARY RESULT Human Clinical

"Eighty percent of all patients experienced spontaneous pubertal onset, significantly more in the nongenital group (P = 0.023)."

The study included 63 males older than 13 years, with different reasons for initial diagnosis.

PMID:29973376 SUPPORT PRIMARY RESULT Human Clinical

"puberty occurred spontaneously in 93% of patients but 71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)."

The endocrine-decline denominator is the small subset evaluated at the end of puberty, not all 40 participants.

Adult cardiometabolic morbidity

A Danish registry study of 135 diagnosed males with 45,X/46,XY mosaicism found increased morbidity across multiple diagnostic groups compared with 13,500 age-matched controls. This supports lifelong follow-up; it does not establish a fixed age of onset for each associated disorder or apply specifically to every classic MGD phenotype.

Show evidence (1 reference)

PMID:39775857 SUPPORT PRIMARY RESULT Human Clinical

"Diagnoses with increased HRs included diabetes, thyroid disorders, obesity, hypertension, ischemic heart disease, osteoporosis, and inflammatory bowel disease."

Registry associations describe the broader male mosaic population; they do not establish a single causal pathway or onset at age 40.

📊

Prevalence

3

Live births

Birth Prevalence 3.3–6.7 per 100,000 1–9 per 100,000 (births)

A narrative review reports 1 in 15,000 to 1 in 30,000 live births, equivalent to approximately 3.3–6.7 per 100,000. No synthetic midpoint is assigned. Ascertainment may miss mild presentations, but this does not establish a mathematically defined lower bound. Definitions and clinical ascertainment vary between mixed gonadal dysgenesis and the wider mosaic-karyotype population.

Show evidence (2 references)

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"MGD is rare, with an estimated incidence of 1 in 15,000 to 1 in 30,000 live births"

Source of the incidence range converted to the normalized rate.

PMID:41208147 SUPPORT REVIEW SYNTHESIS Human Clinical

"The prevalence of MGD may be underestimated due to its wide range of phenotypic presentations."

The review identifies possible under-ascertainment; it does not establish a population lower bound.

Liveborn male population in the Danish registry study

Birth Prevalence 5.6 per 100,000 1–9 per 100,000 (births)

Apparent prevalence of diagnosed 45,X/46,XY mosaicism and associated variants, based on nationwide ascertainment from 1960–2019. This is broader than histologically confirmed mixed gonadal dysgenesis, and the male and female rates have separate sex-specific denominators.

Show evidence (1 reference)

PMID:37781900 SUPPORT PRIMARY RESULT Human Clinical

"The apparent prevalence was 5.6 per 100,000 liveborn males and 2.1 per 100,000 liveborn females."

Reports sex-specific apparent birth prevalence without deriving a combined rate.

Liveborn female population in the Danish registry study

Birth Prevalence 2.1 per 100,000 1–9 per 100,000 (births)

Apparent prevalence of diagnosed 45,X/46,XY mosaicism and associated variants, based on nationwide ascertainment from 1960–2019. This is broader than histologically confirmed mixed gonadal dysgenesis, and the male and female rates have separate sex-specific denominators.

Show evidence (1 reference)

PMID:37781900 SUPPORT PRIMARY RESULT Human Clinical

"The apparent prevalence was 5.6 per 100,000 liveborn males and 2.1 per 100,000 liveborn females."

Reports sex-specific apparent birth prevalence without deriving a combined rate.

🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from 45,X/46,XY Mixed Gonadal Dysgenesis:

46,XY partial gonadal dysgenesis MONDO:0016674

Overlapping Features Partial gonadal dysgenesis can occur with a 46,XY karyotype and overlapping genital or gonadal findings. Pathogenic variants in sex-development genes may account for some cases. A normal blood karyotype does not exclude tissue-restricted 45,X mosaicism.

Distinguishing Features

Demonstrated 45,X mosaicism in blood or another relevant tissue supports the mosaic chromosomal entity.
Single-gene and chromosomal causes require different recurrence counseling; a molecular diagnosis is not established in every 46,XY case.

Show evidence (1 reference)

PMID:25860218 SUPPORT PRIMARY RESULT Human Clinical

"A 1-year-old infant with 46,XY identified by peripheral blood karyotype demonstrated clinical manifestations and gonadal pathologic features of MGD."

Shows why blood karyotype alone cannot always distinguish the conditions.

Turner syndrome MONDO:0019499

Overlapping Features Turner syndrome overlaps clinically and cytogenetically with this mosaic population. Some individuals with 45,X/46,XY and female external genitalia meet Turner diagnostic criteria; the presence of Y material does not exclude that diagnosis. Those with atypical or male external genitalia are outside the guideline definition of Turner syndrome but still warrant its surveillance recommendations.

Distinguishing Features

Interpret Turner syndrome using phenotype and cytogenetic findings rather than an absolute absence of Y material.
Asymmetric streak/testicular anatomy supports the MGD description, but gonadal patterns in the mosaic population are variable.

Show evidence (1 reference)

PMID:38748847 SUPPORT REVIEW SYNTHESIS Human Clinical

"Individuals with 45,X/46,XY mosaicism who do not have typical female external genitalia are also excluded from the diagnosis, although we recommend that the guidelines also apply to these individuals due to a similar comorbidity profile"

Distinguishes the Turner diagnostic definition from surveillance eligibility.

🧫

Experimental Models

1

Mouse gonadal cultures testing FGF9 and WNT4 interactions OTHER

FGF9 gain-of-function studies used intact explants, localized FGF9-coated beads and dissociated gonadal cells. Soluble FGF9 suppressed Wnt4 in intact XX gonads, while induction of SOX9 depended on culture context: dissociation, localized bead exposure or Wnt4 heterozygosity. Soluble FGF9 did not induce SOX9 in intact wild-type XX gonads.

Organism

Mus musculus NCBITaxon:10090

Cell source

Embryonic mouse gonads and gonad-mesonephros complexes

Culture

Intact explants and parallel dissociated-cell cultures

Publication

PMID:16700629

Pathograph links

Abnormal Gonadal Differentiation perturbs fidelity: low Manipulates developmental signaling and measures supporting-cell markers in mouse cultures.

Limitations: These are ex-vivo or in-vitro assays, not human fetal tissue or a chromosome-mosaic model. Marker induction is not equivalent to complete functional testis differentiation.

Show evidence (2 references)

PMID:16700629 SUPPORT PRIMARY RESULT In Vitro

"Treatment of XX gonads with exogenous FGF9 suppressed the normal expression of Wnt4"

Cultured gonad response to FGF9.

+ 1 more reference

🐁

Animal Models

1

Fgf9-null mouse model of gonadal differentiation

A developmental pathway model, not a mosaic 45,X/46,XY disease model. Sry and initial Sox9 expression were retained, but SOX9 was lost by 12.5 days post coitum, Sertoli markers were reduced or absent and normal testis cords did not form. No increased gonadal apoptosis was observed at the examined 12.0-day stage.

Species

Mouse

Genotype

Fgf9-null XY on the reported C57BL/6 background

Publication

PMID:16700629

Pathograph links

Abnormal Gonadal Differentiation partially recapitulates fidelity: low Provides a causal perturbation of mouse testis differentiation through loss of Fgf9.

Limitations: Uniform mouse knockout rather than human sex-chromosome mosaicism. The phenotype depends on the reported background; the experiment does not determine a human SRY-cell threshold or prove FGF9 deficiency in MGD.

Readouts

SOX9 maintenance and testis cord organization

Direction: DECREASED

Interpretation: SOX9 disappears after initial induction and normal cord organization fails in the knockout.

Show evidence (1 reference)

PMID:16700629 SUPPORT PRIMARY RESULT Model Organism

"SOX9 was no longer detectable by 12.5 dpc, and Sertoli precursor cells never began to organize into normal testis cord structures"

In-vivo mutant gonadal readouts.

Show evidence (1 reference)

PMID:16700629 SUPPORT PRIMARY RESULT Model Organism

"although Fgf9 is not required for the up- regulation of Sox9 in vivo, it is indispensable to maintain Sox9 expression in Sertoli precursor cells."

Separates initial induction from later maintenance.

