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Classifications

Harrison's Part

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Inheritance

1

Autosomal recessive HP:0000007

Biallelic GGPS1 missense variants, homozygous in consanguineous families and compound heterozygous elsewhere. Heterozygous parents are unaffected, and heterozygous carriers of loss-of-function GGPS1 alleles are present in gnomAD and expected to be asymptomatic.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Here, we report specific mutations in the gene GGPS1 coding for the enzyme geranylgeranyl diphosphate synthase in 11 patients from 6 families, causing a highly distinctive syndrome of early onset muscular dystrophy combined with congenital sensorineural hearing loss and primary ovarian..."

Establishes biallelic GGPS1 genotypes across six independent families as the cause of the syndrome.

PMID:32403198 SUPPORT Human Clinical

"Rare heterozygous carriers for loss‐of‐function variants in GGPS1 are listed in gnomAD and should therefore be asymptomatic."

Supports the recessive model, and specifically that a single defective allele is not sufficient to cause this disease.

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Discussions and Knowledge Gaps

5

Why does a partial deficit of a universally required lipid modification produce disease in skeletal muscle, cochlea and ovary and spare everything else?

KNOWLEDGE GAP tissue_selectivity_of_prenylation_failure

Attached to

pathophysiology#Deficient Protein Geranylgeranylation of Small GTPases pathophysiology#Cochlear Sensory Failure

Protein geranylgeranylation is required in every cell, and more than a hundred human proteins are predicted substrates, yet these patients have no cardiac, cognitive, haematological or immune phenotype at all. Three explanations are on the table and none has been tested. The first is threshold: muscle, cochlear hair cells and oocytes may simply have the highest demand for prenylated Rab and Rho GTPases, so a 50% deficit crosses a threshold there and nowhere else. The second is that the disease alleles do not act through bulk catalytic output at all -- P15S has wild-type activity and still causes the disease, all the alleles sit outside the catalytic barrel, and the affected domain is conserved in animals but not plants -- so what fails may be a specific protein-protein interaction or a subcellular localisation of GGPPS in those tissues. The third is developmental timing, since Ggps1 is most densely expressed in the embryonic gonad and diffusely in the developing cochlea. Distinguishing these would change what a therapy should aim at.

Proposed experiments

Comparative prenylome and GGPP quantification across affected and unaffected tissues

ggps1_tissue_prenylome

Quantify geranylgeranyl pyrophosphate and the prenylated proteome in myotubes, cochlear organoids or hair-cell-like cells, oocytes or granulosa cells, and an unaffected control tissue such as fibroblasts or cardiomyocytes, all derived from patient induced pluripotent stem cells alongside isogenic corrected controls.

Would support

pathophysiology#Deficient Protein Geranylgeranylation of Small GTPases

Supporting outcome

A prenylation deficit that is selectively larger, or affects a distinct substrate set, in the three affected lineages than in unaffected ones, which would support the threshold or substrate-specificity model.

Refuting outcome

An equal prenylation deficit across affected and unaffected lineages, which would move the explanation away from prenylation stoichiometry entirely and towards a non-catalytic function of GGPPS.

Has the prenylation defect that this entry's mechanism depends on ever been demonstrated in a patient with this syndrome?

KNOWLEDGE GAP unconfirmed_prenylation_deficit_in_patients

Attached to

pathophysiology#Geranylgeranyl Pyrophosphate Depletion pathophysiology#Deficient Protein Geranylgeranylation of Small GTPases

No. This is the most important caveat in the entry and it is easy to lose, because the biochemistry is so tidy. No geranylgeranyl pyrophosphate measurement has been reported in any tissue or cell from an affected individual, and the discovery paper states in its own discussion that it could not find a consistent change in the small GTPases or in the overall prenylome of patient cells. The chain from reduced enzyme activity to deficient prenylation is therefore an inference from enzymology and from mouse work in a different genotype, which is why those two nodes carry `mechanism_confidence: PROVISIONAL` and `HYPOTHETICAL` and why the negative result is curated as a REFUTE evidence item rather than left out. The alternative it leaves open -- that the disease alleles disrupt a localised or interaction-dependent function of GGPPS rather than the cell's bulk GGPP supply -- is supported by the P15S allele, which has normal catalytic activity.

Proposed experiments

Direct measurement of GGPP and Rab prenylation in patient muscle

ggps1_patient_ggpp_assay

Measure geranylgeranyl pyrophosphate, farnesyl pyrophosphate and the unprenylated fraction of Rab and Rho GTPases by mass spectrometry and by in-vitro prenylation assay in muscle biopsy tissue from genotyped patients against age-matched controls, with sufficient replication to detect the modest deficit the enzymology predicts.

Would support

pathophysiology#Geranylgeranyl Pyrophosphate Depletion

Supporting outcome

Reduced GGPP and an increased unprenylated fraction of Rab and Rho GTPases in patient muscle, which would convert the central nodes of this mechanism from inference to observation.

Refuting outcome

Normal GGPP pools and normal prenylation in patient muscle, which would refute the bulk-depletion model outright and redirect the mechanism towards a non-catalytic or localisation-dependent function of the enzyme.

Can any animal model reproduce this syndrome, given that the mouse dies in utero from an allele a human tolerates into adulthood?

HUMAN MODEL MISMATCH no_viable_animal_model

Attached to

animal_models#Ggps1 p.Tyr259Cys homozygous knock-in mouse pathophysiology#Myofiber Degeneration with Disordered Autophagy

The mismatch is stark and quantitative. Homozygous Y259C mice are developmentally delayed from embryonic day 10.5 and are dead by 13.5, while the human compound heterozygotes carrying that same allele walked independently at eighteen months and survived into their twenties. The mouse is therefore not merely a poor model but an inverted one, and the authors say directly that it left them unable to do mechanistic work relevant to the human phenotype. Everything that is known about mechanism in this disease consequently comes from patient-derived cells or from mouse models of a different genotype in a different tissue. What is missing is a milder allelic series -- a knock-in of R261H, which produces the mildest human phenotype, or a hypomorphic allele engineered to leave more residual activity -- and tissue-restricted conditional deletions in muscle and cochlea to match the ovarian one that already exists.

Proposed experiments

Milder Ggps1 knock-in allele plus muscle- and cochlea-restricted conditional knockouts

ggps1_mild_allele_and_conditional_series

Generate homozygous knock-in mice carrying the human R261H allele, and separately cross the existing floxed Ggps1 allele to muscle-restricted and hair-cell-restricted Cre drivers, then phenotype for the human-relevant endpoints: strength and creatine kinase, muscle histology including autophagic and mitochondrial ultrastructure, auditory brainstem responses, and ovarian follicle counts.

Would support

pathophysiology#Myofiber Degeneration with Disordered Autophagy

Supporting outcome

Viable R261H homozygotes with a slowly progressive dystrophy and hearing loss, or tissue-restricted knockouts reproducing the muscle and cochlear phenotypes, either of which would give the field a system in which mechanism and therapy can be tested.

Refuting outcome

R261H homozygotes that are again embryonic lethal or, at the other extreme, entirely unaffected, which would suggest the mouse cannot be made to occupy the narrow window the human disease sits in and would push modelling towards human stem-cell systems.

Does GGPS1 deficiency impair male reproductive function, as the ovarian arm and the mouse expression data would predict?