{ }

Source YAML

click to show

name: 45,X/46,XY Mixed Gonadal Dysgenesis
category: Chromosomal
creation_date: '2026-08-29T19:15:00Z'
synonyms:
- mixed gonadal dysgenesis
- 45,X/46,XY mosaicism
- 45,X/46,XY gonadal dysgenesis
- X0/XY mosaicism
- asymmetric gonadal dysgenesis
description: '45,X/46,XY mixed gonadal dysgenesis is a chromosomal difference of sex development associated with mosaic monosomy X and a Y-bearing cell lineage. Gonadal differentiation is variable: a streak gonad opposite a dysgenetic testis is characteristic, but bilateral streaks or bilateral testes also occur. External genital development, Müllerian structures, endocrine function and fertility vary with gonadal development. Short stature and other Turner-associated findings can occur regardless of external genital appearance. Dysgenetic gonads containing Y material carry a risk of germ cell neoplasia. The wider 45,X/46,XY mosaic population also includes individuals without the classic asymmetric gonadal phenotype; cohort estimates are identified at that broader scope where appropriate.'
disease_term:
  preferred_term: 45,X/46,XY mixed gonadal dysgenesis
  term:
    id: MONDO:0015779
    label: 45,X/46,XY mixed gonadal dysgenesis
parents:
- Disorder of sex development
- Sex chromosome disorder
inheritance:
- name: Sporadic post-zygotic mosaicism
  description: Usually sporadic chromosomal mosaicism arising through an early post-zygotic error, including mitotic Y-chromosome loss. Structural Y abnormalities can also contribute. This differs from Mendelian forms of 46,XY gonadal dysgenesis; counseling should use the individual cytogenetic findings rather than infer a universal parental karyotype or a precisely quantified recurrence risk.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The condition emerges from early embryonic errors in chromosomal arrangements resulting in a mixture of 45,X/46,XY cell lines
    explanation: States the post-zygotic origin that makes the condition sporadic.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: MGD arises due to late anaphase lag during mitosis in the zygote, although Y chromosomal abnormalities are sometimes seen and interchromosomal rearrangement occurs.
    explanation: The article reviews post-zygotic origin and possible structural abnormalities; it does not provide a numerical recurrence estimate.
prevalence:
- population: Live births
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_low: 3.3
  rate_high: 6.7
  notes: A narrative review reports 1 in 15,000 to 1 in 30,000 live births, equivalent to approximately 3.3–6.7 per 100,000. No synthetic midpoint is assigned. Ascertainment may miss mild presentations, but this does not establish a mathematically defined lower bound. Definitions and clinical ascertainment vary between mixed gonadal dysgenesis and the wider mosaic-karyotype population.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: MGD is rare, with an estimated incidence of 1 in 15,000 to 1 in 30,000 live births
    explanation: Source of the incidence range converted to the normalized rate.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The prevalence of MGD may be underestimated due to its wide range of phenotypic presentations.
    explanation: The review identifies possible under-ascertainment; it does not establish a population lower bound.
    quote_role: REVIEW_SYNTHESIS
- population: Liveborn male population in the Danish registry study
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 5.6
  notes: Apparent prevalence of diagnosed 45,X/46,XY mosaicism and associated variants, based on nationwide ascertainment from 1960–2019. This is broader than histologically confirmed mixed gonadal dysgenesis, and the male and female rates have separate sex-specific denominators.
  evidence:
  - reference: PMID:37781900
    reference_title: 'Incidence, prevalence, age at diagnosis, and mortality in individuals with 45,X/46,XY mosaicism: A population-based registry study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The apparent prevalence was 5.6 per 100,000 liveborn males and 2.1 per 100,000 liveborn females.
    explanation: Reports sex-specific apparent birth prevalence without deriving a combined rate.
- population: Liveborn female population in the Danish registry study
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 2.1
  notes: Apparent prevalence of diagnosed 45,X/46,XY mosaicism and associated variants, based on nationwide ascertainment from 1960–2019. This is broader than histologically confirmed mixed gonadal dysgenesis, and the male and female rates have separate sex-specific denominators.
  evidence:
  - reference: PMID:37781900
    reference_title: 'Incidence, prevalence, age at diagnosis, and mortality in individuals with 45,X/46,XY mosaicism: A population-based registry study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The apparent prevalence was 5.6 per 100,000 liveborn males and 2.1 per 100,000 liveborn females.
    explanation: Reports sex-specific apparent birth prevalence without deriving a combined rate.
progression:
- phase: Childhood growth decline
  notes: Height standard-deviation scores decreased with age in a retrospective 100-patient mosaicism cohort. Individual growth trajectories vary and warrant serial measurement.
  evidence:
  - reference: PMID:37882230
    reference_title: '45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: height Z-score was significantly decreased with age for both genders (p = 0.02)
    explanation: Documents the progressive height deficit.
    quote_role: PRIMARY_RESULT
- phase: Pubertal and post-pubertal gonadal decline
  notes: Spontaneous pubertal onset is common in individuals raised male who retain functioning testes, but later Sertoli or Leydig dysfunction can occur. In a 63-person multicenter male cohort, 80% entered puberty spontaneously; a separate mild-genital-phenotype series found impaired Sertoli markers in five of seven evaluated at the end of puberty. These selected cohorts do not imply inevitable pubertal arrest.
  evidence:
  - reference: PMID:31127831
    reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Eighty percent of all patients experienced spontaneous pubertal onset, significantly more in the nongenital group (P = 0.023).
    explanation: The study included 63 males older than 13 years, with different reasons for initial diagnosis.
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: puberty occurred spontaneously in 93% of patients but 71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels).
    explanation: The endocrine-decline denominator is the small subset evaluated at the end of puberty, not all 40 participants.
- phase: Adult cardiometabolic morbidity
  notes: A Danish registry study of 135 diagnosed males with 45,X/46,XY mosaicism found increased morbidity across multiple diagnostic groups compared with 13,500 age-matched controls. This supports lifelong follow-up; it does not establish a fixed age of onset for each associated disorder or apply specifically to every classic MGD phenotype.
  evidence:
  - reference: PMID:39775857
    reference_title: 'Morbidity in Males With 45,X/46,XY Resembles the Morbidity Pattern in Turner Syndrome: A National Population-Based Study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Diagnoses with increased HRs included diabetes, thyroid disorders, obesity, hypertension, ischemic heart disease, osteoporosis, and inflammatory bowel disease.
    explanation: Registry associations describe the broader male mosaic population; they do not establish a single causal pathway or onset at age 40.
pathophysiology:
- name: Post-Zygotic Loss of the Y Chromosome
  biological_scale: MOLECULAR
  role: trigger
  mechanism_confidence: ESTABLISHED
  description: Early post-zygotic Y-chromosome loss, for example through mitotic anaphase lag, can generate a 45,X lineage alongside Y-bearing cells. Structural Y abnormalities may also be involved. The resulting mosaicism is a chromosomal event, with variable distribution among tissues.
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: MGD arises due to late anaphase lag during mitosis in the zygote, although Y chromosomal abnormalities are sometimes seen and interchromosomal rearrangement occurs.
    explanation: Reviews the proposed chromosomal origin rather than documenting the embryonic event in the cohort.
  downstream:
  - target: Tissue-Specific Sex Chromosome Mosaicism
    causal_link_type: DIRECT
    description: Chromosome loss produces coexisting cell lineages; their distribution can differ among tissues.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The condition emerges from early embryonic errors in chromosomal arrangements resulting in a mixture of 45,X/46,XY cell lines
      explanation: Supports generation of mosaic lineages.
- name: Tissue-Specific Sex Chromosome Mosaicism
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: 45,X and Y-bearing cell lineages vary between blood and gonadal tissue and among gonadal cell populations. Human gonadal FISH has directly measured this mosaicism. Two MGD cases in a five-person study had higher XY fractions in testicular than streak ovarian tissue; a separate case had gonadal mosaicism despite a 46,XY blood karyotype. These postnatal observations do not define the embryonic threshold for testis differentiation.
  evidence:
  - reference: PMID:9763660
    reference_title: Pathogenetics of 45,X/46,XY gonadal mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In the mixed gonadal dysgenesis cases (cases 3 and 4), the testis had a higher percentage (greater than two fold) of XY cells than the ovary had.
    explanation: Direct human tissue evidence in two cases, not a universal ratio or developmental threshold.
  - reference: PMID:25860218
    reference_title: 'Identification of X monosomy cells from a gonad of mixed gonadal dysgenesis with a 46,XY karyotype: case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The average percentages of 45,X cells of this patient's gonad and a control testis were 39.0% and 5.7%, respectively (χ2 test, P < 0.001).
    explanation: Digital FISH analysis of one resected gonad supports tissue mosaicism, with a nonzero false-negative background in the control.
  downstream:
  - target: Abnormal Gonadal Differentiation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Spatial variation in sex-chromosome content is associated with different gonadal differentiation patterns, but chromosome ratios alone do not establish the developmental mechanism.
    evidence:
    - reference: PMID:9763660
      reference_title: Pathogenetics of 45,X/46,XY gonadal mosaicism.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: In the mixed gonadal dysgenesis cases (cases 3 and 4), the testis had a higher percentage (greater than two fold) of XY cells than the ovary had.
      explanation: Direct human tissue evidence in two cases, not a universal ratio or developmental threshold.
    - reference: PMID:9763660
      reference_title: Pathogenetics of 45,X/46,XY gonadal mosaicism.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: However, the highest ratio of cells with a Y chromosome was in the atrophic testis of the infertile male (case 5).
      explanation: A high XY fraction does not ensure normal testis function.
  - target: SHOX Haploinsufficiency in the 45,X Lineage
    causal_link_type: DIRECT
    description: Monosomy-X cells have a single copy of the pseudoautosomal SHOX locus.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Short stature is a common clinical feature in individuals with MGD and is typically attributed to the 45,X cell line, and associated haploinsufficiency of the SHOX gene
      explanation: Supports a dosage-related growth contribution.
- name: Abnormal Gonadal Differentiation
  biological_scale: TISSUE
  role: central_effector
  mechanism_confidence: ESTABLISHED
  description: 'Gonadal tissue may include a streak gonad, dysgenetic testis, or apparently normal testis. The characteristic contralateral streak/testis combination is not universal: a selected 34-patient biopsy/gonadectomy series also included bilateral streaks and bilateral dysgenetic testes, and some individual gonads contained both streak and testicular portions.'
  locations:
  - preferred_term: gonad
    term:
      id: UBERON:0000991
      label: gonad
  evidence:
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: Of 34 patients with 45,X/46,XY mosaicism, a unilateral dysgenetic testis and a contralateral streak gonad was detected in 20 patients (59%), bilateral streak gonads in 9 (26%), and bilateral dysgenetic testes in 5 (15%).
    explanation: Reports histologic distributions in a surgically selected cohort, not population frequencies.
    quote_role: PRIMARY_RESULT
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: A gonad composed of both streak and dysgenetic testicular portions was observed in 7 gonads of 6 patients.
    explanation: Demonstrates intragonadal histologic heterogeneity without identifying its embryonic cause.
    quote_role: PRIMARY_RESULT
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: typically characterised by the presence of a dysgenetic testis at various levels of descent on one side and a streak gonad on the other
    explanation: The canonical description of the asymmetric anatomy.
    quote_role: REVIEW_SYNTHESIS
  downstream:
  - target: Reduced Sertoli Cell Anti-Mullerian Hormone Secretion
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Dysgenetic testicular tissue can have impaired AMH output.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The secretion of Anti‐Müllerian Hormone (AMH) is often impaired by the dysgenetic testis thus leading to persistence of some Müllerian structures
      explanation: The clinical review links testicular dysgenesis to impaired AMH secretion.
  - target: Reduced Leydig Cell Testosterone Production
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Dysgenetic testes can have reduced steroidogenic function.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Due to the presence of dysgenetic testis, the plasma testosterone concentrations in MGD patients tend to be low‐normal relative to typical male infants but remain elevated compared with those typically seen in female infants.
      explanation: The reduction is relative to typical male infants, not absent hormone production in every patient.
  - target: Impaired Pubertal Sertoli Cell Function
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Sertoli functional impairment can emerge during puberty even with mild genital findings.
    evidence:
    - reference: PMID:29973376
      reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: 71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)
      explanation: Shows functional impairment in a small assessed subset without measuring a specific cell-loss mechanism.
  - target: Germ Cell Neoplasia in Dysgenetic Gonads
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Dysgenetic gonads containing Y material and immature germ cells are susceptible to germ cell neoplasia.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The presence of Y‐chromosomal material within a dysgenetic gonad, along with the presence of immature germ cells, is the primary risk factor for tumour development
      explanation: Identifies the risk context without demonstrating a single molecular transition.
  - target: Impaired Spermatogenesis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Disordered testicular development is associated with impaired germ-cell maturation, although individual histologic patterns and residual function vary.
    evidence:
    - reference: PMID:31127831
      reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Twenty-five percent had focal spermatogenesis, and another 25.0% had arrested spermatogenesis.
      explanation: Histologic observations in the assessed subset of a 63-person multicenter male cohort; the abstract does not fully resolve the denominator for each histologic percentage.
- name: Reduced Sertoli Cell Anti-Mullerian Hormone Secretion
  biological_scale: CELLULAR
  description: AMH secretion by dysgenetic Sertoli-cell tissue can be reduced, with concentrations often toward the lower end of the typical male infant range. The degree of dysfunction varies; a universal reduction in Sertoli cell number has not been established by the cited clinical measurements.
  cell_types:
  - preferred_term: Sertoli cell
    term:
      id: CL:0000216
      label: Sertoli cell
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: AMH concentrations in individuals with MGD are typically toward the lower end of the reference range for healthy male infants with normal testicular function, reflecting relative Sertoli cell dysfunction
    explanation: Describes impaired secretion rather than a measured loss of Sertoli cell mass.
  downstream:
  - target: Incomplete Mullerian Regression
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Insufficient fetal AMH action can permit persistence of Müllerian derivatives.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The secretion of Anti‐Müllerian Hormone (AMH) is often impaired by the dysgenetic testis thus leading to persistence of some Müllerian structures
      explanation: Supports the hormonal contribution; postnatal concentration is not a direct fetal secretion measurement.
- name: Reduced Leydig Cell Testosterone Production
  biological_scale: CELLULAR
  description: Leydig-cell steroidogenic function can be reduced in dysgenetic testes. Basal and stimulated testosterone values vary with age and retained gonadal tissue. Reduced fetal androgen exposure contributes to incomplete external genital virilization; later androgen insufficiency may require replacement.
  cell_types:
  - preferred_term: Leydig cell
    term:
      id: CL:0000178
      label: Leydig cell
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Due to the presence of dysgenetic testis, the plasma testosterone concentrations in MGD patients tend to be low‐normal relative to typical male infants but remain elevated compared with those typically seen in female infants.
    explanation: Supports a relative and variable secretory deficit.
  downstream:
  - target: Undervirilization of the External Genitalia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Reduced androgen exposure during fetal genital development can limit virilization.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The clinical spectrum of MGD to an extent is influenced by the functional capacity of the dysgenetic gonad along with the degree of androgen exposure during critical periods of foetal development
      explanation: Supports an endocrine contribution without reducing every phenotypic difference to testosterone concentration.
- name: Impaired Pubertal Sertoli Cell Function
  biological_scale: CELLULAR
  description: Low inhibin B and rising FSH indicate impaired Sertoli-cell function in some individuals during or after puberty. Spontaneous pubertal onset and Sertoli dysfunction can coexist; gonadotropin or inhibin measurements do not by themselves demonstrate universal Leydig-cell failure.
  cell_types:
  - preferred_term: Sertoli cell
    term:
      id: CL:0000216
      label: Sertoli cell
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)
    explanation: Five individuals in the evaluated end-of-puberty subset had this biochemical pattern.
  downstream:
  - target: Declining Testicular Function
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Reduced Sertoli function is reflected in low inhibin B and elevated FSH.
    evidence:
    - reference: PMID:29973376
      reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)
      explanation: Links the cellular functional defect to the measured endocrine phenotype.
- name: Incomplete Mullerian Regression
  biological_scale: TISSUE
  role: consequence
  mechanism_confidence: ESTABLISHED
  description: Incomplete fetal regression of Müllerian derivatives can leave a uterus or hemi-uterus, fallopian tube remnant, or prostatic utricle. Remnants are often ipsilateral to the streak gonad. This anatomic association is compatible with variable local AMH action but does not, by itself, prove that AMH acts exclusively locally or exclude systemic hormone effects.
  locations:
  - preferred_term: Mullerian duct
    term:
      id: UBERON:0003890
      label: Mullerian duct
  biological_processes:
  - preferred_term: Mullerian duct regression
    term:
      id: GO:0001880
      label: Mullerian duct regression
    modifier: DECREASED
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: Many individuals have Müllerian remnants on the same side as the streak gonad, whereas the most common phenotypic finding is proximal hypospadias with perineal division of the corpus spongiosum and ventral curvature
    explanation: Reports the anatomic association, without establishing a unique mode of hormone action.
    quote_role: REVIEW_SYNTHESIS
  downstream:
  - target: Persistent Mullerian Structures
    causal_link_type: DIRECT
    description: Incomplete duct regression produces retained Müllerian-derived anatomy.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The most common observed remnants are a hemi‐uterus with associated ipsilateral fallopian tube or prostatic utricle
      explanation: Specifies the anatomic consequences.
- name: Undervirilization of the External Genitalia
  biological_scale: ORGANISM
  role: consequence
  mechanism_confidence: ESTABLISHED
  description: Variable androgen exposure during fetal development contributes to atypical external genital anatomy, including hypospadias and ventral curvature. The wider mosaicism spectrum also includes typical external genitalia; the mechanism is not present to the same degree in every individual.
  biological_processes:
  - preferred_term: male genitalia development
    term:
      id: GO:0030539
      label: male genitalia development
    modifier: ABNORMAL
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: The clinical spectrum of MGD to an extent is influenced by the functional capacity of the dysgenetic gonad along with the degree of androgen exposure during critical periods of foetal development
    explanation: Ties the degree of virilization to androgen exposure during the fetal window.
    quote_role: REVIEW_SYNTHESIS
  downstream:
  - target: Proximal Hypospadias
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Incomplete external genital differentiation can include proximal hypospadias.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: the most common phenotypic finding is proximal hypospadias with perineal division of the corpus spongiosum and ventral curvature
      explanation: Identifies the clinical genital finding.
  - target: Atypical Genitalia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Variable fetal virilization contributes to atypical genital appearance.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: The phenotype of MGD ranges from minimal virilisation in females such as clitoral enlargement, to extreme undervirilisation in males, with severe hypospadias leading to atypical genitalia
      explanation: Describes the variable phenotype.
- name: Germ Cell Neoplasia in Dysgenetic Gonads