KNOWLEDGE GAP unexamined_male_reproductive_involvement

Attached to

phenotypes#Primary Ovarian Insufficiency

The disease is defined in part by primary ovarian insufficiency, so the symmetric question in males is the obvious one, and nobody has asked it. The founding cohort reports that none of its five adult male patients has had children, but states in the same breath that no andrological examination was obtained -- so the observation is consistent with an unrecognised gonadal arm and equally consistent with five men who have not tried. It cannot presently distinguish the two. This is recorded as a gap rather than as a phenotype because curating childlessness as evidence of infertility would be exactly the inference the authors declined to make.

Proposed experiments

Andrological assessment of adult male patients

ggps1_male_gonadal_assessment

Semen analysis, testicular ultrasound, and gonadotrophin and testosterone measurement in postpubertal male patients, compared against the age-matched normal ranges, with the same follicle-equivalent endpoints the ovarian arm uses where an analogue exists.

Would support

phenotypes#Primary Ovarian Insufficiency

Supporting outcome

Impaired spermatogenesis or a hypergonadotropic pattern in affected males, which would recast the ovarian phenotype as one arm of a general gonadal involvement.

Refuting outcome

Normal semen parameters and normal gonadotrophins, which would make the ovarian involvement genuinely sex-specific and sharpen the tissue-selectivity question the entry already carries.

Is there a metabolite or pathway intervention that could bypass the GGPS1 block, and has anything been tried?

KNOWLEDGE GAP no_directed_therapy

Attached to

treatments# pathophysiology#Geranylgeranyl Pyrophosphate Depletion

Very little has been tried, and the arithmetic of the pathway is discouraging in a specific way. The block here sits below the branch point, so supplying mevalonate -- the approach that produced measurable benefit in the one treated patient with the upstream HMGCR disease -- would not bypass it. The obvious candidate is geranylgeraniol, the alcohol precursor of GGPP, which reverses the fiber-type loss of muscle-specific Hmgcr knockout mice and is the exact metabolite this enzyme fails to make enough of; it has never been tested in a GGPS1 patient or model. The one metabolite that has been tried, coenzyme Q10, produced no improvement in the single patient given it, and muscle coenzyme Q10 was normal in another patient, so the ubiquinone branch is probably not where the disease sits. Any trial would also have to confront the fact that the prenylation deficit it is meant to correct has not yet been demonstrated in a patient.

Proposed experiments

Geranylgeraniol rescue in patient-derived myotubes and in a conditional Ggps1 model

ggps1_geranylgeraniol_preclinical

Test whether geranylgeraniol supplementation restores membrane resealing kinetics in the patient-derived MyoD-converted myotube laser-injury assay, and whether it rescues the muscle phenotype of a muscle-restricted conditional Ggps1 knockout, before any consideration of human use.

Would support

pathophysiology#Geranylgeranyl Pyrophosphate Depletion

Supporting outcome

Normalisation of membrane resealing in patient myotubes and of the muscle phenotype in the conditional knockout, which would both confirm GGPP depletion as the operative lesion and identify a candidate therapy.

Refuting outcome

No rescue by geranylgeraniol despite adequate cellular uptake, which would argue that the disease alleles act through something other than the cell's bulk GGPP supply and would close off the most obvious therapeutic route.

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Pathophysiology

8

Biallelic Hypomorphic GGPS1 Missense Variants

Mechanism confidence: Established

All reported disease alleles are missense. In the founding cohort four of the five clustered in a five-amino-acid stretch at the start of the eleventh alpha-helix, on the outward-facing surface of the hexamer rather than in the catalytic barrel, and the fifth (P15S) sits in the helix involved in assembling the hexamer. The alleles are hypomorphic rather than null: they leave measurable enzyme activity, and a complete loss of GGPPS is incompatible with multicellular life, so a biallelic null genotype is not expected to be seen in a living patient.

Genetic context GGPS1 hgnc:4249 allele_type: SNV variant_origin: GERMLINE functional_impact_category: PARTIAL_LOSS_OF_FUNCTION

Reported genotypes are homozygous missense in consanguineous families and compound heterozygous missense elsewhere. No biallelic null genotype has been reported.

Downstream

Reduced Geranylgeranyl Diphosphate Synthase Activity The missense substitutions reduce the catalytic output of the enzyme they sit in.

Show evidence (3 references)

PMID:32403198 SUPPORT Human Clinical

"The pathogenic variants fell within a specific 5 amino acid region toward the C terminus around the start of helix 11, with as of yet unclear function"

Establishes the narrow positional clustering of the disease alleles outside the catalytic core.

PMID:32403198 SUPPORT In Vitro

"The mutations do not abolish enzymatic activity of this essential enzyme, but with a highly distinctive genotype/phenotype correlation define the mevalonate pathway as essential for muscle, hearing, and endocrine functions."

The authors' own statement that the alleles are hypomorphic rather than amorphic, which is the basis for the PARTIAL_LOSS_OF_FUNCTION classification.

PMID:32403198 SUPPORT Other

"Organism‐wide complete inactivation of GGPPS function is not compatible with multicellular survival."

Supports the constraint that a surviving genotype must retain partial activity, which is why every reported allele is missense.

Reduced Geranylgeranyl Diphosphate Synthase Activity

Mechanism confidence: Established

Recombinant mutant enzymes retain roughly 70 to 85% of wild-type activity, and GGPPS activity measured in patient-derived myoblasts is about half that of pooled controls. The deficit is therefore partial in both a purified and a cellular assay, which is consistent with the position of the variants outside the catalytic barrel and is the quantitative basis for calling the disease a hypomorphic state rather than an enzyme deficiency in the classical inborn-error sense.

geranylgeranyl diphosphate synthase activity GO:0004311 ↓ DECREASED

Downstream

Geranylgeranyl Pyrophosphate Depletion GGPPS catalyses the only route from farnesyl pyrophosphate to geranylgeranyl pyrophosphate, so reduced activity reduces the product.

Show evidence (2 references)

PMID:32403198 SUPPORT In Vitro

"consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"

Quantifies the residual activity of the recombinant disease alleles.

PMID:32403198 SUPPORT In Vitro

"We found that enzymatic activity in samples pooled from 4 patients (Patients P1, P2, P6, and P8) was decreased to about 50% of the activity in a pooled normal control sample."

The same deficit measured in patient-derived myogenic cells rather than in recombinant protein, which is the closer approximation to the tissue in which the disease is expressed.

Geranylgeranyl Pyrophosphate Depletion

Mechanism confidence: Provisional

Reduced GGPPS activity is taken to lower the cellular geranylgeranyl pyrophosphate pool. This step is inferred rather than measured: no GGPP measurement has been reported in tissue or cells from a patient with this syndrome. It is marked provisional for that reason. Independent support that GGPP depletion is a mechanistically consequential state in muscle comes from mouse work on the upstream enzyme HMG-CoA reductase, where the myopathy of HMGCR deficiency is attributed to GGPP depletion.

geranylgeranyl diphosphate biosynthetic process GO:0033386 ↓ DECREASED isoprenoid biosynthesis GO:0008299 ↓ DECREASED

Downstream

Deficient Protein Geranylgeranylation of Small GTPases GGPP is the lipid donor for geranylgeranylation, so its depletion limits the modification.

Show evidence (1 reference)

PMID:42323079 SUPPORT INDIRECT Model Organism

"Our findings demonstrate that myopathy induced by HMGCR deficiency is primarily driven by GGPP depletion in a mouse model."

This result is about HMGCR, not GGPS1: it concerns mice lacking the rate-limiting enzyme two steps upstream, and it is cited here only to establish that depletion of GGPP is by itself sufficient to cause myopathy. It says nothing about GGPP levels in GGPS1 patients.

Deficient Protein Geranylgeranylation of Small GTPases

Mechanism confidence: Hypothetical

The proposed proximate lesion: too little GGPP to geranylgeranylate the Rab and Rho/Rac family GTPases that require it for membrane anchoring, with predicted consequences for autophagic and endosomal trafficking, mitochondrial dynamics and actin regulation. This node is the weakest link in the chain and is marked hypothetical deliberately. The discovery paper proposes it as a prediction, and reports in the same discussion that it could not find a consistent change in the small GTPases or the prenylome of patient cells. The best direct support is from mouse oocytes, where selective GGPP depletion demonstrably inhibits Rho GTPase geranylgeranylation.

protein geranylgeranylation GO:0018344 ↓ DECREASED protein prenylation GO:0018342 ↓ DECREASED

Animal models

Oocyte-specific Ggpps conditional knockout mouse Mouse recapitulates The one system in which the prenylation step this entry's mechanism turns on has actually been shown to fail: GGPP depletion inhibits Rho GTPase geranylgeranylation and its GTPase activity.

Downstream

Impaired Sarcolemmal Membrane Repair Membrane resealing depends on vesicle trafficking driven by prenylated Rab GTPases; which Rab is limiting here is not established.

Ovarian Follicle Depletion In mouse oocytes the same prenylation deficit blocks the primary-to-secondary follicle transition through loss of Rho GTPase geranylgeranylation.

Cochlear Sensory Failure Asserted only as the route from the shared molecular lesion to the auditory phenotype. Nothing is known about which prenylated protein or which cochlear cell type is involved.

Show evidence (4 references)

PMID:32403198 SUPPORT Other

"Possible downstream effects of GGPPS dysfunction and thus GGPP deficiency would be predicted to include impaired geranylgeranylation of small GTPases of the Rab, and Rho/Rac families with consequences on organelles involved in autophagy (such as Rabs23/24/7b), mitochondrial fission and fusion..."

The authors' predicted downstream mechanism, quoted as the prediction it is. It names the GTPase families and the cellular processes this node claims are affected.

PMID:32403198 REFUTE In Vitro

"In ongoing work, however, we have not yet been able to pinpoint a consistent change in the small GTPases or in the overall prenylome of the cells (not shown)."

The same paper's negative result. A deficient-prenylation node predicts a measurable change in prenylated GTPases in patient cells, and none was found; this is recorded as a refutation rather than omitted, because it is the reason the node is marked hypothetical.

PMID:28072828 SUPPORT INDIRECT Model Organism

"oocyte geranylgeranyl diphosphate (GGPP), a metabolic intermediate involved in protein geranylgeranylation, is required to establish the oocyte-granulosa cell communication."

Mouse evidence that GGPP-dependent geranylgeranylation is a real and non-redundant requirement in at least one of the three affected tissues.

+ 1 more reference

Impaired Sarcolemmal Membrane Repair

Mechanism confidence: Established

Patient-derived myoblasts and myotubes reseal a focal laser wound more slowly than controls and are about twice as likely to fail to reseal at all. This is the only cellular phenotype demonstrated directly in patient material, and it is the mechanistic bridge from a prenylation defect to a dystrophy: repeated failure of membrane repair is the same final pathway that makes dysferlinopathy a muscular dystrophy, reached from a metabolic rather than a structural lesion.

patient-derived MyoD-converted myoblast CL:0000515

plasma membrane repair GO:0001778 ↓ DECREASED

Experimental models

Patient-derived MyoD-converted myoblasts and myotubes with laser membrane injury PRIMARY CELL CULTURE Reproduces, in cells carrying the patients' own genotypes, a delay in resealing the wounded plasma membrane and a roughly twofold increase in the proportion of cells that fail to reseal at all.

Downstream

Myofiber Degeneration with Disordered Autophagy Failure to reseal the wounded sarcolemma drives the cycle of fiber damage, degeneration and regeneration that defines a dystrophy.

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"We observed greater dye entry, indicating a poor cell membrane repair, in both the patient myoblasts and myotubes as compared to the healthy controls"

The direct measurement of delayed membrane resealing in patient myogenic cells.

Myofiber Degeneration with Disordered Autophagy

Mechanism confidence: Established

Muscle shows a dystrophic process -- degeneration, regeneration and internalised nuclei -- with two additional ultrastructural features that a purely membrane-centred dystrophy would not predict: excess autophagic material, including myeloid bodies and positive LC3B staining, and enlarged though structurally normal mitochondria. Whether the autophagic and mitochondrial changes are a second consequence of failed Rab-dependent trafficking or a downstream response to chronic fiber injury is not established. Fatty infiltration is visible on muscle MRI, with relative sparing of rectus femoris, sartorius and gracilis and conspicuously asymmetric involvement.

skeletal muscle fiber CL:0008002

autophagy GO:0006914 ↑ INCREASED

Animal models

Ggps1 p.Tyr259Cys homozygous knock-in mouse Mouse fails to recapitulate Homozygous animals die as embryos and never develop a postnatal muscular dystrophy, so no muscle phenotype, hearing phenotype or ovarian phenotype can be observed.

Downstream

Proximal Muscle Weakness Loss of contractile tissue in the limb-girdle muscles produces the weakness.

Elevated Serum Creatine Kinase Ongoing myofiber breakdown releases creatine kinase into the circulation.

Respiratory Insufficiency The same process involves the respiratory musculature and determines survival.

Scoliosis Weakness of the axial musculature allows progressive spinal deformity.

Joint Contractures Contractures follow the weakness and the immobility it imposes.

Show evidence (3 references)

PMID:32403198 SUPPORT Human Clinical

"Histology was dystrophic, with evidence of degeneration and regeneration and internalized nuclei."

Establishes the dystrophic tissue process on biopsy in nine patients.

PMID:32403198 SUPPORT Human Clinical

"Electron microscopy revealed ultrastructural evidence of enlarged but structurally normal mitochondria (Patient P8) as well as evidence of excess autophagic material (Patients P1 and P8; Fig 2)."

The ultrastructural autophagic and mitochondrial findings that this node names alongside the dystrophic change.

PMID:32403198 SUPPORT Human Clinical

"Whole‐body muscle magnetic resonance imaging was performed in Patients P4–P6 and demonstrates variable increase in T1 signal in select muscles, resulting from fatty infiltration and thus consistent with an underlying muscular dystrophy"

Imaging evidence of fatty replacement, the tissue-level correlate of chronic fiber loss.

Ovarian Follicle Depletion

Mechanism confidence: Provisional

The ovarian arm. In mouse, depleting GGPP selectively in oocytes blocks the primary-to-secondary follicle transition, impairs granulosa cell proliferation and causes near-total follicle loss with subfertility, and the defect is reversed by supplying GGPP. Nothing equivalent has been measured in a human with this syndrome: the human evidence is the clinical and hormonal phenotype, not ovarian histology. Ggps1 is expressed most densely in germ cells and embryonic gonad cells in the mouse E14.5 female gonad, which is at least consistent with an early follicular lesion.

oocyte CL:0000023 granulosa cell CL:0000501

ovarian follicle development GO:0001541 ↓ DECREASED

Animal models

Oocyte-specific Ggpps conditional knockout mouse Mouse partially recapitulates Reproduces follicle loss and infertility from loss of GGPP in the oocyte, and identifies the failing step as Rho GTPase geranylgeranylation. The rescue by GGPP is what makes the attribution causal rather than correlative.