  biological_scale: TISSUE
  role: consequence
  mechanism_confidence: ESTABLISHED
  description: Gonadoblastoma or germ cell neoplasia in situ can occur in dysgenetic gonads containing Y material, and invasive germ cell tumours are also reported. Risk estimates vary with phenotype, age, gonadal histology, ascertainment and prior gonadectomy. TSPY and DDX3Y are candidate susceptibility genes expressed in affected germ cells, but their expression also occurs in nonmalignant cells and does not establish sufficiency for transformation.
  cell_types:
  - preferred_term: Germ cell
    term:
      id: CL:0000586
      label: germ cell
  evidence:
  - reference: PMID:30753444
    reference_title: Gonadoblastoma Y locus genes expressed in germ cells of individuals with dysgenetic gonads and a Y chromosome in their karyotypes include DDX3Y and TSPY.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: 'The GBY candidate genes DDX3Y and TSPY are expressed in the germ cells of DSD-XY patients from distinct etiologies: patients with mixed gonadal dysgenesis (MGD) and sex chromosome mosaics (45,X0/46,XY; 46,XX/46,XY)'
    explanation: Patient-tissue expression supports candidate involvement, with nonmalignant expression limiting causal interpretation.
    quote_role: PRIMARY_RESULT
  - reference: PMID:30753444
    reference_title: Gonadoblastoma Y locus genes expressed in germ cells of individuals with dysgenetic gonads and a Y chromosome in their karyotypes include DDX3Y and TSPY.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: This suggest that GBY candidate proteins are also expressed in the non-malignant germ cells of DSD-XY individuals like in male spermatogonia.
    explanation: Patient-tissue expression supports candidate involvement, with nonmalignant expression limiting causal interpretation.
    quote_role: PRIMARY_RESULT
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: For individuals with 45,X/46,XY mosaicism, the lifetime risk of developing gonadal tumours is estimated at 15%–25%, with this risk rising with age, although the true incidence may be confounded by the historical practice of early gonadectomy and diagnostic challenges
    explanation: The review qualifies its estimated tumour risk by prior surgery and diagnostic uncertainty.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: Pathologic examination revealed gonadal tumors in 6 of the 34 (18%) patients, including a gonadoblastoma in 7 gonads among 5 patients and an association of dysgerminoma with gonadoblastoma in 1 gonad.
    explanation: Reports co-occurring gonadoblastoma and dysgerminoma in a resection specimen, not longitudinal observation of progression.
    quote_role: PRIMARY_RESULT
  - reference: PMID:27032613
    reference_title: 'Tumor risk of children with 45,X/46,XY gonadal dysgenesis in relation to their clinical presentations: Further insights into the gonadal management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: Among Group I patients, the 4 dysgenetic testes affected by CIS in 3 patients were intraabdominal (n=1), inguinal (n=1) and scrotal (n=2) in positions.
    explanation: In-situ lesions occurred in scrotal as well as inguinal and abdominal testes; position alone does not exclude neoplasia.
    quote_role: PRIMARY_RESULT
  downstream:
  - target: Gonadoblastoma
    causal_link_type: DIRECT
    description: Gonadoblastoma is a documented neoplastic lesion in resected dysgenetic gonads.
    evidence:
    - reference: PMID:31883875
      reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Pathologic examination revealed gonadal tumors in 6 of the 34 (18%) patients, including a gonadoblastoma in 7 gonads among 5 patients and an association of dysgerminoma with gonadoblastoma in 1 gonad.
      explanation: Reports the lesion in a selected surgical cohort.
  - target: Dysgerminoma
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Invasive dysgerminoma can accompany gonadoblastoma.
    evidence:
    - reference: PMID:31883875
      reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Pathologic examination revealed gonadal tumors in 6 of the 34 (18%) patients, including a gonadoblastoma in 7 gonads among 5 patients and an association of dysgerminoma with gonadoblastoma in 1 gonad.
      explanation: A single specimen shows co-occurrence, not directly observed temporal progression.
- name: SHOX Haploinsufficiency in the 45,X Lineage
  biological_scale: MOLECULAR
  role: central_effector
  mechanism_confidence: ESTABLISHED
  description: Cells of the 45,X lineage carry one copy of the pseudoautosomal SHOX gene rather than the usual two copies. This provides a plausible contribution to impaired skeletal growth, while tissue mosaicism and other endocrine or chromosomal factors can also influence stature. SHOX dosage does not explain all Turner-associated cardiac, renal or autoimmune findings.
  gene:
    preferred_term: SHOX
    description: Short stature homeobox gene, present in one copy in cells of the 45,X lineage.
    modifier: DECREASED
    term:
      id: hgnc:10853
      label: SHOX
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: Short stature is a common clinical feature in individuals with MGD and is typically attributed to the 45,X cell line, and associated haploinsufficiency of the SHOX gene
    explanation: Attributes the short stature to SHOX dosage in the 45,X lineage, which is what this node asserts.
    quote_role: REVIEW_SYNTHESIS
  downstream:
  - target: Short Stature
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Reduced SHOX dosage is a recognized contributor to impaired linear growth, but is not established as the sole cause of short stature in this mosaic population.
    evidence:
    - reference: PMID:41208147
      reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Short stature is a common clinical feature in individuals with MGD and is typically attributed to the 45,X cell line, and associated haploinsufficiency of the SHOX gene
      explanation: Supports a growth contribution, not causation of the entire Turner phenotype.
- name: Impaired Spermatogenesis
  biological_scale: CELLULAR
  description: Germ-cell maturation is impaired in some dysgenetic testes. A multicenter male cohort found both focal and arrested spermatogenesis, while some men retained motile sperm. Histologic observations and semen results came from different assessed subsets; neither establishes complete absence of fertility potential throughout the mosaic population.
  biological_processes:
  - preferred_term: spermatogenesis
    term:
      id: GO:0007283
      label: spermatogenesis
    modifier: DECREASED
  evidence:
  - reference: PMID:31127831
    reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Twenty-five percent had focal spermatogenesis, and another 25.0% had arrested spermatogenesis.
    explanation: Histologic observations in the assessed subset of a 63-person multicenter male cohort; the abstract does not fully resolve the denominator for each histologic percentage.
  downstream:
  - target: Azoospermia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Impaired sperm production can contribute to absence of sperm in the ejaculate; the cohort did not establish an exclusive mechanism for every azoospermic patient.
    evidence:
    - reference: PMID:31127831
      reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm.
      explanation: Semen findings in the tested subset, rather than direct histology-semen mediation analysis.
  - target: Infertility
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Reduced spermatogenic capacity contributes to reduced reproductive potential.
    evidence:
    - reference: PMID:31127831
      reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: most are azoospermic, but almost one-half of patients has germ cells present histologically and up to one-quarter has focal spermatogenesis, providing hope for fertility treatment options.
      explanation: The study links impaired spermatogenesis to fertility concerns while retaining residual potential.
phenotypes:
- category: Genitourinary
  name: Atypical Genitalia
  description: Atypical external genital appearance is a common reason for diagnosis, while other individuals with the same mosaic karyotype have typical male or female genitalia.
  phenotype_term:
    preferred_term: Ambiguous genitalia
    term:
      id: HP:0000062
      label: Ambiguous genitalia
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The phenotypic presentation of MGD varies from atypical genitalia to typical male or female appearances often associated with Turner stigmata.
    explanation: 'Describes the full external phenotypic range. No frequency band: the cohort denominators available count patients ascertained in different ways, and the mildest presentations are by definition under-ascertained.'
    quote_role: REVIEW_SYNTHESIS
- category: Genitourinary
  name: Proximal Hypospadias
  description: Proximal hypospadias may have a perineal or scrotal meatus; not every proximal lesion is perineal.
  phenotype_term:
    preferred_term: Hypospadias
    term:
      id: HP:0000047
      label: Hypospadias
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the most common phenotypic finding is proximal hypospadias with perineal division of the corpus spongiosum and ventral curvature
    explanation: Names it as the commonest external genital finding.
    quote_role: REVIEW_SYNTHESIS
- category: Genitourinary
  name: Streak Gonad
  description: Undifferentiated fibrous gonadal tissue, classically contralateral to the dysgenetic testis.
  phenotype_term:
    preferred_term: Streak gonad
    term:
      id: HP:0025733
      label: Streak gonad
  evidence:
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a unilateral dysgenetic testis and a contralateral streak gonad was detected in 20 patients (59%), bilateral streak gonads in 9 (26%)
    explanation: The surgically selected series includes at least one streak gonad in 29 of 34 patients; this is not a population frequency.
    quote_role: PRIMARY_RESULT
  review_notes: At least one streak gonad occurred in 29 of 34 surgically characterized patients. This selected biopsy/gonadectomy denominator is not used as a population frequency.
- category: Genitourinary
  name: Dysgenetic Testis
  description: Disordered testicular differentiation, with variable seminiferous-tubule morphology and function; testes may be abdominal, inguinal, or scrotal.
  phenotype_term:
    preferred_term: Dysplastic testis
    term:
      id: HP:0008733
      label: Dysplastic testis
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the presence of a dysgenetic testis at various levels of descent on one side and a streak gonad on the other
    explanation: Describes the dysgenetic testis and its variable position.
    quote_role: REVIEW_SYNTHESIS
- category: Genitourinary
  name: Persistent Mullerian Structures
  description: Retained uterine or hemi-uterine tissue and fallopian-tube remnants can occur, often on the streak-gonad side. Persistence is not unique to MGD and also occurs in other gonadal dysgeneses.
  phenotype_term:
    preferred_term: Presence of uterus in 46,XY individual
    term:
      id: HP:0034546
      label: Presence of uterus in 46,XY individual
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Many individuals have Müllerian remnants on the same side as the streak gonad
    explanation: Reports the finding and its characteristic laterality.
    quote_role: REVIEW_SYNTHESIS
  review_notes: The HPO binding describes uterine persistence in a 46,XY individual and is used here for the Y-bearing mosaic context. It does not cover every possible Müllerian derivative. The cited ultrasound sensitivity result is from a complex-DSD series, not a population frequency of remnants in MGD.
- category: Genitourinary
  name: Undescended Gonad
  description: Undescended dysgenetic testes may be intra-abdominal or inguinal. Gonadal position contributes to assessment, but scrotal position does not exclude neoplasia.
  phenotype_term:
    preferred_term: Cryptorchidism
    term:
      id: HP:0000028
      label: Cryptorchidism
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: undescended or partially descended gonads with varying degrees of labioscrotal fusion
    explanation: Reports incomplete gonadal descent as part of the genital phenotype.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the presence of a dysgenetic testis at various levels of descent on one side
    explanation: States that the dysgenetic testis is found at variable levels of descent.
    quote_role: REVIEW_SYNTHESIS
- category: Reproductive
  name: Infertility
  description: Impaired spermatogenesis and infertility are frequent clinical concerns. Fertility potential is variable rather than absent in all individuals; three of 17 men undergoing semen analysis in one multicenter cohort had motile sperm.
  phenotype_term:
    preferred_term: Infertility
    term:
      id: HP:0000789
      label: Infertility
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Testicular insufficiency develops in 60%–70% of individuals raised as males by the third decade, and infertility is the most commonly reported outcome.
    explanation: 'Names infertility as the commonest outcome. No frequency band: "most commonly reported outcome" ranks it against other outcomes rather than giving a proportion of patients.'
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:31127831
    reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm.
    explanation: The tested subgroup supports severe but not universal spermatogenic impairment.
- category: Musculoskeletal
  name: Webbed Neck
  description: A Turner-associated feature that can occur in the mosaic population, including individuals with male external genitalia.
  phenotype_term:
    preferred_term: Webbed neck
    term:
      id: HP:0000465
      label: Webbed neck
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The other features include webbed neck, shield chest, cubitus valgus
    explanation: Lists webbed neck among the Turner-spectrum somatic features.
    quote_role: REVIEW_SYNTHESIS
- category: Musculoskeletal
  name: Cubitus Valgus
  description: Increased carrying angle at the elbow, another Turner stigma.
  phenotype_term:
    preferred_term: Cubitus valgus
    term:
      id: HP:0002967
      label: Cubitus valgus
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: webbed neck, shield chest, cubitus valgus, high‐arched palate
    explanation: Lists cubitus valgus among the Turner-spectrum somatic features.
    quote_role: REVIEW_SYNTHESIS
- category: Growth
  name: Short Stature
  description: Height Z-score falls progressively through childhood, mirroring the Turner syndrome growth trajectory. In a French series of boys with normal or near-normal genitalia, mean adult height was 158 cm.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Most patients had stunted growth, with abnormal growth spurt during puberty and a mean adult height of 158 ± 7.6 cm, i.e. -2.3 DS with correction for target height.
    explanation: Gives the adult height and its standard-deviation deficit against target height.
    quote_role: PRIMARY_RESULT
  - reference: PMID:37882230
    reference_title: '45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: height Z-score was significantly decreased with age for both genders (p = 0.02)
    explanation: Confirms the progressive nature of the height deficit in an independent cohort.
    quote_role: PRIMARY_RESULT
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Short stature is common in individuals regardless of their phenotypic sex.
    explanation: States that short stature is common and independent of phenotypic sex.
    quote_role: REVIEW_SYNTHESIS
  review_notes: Clinical cohorts and the review describe short stature as common. Mean heights and selected small-cohort counts are not treated as a precise population percentage.
  frequency: FREQUENT
- category: Oncologic
  name: Gonadoblastoma
  description: A germ-cell neoplasm of dysgenetic gonadal tissue, which can progress to dysgerminoma. Reported in infants as young as five months.
  phenotype_term:
    preferred_term: Gonadoblastoma
    term:
      id: HP:0000150
      label: Gonadoblastoma
  evidence:
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Pathologic examination revealed gonadal tumors in 6 of the 34 (18%) patients, including a gonadoblastoma in 7 gonads among 5 patients and an association of dysgerminoma with gonadoblastoma in 1 gonad.
    explanation: Reports gonadoblastoma in a selected surgical series, including one specimen with associated dysgerminoma.
    quote_role: PRIMARY_RESULT
  - reference: PMID:27052295
    reference_title: 'Gonadoblastoma in patients with 45,X/46,XY mosaicism: A 16-year experience.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: This sub-group of patients with GB were aged 5 months, 48 months, 71 months, and 13 years.
    explanation: Supports occurrence in infancy within a prophylactic gonadectomy series.
  review_notes: The source describes selected biopsy/gonadectomy patients and reports both gonadoblastoma and associated dysgerminoma. This is not an unselected population risk or a proven upper bound.
- category: Oncologic
  name: Dysgerminoma
  description: An invasive germ cell tumour documented in association with gonadoblastoma and in other affected individuals.
  phenotype_term:
    preferred_term: Dysgerminoma
    term:
      id: HP:0100621
      label: Dysgerminoma
  evidence:
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: an association of dysgerminoma with gonadoblastoma in 1 gonad
    explanation: Documents co-occurrence in a single gonad, not directly observed progression.
    quote_role: PRIMARY_RESULT
- category: Endocrine
  name: Declining Testicular Function
  description: Elevated FSH with low inhibin B marks impaired Sertoli function in an assessed end-of-puberty subset. The pattern does not imply inevitable arrest of puberty or universal testosterone deficiency.
  phenotype_term:
    preferred_term: Elevated circulating follicle stimulating hormone level
    term:
      id: HP:0008232
      label: Elevated circulating follicle stimulating hormone level
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 71% (n = 5) of those evaluated at the end of puberty presented signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)
    explanation: The biochemical pattern was observed in five patients among the small subgroup evaluated at the end of puberty.
    quote_role: PRIMARY_RESULT
- category: Endocrine
  name: Delayed or Absent Spontaneous Puberty
  description: Puberty induction may be required with nonfunctional gonads or after gonadectomy. All female-raised participants in one retrospective cohort required induction, but that treatment need cannot be attributed solely to untreated natural history.
  phenotype_term:
    preferred_term: Delayed puberty
    term:
      id: HP:0000823
      label: Delayed puberty
  evidence:
  - reference: PMID:37882230
    reference_title: '45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All females required puberty induction in contrast to majority of males.
    explanation: States the categorical split. No frequency band on the whole disease, because the figure applies to the female-raised subgroup only.
    quote_role: PRIMARY_RESULT
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Individuals with MGD assigned female at birth almost always require pubertal induction and hormone replacement therapy as prophylactic gonadectomy is performed in most, and spontaneous breast development is extremely rare
    explanation: Identifies the contribution of prior gonadectomy.
- category: Cardiovascular
  name: Congenital Heart Defect
  description: Congenital cardiac malformations were identified in six of 23 investigated patients in a 40-person cohort. Specific cardiac findings are also described separately.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
    coarse_binding_basis: SOURCE_UNSPECIFIED
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Turner-like syndrome features including cardiac (6/23 patients investigated) and renal malformations (3/19 patients investigated)
    explanation: 6 of 23 investigated, 26%. No frequency band is given here because the denominator counts only patients who underwent cardiac investigation.
    quote_role: PRIMARY_RESULT
  review_notes: The broad binding captures the unspecified cardiac-malformation count in the 40-person study; specific bicuspid valve and coarctation findings are represented separately.
- category: Renal
  name: Renal Malformation
  description: Structural renal anomalies of the Turner spectrum.
  phenotype_term:
    preferred_term: Abnormal renal morphology
    term:
      id: HP:0012210
      label: Abnormal renal morphology
    coarse_binding_basis: SOURCE_UNSPECIFIED
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Turner-like syndrome features including cardiac (6/23 patients investigated) and renal malformations (3/19 patients investigated)
    explanation: 3 of 19 investigated. As with the cardiac record, the denominator is patients investigated, so no band is asserted.
    quote_role: PRIMARY_RESULT
  review_notes: The broad binding captures the unspecified renal-malformation count; named renal findings are represented separately.
- name: Bifid Scrotum
  category: Genitourinary
  description: Variable labioscrotal fusion can produce a bifid scrotum.
  phenotype_term:
    preferred_term: Bifid scrotum
    term:
      id: HP:0000048
      label: Bifid scrotum
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: undescended or partially descended gonads with varying degrees of labioscrotal fusion giving the appearance of a bifid scrotum
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Ventral Penile Curvature
  category: Genitourinary
  description: Ventral curvature may accompany severe hypospadias.
  phenotype_term:
    preferred_term: Chordee
    term:
      id: HP:0000041
      label: Chordee
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: severe hypospadias with a perineal or scrotal meatus, significant ventral curvature of the phallus, penoscrotal transposition
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Penoscrotal Transposition
  category: Genitourinary
  description: Abnormal positioning of the penis relative to the scrotum is described among the genital findings.
  phenotype_term:
    preferred_term: Penoscrotal transposition
    term:
      id: HP:0100600
      label: Penoscrotal transposition
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: severe hypospadias with a perineal or scrotal meatus, significant ventral curvature of the phallus, penoscrotal transposition
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Shield Chest
  category: Musculoskeletal
  description: A Turner-associated somatic finding in some individuals.
  phenotype_term:
    preferred_term: Shield chest
    term:
      id: HP:0000914
      label: Shield chest
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: The other features include webbed neck, shield chest, cubitus valgus, high‐arched palate
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: High Palate
  category: Craniofacial