Downstream

Primary Ovarian Insufficiency Depletion of the follicle pool is what presents clinically as hypergonadotropic ovarian insufficiency.

Show evidence (3 references)

PMID:28072828 SUPPORT INDIRECT Model Organism

"The selective depletion of GGPP in mouse oocytes impaired the proliferation of granulosa cells, primary-secondary follicle transition and female fertility."

Mouse oocyte-specific Ggpps depletion, not a human GGPS1 hypomorph, so this supports the node by mechanism rather than by observation in patients. It is the experiment that makes an ovarian phenotype expected from a GGPP deficit.

PMID:32399598 SUPPORT INDIRECT Other

"whose enzymatic product is required for mouse folliculogenesis."

An independent group, working from a Perrault cohort rather than a muscular dystrophy cohort, reaching the same conclusion about the relevance of the GGPPS product to folliculogenesis in mouse.

PMID:35869884 SUPPORT INDIRECT Model Organism

"Global view of Ggps1 expression in the E14.5 female gonad showed clusters most densely in the germ cells and embryonic gonad cells"

Mouse single-cell expression data placing Ggps1 in the germ cells of the developing female gonad, which is consistent with an ovarian lesion but does not demonstrate one.

Cochlear Sensory Failure

Mechanism confidence: Hypothetical

The auditory arm, and the emptiest node in this entry. No cochlear tissue from an affected individual has been examined and no cochlear mechanism has been demonstrated. What exists is an inference: cochlear implantation was highly effective in all four implanted patients in the founding cohort, which places the lesion in the sensory organ rather than in the auditory nerve or central pathway, and Ggps1 is diffusely expressed in the mouse cochlear epithelium through embryonic and early postnatal development. The node is retained because the phenotype has to connect to the molecular lesion somewhere, and it is marked hypothetical because that connection is entirely unobserved.

organ of Corti UBERON:0002227

Downstream

Congenital Sensorineural Hearing Loss Failure of the cochlear sensory organ presents as sensorineural hearing loss.

Show evidence (2 references)

PMID:32403198 SUPPORT INDIRECT Human Clinical

"The sensorineural hearing loss observed in patients with GGPS1‐related muscular dystrophy is most likely sensory organ–related and localized to the organ of Corti, consistent with cochlear implantation being highly effective in all 4 patients in our cohort who underwent implantation."

The localisation is an inference from therapeutic response rather than an observation of the cochlea, which is exactly the strength of evidence this node carries.

PMID:35869884 SUPPORT INDIRECT Model Organism

"Single‐cell RNA sequencing of the cochlear epithelium in the E14, P1, and P7 mouse shows Ggps1 with a sustained, diffuse expression at these timepoints"

Mouse cochlear expression data. Expression in a tissue is consistent with a lesion there and is not evidence of one; it is cited for what it is.

✶

Histopathology

1

Dystrophic muscle with excess autophagic material and enlarged mitochondria

Biopsies from nine patients showed a dystrophic process with degeneration, regeneration and internalised nuclei, occasional rimmed vacuoles, and irregular oxidative staining with core-like regions; ragged red and cytochrome-oxidase-negative fibers were seen in one patient. Electron microscopy added excess autophagic material including myeloid bodies, positive LC3B staining, and enlarged but structurally normal mitochondria. The combination of a dystrophic pattern with disordered autophagy is what makes the biopsy suggestive rather than merely non-specific.

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Histology was dystrophic, with evidence of degeneration and regeneration and internalized nuclei."

The light-microscopic dystrophic pattern.

PMID:32403198 SUPPORT Human Clinical

"Electron microscopy revealed ultrastructural evidence of enlarged but structurally normal mitochondria (Patient P8) as well as evidence of excess autophagic material (Patients P1 and P8; Fig 2)."

The ultrastructural findings that distinguish this biopsy from a purely sarcolemmal dystrophy.

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Pathograph

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

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Phenotypes

21

Cardiovascular 1

Absence of Cardiac Involvement Abnormal heart morphology HP:0001627

Show evidence (1 reference)

PMID:32403198 REFUTE Human Clinical

"Of note, no cardiac or cognitive involvement has been noted in this cohort."

Graded REFUTE against the claim that cardiac involvement is a feature of this disease, which is what this phenotype item asks.

Digestive 1

Poor Suck HP:0002033

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"The index patient (Patient P1; Fig 1) manifested symptoms prenatally with decreased fetal movements, and neonatally with a weak cry and a poor suck."

Documents poor suck as a neonatal presenting sign.

Ear 1

Congenital Sensorineural Hearing Loss FREQUENT Congenital sensorineural hearing impairment HP:0008527

Show evidence (3 references)

PMID:32403198 SUPPORT Human Clinical

"Sensorineural hearing loss was present in all but one patient in this cohort and was the first symptom identified in those patients with milder motor phenotypes."

Records the near-universal hearing loss of the founding cohort and its role as the presenting symptom in milder patients.

PMID:35869884 SUPPORT Human Clinical

"hearing loss was present in only 46% of the individuals."

The counterweight from the second cohort, which is why this is curated as FREQUENT rather than VERY_FREQUENT.

PMID:38129970 SUPPORT Human Clinical

"The patient presented with only proximal muscle weakness, and elevated liver transaminases with spared hearing function."

A genotype-confirmed patient with normal hearing, confirming that the auditory feature can be absent entirely.

Genitourinary 1

Primary Ovarian Insufficiency FREQUENT Premature ovarian insufficiency HP:0008209

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Primary ovarian insufficiency, also known as premature ovarian failure, has been diagnosed in all postpubertal females in this cohort, as confirmed by menopausal levels of follicle‐stimulating hormone (FSH) in the setting of a history of amenorrhea"

Establishes the ovarian phenotype and the hormonal criterion used to diagnose it in every postpubertal female of the cohort.

PMID:35869884 SUPPORT Human Clinical

"This report consolidates the disease-causing role of biallelic variants in GGPS1 and demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy."

States that ovarian insufficiency, like hearing loss, is variable rather than obligatory, which is the basis for the FREQUENT rather than OBLIGATE frequency.

Limbs 1

Calf Muscle Hypertrophy FREQUENT HP:0008981

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12),..."

Reports calf hypertrophy in 4 of 12 individuals examined.

Metabolism 2

Elevated Serum Creatine Kinase FREQUENT Elevated circulating creatine kinase activity HP:0003236

Temporal: RECURRENT

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably..."

Names episodic creatine kinase elevation as part of the syndrome's recognisable phenotype.

PMID:32403198 SUPPORT Human Clinical

"In Patients P1, P2, and P7, there was a history of episodic worsening of weakness concomitant with higher CK elevations during episodes of diarrhea."

Names an intercurrent-illness trigger for the episodic rises, which is the most clinically actionable observation in the founding report: a treating physician seeing a diarrhoeal illness in one of these patients should expect a CK spike and transient worsening of weakness rather than a new process.

Elevated Hepatic Transaminases VERY_RARE Elevated circulating hepatic transaminase concentration HP:0002910

Show evidence (1 reference)

PMID:38129970 SUPPORT Human Clinical

"The patient presented with only proximal muscle weakness, and elevated liver transaminases with spared hearing function."

The single reported patient in whom transaminase elevation was described as part of the phenotype.

Musculoskeletal 6

Skeletal Muscle Atrophy VERY_FREQUENT HP:0003202

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12),..."

The neuromuscular examination sentence, which reports muscular atrophy in 12 of 12 individuals examined.

Hypotonia FREQUENT HP:0001252

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12),..."

Reports hypotonia in 10 of 13 individuals in the second cohort.

Proximal Muscle Weakness VERY_FREQUENT HP:0003701

Course: PROGRESSIVE

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably..."

Names proximal muscle weakness as part of the recognisable syndrome across the founding cohort.

PMID:35869884 SUPPORT Human Clinical

"Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural..."

Quantifies proximal or generalised weakness at twelve of thirteen individuals in the second cohort.

Respiratory Insufficiency FREQUENT Respiratory insufficiency due to muscle weakness HP:0002747

Course: PROGRESSIVE

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"She developed respiratory insufficiency, necessitating noninvasive ventilation, progressing to tracheostomy."

The progression from non-invasive ventilation to tracheostomy in the index patient.

PMID:35869884 SUPPORT Human Clinical

"Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural..."

Quantifies respiratory insufficiency and ventilatory requirement across the second cohort.

Scoliosis FREQUENT HP:0002650

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"Thus, progressive muscle weakness and joint contractures resulting in loss of independent ambulation, respiratory insufficiency necessitating ventilation dependence, and severe scoliosis were seen in Patients P1, P2, P3, and P9, whereas the other patients had a less severe progression of weakness."

Records severe scoliosis alongside the other features of the severe end of the spectrum.

Joint Contractures FREQUENT HP:0034392

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural..."

Reports joint contractures in seven of twelve assessed individuals.

Nervous System 3

Areflexia VERY_FREQUENT HP:0001284

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12),..."

Reports hyporeflexia/areflexia in 12 of 12 individuals examined, as a single combined count.

Loss of Ambulation FREQUENT HP:0002505

Course: PROGRESSIVE

Show evidence (2 references)

PMID:35869884 SUPPORT Human Clinical

"Six affected individuals lost ambulation at the mean age of 8.1"

Quantifies how many individuals lost ambulation and at what age.

PMID:32403198 SUPPORT Human Clinical

"Thus, progressive muscle weakness and joint contractures resulting in loss of independent ambulation, respiratory insufficiency necessitating ventilation dependence, and severe scoliosis were seen in Patients P1, P2, P3, and P9, whereas the other patients had a less severe progression of weakness."

Records loss of independent ambulation in the severely affected patients and its absence in the rest.

Motor Delay FREQUENT HP:0001270

Show evidence (2 references)

PMID:35869884 SUPPORT Human Clinical

"The disease onset ranged from prenatal (3/13) to pre‐schooler age"

Establishes the onset window within which the motor delay was recognised.

PMID:32403198 SUPPORT Human Clinical

"Of note, no cardiac or cognitive involvement has been noted in this cohort."

Cited for the negative half of this item: cognition is unaffected, so the motor delay is a motor problem and not part of a global developmental one.

Prenatal and Birth 1

Decreased Fetal Movement HP:0001558

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"The index patient (Patient P1; Fig 1) manifested symptoms prenatally with decreased fetal movements, and neonatally with a weak cry and a poor suck."

Documents prenatal onset in the index patient.

Voice 1

Weak Cry HP:0001612

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"The index patient (Patient P1; Fig 1) manifested symptoms prenatally with decreased fetal movements, and neonatally with a weak cry and a poor suck."

Documents weak cry as a neonatal presenting sign.

Constitutional 1

Myalgia FREQUENT HP:0003326

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12),..."

Reports myalgia in 6 of 10 individuals in whom it was assessed.

Growth 2

Short Stature FREQUENT HP:0004322

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12),..."

Reports short stature in 8 of 13 individuals, counted separately from failure to thrive.

Failure to Thrive FREQUENT HP:0001508

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"Eight patients had evidence of failure to thrive and/or short stature, potentially suggestive of further endocrinologic involvement."

Reports the frequency and the authors' own hedged interpretation of it.

🧬

Genetic Associations

1

GGPS1 (geranylgeranyl diphosphate synthase 1)

Gene: GGPS1 hgnc:4249 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (3 references)

PMID:32403198 SUPPORT Human Clinical

"Here, we report specific mutations in the gene GGPS1 coding for the enzyme geranylgeranyl diphosphate synthase in 11 patients from 6 families, causing a highly distinctive syndrome of early onset muscular dystrophy combined with congenital sensorineural hearing loss and primary ovarian..."

Establishes GGPS1 causality across eleven patients in six families.

PMID:32403198 SUPPORT Human Clinical

"The pathogenic variants fell within a specific 5 amino acid region toward the C terminus around the start of helix 11, with as of yet unclear function"

Characterises the positional clustering that defines the allelic spectrum.

PMID:35869884 SUPPORT Human Clinical

"Here, we describe 11 affected individuals from four unpublished families with ultra-rare missense variants in GGPS1 and provide follow-up details from a previously reported family."

Independent replication of GGPS1 causality in four further previously unreported families.

🔬

Variants

4

NM_004837.4 p.(Tyr259Cys) Pathogenic

Gene: GGPS1 hgnc:4249 missense variant

Carried in compound heterozygosity with R261G by the two index siblings. It has the highest in-silico damage score of the founding alleles, which is why it was chosen for the mouse knock-in, and the resulting homozygous animals die in utero.

Functional effects

geranylgeranyl diphosphate synthase catalytic activity partial loss of function

Retains roughly 70 to 85% of wild-type activity as recombinant protein.

Show evidence (2 references)

PMID:32403198 SUPPORT In Vitro

"consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"

Reports the partial activity retained by this and the other C-terminal alleles.

PMID:32403198 SUPPORT Model Organism

"homozygote Y259C knock‐in embryos developed up to embryonic day (ED)12.5, with no live embryos observed after this point."

The embryonic lethality of the homozygous knock-in, which is the strongest evidence that this allele is severely hypomorphic.

NM_004837.4 p.(Arg261Gly) and p.(Arg261His)

Gene: GGPS1 hgnc:4249 missense variant

Two substitutions at the same residue. R261G was found in compound heterozygosity in two families, and R261H homozygously in two families whose patients had the mildest motor phenotype, retaining independent ambulation into adulthood while still having sensorineural hearing loss and ovarian insufficiency. Both are ultra-rare in gnomAD.

Functional effects

geranylgeranyl diphosphate synthase catalytic activity partial loss of function

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"

Measures the residual activity of both R261 substitutions alongside the other alleles.

NM_004837.4 p.(Phe257Cys)

Gene: GGPS1 hgnc:4249 missense variant

Homozygous in two families, one with a single affected child and one with three affected siblings spanning a moderate-to-severe range, which is an intrafamilial demonstration that genotype does not fix severity.

Functional effects

geranylgeranyl diphosphate synthase catalytic activity partial loss of function

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"

Reports this allele among those with reduced catalytic rate.