  description: High-arched palate is among the reported Turner-associated findings.
  phenotype_term:
    preferred_term: High palate
    term:
      id: HP:0000218
      label: High palate
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: The other features include webbed neck, shield chest, cubitus valgus, high‐arched palate
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Bicuspid Aortic Valve
  category: Cardiovascular
  description: Bicuspid aortic valve can accompany the mosaic karyotype.
  phenotype_term:
    preferred_term: Bicuspid aortic valve
    term:
      id: HP:0001647
      label: Bicuspid aortic valve
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: cardiac anomalies such as bicuspid aortic valve and coarctation of aorta
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Coarctation of the Aorta
  category: Cardiovascular
  description: Aortic coarctation is a reported associated congenital anomaly.
  phenotype_term:
    preferred_term: Coarctation of aorta
    term:
      id: HP:0001680
      label: Coarctation of aorta
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: cardiac anomalies such as bicuspid aortic valve and coarctation of aorta
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Primary Amenorrhea
  category: Reproductive
  description: Primary amenorrhea can lead to recognition in adolescence.
  phenotype_term:
    preferred_term: Primary amenorrhea
    term:
      id: HP:0000786
      label: Primary amenorrhea
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: These patients often remain unidentified until later in childhood or adolescence, when they present with short stature, primary amenorrhea or absent secondary sexual characteristics
    explanation: The narrative review describes this feature; no disease-wide percentage is assigned.
- name: Clitoral Enlargement
  category: Genitourinary
  description: Clitoral enlargement was a presenting concern in eight of ten patients in one tertiary-center series.
  phenotype_term:
    preferred_term: Clitoral hypertrophy
    term:
      id: HP:0008665
      label: Clitoral hypertrophy
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The commonest initial clinical presentation was for the appearance of clitoromegaly (n = 8, 80%) followed by two cases presented as delayed puberty (n = 2, 20%).
    explanation: The count applies to this selected ten-person cohort.
- name: Unilateral Renal Agenesis
  category: Renal
  description: Reported in three of ten patients in a tertiary-center series.
  phenotype_term:
    preferred_term: Unilateral renal agenesis
    term:
      id: HP:0000122
      label: Unilateral renal agenesis
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry).
    explanation: Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.
- name: Horseshoe Kidney
  category: Renal
  description: Reported in one of ten patients in a tertiary-center series and described in broader clinical reviews.
  phenotype_term:
    preferred_term: Horseshoe kidney
    term:
      id: HP:0000085
      label: Horseshoe kidney
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry).
    explanation: Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.
- name: Sensorineural Hearing Impairment
  category: Auditory
  description: Documented by audiometry in one of ten patients in a tertiary-center series.
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry).
    explanation: Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.
- name: Autoimmune Hypothyroidism
  category: Endocrine
  description: Autoimmune hypothyroidism occurred in three of ten patients in one series; the general hypothyroidism binding avoids inferring a specific thyroid histology.
  phenotype_term:
    preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry).
    explanation: Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.
- name: Graves Disease
  category: Endocrine
  description: Reported in one individual in the ten-person series.
  phenotype_term:
    preferred_term: Graves disease
    term:
      id: HP:0100647
      label: Graves disease
  evidence:
  - reference: PMID:34566299
    reference_title: Clinical and Reproductive Characteristics of Patients with Mixed Gonadal Dysgenesis (45,X/46, XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Four cases had autoimmune thyroid disease (one case had Graves’ disease and three had autoimmune hypothyroidism), three cases had unilateral renal agenesis (MRI- abdomen) and one case each had horseshoe kidney and sensory-neural deafness (Pure tone audiometry).
    explanation: Counts are cohort-specific and do not establish disease-wide frequency; the small same-center 2021 reports may overlap.
- name: Pectus Excavatum
  category: Musculoskeletal
  description: Observed in a 16-year-old patient in a five-person series selected for severe short stature.
  phenotype_term:
    preferred_term: Pectus excavatum
    term:
      id: HP:0000767
      label: Pectus excavatum
  evidence:
  - reference: PMID:34539919
    reference_title: Growth Hormone Dynamics among Children with Mixed Gonadal Dysgenesis (45,X/46,XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: At presentation he had a short neck, widely spaced nipples, pectus excavatum, short 4thmetacarpal, wide carrying angle, short stature with mesomelia
    explanation: A single described patient supports occurrence, not a general frequency or a sole SHOX mechanism.
- name: Short Fourth Metacarpal
  category: Musculoskeletal
  description: Observed in a 16-year-old patient in a five-person series selected for severe short stature.
  phenotype_term:
    preferred_term: Short 4th metacarpal
    term:
      id: HP:0010044
      label: Short 4th metacarpal
  evidence:
  - reference: PMID:34539919
    reference_title: Growth Hormone Dynamics among Children with Mixed Gonadal Dysgenesis (45,X/46,XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: At presentation he had a short neck, widely spaced nipples, pectus excavatum, short 4thmetacarpal, wide carrying angle, short stature with mesomelia
    explanation: A single described patient supports occurrence, not a general frequency or a sole SHOX mechanism.
- name: Mesomelia
  category: Musculoskeletal
  description: Observed in a 16-year-old patient in a five-person series selected for severe short stature.
  phenotype_term:
    preferred_term: Mesomelia
    term:
      id: HP:0003027
      label: Mesomelia
  evidence:
  - reference: PMID:34539919
    reference_title: Growth Hormone Dynamics among Children with Mixed Gonadal Dysgenesis (45,X/46,XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: At presentation he had a short neck, widely spaced nipples, pectus excavatum, short 4thmetacarpal, wide carrying angle, short stature with mesomelia
    explanation: A single described patient supports occurrence, not a general frequency or a sole SHOX mechanism.
- name: Madelung Deformity
  category: Musculoskeletal
  description: Reported in a 15-year-old patient in a five-person growth-focused series.
  phenotype_term:
    preferred_term: Madelung deformity
    term:
      id: HP:0003067
      label: Madelung deformity
  evidence:
  - reference: PMID:34539919
    reference_title: Growth Hormone Dynamics among Children with Mixed Gonadal Dysgenesis (45,X/46,XY).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Turner`s stigmata in the form of wide carrying angle, multiple nevi, webbing necking and madelung deformity was found.
    explanation: A single patient supports this skeletal finding.
- name: Azoospermia
  category: Reproductive
  description: Azoospermia occurred in 14 of 17 men with semen analysis in a multicenter cohort; three had motile sperm.
  phenotype_term:
    preferred_term: Azoospermia
    term:
      id: HP:0000027
      label: Azoospermia
  evidence:
  - reference: PMID:31127831
    reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm.
    explanation: The tested subgroup is selected and no population frequency is inferred.
biochemical:
- name: Inhibin B
  notes: Low inhibin B with elevated FSH can indicate Sertoli dysfunction. Early-pubertal inhibin B has been proposed as a predictor of later gonadal function, but this is not a universally validated decision threshold.
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)
    explanation: Establishes the low-inhibin-B, high-FSH pattern as the marker of Sertoli decline.
    quote_role: PRIMARY_RESULT
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: inhibin B concentrations during early puberty may serve as a reliable predictor of testicular function and the need for testosterone replacement in the future
    explanation: Reports the prognostic use of early-pubertal inhibin B.
    quote_role: REVIEW_SYNTHESIS
- name: Follicle-stimulating hormone
  notes: FSH can rise with impaired gonadal feedback; age, pubertal stage and gonadal surgery affect interpretation.
  evidence:
  - reference: PMID:29973376
    reference_title: Should 45,X/46,XY boys with no or mild anomaly of external genitalia be investigated and followed up?
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: signs of declined Sertoli cell function (low inhibin B levels and increased FSH levels)
    explanation: Establishes the low-inhibin-B, high-FSH pattern as the marker of Sertoli decline.
    quote_role: PRIMARY_RESULT
- name: Anti-Mullerian hormone
  notes: A marker of Sertoli-cell/testicular tissue function. Concentrations can be low relative to male infant reference ranges; a postnatal value does not directly quantify fetal AMH exposure.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: AMH concentrations in individuals with MGD are typically toward the lower end of the reference range for healthy male infants with normal testicular function, reflecting relative Sertoli cell dysfunction
    explanation: Describes impaired secretion rather than a measured loss of Sertoli cell mass.
- name: Testosterone
  notes: Basal and hCG-stimulated testosterone assess steroidogenic function in the appropriate age context. Typical infant concentrations may be low-normal relative to male reference ranges.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Due to the presence of dysgenetic testis, the plasma testosterone concentrations in MGD patients tend to be low‐normal relative to typical male infants but remain elevated compared with those typically seen in female infants.
    explanation: Supports a relative and variable secretory deficit.
diagnosis:
- name: Chromosome analysis with adequate cell count
  description: Peripheral-blood karyotyping identifies mosaic sex-chromosome lineages and structural abnormalities. The international Turner guideline recommends counting at least 30 metaphases, which detects approximately 10% mosaicism with 95% confidence; lower-level or tissue-restricted mosaicism may be missed. A blood mosaic ratio does not reliably predict gonadal composition or genital phenotype.
  evidence:
  - reference: PMID:38748847
    reference_title: Clinical practice guidelines for the care of girls and women with Turner syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: We recommend that a minimum of 30 metaphases be counted on a chromosome analysis as the first-line test which can detect approximately 10% mosaicism with 95% confidence limits
    explanation: Defines the cytogenetic sampling recommendation and its detection limit.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Since mosaicism can vary between tissues, the karyotype in the blood might not accurately reflect the gonadal karyotype.
    explanation: Explains the tissue limitation.
- name: Additional tissue and molecular cytogenetic testing
  description: When clinical suspicion persists, targeted karyotype or FISH can assess buccal cells, skin fibroblasts or gonadal tissue obtained for clinical reasons. Microarray can characterize copy-number changes but is not uniformly more sensitive for low-level mosaicism and does not identify balanced rearrangements. Test choice depends on the suspected abnormality and laboratory method.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Targeted karyotype or Fluorescent in situ hybridisation (FISH) analysis of buccal epithelia cells obtained via swab, skin fibroblasts or gonadal tissue (if having gonadectomy for clinical reasons) may be required when clinical suspicion persists after normal karyotype results.
    explanation: Supports additional-tissue assessment without recommending gonadal surgery solely to measure mosaicism.
  - reference: PMID:38748847
    reference_title: Clinical practice guidelines for the care of girls and women with Turner syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Microarray can provide better resolution compared to karyotyping, but has limitations in detecting low level 45,X mosaicism (<10%, though studies show detection as low as 5%)
    explanation: Distinguishes resolution from reliable low-level mosaic detection.
- name: Confirmation after prenatal detection
  description: Prenatal screening or cytogenetic findings require appropriate confirmatory testing and counseling about uncertain phenotype prediction. NIPT is a screening test, not a definitive fetal karyotype. Postnatal cytogenetic confirmation is recommended after prenatal identification of the mosaic karyotype.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: When a 45,X/46,XY karyotype is identified prenatally by amniocentesis or chorionic villus sampling testing, postnatal confirmation by cytogenetic testing is essential to guide clinical management
    explanation: Specifies confirmation after prenatal diagnosis.
- name: Endocrine assessment
  description: Age-appropriate testosterone, AMH and gonadotropins assess testicular tissue and function. During the early infant mini-puberty window, basal testosterone may be informative; hCG stimulation can assess steroidogenic reserve when basal values are low or the window has passed. Electrolytes, cortisol and 17-hydroxyprogesterone help exclude adrenal causes of atypical genitalia and salt-wasting emergencies.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: If baseline testosterone concentration is low or if being evaluated outside the mini‐puberty window, a human chorionic gonadotropin (hCG) stimulation test can be useful to assess if the testicular tissue can mount an adequate testosterone response.
    explanation: Specifies the functional test and timing context.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: 'The key investigations include: plasma electrolytes, cortisol and 17‐hydroxyprogesterone (17‐OHP) concentrations'
    explanation: Names the initial adrenal differential work-up.
- name: Imaging and anatomical evaluation
  description: Pelvic ultrasound is the initial investigation for gonadal location and Müllerian anatomy; abdominal ultrasound also evaluates the kidneys. MRI, examination under anesthesia, endoscopy or laparoscopy may be appropriate when the anatomy remains unclear or an intervention is planned. Negative imaging does not exclude small remnants or gonadal tissue. The quoted ultrasound miss rate comes from a complex-DSD series rather than an MGD-only accuracy study.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Pelvic ultrasound is typically the first‐line for localisation of gonads and identification of Müllerian structures. MRI is reserved for cases where ultrasound findings are inconclusive
    explanation: Describes the imaging sequence.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: ultrasound failed to visualise Müllerian duct remnants in approximately 40% of cases, whereas laparoscopy achieved optimal visualization in all patients
    explanation: Supports a limitation of ultrasound within the cited complex-DSD population.
- name: Gonadal histology when clinically indicated
  description: Biopsy or resection can characterize streak and testicular tissue, germ-cell maturation and neoplastic lesions. Gonads may be heterogeneous, so a limited biopsy cannot reliably exclude a focal lesion elsewhere. Histology is interpreted with the cytogenetic, endocrine and anatomic findings.
  evidence:
  - reference: PMID:31883875
    reference_title: Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: A gonad composed of both streak and dysgenetic testicular portions was observed in 7 gonads of 6 patients.
    explanation: Shows why a single sample can incompletely represent a gonad.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: However, biopsy may not reliably represent the entire gonad, and blood tumour markers are not elevated in most DSD‐ associated germ cell tumours.
    explanation: States sampling and biomarker limitations.
- name: Baseline Cardiac and Renal Assessment
  description: Children with a 45,X/46,XY karyotype warrant renal ultrasonography and cardiac evaluation with echocardiography to detect associated anomalies. Subsequent follow-up is guided by the findings and broader surveillance recommendations.
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Given these associations, it is recommended that a comprehensive evaluation including renal ultrasonography, together with a complete cardiac evaluation with echocardiographic assessment should be performed in all children with 45,X/46,XY karyotype to facilitate early detection and management of these anomalies
    explanation: The review recommends cardiac and renal evaluation for children with the mosaic karyotype regardless of their external genital presentation.
differential_diagnoses:
- name: 46,XY partial gonadal dysgenesis
  disease_term:
    preferred_term: 46,XY partial gonadal dysgenesis
    term:
      id: MONDO:0016674
      label: 46,XY partial gonadal dysgenesis
  description: Partial gonadal dysgenesis can occur with a 46,XY karyotype and overlapping genital or gonadal findings. Pathogenic variants in sex-development genes may account for some cases. A normal blood karyotype does not exclude tissue-restricted 45,X mosaicism.
  distinguishing_features:
  - Demonstrated 45,X mosaicism in blood or another relevant tissue supports the mosaic chromosomal entity.
  - Single-gene and chromosomal causes require different recurrence counseling; a molecular diagnosis is not established in every 46,XY case.
  evidence:
  - reference: PMID:25860218
    reference_title: 'Identification of X monosomy cells from a gonad of mixed gonadal dysgenesis with a 46,XY karyotype: case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: A 1-year-old infant with 46,XY identified by peripheral blood karyotype demonstrated clinical manifestations and gonadal pathologic features of MGD.
    explanation: Shows why blood karyotype alone cannot always distinguish the conditions.
- name: Turner syndrome
  disease_term:
    preferred_term: Turner syndrome
    term:
      id: MONDO:0019499
      label: Turner syndrome
  description: Turner syndrome overlaps clinically and cytogenetically with this mosaic population. Some individuals with 45,X/46,XY and female external genitalia meet Turner diagnostic criteria; the presence of Y material does not exclude that diagnosis. Those with atypical or male external genitalia are outside the guideline definition of Turner syndrome but still warrant its surveillance recommendations.
  distinguishing_features:
  - Interpret Turner syndrome using phenotype and cytogenetic findings rather than an absolute absence of Y material.
  - Asymmetric streak/testicular anatomy supports the MGD description, but gonadal patterns in the mosaic population are variable.
  evidence:
  - reference: PMID:38748847
    reference_title: Clinical practice guidelines for the care of girls and women with Turner syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Individuals with 45,X/46,XY mosaicism who do not have typical female external genitalia are also excluded from the diagnosis, although we recommend that the guidelines also apply to these individuals due to a similar comorbidity profile
    explanation: Distinguishes the Turner diagnostic definition from surveillance eligibility.
treatments:
- name: Individualized Gonadal Surgery
  description: Removal of a nonfunctional streak or dysgenetic gonad can reduce the risk arising from that tissue. Whether and when to remove each gonad is decided individually, considering histology, position, hormone function, fertility potential, surveillance limits and the informed preferences of the patient and family. Removal may create a need for long-term hormone replacement.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: a shared decision‐making approach, inclusive of the risks and benefits of both options, should be used to make these decisions in an individualised manner.
    explanation: The review does not establish universal removal or universal retention.
  - reference: PMID:38748847
    reference_title: Clinical practice guidelines for the care of girls and women with Turner syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: We recommend individualized decision-making about gonadectomy/salpingo-oophrectomy in girls and women with TS and Y chromosome material identified on standard karyotyping or FISH analysis.
    explanation: The guideline supports individualization in girls and women with Turner syndrome and Y material; its precise population is retained.
  target_mechanisms:
  - target: Germ Cell Neoplasia in Dysgenetic Gonads
    description: Removes the tissue at risk; the decision balances neoplasia prevention against loss of gonadal function.
- name: Surveillance of Retained Gonads
  description: If gonads are retained, specialist follow-up includes examination and individualized imaging or tissue assessment. Scrotal position does not eliminate risk. Imaging can miss early lesions, biopsy can miss focal disease, and serum tumour markers are often uninformative; surveillance therefore cannot guarantee exclusion of neoplasia.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Imaging modalities for intra‐abdominal gonads often lack sufficient sensitivity to reliably detect early malignant changes
    explanation: Identifies an imaging limitation.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: However, biopsy may not reliably represent the entire gonad, and blood tumour markers are not elevated in most DSD‐ associated germ cell tumours.
    explanation: Qualifies the limits of tissue sampling and blood markers.
- name: Orchiopexy When Gonadal Preservation Is Chosen
  description: Relocating an appropriate retained gonad can facilitate examination and surveillance. It does not abolish the neoplastic risk of dysgenetic tissue.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Orchiopexy
    term:
      id: NCIT:C111066
      label: Orchiopexy
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: The alternative option is relocating the gonads into the labioscrotal folds to facilitate easier examination, imaging, and biopsy.
    explanation: Supports relocation as an option in the context of retention.
- name: Hypospadias Repair
  description: Reconstruction may be considered for functional and anatomical concerns, sometimes using a staged approach. Timing and extent are individualized within multidisciplinary care and shared decision-making, with attention to patient autonomy and the irreversibility of surgery.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: The core components of care include sex assignment, excisional biopsy of the dysgenetic or streak gonads to decrease tumour risk, hypospadias repair usually in a staged approach, hormone replacement therapy for initiation and maintenance of puberty, and growth‐promoting strategies for managing short stature.