NM_004837.4 p.(Pro15Ser)

Gene: GGPS1 hgnc:4249 missense variant

The exception to the C-terminal clustering, and the exception to the activity deficit: it lies in the first alpha-helix, which mediates assembly of the hexamer from dimers, and it had the same catalytic activity as wild-type in the recombinant assay. It was found in compound heterozygosity with R261G. That an allele can cause this disease without reducing bulk catalytic rate is the main argument that the pathogenic mechanism is not simply loss of enzyme output.

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"

The same measurement, quoted here for its exclusion of P15S: the reduced-activity finding applies to the other four alleles and not to this one.

💊

Medical Actions

3

Cochlear implantation

Action: cochlear device implantation Ontology label: Surgical Procedure NCIT:C15329

Platform: Surgery

The most effective intervention reported in this disease. All four patients implanted in the founding cohort responded well, which is also the observation that localises the auditory lesion to the sensory organ rather than to the nerve.

Mechanism Target:

Cochlear Sensory Failure — Bypasses the failed cochlear sensory transduction by stimulating the auditory nerve directly; it does not modify the underlying metabolic lesion.

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"The sensorineural hearing loss observed in patients with GGPS1‐related muscular dystrophy is most likely sensory organ–related and localized to the organ of Corti, consistent with cochlear implantation being highly effective in all 4 patients in our cohort who underwent implantation."

Reports the implant response and the authors' inference from it about where the lesion sits, which is the rationale for this intervention.

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"The sensorineural hearing loss observed in patients with GGPS1‐related muscular dystrophy is most likely sensory organ–related and localized to the organ of Corti, consistent with cochlear implantation being highly effective in all 4 patients in our cohort who underwent implantation."

The clinical outcome of implantation in the four patients who received it.

Non-invasive and invasive ventilatory support

Action: mechanical ventilation Ontology label: Mechanical Ventilation NCIT:C70909

Platform: Device

Nocturnal non-invasive ventilation progressing to tracheostomy in the severely affected. This is the supportive measure that determines survival, as it is in every congenital muscular dystrophy with respiratory involvement.

Mechanism Target:

Respiratory Insufficiency — Substitutes for the failing respiratory musculature without modifying the myopathy.

Show evidence (1 reference)

PMID:35869884 SUPPORT Human Clinical

"Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural..."

Ties the ventilatory requirement to the measured respiratory insufficiency across the cohort.

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"She developed respiratory insufficiency, necessitating noninvasive ventilation, progressing to tracheostomy."

Documents the escalation from non-invasive ventilation to tracheostomy.

Spinal fusion for progressive scoliosis

Action: spinal fusion Ontology label: Orthopedic Surgical Procedure NCIT:C16186

Platform: Surgery

Orthopaedic stabilisation of the neuromuscular scoliosis. Reported in the index patient at eleven years; no series and no outcome data exist for this disease specifically.

Mechanism Target:

Scoliosis — Corrects and stabilises the spinal deformity produced by axial weakness.

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"Progressive scoliosis necessitated spinal fusion at age 11 years."

The single reported instance, quoted rather than generalised.

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"Progressive scoliosis necessitated spinal fusion at age 11 years."

Records that spinal fusion was performed for the progressive scoliosis.

🔬

Biochemical Markers

2

Normal Muscle Coenzyme Q10 (Absent)

Show evidence (2 references)

PMID:32403198 REFUTE Human Clinical

"The CoQ10 level in muscle was determined to be normal in Patient P1."

Graded REFUTE against the claim that this disease is a muscle coenzyme Q10 deficiency state, which is the claim this biochemical item exists to test.

PMID:32403198 REFUTE Human Clinical

"Patient P3 was given an empirical treatment trial of oral CoQ10, which did not result in any noted improvement of symptoms."

The corresponding therapeutic test, also negative. One uncontrolled patient is weak evidence, but it is the only evidence there is.

Elevated Serum Follicle-Stimulating Hormone (INCREASED)

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"Primary ovarian insufficiency, also known as premature ovarian failure, has been diagnosed in all postpubertal females in this cohort, as confirmed by menopausal levels of follicle‐stimulating hormone (FSH) in the setting of a history of amenorrhea"

Gives the measured FSH values and the diagnostic use made of them.

🔬

Diagnosis

6

Molecular diagnosis by exome or genome sequencing

The diagnosis is molecular. The syndrome was found by whole exome sequencing combined with shared-haplotype analysis in the index siblings, and further families were ascertained either by targeted GGPS1 Sanger sequencing on the strength of a suggestive phenotype or by exome sequencing. The clinical trigger worth acting on is the combination itself: a congenital or early-onset muscular dystrophy with sensorineural hearing loss, in a girl or woman with amenorrhoea or infertility, has no other recognised genetic cause.

whole exome sequencing NCIT:C101295

Show evidence (3 references)

PMID:32403198 SUPPORT Human Clinical

"We applied whole exome sequencing (WES) superimposed on shared haplotype regions to identify the initial biallelic variants in GGPS1 followed by GGPS1 Sanger sequencing or WES in 5 additional families with the same phenotype."

Names the sequencing strategy that made the diagnosis in the index family and in five further families.

PMID:32403198 SUPPORT Human Clinical

"In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably..."

Describes the recognisable phenotype that should prompt GGPS1 testing.

PMID:35869884 SUPPORT Human Clinical

"Here, we describe 11 affected individuals from four unpublished families with ultra-rare missense variants in GGPS1 and provide follow-up details from a previously reported family."

The second cohort was likewise ascertained by sequencing rather than by any biochemical test.

Audiometric assessment

Formal audiometry, including brainstem auditory evoked response testing in infancy, is what identifies the hearing loss and dates its onset. The point the discovery authors make is a practical one: the hearing loss was called congenital only because audiometry was performed, and in patients tested later in childhood the age at diagnosis reflects when the test was done rather than when the deafness began. Audiometry is also what established the absence of hearing loss in the patients of the second cohort who did not have it, which is why that negative is credible.

audiometric testing NCIT:C38036

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Given that the hearing loss was diagnosed in some patients in the neonatal period and in others during childhood, the onset is likely congenital, as diagnosis relies on a formal audiometric evaluation."

States that the determination of congenital onset rests on formal audiometric evaluation.

PMID:32403198 SUPPORT Human Clinical

"she was diagnosed with bilateral sensorineural hearing loss (via brainstem auditory evoked response testing)."

The specific audiological modality used in the index patient in infancy.

Serum creatine kinase

Creatine kinase is the screening abnormality that places the weakness in muscle. It is raised episodically rather than continuously, reaching 18,025 U/l in the index patient at nineteen months, and the episodic rises accompanied intercurrent diarrhoeal illness in three patients. A single normal value therefore does not exclude the disease.

creatine kinase measurement NCIT:C64489

Markers: Serum creatine kinase activity

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"muscle weakness, and elevated CK (up to 18,025U/l at 19 months of age)."

Gives the magnitude of the creatine kinase elevation and the setting in which it was measured.

PMID:32403198 SUPPORT Human Clinical

"In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably..."

Records that the elevation is episodic and variable rather than sustained, which is what makes a single value uninformative.

Muscle biopsy

Biopsy establishes that the process is dystrophic rather than neurogenic or inflammatory, and adds the two ultrastructural features that point towards this diagnosis specifically: excess autophagic material and enlarged mitochondria. It was performed in nine of the eleven patients of the founding cohort. It is not a confirmatory test -- nothing on the biopsy is specific to GGPS1 -- and a biopsy taken very early can be normal.

muscle biopsy NCIT:C51895

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Muscle biopsies were performed in 9 patients (Patients P1–P9)."