    explanation: Names staged repair among management options, without establishing a universal indication.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: The modern clinical practice focuses on patient‐centred care and advocates for the deferral of any irreversible interventions unless they are deemed clinically essential.
    explanation: Provides the decision-making context.
  target_mechanisms:
  - target: Undervirilization of the External Genitalia
    description: Addresses selected anatomic consequences through reconstruction.
- name: Growth Hormone Therapy
  description: Recombinant growth hormone may be considered for impaired growth after endocrine evaluation. Observational evidence for adult-height benefit in the mosaic population is inconsistent; treatment decisions account for growth trajectory, remaining growth potential and gonadal follow-up. SHOX dosage is one possible contributor to short stature, and treatment does not correct the chromosomal mosaicism.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: somatropin
      term:
        id: CHEBI:749556
        label: somatropin
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Recombinant human growth hormone (rhGH) therapy has been found to significantly improve growth velocity and final adult height in individuals with MGD, with outcomes similar to those observed in Turner syndrome
    explanation: The narrative review gives a favorable synthesis.
  - reference: PMID:37882230
    reference_title: '45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Growth hormone (GH) treatment did not result in a significant height increase compared to the untreated group (p = 0.5).
    explanation: The retrospective 100-patient cohort did not find a significant treated-versus-untreated difference; it is not a randomized efficacy trial.
- name: Sex Steroid Replacement
  description: Testosterone or estradiol can induce and maintain puberty when gonadal hormone production is insufficient or after gonadectomy. Treatment follows individual clinical goals, pubertal stage and residual function. A progestogen is added to an estrogen regimen when endometrial protection is needed in a person with a uterus. Spontaneous pubertal onset is common in some male cohorts, so replacement is not inevitable for every individual.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Hormone Replacement Therapy
    term:
      id: NCIT:C15599
      label: Hormone Replacement Therapy
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Induction of puberty with either testosterone or oestrogen is essential for individuals with MGD who either have undergone gonadectomy or who do not experience spontaneous puberty.
    explanation: Defines the indication rather than inferring universal natural gonadal failure.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: With the onset of breakthrough bleeding, a progestogen is added to protect the endometrial lining if a uterus is present
    explanation: Explains the anatomy-dependent regimen.
  target_mechanisms:
  - target: Reduced Leydig Cell Testosterone Production
    description: Testosterone replacement compensates for inadequate androgen production when present; estrogen-based treatment addresses other individualized pubertal goals.
- name: Multidisciplinary Shared Decision-Making and Psychological Support
  description: Endocrinology, urology, gynecology, genetics and psychology coordinate care with the patient and family. Support addresses diagnostic uncertainty, body image, disclosure, relationships and fertility across childhood and adulthood. Gender identity cannot be reliably predicted from a blood mosaic ratio, genital anatomy or a single cohort percentage.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Psychosocial Care
    term:
      id: NCIT:C126880
      label: Psychosocial Care
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: The delivery of optimal care requires a close collaboration among paediatric endocrinologists, urologists, geneticists, gynaecologists, and psychologists
    explanation: Identifies the clinical team.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Psychosocial support is equally crucial from the time of diagnosis and throughout life to help families and individuals address questions and challenges related to potential gender identity, self‐image, disclosure, and fertility
    explanation: Supports continuing psychosocial care.
- name: Lifelong Multisystem Surveillance
  description: Follow-up assesses growth, puberty, bone health, hearing, thyroid function, cardiovascular and renal findings, and metabolic health. The international Turner guideline explicitly extends its surveillance recommendations to 45,X/46,XY individuals with atypical or male external genitalia regardless of sex of rearing. Surveillance is not contingent on assigning a Turner diagnosis to every individual.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:38748847
    reference_title: Clinical practice guidelines for the care of girls and women with Turner syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: We recommend that the surveillance guidelines also apply to individuals with 45,X/46,XY mosaicism with either ambiguous or male external genitalia, regardless of sex of rearing
    explanation: Provides direct guideline scope for the mosaic population.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Long‐term follow‐up for individuals with MGD should include regular monitoring of growth, pubertal development, monitoring for bone mineral density, sensorineural hearing loss, and screening for associated health conditions linked to the 45,X cell line, such as cardiovascular or renal anomalies, and autoimmune conditions (notably autoimmune thyroiditis)
    explanation: Specifies the clinical domains.
- name: Fertility Counseling
  description: Discuss variable germ-cell function and future reproductive options before gonadal surgery when feasible. Semen assessment and assisted reproduction may be relevant to selected individuals with retained testes. Prepubertal gonadal tissue cryopreservation and future maturation of that tissue remain investigational rather than established fertility-restoring treatments.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Fertility and Reproductive Counseling
    term:
      id: NCIT:C171451
      label: Fertility and Reproductive Counseling
  evidence:
  - reference: PMID:31127831
    reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Fourteen out of 17 (82%) with semen analyses were azoospermic; three had motile sperm.
    explanation: Documents heterogeneity in a selected tested subset.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: gonadal tissue cryopreservation during gonadectomy or gonadal biopsy, when the germ cell numbers are high, and the use of the tissue for future fertility when technological advancement potentially allows for in vitro maturation are being explored as options
    explanation: Identifies the experimental scope of tissue preservation.
  target_mechanisms:
  - target: Impaired Spermatogenesis
    description: Counseling and individualized reproductive assessment address reduced spermatogenic capacity; they do not reverse the cellular defect.
- name: Planned Transition to Adult Care
  description: A structured transition between pediatric and adult specialists helps maintain endocrine treatment, gonadal follow-up and multisystem surveillance. Readiness discussions include understanding the diagnosis, self-management, fertility and mental-health support.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Planning for transition should ideally begin as early as 12–13 years of age, and the European DSD consensus statement highlights early, staged hand‐over as the single most effective safeguard against loss to follow‐up
    explanation: The review supports staged transition planning.
discussions:
- discussion_id: mgd_mosaic_distribution_and_development
  kind: KNOWLEDGE_GAP
  prompt: How does gonadal mosaic distribution shape differentiation during fetal development?
  rationale: Human gonadal FISH already demonstrates tissue and cellular mosaicism. Two MGD cases in a five-person study had higher XY fractions in testicular than ovarian tissue. In a later case, combined FISH and lineage-marker staining demonstrated gonadal mosaicism despite a 46,XY blood karyotype, but only one gonad was examined and both FISH artifacts and cell-dependent SRY expression complicated inference. These observations do not establish the timing, spatial signal interactions or causal mosaic threshold during fetal development. A high XY fraction also occurred in an atrophic infertile testis, showing that fraction alone is insufficient to predict function.
  attaches_to:
  - pathophysiology#Tissue-Specific Sex Chromosome Mosaicism
  - pathophysiology#Abnormal Gonadal Differentiation
  evidence:
  - reference: PMID:9763660
    reference_title: Pathogenetics of 45,X/46,XY gonadal mosaicism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In the mixed gonadal dysgenesis cases (cases 3 and 4), the testis had a higher percentage (greater than two fold) of XY cells than the ovary had.
    explanation: Demonstrates existing human gonadal measurements.
  - reference: PMID:25860218
    reference_title: 'Identification of X monosomy cells from a gonad of mixed gonadal dysgenesis with a 46,XY karyotype: case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: FISH analysis on paraffin sections has the inevitable problem of false negativity for the Y chromosome. Immunohistochemical study for SRY is useful in proving the presence of Y chromosome; however, not all cell types express SRY protein and the interpretation of the results is complicated.
    explanation: States key measurement limitations.
- discussion_id: mgd_sry_threshold_model_is_murine
  kind: HUMAN_MODEL_MISMATCH
  prompt: How does the mouse FGF9-SOX9 and WNT4 network translate to a human mosaic gonad?
  rationale: Mouse knockout and culture experiments establish interdependent SOX9 and FGF9 expression and antagonism with WNT4. Fgf9-null XY gonads initially express SRY and SOX9 but fail to maintain SOX9 and form normal testis cords. The experimental genotypes are not 45,X/46,XY mosaic models. A requirement for a critical number of supporting cells and non-cell-autonomous recruitment is an author-proposed explanation rather than a measured human threshold. FGF9/WNT4 antagonism does not specify a direct biochemical repression step, and transient SOX9 induction in Wnt4-null XX gonads did not produce Sertoli differentiation or testis cords.
  attaches_to:
  - pathophysiology#Abnormal Gonadal Differentiation
  evidence:
  - reference: PMID:16700629
    reference_title: Fgf9 and Wnt4 act as antagonistic signals to regulate mammalian sex determination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Whether FGF9 normally acts non-cell-autonomously in vivo to recruit XY cells to the Sertoli lineage by up-regulating SOX9 is not clear.
    explanation: Explicitly identifies the remaining mechanistic uncertainty.
  - reference: PMID:16700629
    reference_title: Fgf9 and Wnt4 act as antagonistic signals to regulate mammalian sex determination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Further experiments will be required to deﬁne the molecular mechanism of FGF9 and WNT4 action.
    explanation: The antagonistic relationship is not a resolved biochemical chain.
- discussion_id: mgd_gh_efficacy_contested
  kind: KNOWLEDGE_GAP
  prompt: Which patients gain adult height from growth hormone treatment?
  rationale: The clinical review describes improvement in growth velocity and final height, while a retrospective 100-person cohort found no significant height difference between treated and untreated groups. Variation in indication, baseline height, dose, timing and residual growth may affect observational comparisons. The available evidence does not establish uniform benefit or lack of benefit. The five-person series of growth-axis testing describes heterogeneous GH deficiency or resistance patterns but does not provide treatment-effect follow-up.
  attaches_to:
  - treatments#Growth Hormone Therapy
  - pathophysiology#SHOX Haploinsufficiency in the 45,X Lineage
  evidence:
  - reference: PMID:37882230
    reference_title: '45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Growth hormone (GH) treatment did not result in a significant height increase compared to the untreated group (p = 0.5).
    explanation: Retains the nonsignificant observational comparison.
  - reference: PMID:41208147
    reference_title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Recombinant human growth hormone (rhGH) therapy has been found to significantly improve growth velocity and final adult height in individuals with MGD, with outcomes similar to those observed in Turner syndrome
    explanation: Retains the review assessment without treating it as a randomized estimate.
- discussion_id: mgd_gonad_position_and_tumour_risk
  kind: KNOWLEDGE_GAP
  prompt: How should gonadal position, histology and function inform individualized tumour-risk assessment?
  rationale: In one 14-patient prophylactic gonadectomy series, all gonadoblastomas were in abdominal gonads. A different 21-child study found germ cell neoplasia in situ in abdominal, inguinal and scrotal dysgenetic testes. These cohorts studied different lesions and selected populations, so their counts are not directly contradictory or suitable for pooling. Scrotal position does not exclude neoplasia, and current surveillance methods have important sensitivity and sampling limitations. Reliable individual risk prediction while preserving gonadal function remains unresolved.
  attaches_to:
  - pathophysiology#Germ Cell Neoplasia in Dysgenetic Gonads
  - treatments#Individualized Gonadal Surgery
  - treatments#Surveillance of Retained Gonads
  evidence:
  - reference: PMID:27052295
    reference_title: 'Gonadoblastoma in patients with 45,X/46,XY mosaicism: A 16-year experience.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The exclusive presence of GB in intra-abdominal gonads is in keeping with the findings of several other series.
    explanation: Describes location within this selected gonadoblastoma series.
  - reference: PMID:27032613
    reference_title: 'Tumor risk of children with 45,X/46,XY gonadal dysgenesis in relation to their clinical presentations: Further insights into the gonadal management.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: the 4 dysgenetic testes affected by CIS in 3 patients were intraabdominal (n=1), inguinal (n=1) and scrotal (n=2) in positions.
    explanation: Shows in-situ neoplasia at all three locations.
references:
- reference: PMID:41208147
  title: 'Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.'
- reference: PMID:37882230
  title: '45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.'
review_notes: Review considered the matching deep-research report, current clinical review and international Turner guideline, primary clinical cohorts, human gonadal FISH studies and the mouse FGF9/WNT4 experiments. Source-specific limitations include overlap between small same-center cohorts, surgery-confounded pubertal outcomes, selected gonadal tumour denominators, and abstract-only access for several older or registry studies. Direct human tissue mapping replaces the earlier claim that no such measurement exists. GeneReviews and StatPearls checks found no directly matching chapter.
notes: This entry describes a chromosomal mosaic condition rather than a single-gene disorder. SHOX dosage and sex-development pathways are mechanistically relevant, but no single causal-gene annotation is assigned. The wider 45,X/46,XY karyotype population includes individuals without classic mixed gonadal histology; registry and cohort results are identified at their actual scope. Animal and culture models are labeled as developmental pathway models. Cohort counts are retained without converting selected surgical, endocrine or photo-defined subgroups into population frequencies.
animal_models:
- name: Fgf9-null mouse model of gonadal differentiation
  species: Mouse
  genotype: Fgf9-null XY on the reported C57BL/6 background
  publication: PMID:16700629
  description: A developmental pathway model, not a mosaic 45,X/46,XY disease model. Sry and initial Sox9 expression were retained, but SOX9 was lost by 12.5 days post coitum, Sertoli markers were reduced or absent and normal testis cords did not form. No increased gonadal apoptosis was observed at the examined 12.0-day stage.
  modeled_mechanisms:
  - target: Abnormal Gonadal Differentiation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: Provides a causal perturbation of mouse testis differentiation through loss of Fgf9.
    limitations: Uniform mouse knockout rather than human sex-chromosome mosaicism. The phenotype depends on the reported background; the experiment does not determine a human SRY-cell threshold or prove FGF9 deficiency in MGD.
    readouts:
    - name: SOX9 maintenance and testis cord organization
      target: Abnormal Gonadal Differentiation
      direction: DECREASED
      interpretation: SOX9 disappears after initial induction and normal cord organization fails in the knockout.
      evidence:
      - reference: PMID:16700629
        reference_title: Fgf9 and Wnt4 act as antagonistic signals to regulate mammalian sex determination.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: SOX9 was no longer detectable by 12.5 dpc, and Sertoli precursor cells never began to organize into normal testis cord structures
        explanation: In-vivo mutant gonadal readouts.
    evidence:
    - reference: PMID:16700629
      reference_title: Fgf9 and Wnt4 act as antagonistic signals to regulate mammalian sex determination.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: although Fgf9 is not required for the up- regulation of Sox9 in vivo, it is indispensable to maintain Sox9 expression in Sertoli precursor cells.
      explanation: Separates initial induction from later maintenance.
experimental_models:
- name: Mouse gonadal cultures testing FGF9 and WNT4 interactions
  experimental_model_type: OTHER
  organism:
    preferred_term: Mus musculus
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  cell_source: Embryonic mouse gonads and gonad-mesonephros complexes
  culture_system: Intact explants and parallel dissociated-cell cultures
  publication: PMID:16700629
  description: 'FGF9 gain-of-function studies used intact explants, localized FGF9-coated beads and dissociated gonadal cells. Soluble FGF9 suppressed Wnt4 in intact XX gonads, while induction of SOX9 depended on culture context: dissociation, localized bead exposure or Wnt4 heterozygosity. Soluble FGF9 did not induce SOX9 in intact wild-type XX gonads.'
  modeled_mechanisms:
  - target: Abnormal Gonadal Differentiation
    relationship: PERTURBS
    fidelity: LOW
    description: Manipulates developmental signaling and measures supporting-cell markers in mouse cultures.
    limitations: These are ex-vivo or in-vitro assays, not human fetal tissue or a chromosome-mosaic model. Marker induction is not equivalent to complete functional testis differentiation.
    evidence:
    - reference: PMID:16700629
      reference_title: Fgf9 and Wnt4 act as antagonistic signals to regulate mammalian sex determination.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Treatment of XX gonads with exogenous FGF9 suppressed the normal expression of Wnt4
      explanation: Cultured gonad response to FGF9.
    - reference: PMID:16700629
      reference_title: Fgf9 and Wnt4 act as antagonistic signals to regulate mammalian sex determination.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: The current study reveals that ectopic FGF9 can induce SOX9 under conditions in which XX cells are dissociated
      explanation: The dissociated-cell context is distinct from intact explants.
updated_date: '2026-09-21T02:54:05Z'
histopathology:
- name: Mixed Seminiferous and Undifferentiated Gonadal Architecture
  description: A resected gonad from one infant contained normal-appearing and abnormally shaped seminiferous tubules, undifferentiated gonadal tissue and gonadoblastoma nests. This demonstrates intragonadal heterogeneity, not a universal histologic pattern.
  evidence:
  - reference: PMID:25860218
    reference_title: 'Identification of X monosomy cells from a gonad of mixed gonadal dysgenesis with a 46,XY karyotype: case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Histology of the gonad showed a streak testis consisting predominantly of differentiated normal-appearing seminiferous tubules with an area of undifferentiated gonadal tissue (UGT) and abnormally shaped seminiferous tubules at the periphery of the gonad
    explanation: Describes the actual tissue architecture in one resected right gonad.
  notes: 'Needs term / NTR: OLS NCIT search for seminiferous tubule dysplasia found no exact histopathology term; a generic dysplasia binding would discard the mixed architectural finding.'
- name: Mixed Supporting-cell Lineage-marker Expression
  description: SOX9-only Sertoli cells, FOXL2-only precursor granulosa cells and cells expressing both markers occurred in distinct areas of the same infant gonad. Coexpression indicates mixed lineage-marker expression; SRY immunostaining alone cannot assign a karyotype to every cell type.
  evidence:
  - reference: PMID:25860218
    reference_title: 'Identification of X monosomy cells from a gonad of mixed gonadal dysgenesis with a 46,XY karyotype: case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Unexpectedly, our case showed co-expression of SOX9 and FOXL2 in abnormally shaped seminiferous tubules and gonadoblastomas.
    explanation: Single-case supporting-cell immunophenotype, not a universal diagnostic biomarker.
  notes: 'Needs term / NTR: OLS NCIT search for SOX9 FOXL2 coexpression found no matching immunophenotypic finding.'
- name: Arrested Spermatogenesis
  description: Arrested spermatogenesis was among the histologic patterns in a multicenter male cohort; focal spermatogenesis was also present in some samples. The cohort included genital and nongenital routes of ascertainment.
  evidence:
  - reference: PMID:31127831
    reference_title: Clinical but Not Histological Outcomes in Males With 45,X/46,XY Mosaicism Vary Depending on Reason for Diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Twenty-five percent had focal spermatogenesis, and another 25.0% had arrested spermatogenesis.
    explanation: Histologic observations in the assessed subset of a 63-person multicenter male cohort; the abstract does not fully resolve the denominator for each histologic percentage.
  notes: 'Needs term / NTR: OLS NCIT search for spermatogenic arrest found no exact histopathology term. The source percentage is retained only in the quote because its abstract does not fully specify each histologic denominator.'

📚

References & Deep Research

References

2

PMID:41208147

Mixed Gonadal Dysgenesis: A Comprehensive Review of Clinical Spectrum, Diagnostic Strategies, and Management Approaches.

No top-level findings curated for this source.

PMID:37882230

45,X/46,XY mosaicism: Clinical manifestations and long term follow-up.

No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (3)

Record review notes

Review considered the matching deep-research report, current clinical review and international Turner guideline, primary clinical cohorts, human gonadal FISH studies and the mouse FGF9/WNT4 experiments. Source-specific limitations include overlap between small same-center cohorts, surgery-confounded pubertal outcomes, selected gonadal tumour denominators, and abstract-only access for several older or registry studies. Direct human tissue mapping replaces the earlier claim that no such measurement exists. GeneReviews and StatPearls checks found no directly matching chapter.

Review mixed gonadal dysgenesis mechanisms, clinical scope and care · 2026-09-21T02:54:05Z · View source

Full disorder review against the matching deep-research report, generated references, the clinical review and international Turner guideline, and primary human gonadal FISH, clinical cohort, registry and developmental mouse evidence. Corrected the claim that human gonadal lineage mapping had not been performed; separated AMH, testosterone, Sertoli-function and spermatogenic mechanisms; removed unsupported population bands and surgery-confounded natural-history claims; corrected microarray sensitivity and Turner-with-Y distinctions; added specific clinical and histologic findings, individualized care and explicit model limitations. All 141 snippets verify against cached sources; schema and ontology validation pass, with causal-target/coarse/source-claim and snippet-ratchet checks passing. Independent peer mechanism/source audit found no unresolved substantive issue. GeneReviews/StatPearls online checks found no matching chapter. No reference caches were hand-edited and the frozen dataset cache was not accessed.

Create: 45,X/46,XY Mixed Gonadal Dysgenesis · 2026-08-29T20:10:17Z · View source

Created kb/disorders/45_X_46_XY_Mixed_Gonadal_Dysgenesis.yaml for MONDO:0015779. Deep research used the claude_code provider. preflight-dr returned SKIP because MONDO records no causal gene for this term, so disease identity was checked manually as the dismech-references skill requires: the report distinguishes MGD from 46,XY partial gonadal dysgenesis, Swyer syndrome and persistent Mullerian duct syndrome, and its top gene mentions are the sex-determination cascade SRY, SOX9, WNT4 and AMH, matching the MONDO definition of Y-chromosome mosaicism causing abnormal gonadal development. Term validation of the report flagged HP:0000850 as unresolved and four CURIEs the ontology names as something else, HP:0000053, HP:0000407, CL:0000501 and UBERON:0000991 in a mislabelled context; separately UBERON:0003508 proved to be pedal digit blood vessel rather than Mullerian duct and GO:0060065 uterus development rather than Wnt signalling in female gonad development. None of the flagged CURIEs was bound. Nine references cited, all cached; 50 of 50 snippets verified. Modelled as two parallel arms from the mosaicism, a gonadal arm through regional SRY dosage and an independent SHOX arm, with three discussions recording contested growth hormone efficacy, contested gonadal-position tumour risk, and the absence of any molecular profile of a human MGD gonad. No genetic section, no animal models and no has_subtypes, each with the reasoning recorded in notes.

Claude Code ▸

45,X/46,XY Mixed Gonadal Dysgenesis: Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 21 citations 2026-08-29T19:42:01.621445

45,X/46,XY Mixed Gonadal Dysgenesis: Comprehensive Research Report

1. Disease Information

Overview. 45,X/46,XY Mixed Gonadal Dysgenesis (MGD; also called 45,X/46,XY mosaicism) is a chromosomal disorder of sex development (DSD) caused by somatic mosaicism for a 45,X cell line and a 46,XY cell line arising from post-zygotic mitotic loss of the Y chromosome (or, more rarely, loss/structural rearrangement of the Y in a subset of cells). The defining anatomic feature is asymmetric gonadal development: classically a streak (undifferentiated fibrous) gonad on one side and a dysgenetic-to-normal testis on the other, with variably persistent Müllerian structures (hemi-uterus, fallopian tube remnant) reflecting incomplete anti-Müllerian hormone (AMH) action from the dysgenetic testis (Wikipedia; NORD; StatPearls — PMID:2294747, PMID:22605431, PMID:27064253).

Identifiers. - MONDO: MONDO:0015779 (45,X/46,XY mixed gonadal dysgenesis) — Monarch Initiative record aggregates OMIM/Orphanet/UMLS cross-references, though the live page content could not be fully retrieved in this session; verify the CURIE against the dismech term-validation pipeline before curation use. - Orphanet: A related, broader entry exists for "46,XY partial gonadal dysgenesis" (Orphanet ORPHA:251510); MGD itself (with the 45,X cell line) is generally indexed as a DSD-sex-chromosome-abnormality subtype distinct from pure 46,XY partial gonadal dysgenesis (PGD), which lacks the 45,X line (tp.amegroups.org case report; ScienceDirect "Genetics of 46,XY gonadal dysgenesis"). - MedGen: Concept ID CN279762 ("45,X/46,XY mixed gonadal dysgenesis") (NCBI MedGen). - GARD/NORD: Listed as a rare disease; GARD notes detailed symptom/cause/treatment fields are still sparse in that particular resource, underscoring reliance on primary literature (rarediseases.info.nih.gov). - ICD‑10/ICD‑11: Falls under Q99.1 (Chromosomal mosaic, sex chromosomes) / general "gonadal dysgenesis" categories in ICD-10-CM; ICD-11 codes it under disorders of sex development due to chromosome anomalies (LD2A.Y-type entries) — exact codes vary by coding system and were not independently confirmed against a primary ICD source in this pass. - Synonyms: X0/XY mosaicism; 45,X/46,XY mosaicism; mixed gonadal dysgenesis; asymmetric gonadal dysgenesis (Wikipedia; GARD).

Distinction from related entities. MGD (with a 45,X line) is distinguished from: - 46,XY partial gonadal dysgenesis (PGD): karyotype is pure 46,XY (no 45,X line), typically due to monogenic causes (SRY, NR5A1/SF1, MAP3K1 variants) rather than chromosomal mosaicism, and lacks Turner-syndrome stigmata (PMC3827999; NORD PGD page). - Complete gonadal dysgenesis (Swyer syndrome): 46,XY karyotype with bilateral streak gonads and female phenotype. - Persistent Müllerian Duct Syndrome (PMDS): normal testicular differentiation with isolated failure of AMH/AMHR2 signaling; gonadal histology is normal testis (not dysgenetic), distinguishing it from MGD on biopsy (PMC10411253).

Data provenance. Information in the literature is drawn overwhelmingly from aggregated case series and retrospective single/multi-center cohorts (e.g., 10–38 patient series) rather than large-scale EHR/registry studies, reflecting the rarity of the condition; a 2025 systematic narrative review (Giri et al., Clinical Endocrinology, PMID:41208147) synthesizes literature from 2000–2024.

2. Etiology

Disease Causal Mechanism

MGD arises from postzygotic mitotic non-disjunction or anaphase lag affecting the Y chromosome (or, less commonly, structural instability of a rearranged/dicentric Y) during early cleavage divisions, producing two (or more) cell lineages: 45,X and 46,XY, distributed in varying proportions across tissues, including the gonads themselves (Wikipedia, citing StatPearls mechanistic description; PMC11521797 case of idic(Y) mosaicism). This is fundamentally a somatic mosaicism / chromosomal instability mechanism rather than a single-gene Mendelian defect.

Molecular consequence. The presence or absence of a functional SRY-bearing Y chromosome in individual gonadal ridge cells determines whether that region differentiates toward testis (SRY⁺ Sertoli cell precursors activate SOX9, which establishes a SOX9–FGF9 positive-feedback loop while repressing the pro-ovarian WNT4/RSPO1/β-catenin pathway) or toward ovary/streak tissue (SRY-negative cells default toward WNT4-driven pre-granulosa fate) (PMC7291083; journals.biologists.com Sry critical-window study; PMC3735148). Because the two cell lines are admixed in variable ratios across and within the gonads, one gonad can differentiate predominantly along the testicular pathway (dysgenetic testis) while the contralateral gonad, dominated by the 45,X line, fails to organize (streak gonad) — the anatomic hallmark of MGD.

Y-chromosome structural abnormalities. A substantial subset of 45,X/46,XY cases actually involve a structurally abnormal Y (isodicentric Y, ring Y, Yp or Yq deletions) rather than a normal Y in the second line; such abnormal Y chromosomes are mitotically unstable and predispose to secondary loss of a normal-appearing X0 line, which is proposed as the origin mechanism for many 45,X/46,XY mosaics (PMC11521797; PMC3827999 on Y-microdeletion screening).

Genetic Risk Factors

SRY gene status/dosage: Presence and expression level of SRY on the retained Y chromosome is the principal driver of the degree of virilization; irregular/mosaic SRY and downstream SOX9 expression are implicated in the partial/mixed phenotype (WebSearch synthesis; PMC3055899 SOX9 regulation failure in 46,XY DSD).
Y-chromosome microdeletions (AZF regions): A high frequency of Y-chromosome microdeletions has been reported specifically in males with 45,X/46,XY mosaicism presenting with infertility, and in 46,XY PGD patients screened alongside 45,X/46,XY variants (PMC3827999; PMC7025455 "High frequency of Y chromosome microdeletions in male infertility patients with 45,X/46,XY mosaicism").
SHOX haploinsufficiency: The short-stature Turner-like phenotype is attributed to dosage loss of the SHOX gene (pseudoautosomal region) in the 45,X-predominant tissue fraction, analogous to classic Turner syndrome (Wikipedia; Giri et al. 2025 review).
DAX1 (NR0B1): Proposed as an X-linked "anti-testis" gene whose relative dosage in 45,X/46,XY mosaics may suppress testicular differentiation, contributing to the streak-gonad phenotype (WebSearch synthesis of NORD/Malacards content; note this remains a hypothesis rather than an established mechanism and should be treated cautiously in curation).
MAP3K1: Implicated in 13–18% of 46,XY gonadal dysgenesis broadly (not MGD-specific), acting via decreased SOX9 expression (StatPearls, PMC12757904 synthesis).
NR5A1 (SF1): A recognized monogenic cause of 46,XY PGD, occasionally invoked in the differential/overlap literature for atypical MGD-like presentations (PMC10754607 case report).

Environmental Risk Factors

No established environmental, toxin, or exposure-related risk factors were identified in the literature searched; MGD is understood as a stochastic, sporadic post-zygotic chromosomal event rather than an exposure-driven condition. Advanced parental age or other epidemiologic risk modifiers were not substantiated by the sources reviewed.

Protective Factors

No specific genetic or environmental protective factors against MGD were identified in the literature. This reflects the mosaic/stochastic mitotic origin of the condition rather than absence of research — a de novo somatic event has no established "susceptibility-lowering" allele analog.

Gene–Environment Interactions

Not applicable/not documented; no GxE data were found for this condition.

3. Phenotypes

The phenotypic spectrum of 45,X/46,XY mosaicism is exceptionally broad — from phenotypically normal males, through the full range of atypical/ambiguous genitalia, to phenotypically normal females with Turner-syndrome features (Wikipedia; PMC8418569; multiple case series PMID:3595646, PMID:10429013, PMID:25351753, PMID:26759215).

Genital/Reproductive Phenotypes

Phenotype	Frequency/Notes	Suggested HPO term
Ambiguous/atypical genitalia	Most reported presentation in DSD referral cohorts (~5–15% of atypical genitalia cases attributable to MGD)	HP:0000062 (Ambiguous genitalia)
Clitoromegaly	80% of initial presentations in one 10-patient cohort (PMC8418569)	HP:0000053 (Clitoral hypertrophy)
Hypospadias (perineal/scrotal)	Common in phallus-predominant presentations	HP:0000047 (Hypospadias)
Bifid/labioscrotal fusion	Reported in neonatal presentation spectrum	HP:0000048 (Bifid scrotum)
Micropenis / ventral chordee	Part of the atypical-genitalia spectrum	HP:0000054 (Micropenis)
Cryptorchidism / non-palpable gonad	Streak gonad classically non-palpable; dysgenetic testis variably descended	HP:0000028 (Cryptorchidism)
Persistent Müllerian structures (hemi-uterus, fallopian tube)	Reflects incomplete AMH action; ultrasound under-detects vs. laparoscopy (~40% miss rate by US)	HP:0000130 (Uterus present in an individual with a Y chromosome) / HP:0008734
Delayed puberty / primary amenorrhea	20% of one cohort; common in undiagnosed female-reared cases presenting in adolescence	HP:0000823 (Delayed puberty)
Infertility (near-universal)	Testicular insufficiency in 60–70% of males by third decade; spontaneous fertility "extremely rare"	HP:0000789 (Infertility)

Turner-like Somatic Phenotypes

Phenotype	Notes	HPO term
Short stature	Universal/near-universal finding; mean height SDS ≈ −3.77 in one cohort	HP:0004322 (Short stature)
Webbed neck	Classic Turner stigma	HP:0000465 (Webbed neck)
Shield chest / widely spaced nipples	Turner-overlap feature	HP:0000900 (Broad chest); HP:0006610
Cubitus valgus	Reported Turner stigma	HP:0002967 (Cubitus valgus)
High-arched palate	Reported	HP:0000218 (High palate)
Low posterior hairline	Reported (Johansen 2012)	HP:0002162 (Low posterior hairline)
Renal anomalies (horseshoe kidney, unilateral agenesis)	40% in one cohort (30% unilateral agenesis, 10% horseshoe kidney)	HP:0000085 (Horseshoe kidney); HP:0000122
Cardiac defects (bicuspid aortic valve, coarctation of aorta)	Documented in reviews, though absent in some smaller cohorts	HP:0001647 (Bicuspid aortic valve); HP:0001680 (Coarctation of aorta)
Sensorineural hearing loss	10% in one cohort	HP:0000407
Autoimmune thyroid disease (Hashimoto's/Graves')	40% in one cohort (autoimmune hypothyroidism + Graves')	HP:0000850 / HP:0100647
Mild intellectual disability, autism, facial dysmorphism	Reported in a minority (Johansen 2012 synthesis) — "Normal psychomotor development" also reported in other series, indicating this is not a core/consistent feature	HP:0001256; HP:0000717

Laboratory/Endocrine Phenotypes

Elevated gonadotropins (LH/FSH) — hypergonadotropic state when gonads are non-functional.
Low or low-normal testosterone in males, with blunted hCG-stimulated testosterone response reflecting Leydig cell dysfunction.
Low-to-normal AMH — toward the lower end of the male reference range, reflecting Sertoli cell dysfunction in the dysgenetic testis.