Records how many patients were biopsied, which is what makes the histological description a cohort finding rather than a case report.

PMID:32403198 SUPPORT Human Clinical

"Histology was dystrophic, with evidence of degeneration and regeneration and internalized nuclei."

The dystrophic pattern the biopsy is performed to demonstrate.

Endocrine evaluation of postpubertal females

Follicle-stimulating hormone measurement in the setting of amenorrhoea or infertility is what establishes the ovarian component, and without it the feature is systematically missed: in the founding cohort the affected men were never formally assessed, and in the 2022 cohort only one woman had reached adulthood. Prepubertal girls and all males are effectively unassessable for this feature at the time of diagnosis, so a negative ovarian history in a child says nothing.

follicle stimulating hormone measurement NCIT:C74783

Markers: Serum follicle-stimulating hormone

Show evidence (1 reference)

PMID:32403198 SUPPORT Human Clinical

"Primary ovarian insufficiency, also known as premature ovarian failure, has been diagnosed in all postpubertal females in this cohort, as confirmed by menopausal levels of follicle‐stimulating hormone (FSH) in the setting of a history of amenorrhea"

Names the hormonal criterion, gives the measured values, and states the clinical settings in which it was applied.

Muscle magnetic resonance imaging

Whole-body muscle MRI shows the fatty infiltration that confirms a dystrophic process and, in the three patients imaged, a pattern that may prove diagnostically useful: relative sparing of rectus femoris, sartorius and gracilis, with conspicuously asymmetric involvement. Three patients is not enough to call this a signature, and the authors say as much.

muscle magnetic resonance imaging NCIT:C16809

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Whole‐body muscle magnetic resonance imaging was performed in Patients P4–P6 and demonstrates variable increase in T1 signal in select muscles, resulting from fatty infiltration and thus consistent with an underlying muscular dystrophy"

Reports the imaging finding and its interpretation as evidence of an underlying muscular dystrophy.

PMID:32403198 SUPPORT Human Clinical

"The relative sparing of the rectus femoris, sartorius, and gracilis muscles and asymmetric involvement of muscles in this clinical context may be diagnostically helpful"

The part of the imaging finding that could actually discriminate. The authors' own "may be" is preserved: the pattern comes from three imaged patients, which is not enough to call it a signature.

📈

Progression

2

Onset

Age: prenatal to preschool age

Onset ranges from the prenatal period, presenting as decreased fetal movement or a weak cry, to preschool age, with a mean age at first symptom of about sixteen months in the 2022 cohort. Delayed motor milestones are the commonest first presentation, and in the milder patients the hearing loss is identified before the weakness.

Show evidence (2 references)

PMID:35869884 SUPPORT Human Clinical

"The disease onset ranged from prenatal (3/13) to pre‐schooler age"

Gives the onset window and the mean age at first symptom.

PMID:32403198 SUPPORT Human Clinical

"Sensorineural hearing loss was present in all but one patient in this cohort and was the first symptom identified in those patients with milder motor phenotypes."

Records that hearing loss is the first symptom identified in the patients with milder motor involvement.

Progression

Two courses rather than one. The severe course runs from progressive weakness and contractures to loss of ambulation in the first or second decade, ventilator dependence and severe scoliosis; the milder course preserves independent ambulation into adulthood. Ninety-two per cent of the 2022 cohort progressed slowly, and six of thirteen lost ambulation at a mean of about eight years. Severity of the hearing loss and of the ovarian insufficiency does not track with severity of the muscular dystrophy.

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Thus, progressive muscle weakness and joint contractures resulting in loss of independent ambulation, respiratory insufficiency necessitating ventilation dependence, and severe scoliosis were seen in Patients P1, P2, P3, and P9, whereas the other patients had a less severe progression of weakness."

Separates the severely affected patients from the rest within the same cohort.

PMID:35869884 SUPPORT Human Clinical

"Six affected individuals lost ambulation at the mean age of 8.1"

Quantifies the loss of ambulation in the second cohort.

📊

Prevalence

1

Worldwide, published cases

Cases In Literature Ultra Rare

No population prevalence estimate exists for this syndrome and none is asserted. The published case count is the honest measure: eleven individuals from six families in the 2020 defining report, eleven further individuals from four previously unreported families in 2022 (whose thirteen-person cohort also included follow-up on two individuals reported from a Perrault cohort in 2020), and one further patient in 2024 -- at least twenty-three published individuals, in at least twelve families, as of 2026. All reported alleles are ultra-rare or absent in gnomAD.

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Here, we report specific mutations in the gene GGPS1 coding for the enzyme geranylgeranyl diphosphate synthase in 11 patients from 6 families, causing a highly distinctive syndrome of early onset muscular dystrophy combined with congenital sensorineural hearing loss and primary ovarian..."

The founding cohort's case count.

PMID:35869884 SUPPORT Human Clinical

"Here, we describe 11 affected individuals from four unpublished families with ultra-rare missense variants in GGPS1 and provide follow-up details from a previously reported family."

The second cohort's case count, which is what the total above is built from.

🔀

Differential Diagnoses

5

Conditions with similar clinical presentations that must be differentiated from Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome:

Perrault syndrome MONDO:0017312

Overlapping Features The closest differential and the reason the lump/split decision for this entry is a real one. Perrault syndrome is sensorineural hearing loss with primary ovarian insufficiency in 46,XX individuals -- two of this disease's three cardinal features -- and GGPS1 was independently nominated as a Perrault candidate gene from a Perrault cohort in the same year this syndrome was named. dismech curates Perrault syndrome separately in `kb/disorders/Perrault_Syndrome.yaml`, where GGPS1 appears as a gene whose phenotype overlaps Perrault syndrome. The two entries are deliberately cross-referenced rather than merged.

Distinguishing Features

Perrault syndrome does not include muscle disease; the discovery paper for this syndrome states that Perrault syndrome manifests with hearing loss and ovarian insufficiency but without muscle involvement.
Here the muscular dystrophy is the constant feature and the two Perrault features are the variable ones, which inverts the Perrault definition: hearing loss was present in only 46% of one cohort and a 2024 patient had normal hearing.
The mechanisms are different in kind. Perrault syndrome is unified by failure of mitochondrial gene expression and proteostasis, with peroxisomal exceptions; this is an isoprenoid and protein-prenylation lesion.
MONDO and OMIM assign a separate identity (MONDO:0859189, OMIM:619518) rather than a numbered PRLTS designation, and MONDO does not place this term under Perrault syndrome.
The practical discriminator is a creatine kinase and a muscle examination in anyone presenting with the Perrault dyad, since the dystrophy is what changes management.
The case against this separation should be stated too: a 2026 review lists GGPS1 among the fifteen principal Perrault syndrome genes, so a reader who takes that classification is entitled to regard this disease as a Perrault subtype with muscle involvement.

Show evidence (3 references)

PMID:32403198 SUPPORT Human Clinical

"Perrault syndrome, caused by mutations in various mitochondrial and peroxisomal genes, clinically manifests with sensorineural hearing loss and primary ovarian insufficiency but without muscle involvement"

States the nosological boundary this differential draws, that Perrault syndrome lacks muscle involvement.

PMID:35869884 SUPPORT Human Clinical

"a constellation of all these three features had not been previously recognized prior to the Foley"

Confirms independently that the three-feature constellation was not a recognised entity before 2020.