Onset, Severity, Progression

Onset: Congenital (present from birth in genital phenotype), but diagnosis timing varies: prenatal (amniocentesis), neonatal (atypical genitalia), or later childhood/adolescence (short stature, delayed puberty) when genitalia are near-normal at birth.
Severity/course: Highly variable and largely determined by the tissue distribution of the two cell lines; not a progressive degenerative disease per se, though gonadal function (Leydig/germ cell) can decline with age, and short stature/height-SDS reduction is progressive without growth hormone intervention.
Quality of life: Long-term sex-of-rearing satisfaction reported at 80–85% in reviewed cohorts, with persistent body-image and short-stature-related dissatisfaction as leading QoL detractors; ~50% of parents report unmet psychosocial-support needs during the neonatal/diagnostic period (PMC12757904/Giri et al. 2025).

4. Genetic/Molecular Information

Karyotype/chromosomal basis: 45,X/46,XY mosaicism (most common); rarer variants include 45,X/47,XYY and 45,X/46,X,idic(Y), 45,X/46,X,der(Y) (ring or isodicentric Y), and higher-order mosaics such as 45,X/46,XY/47,XYY (multiple case reports: PMC11521797, PMC3625110). Low-level mosaicism can be missed by standard peripheral-blood karyotyping and requires chromosomal microarray, FISH, or tissue-specific (buccal/skin/gonadal) analysis to detect.

Causal/associated genes: - SRY (Yp11.2) — master testis-determining switch; irregular expression across the mosaic cell population drives partial masculinization (no HGNC/OMIM number retrieved in this pass beyond general Y-linked SRY locus). - SOX9 — downstream of SRY, essential for Sertoli cell/testis-cord formation; failure of SOX9 up-regulation is implicated in 46,XY DSD broadly (PMC3055899). - AMH / AMHR2 — anti-Müllerian hormone and its receptor; reduced Sertoli-cell AMH output in the dysgenetic testis underlies persistent Müllerian structures (differentiates MGD from isolated PMDS, where testis histology is otherwise normal) (PMC10411253). - SHOX (Xp22.33/Yp11.32, pseudoautosomal region) — haploinsufficiency from the 45,X cell fraction drives short stature. - MAP3K1 — implicated in a minority (13–18%) of 46,XY gonadal dysgenesis cases generally, via decreased SOX9 expression. - NR5A1/SF1 — monogenic cause in overlapping 46,XY PGD phenotypes; occasionally cited in atypical MGD differential work-ups. - DAX1/NR0B1 — hypothesized X-linked antagonist of testis differentiation whose relative dosage may influence the streak-gonad phenotype in 45,X/46,XY mosaics (hypothesis-level; treat cautiously). - WT1 — associated with complete gonadal dysgenesis/absence in related but distinct syndromes (Denys-Drash/Frasier spectrum), cited as part of the broader gonadal-dysgenesis gene landscape rather than MGD-specific.

Variant classification/type: The primary "variant" is chromosomal-scale mosaicism/aneuploidy rather than a discrete point variant; secondary contributory findings (Y microdeletions in AZF regions, structural Y rearrangements) are structural/copy-number in nature. No systematic ClinVar/gnomAD allele-frequency data apply, since this is not a classic single-locus Mendelian disorder.

Somatic vs. germline origin: The 45,X/46,XY mosaicism itself is somatic in origin (post-zygotic mitotic error), not inherited in a Mendelian sense — recurrence risk to future pregnancies is not elevated by parental carrier status. This is a key genetic-counseling point.

Functional consequences: Loss-of-function-like effect at the tissue level — SRY⁺ cells drive testis differentiation while SRY-negative (45,X) cells default to streak/ovarian-like tissue; net phenotype reflects the spatial/proportional mixture rather than a single gain- or loss-of-function allele.

Epigenetics: No disease-specific DNA methylation/chromatin literature was identified in this search; this remains an underexplored area for MGD specifically (in contrast to better-studied epigenetic regulation of Sox9/enhancer elements in general testis-determination biology).

Chromosomal abnormality detail: Structural Y anomalies (isodicentric Y, ring Y) are mitotically unstable and are hypothesized as a common upstream cause generating the associated 45,X cell line via secondary loss during subsequent divisions (PMC11521797).

5. Environmental Information

No environmental toxin, occupational, radiation, or infectious contributing factors were identified in the literature for 45,X/46,XY MGD — consistent with its origin as a stochastic post-zygotic mitotic chromosomal error rather than an environmentally triggered condition. No lifestyle risk-factor or infectious-agent data apply. (This is a genuine absence of evidence in the literature searched, not merely an unresearched gap — the mitotic-error mechanism does not have an established environmental trigger analogous to, e.g., maternal age in meiotic non-disjunction trisomies.)

6. Mechanism / Pathophysiology

Causal Chain (Upstream → Downstream)

Initiating event (molecular/chromosomal): Post-zygotic mitotic non-disjunction or anaphase lag of the Y chromosome (often a structurally unstable Y — isodicentric/ring Y) during early cleavage divisions → generation of two coexisting cell lineages, 45,X and 46,XY, distributed stochastically across tissues including the bipotential gonadal ridge.
Gonadal ridge patterning (cellular, ~E10.5–E12.5 equivalent in human development): In SRY⁺ (46,XY) somatic-cell-dominant regions of the ridge, SRY expression in pre-Sertoli cells activates SOX9, establishing a SOX9–FGF9 positive-feedback loop that (a) drives Sertoli cell and testis-cord differentiation and (b) actively represses the pro-ovarian WNT4/RSPO1/β-catenin pathway. In SRY-negative (45,X-dominant) regions, the absence of this switch allows default WNT4-driven pre-granulosa-like differentiation, which under monosomy-X conditions fails to sustain a functional ovary and instead regresses to fibrous streak gonad tissue (PMC7291083; journals.biologists.com Sry critical-window paper; PMC3735148).
Asymmetric gonadal outcome (tissue level): Because the two cell lines are unevenly distributed left-to-right and within each gonadal primordium, one gonad differentiates along a (variably dysgenetic) testicular pathway while the contralateral gonad fails to organize — the defining streak gonad + dysgenetic/normal testis anatomy of MGD.
Sertoli/Leydig cell dysfunction (endocrine level): The dysgenetic testis has quantitatively reduced Sertoli cell mass, yielding low-to-low-normal AMH (insufficient to fully regress Müllerian ducts, hence persistent hemi-uterus/fallopian tube) and reduced Leydig cell steroidogenic capacity, yielding low/low-normal testosterone with blunted hCG-stimulated response — the proximate cause of incomplete virilization/ambiguous genitalia.
Systemic (organism level) consequences of the 45,X cell fraction: SHOX haploinsufficiency in 45,X-predominant tissue → short stature; broader Turner-like somatic phenotype (renal anomalies, cardiac defects, lymphatic-derived webbed neck, autoimmune thyroiditis) via mechanisms shared with classic Turner syndrome, though the degree of expression depends on the tissue-specific 45,X:46,XY ratio (mosaic "dilution" of the Turner phenotype).
Neoplastic transformation risk (downstream, age-dependent): Retained Y-chromosome material (specifically the GBY locus, containing TSPY, on the Y short arm — implicated generally in Y-bearing dysgenetic gonad tumorigenesis, though not explicitly detailed in the sources retrieved here) in a dysgenetic gonadal microenvironment predisposes resident primordial/immature germ cells to arrest and malignant transformation, driving the well-documented gonadoblastoma → dysgerminoma progression pathway, particularly in intra-abdominal (undescended) gonads (75% premalignant-neoplasm risk vs. 16% inguinal, 9% scrotal) (PMC12757904/Giri et al. 2025; PMID:31883875; PMID:27032613).

Cell Types Involved

Sertoli cells (dysfunctional/reduced in dysgenetic testis) — CL:0000216
Leydig cells (steroidogenically impaired) — CL:0000178
Primordial/immature germ cells (arrested, tumor-initiating population) — CL:0000670 / CL:0000586
Granulosa-like/pre-granulosa cells (in streak gonad remnant tissue) — CL:0000501 (approximate)
Gonadal stromal/supporting cells

Biological Processes (suggested GO terms)

Male sex determination: GO:0030238
Testis development: GO:0009888 / GO:0001708 (cell fate specification)
Sertoli cell differentiation: GO:0060008
Anti-Müllerian hormone signaling / Müllerian duct regression: GO:0001880 (Müllerian duct regression)
Wnt signaling pathway involved in female gonad development: GO:0060065
Germ cell development: GO:0007281
Positive regulation of transcription (SOX9-driven testis program): GO:0045893

Molecular Profiling

No disease-specific transcriptomic/proteomic/single-cell atlases for MGD gonadal tissue were identified in this search (a plausible knowledge gap — human dysgenetic-gonad single-cell profiling is more developed for Turner-syndrome ovaries and general DSD cohorts than for MGD specifically). Mouse single-cell gonadal atlases (from the SRY/SOX9/WNT4 mechanistic studies cited above) are the closest available molecular-profiling proxy and would need explicit HUMAN_MODEL_MISMATCH framing if cited for MGD curation, since murine gonadal-ridge chimera/knockout models are not MGD per se but rather models of the underlying testis-vs-ovary determination pathway.

7. Anatomical Structures Affected

Organ level: - Primary: Gonads (asymmetric — one streak, one dysgenetic/normal testis), internal genital ducts (Müllerian remnants: hemi-uterus, fallopian tube, prostatic utricle; Wolffian derivatives variably present), external genitalia (variable ambiguous phenotype). - Secondary/associated: Kidneys (horseshoe kidney, unilateral agenesis), heart/great vessels (bicuspid aortic valve, coarctation of aorta), thyroid (autoimmune thyroiditis/Graves'), skeletal system (short stature via SHOX, cubitus valgus), inner ear (sensorineural hearing loss). - Systems involved: Reproductive/endocrine (primary), renal, cardiovascular, musculoskeletal, immune (autoimmune thyroid disease).

Tissue/cell level: - Gonadal ridge-derived tissue: dysgenetic seminiferous tubules with reduced Sertoli/Leydig cell content on the testicular side; fibrous streak tissue (devoid of germ cells, composed of ovarian-type stroma) on the contralateral side. - Suggested UBERON terms: gonad (UBERON:0000991), testis (UBERON:0000473), ovary (UBERON:0000992), uterus (UBERON:0000995), Müllerian duct (UBERON:0003508), Wolffian duct/mesonephric duct (UBERON:0001301), kidney (UBERON:0002113), thyroid gland (UBERON:0002046).

Subcellular level: No MGD-specific subcellular pathology (e.g., organelle-level defect) was identified; the mechanism operates at the chromosomal/cell-fate-decision level rather than a subcellular organelle dysfunction.

Localization/laterality: By definition asymmetric/unilateral discordant gonadal differentiation is the hallmark finding (streak vs. testis, left vs. right variable), though bilateral streak or bilateral dysgenetic-testis variants also occur within the phenotypic spectrum.

8. Temporal Development

Onset: Congenital (chromosomal mosaicism established at the post-zygotic cleavage stage; gonadal/genital phenotype is present from fetal development), but clinical recognition spans the full life course — prenatal (incidental karyotype finding at amniocentesis), neonatal (atypical genitalia), childhood (short stature, incidentally discovered), or adolescence (delayed puberty, primary amenorrhea).
Progression: Not a classically "progressive" degenerative disease; however, individual components evolve with age — testicular (Leydig/germ cell) function commonly declines, with testicular insufficiency reported in 60–70% of males by the third decade; height-SDS deficit worsens over childhood without growth-hormone intervention; gonadal tumor risk rises with age (though cases before age 20 are described as rare, risk is cumulative and lifelong for retained dysgenetic gonadal tissue).
Disease course pattern: Largely stable/static with respect to the core chromosomal mosaicism, but the endocrine and oncologic sequelae are age-dependent and require lifelong surveillance.
Critical periods: The "mini-puberty" window (first ~3 months of life) is clinically important for assessing baseline Leydig cell (testosterone) function; the prenatal/early postnatal period is critical for sex-of-rearing and gonadectomy decision-making; puberty (age 11–13) is a critical window for hormone-replacement initiation and for gender-identity development/disclosure counseling.

9. Inheritance and Population

Epidemiology: - Incidence estimates range from 1 in 15,000 to 1 in 30,000 live births across sources (Wikipedia/StatPearls cite ~1/15,000; PMC12757904 cites the 1/15,000–1/30,000 range). - Among infants presenting with atypical/ambiguous genitalia, MGD accounts for ~5–15% of cases (Giri et al. 2025). - 45,X/46,XY mosaic is described as the most common karyotype underlying the mixed-gonadal-dysgenesis phenotype. - True population prevalence is likely underestimated because many individuals with near-normal male or female phenotypes are never karyotyped.

Inheritance pattern: Sporadic — arises from a post-zygotic somatic mitotic error, not inherited via a Mendelian mechanism; parental karyotypes are typically normal, and recurrence risk in subsequent pregnancies is not increased above general population risk. This is an important genetic-counseling distinction from single-gene 46,XY PGD causes (e.g., NR5A1, MAP3K1), which may have autosomal patterns.

Penetrance/expressivity: Effectively 100% "penetrant" in the sense that mosaicism is present from conception, but expressivity is extremely variable — phenotype is determined by the proportion and tissue distribution of the 45,X vs. 46,XY cell lines, which cannot be reliably predicted from a peripheral-blood karyotype or amniotic-fluid cell ratio alone (explicitly noted: "amniotic fluid 45,X cell proportion cannot predict phenotypic outcomes").

Founder effects/consanguinity/carrier frequency: Not applicable, given the somatic/sporadic mechanism.

Population demographics: No specific ethnic or geographic predilection was identified in the literature reviewed; cohorts span Danish (Johansen 2012), Chinese (PMC10154695, 38 patients), Brazilian (PMID:25351753, 14 patients), and other national referral-center series, suggesting a broadly similar global distribution, though systematic multi-population prevalence comparisons were not found.

Sex ratio: Not meaningfully applicable as a simple M:F ratio, since "sex" itself is the variable clinical outcome in this condition; cohorts show a spread across female-reared, male-reared, and intersex presentations (e.g., 9 female-reared : 1 male-reared in one 10-patient cohort, though this reflects referral/rearing patterns rather than an underlying biological ratio).

10. Diagnostics

Chromosomal/genetic testing: - QF-PCR: first-line rapid screen for SRY presence. - Standard peripheral-blood karyotype: confirms 45,X/46,XY mosaicism; sensitivity limited for low-level mosaicism. - Chromosomal microarray (CGH/SNP array): detects low-level mosaicism and submicroscopic Y copy-number variation missed by standard karyotype. - FISH: rapid (within 24h) detection of monosomy X; can be applied to buccal, skin, or gonadal tissue when blood karyotype is normal but clinical suspicion persists (tissue-specific mosaicism). - Y-chromosome microdeletion (AZF) screening: recommended in males with 45,X/46,XY presenting with infertility, given high reported frequency of microdeletions in this subgroup (PMC3827999, PMC7025455).

Imaging: - Pelvic ultrasound: gonadal localization, uterus/Müllerian structure identification (though ultrasound reportedly misses Müllerian remnants in ~40% of cases vs. 100% detection by laparoscopy). - Abdominal ultrasound: renal anomaly screening. - MRI: reserved for ultrasound-inconclusive cases. - Echocardiography: cardiac anomaly screening (bicuspid aortic valve, coarctation of aorta). - Laparoscopy: considered superior for definitive anatomic delineation and enables targeted gonadal biopsy/removal.

Endocrine evaluation: - Serum electrolytes, cortisol, 17-hydroxyprogesterone: to exclude congenital adrenal hyperplasia as an alternative/co-existing cause of atypical genitalia. - Testosterone (ideally within the "mini-puberty" window, first 3 months of life): indicates Leydig cell function. - hCG stimulation test: assesses testicular testosterone reserve outside the mini-puberty window or when baseline is low. - AMH: marker of testicular (Sertoli cell) tissue presence/function. - LH/FSH: elevation indicates a hypergonadotropic state from non-functional gonadal tissue.

Histopathology: Gonadal biopsy remains important for distinguishing MGD (streak + dysgenetic testis) from related entities (e.g., PMDS, where testicular histology is normal) and for detecting occult germ cell neoplasia in situ/gonadoblastoma.

Differential diagnosis: 46,XY partial gonadal dysgenesis (no 45,X line), Swyer syndrome (complete gonadal dysgenesis, bilateral streaks), persistent Müllerian duct syndrome, congenital adrenal hyperplasia (as an alternative cause of atypical genitalia), NR5A1-related DSD.

Screening: No population-level newborn screening program exists for MGD specifically (unlike, e.g., metabolic newborn screening panels); detection is via prenatal incidental karyotype finding, or postnatal clinical suspicion (atypical genitalia, short stature, delayed puberty) prompting targeted karyotyping.

11. Outcome/Prognosis

Gonadal malignancy: Lifetime risk estimated at 15–25%, with strong risk-stratification by gonadal location: ~75% premalignant-neoplasm risk for intra-abdominal (undescended) gonads, ~16% for inguinal, ~9% for scrotal position — underscoring why gonadal position drives management urgency (PMC12757904/Giri et al. 2025). Independent series report gonadal tumors (gonadoblastoma ± dysgerminoma) in ~18% of surgically assessed patients (6/34), rising to 37.5–54.5% in subgroups with significant genital ambiguity or female phenotype (PMID:31883875-related synthesis).
Testicular function: Testicular insufficiency develops in an estimated 60–70% of males by the third decade of life.
Fertility: Spontaneous fertility is "extremely rare"; assisted reproduction (testicular sperm extraction, gonadal tissue cryopreservation in prepubertal patients) is an emerging but still largely experimental option.
Growth/height: Progressive height-SDS reduction with age if untreated; recombinant human growth hormone therapy improves growth velocity and final height (reported improvement of 0.42 SDS), with response paralleling that seen in classic Turner syndrome; typically initiated age 4–6 years.
Metabolic/cardiovascular morbidity: A population-based study cited in the 2025 review identified a Turner-like long-term morbidity pattern — hypertension, dyslipidemia, and type 2 diabetes emerging by around age 40.
Psychosocial/gender outcomes: Long-term satisfaction with sex of rearing reported at 80–85%; gender incongruence prevalence reported at 12–15% in MGD cohorts; persistent body-image concerns (short stature prominent) are the most cited long-term dissatisfaction driver. A 2025 case-based ethics/psychology paper (PMID:40888655) specifically examines a child assigned female at birth who later expressed male gender identity, highlighting the complexity of early, potentially irreversible sex-assignment decisions.
Mortality: No MGD-specific mortality/survival statistics (e.g., 5-/10-year survival rates) were identified — consistent with this being primarily a developmental/endocrine/oncologic-risk condition rather than one with an intrinsically shortened lifespan, aside from the malignancy risk mitigated by gonadal surveillance/gonadectomy.

12. Treatment

Sex assignment/multidisciplinary management: Modern practice has shifted from historical universal female assignment with prophylactic gonadectomy toward individualized, patient/family-centered, multidisciplinary decision-making that weighs genital anatomy, internal reproductive structures, gonadal function, fertility potential, prenatal androgen exposure, malignancy risk, and psychosocial/cultural factors, with a general trend toward deferring irreversible interventions where feasible (PMC12757904/Giri et al. 2025).

Surgical management (NCIT-mappable): - Gonadectomy — bilateral for female-assigned patients with non-functional streak gonads (early childhood); early removal of a retained dysgenetic testis in most cases unless testosterone production is adequate and formal surveillance is feasible; preservation favored for a morphologically normal, fully descended testis (with lifelong self-exam/imaging surveillance). → NCIT:C15329 (Surgical Procedure) or a more specific gonadectomy/orchiectomy NCIT term if available. - Laparoscopic streak-gonad excision — preferred approach given malignancy risk. - Hypospadias repair — staged, typically after confirmation of male sex of rearing. → NCIT:C15329 / relevant urologic-procedure term. - Gonadal relocation (intra-abdominal gonad repositioned to labioscrotal fold) to facilitate examination/surveillance. - Clitoral recession — reported in female-reared cases with clitoromegaly. - Gonadal tissue cryopreservation — emerging fertility-preservation strategy performed at the time of gonadectomy in patients with retained germ cells.

Hormonal therapies (NCIT:C15986 Pharmacotherapy, generally): - Growth hormone (recombinant human GH): improves growth velocity/final height (paralleling Turner syndrome response); typical initiation age 4–6 years. - Puberty induction, males: low-dose intramuscular testosterone injections (every 4–6 weeks) with gradual dose escalation over several years; transdermal formulations for maintenance. - Puberty induction, females: low-dose transdermal or oral estradiol starting ~age 11–12, gradually increased over 2–3 years; progestogen added if breakthrough bleeding occurs and a uterus is present; long-term hormone replacement continued to approximate natural menopause age (~50 years).

Assisted reproduction: Testicular sperm extraction (TESE) reported in isolated cases; gonadal tissue cryopreservation for prepubertal fertility preservation is an active area of clinical development rather than standard-of-care.

Supportive/psychosocial care: Proactive psychological support for parents around diagnosis disclosure, and for patients around body image and evolving gender identity through childhood/adolescence, is increasingly emphasized given documented gaps in current provision (~50% of parents reporting unmet psychosocial-support needs).

Emerging/experimental approaches: - Biomarker-driven surveillance — circulating microRNA markers (notably miR-371a-3p) are being investigated as liquid-biopsy tools for early germ cell tumor detection, potentially allowing more conservative (gonad-sparing) surveillance strategies instead of universal prophylactic gonadectomy. - Shared decision-making tools — web-based decision aids for gonadal/genital surgery choices are in development and validation.

Treatment strategy/algorithm: Management is explicitly multidisciplinary team (MDT)-based (pediatric endocrinology, urology/surgery, genetics, psychology, and the family), with transition planning to adult care ideally beginning at age 12–13, and dedicated transition clinics or joint pediatric–adult MDT models cited as improving long-term follow-up adherence.

Reported treatment outcomes: In one 10-patient cohort, gonadectomy was followed by spontaneous partial regression of phallus size (0.5–1 cm reduction over 6 months–1 year) in female-reared cases; no patients in that cohort opted for GH therapy, illustrating real-world variability in uptake of available interventions.

13. Prevention

MGD arises from a sporadic post-zygotic somatic chromosomal event, so there is no established primary prevention (no known modifiable risk factor to intervene upon) — this parallels the absence of identified environmental/lifestyle risk factors in Section 5.

Secondary prevention (early detection/treatment): - Prenatal detection via amniocentesis karyotype (incidental finding, e.g., in the context of NIPT flagging or other indications) allows early counseling and postnatal targeted evaluation, though phenotype cannot be reliably predicted from amniotic-fluid cell-line ratios, which is a significant counseling limitation. - Postnatal clinical vigilance for atypical genitalia at birth, or short stature/delayed puberty in later childhood, prompts karyotype-based diagnosis.

Tertiary prevention (preventing complications in diagnosed individuals): - Gonadal malignancy prevention: risk-stratified gonadectomy or biomarker-based surveillance (see Treatment section) is the primary tertiary-prevention strategy, directly reducing progression from gonadoblastoma/germ cell neoplasia in situ to invasive dysgerminoma. - Growth hormone therapy as tertiary prevention of adult short stature. - Cardiovascular/renal/metabolic surveillance (echocardiography, renal imaging, blood pressure, lipid/glucose monitoring into adulthood) to preempt the Turner-like long-term morbidity pattern (hypertension, dyslipidemia, type 2 diabetes by ~age 40). - Autoimmune thyroid screening given the ~40% prevalence of autoimmune thyroid disease in some cohorts.

Genetic counseling: Central to prevention/family-planning discussion is communicating the sporadic, non-heritable nature of the mosaicism (low recurrence risk in future pregnancies) while managing the substantial uncertainty in prenatal phenotype prediction.

Screening programs: No population-based newborn or prenatal screening program specific to MGD exists; detection remains opportunistic (incidental prenatal karyotype, or postnatal clinical suspicion).

14. Other Species / Natural Disease

No literature was identified describing naturally occurring 45,X/46,XY mosaic gonadal dysgenesis as a spontaneous veterinary disease (e.g., in OMIA or companion-animal case series) in this search pass — this is a plausible gap rather than a confirmed absence, and a dedicated OMIA/veterinary-literature search would be needed to confirm whether analogous XX/XY chimerism-associated intersex conditions are documented in domestic species (freemartinism in cattle, driven by placental blood-chimerism rather than post-zygotic mosaicism, is a related but mechanistically distinct veterinary phenomenon and was not directly evaluated here).

Comparative biology: The core testis-determination pathway (SRY → SOX9 → FGF9, antagonized by WNT4/RSPO1/β-catenin) is evolutionarily conserved across mammals, and the mechanistic insight into MGD's cellular basis is drawn substantially from mouse developmental biology (see Section 15), rather than from naturally occurring disease in other species.

Zoonotic potential / transmission: Not applicable — MGD is a non-infectious, developmental chromosomal condition.

15. Model Organisms

No direct animal model of 45,X/46,XY mosaic MGD (i.e., a mouse engineered or arising spontaneously with somatic X0/XY mosaicism reproducing asymmetric gonadal dysgenesis) was identified in this search. Instead, the relevant model-organism literature addresses the underlying testis-determination pathway that MGD's asymmetric SRY-mosaic gonads perturb:

Sry/Sox9/Wnt4 mouse genetic models: Studies of Sox9 conditional knockout, Wnt4 knockout, and Sox9;Wnt4 double-mutant mice define how SRY-driven SOX9 activity antagonizes WNT4/RSPO1/β-catenin signaling to commit supporting cells to a testicular vs. ovarian fate (PMC7291083, "Mouse Gonad Development in the Absence of the Pro-Ovary Factor WNT4 and the Pro-Testis Factor SOX9," PMID:32365547). Key finding: Sox9 deletion in XY gonads causes ovarian-like development with ectopic WNT/β-catenin signaling, and SRY-positive supporting-cell precursors can adopt a female-like (pre-granulosa) identity; SOX9 is required for early male-supporting-cell specification independently of its role repressing RSPO1/WNT4/β-catenin.
Sry timing/chimera studies: "A critical time window of Sry action in gonadal sex determination in mice" (journals.biologists.com) defines the developmental window (~E10.5–E12.5) during which Sry must act to commit the gonad to a testicular fate — directly relevant to understanding how variable SRY⁺ cell proportion/timing in a mosaic human gonad could yield partial/asymmetric differentiation.
Other XY sex-reversal mouse models (cited peripherally in search results, not detailed here): Nedd4 loss-of-function causing complete XY gonadal sex reversal (PMC8786929); Fgfr2 "hobbyhorse" mutant causing complete XY gonadal sex reversal (PMC4067367) — these illustrate the broader genetic network in which SRY/SOX9 operate but are models of complete, not mosaic/asymmetric, sex reversal, and are not direct models of the human mosaic 45,X/46,XY karyotype.

Model limitations for dismech curation purposes: None of the mouse models identified reproduce the defining somatic chromosomal mosaicism of human MGD (they are typically full-body monogenic knockouts, not mitotic-mosaic chimeras of 45,X vs. 46,XY cell lines). Any pathophysiology node curated from these mouse studies should be flagged with evidence_source: MODEL_ORGANISM and, given the mechanistic (not mosaic-karyotype) nature of the models, likely warrants a HUMAN_MODEL_MISMATCH discussion node under dismech's schema — the models establish the SRY/SOX9/WNT4 causal logic convincingly, but do not themselves recapitulate the human mosaic/asymmetric-gonad phenomenon.

Applications: These models are primarily used to dissect the transcriptional antagonism between testis- and ovary-determining pathways at the cell-fate-decision level, which is directly explanatory (if not literally recapitulative) for why a mosaic human gonad can differentiate asymmetrically depending on local SRY⁺ cell fraction and timing.

Summary of Key Ontology-Term Suggestions for Curation

Category	Suggested terms
MONDO	MONDO:0015779 (verify via `just validate-terms` before use)
HPO (phenotype)	HP:0000062 Ambiguous genitalia; HP:0000053 Clitoral hypertrophy; HP:0000047 Hypospadias; HP:0000028 Cryptorchidism; HP:0004322 Short stature; HP:0000465 Webbed neck; HP:0002967 Cubitus valgus; HP:0000085 Horseshoe kidney; HP:0001647 Bicuspid aortic valve; HP:0001680 Coarctation of aorta; HP:0000823 Delayed puberty; HP:0000789 Infertility; HP:0000850/HP:0100647 Autoimmune thyroid disease
GO (biological process)	GO:0030238 Male sex determination; GO:0060008 Sertoli cell differentiation; GO:0001880 Müllerian duct regression; GO:0060065 Wnt signaling involved in female gonad development; GO:0007281 Germ cell development
CL (cell type)	CL:0000216 Sertoli cell; CL:0000178 Leydig cell; CL:0000670/CL:0000586 Primordial/germ cell
UBERON (anatomy)	UBERON:0000991 gonad; UBERON:0000473 testis; UBERON:0000992 ovary; UBERON:0000995 uterus; UBERON:0003508 Müllerian duct; UBERON:0001301 mesonephric (Wolffian) duct
HGNC (genes)	SRY; SOX9; AMH; AMHR2; SHOX; MAP3K1; NR5A1; NR0B1 (DAX1); WT1
NCIT (treatment)	NCIT:C15329 Surgical Procedure (gonadectomy, hypospadias repair); NCIT:C15986 Pharmacotherapy (testosterone/estradiol replacement, GH therapy)

Notable evidence gaps for curation: (1) no MGD-specific molecular/single-cell profiling of human dysgenetic gonadal tissue was located; (2) the DAX1-suppression hypothesis and several Turner-overlap CNS features (mild intellectual disability, autism) are reported inconsistently across cohorts and should be curated with appropriate frequency/directness caveats; (3) no dedicated animal model reproduces the mosaic karyotype itself, only the downstream SRY/SOX9/WNT4 pathway logic — curate any mouse-derived pathophysiology nodes as MODEL_ORGANISM evidence with a HUMAN_MODEL_MISMATCH discussion where appropriate; (4) OMIM/Orphanet/ICD numeric identifiers should be independently re-verified against primary sources (OMIM.org, Orphanet, WHO ICD-11 browser) before being written into a Disease.mappings block, since this session's GARD/Monarch fetches did not return the specific codes.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	29
Resolved	29
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	29
On topic	18
Off topic	0

All extracted references resolved successfully.

Term Validation

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

Outcome	Count
Terms checked	51
Resolved	49
Unresolved (possible confabulation)	1
Obsolete	0
Unverifiable	1
Terms whose name was checked	20
Terms named correctly	14
Terms named as a different term	5
Terms whose name is worth a second look	1

Terms the report names something else

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

MONDO:0015779 (4 mentions) - the report calls it "45,X/46,XY mixed gonadal dysgenesis", "verify via just validate-terms before use"; MONDO calls it 45,X/46,XY mixed gonadal dysgenesis
HP:0000053 (2 mentions) - the report calls it "Clitoral hypertrophy"; HP calls it Macroorchidism
HP:0000407 (1 mention) - the report calls it "10% in one cohort"; HP calls it Sensorineural hearing impairment
CL:0000501 (1 mention) - the report calls it "approximate"; CL calls it granulosa cell
UBERON:0000991 (2 mentions) - the report calls it "Suggested UBERON terms: gonad"; UBERON calls it gonad

Unresolved terms

These identifiers do not exist in an ontology that resolved other terms from the same prefix, so they were most likely invented:

HP:0000850 (2 mentions) - HP does not contain this term

Terms whose name is worth a second look

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

GO:0001880 (2 mentions) - the report calls it "Müllerian duct regression"; GO calls it Mullerian duct regression

Terms named inconsistently

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

MONDO:0015779 - called "45,X/46,XY mixed gonadal dysgenesis", "verify via just validate-terms before use"

Prefixes with no resolver

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

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Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Histopathology

Pathograph

Phenotypes

Medical Actions

Biochemical Markers

Diagnosis

Progression

Prevalence

Differential Diagnoses

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

45,X/46,XY Mixed Gonadal Dysgenesis: Comprehensive Research Report

1. Disease Information

2. Etiology

Disease Causal Mechanism

Genetic Risk Factors

Environmental Risk Factors

Protective Factors

Gene–Environment Interactions

3. Phenotypes

Genital/Reproductive Phenotypes

Turner-like Somatic Phenotypes

Laboratory/Endocrine Phenotypes

Onset, Severity, Progression

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal Chain (Upstream → Downstream)

Cell Types Involved

Biological Processes (suggested GO terms)

Molecular Profiling

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Ontology-Term Suggestions for Curation

Reference Validation

Term Validation

Terms the report names something else

Unresolved terms

Terms whose name is worth a second look

Terms named inconsistently

Prefixes with no resolver