PMID:42283975 SUPPORT Other

"highlighting mutations in fifteen principal genes: HSD17B4, HARS2, CLPP, LARS2, TWNK, ERAL1, RMND1, DAP3, PRORP, MRPL50, MRPL49, MRPS7, PEX6, GGPS1, and TFAM."

The counter-argument, curated rather than omitted: a recent Perrault review counts GGPS1 among the Perrault genes, which is the strongest published statement of the lumping position this entry declines. Note that the same review characterises all fifteen genes as acting in mitochondrial or peroxisomal processes, which is not true of GGPS1.

Muscular dystrophy, limb-girdle, autosomal recessive 28 (HMGCR-related) MONDO:0957270

Overlapping Features The other Mendelian muscular dystrophy of the mevalonate pathway, curated in `kb/disorders/Muscular_Dystrophy_Limb-girdle_Autosomal_Recessive_28.yaml`. HMGCR catalyses the rate-limiting step at the head of the pathway; GGPS1 catalyses a committed step in the isoprenoid branch several steps below it. The two entries agree mechanistically rather than competing: the LGMDR28 entry argues from mouse rescue experiments that the myopathy of HMGCR deficiency is caused by depletion of the geranylgeranyl branch rather than of sterol, and this disease is what a lesion placed directly in that branch looks like. Both are hypomorphic-missense diseases of an essential enzyme whose complete loss is lethal.

Distinguishing Features

LGMDR28 is a limb-girdle dystrophy with markedly raised creatine kinase and no hearing or ovarian involvement; this syndrome adds congenital sensorineural hearing loss and primary ovarian insufficiency.
The LGMDR28 biopsy is characteristically unremarkable, without necrosis, fibrosis or inflammation; the biopsy here is frankly dystrophic and adds excess autophagic material and enlarged mitochondria.
LGMDR28 onset spans birth to the fourth decade and is often adult; this syndrome is congenital to preschool in onset.
LGMDR28 has a directed metabolite-replacement candidate, oral mevalonolactone, which supplies the pathway product below the block; there is no equivalent for GGPS1, since the block is below the branch point and mevalonate would not bypass it.

Show evidence (1 reference)

PMID:42323079 SUPPORT INDIRECT Model Organism

"Our findings demonstrate that myopathy induced by HMGCR deficiency is primarily driven by GGPP depletion in a mouse model."

This result is about HMGCR-deficient mice, not GGPS1. It is cited to show that the two diseases are placed on one pathway by the same argument, since the HMGCR myopathy is attributed to depletion of the very metabolite GGPS1 makes.

GGPS1-associated bisphosphonate-related atypical femoral fracture

Overlapping Features Not a disease entry and deliberately not merged into this one. Monoallelic GGPS1 variants, notably p.Asp188Tyr in three sisters, have been reported as a risk factor for atypical femoral fractures in women on nitrogen-containing bisphosphonates, which inhibit GGPPS pharmacologically; the variant reduces catalytic activity roughly fourfold in vitro. This is a heterozygous drug-response susceptibility with no disease phenotype in the absence of the drug, and it has no MONDO term. It is recorded here because it is the single largest source of GGPS1 literature that is not about this syndrome, and because both the discovery paper and the replication cohort take care to distinguish the two.

Distinguishing Features

Monoallelic, and expressed only under bisphosphonate exposure; this syndrome is biallelic and expressed without any drug.
The phenotype is a fracture in an adult on treatment, not a congenital muscular dystrophy with hearing and ovarian involvement.
Heterozygous GGPS1 loss-of-function carriers are present in gnomAD and are expected to be asymptomatic, so a single defective allele does not produce this syndrome.

Show evidence (3 references)

PMID:35869884 SUPPORT Human Clinical

"While monoallelic variants in GGPS1 have been identified as a risk factor for atypical femoral bone fractures in females exposed to bisphosphonates, ultra‐rare biallelic pathogenic missense variants in GGPS1 have recently been associated with muscular dystrophy/hearing loss/ovarian insufficiency..."

Draws the monoallelic-versus-biallelic distinction between the two GGPS1 associations in a single sentence.

PMID:32403198 SUPPORT Human Clinical

"Although thus far there has been no human monogenic disease linked to mutations in GGPS1, it has been identified as a risk factor for atypical femoral bone fractures in females exposed to bisphosphonates."

Records that before 2020 the only GGPS1 disease association was the bisphosphonate fracture risk factor.

PMID:30275041 SUPPORT INDIRECT In Vitro

"the D188Y mutation leads to ∼4-fold catalytic activity decrease."

This is about the atypical-femoral-fracture allele D188Y, not about any allele in this syndrome. It is cited to show that the fracture-associated variant is also a partial loss-of-function allele, which is why the two associations are easy to conflate.

Facioscapulohumeral muscular dystrophy MONDO:0001347

Overlapping Features The other muscular dystrophy in which sensorineural hearing loss is an accepted feature, specifically in the early-onset infantile form. It is curated in `kb/disorders/Facioscapulohumeral_Muscular_Dystrophy.yaml`.

Distinguishing Features

FSHD is dominantly inherited and caused by D4Z4 contraction or SMCHD1 variants, not by a recessive metabolic-enzyme genotype.
FSHD has a characteristic facial, scapular and humeral distribution with marked asymmetry; the weakness here is limb-girdle or generalised.
Retinal vasculopathy accompanies the hearing loss in infantile FSHD, and primary ovarian insufficiency is not a feature.

Show evidence (1 reference)

PMID:32403198 SUPPORT Other

"Congenital sensorineural hearing loss rarely manifests in association with muscular dystrophy but has been reported in early onset facioscapulohumeral muscular dystrophy."

Names early-onset facioscapulohumeral muscular dystrophy as the other muscular dystrophy in which congenital sensorineural hearing loss occurs, which is what makes it a differential for this syndrome.

Vici syndrome MONDO:0009452

Overlapping Features An EPG5-related multisystem disorder combining a vacuolar myopathy with sensorineural hearing loss, which the discovery authors raise because it makes the same connection between disordered autophagy, myopathy and deafness that the ultrastructural findings here suggest. It is the differential most worth knowing about mechanistically rather than clinically.

Distinguishing Features

Vici syndrome has agenesis of the corpus callosum, cataracts, hypopigmentation, cardiomyopathy and immunodeficiency; none of these occurs in GGPS1 disease, which has no cardiac or cognitive involvement.
Ovarian insufficiency is not a feature of Vici syndrome.
The autophagy defect in Vici syndrome is a primary lesion in an autophagy regulator; here disordered autophagy is an ultrastructural finding whose place in the mechanism is unresolved.

Show evidence (2 references)

PMID:32403198 SUPPORT Human Clinical

"Of note, no cardiac or cognitive involvement has been noted in this cohort."

Records the absence of cardiac and cognitive involvement, which is the clearest clinical separation from Vici syndrome.

PMID:32403198 SUPPORT Other

"Vici syndrome, a complex congenital multisystemic disorder caused by recessive mutations in autophagy regulator EPG5 gene, which can also be associated with sensorineural hearing loss,"

Identifies Vici syndrome and its cause, and names the hearing loss that it shares with this syndrome, which is why the discovery authors raise it.

🧫

Experimental Models

1

Patient-derived MyoD-converted myoblasts and myotubes with laser membrane injury PRIMARY_CELL_CULTURE

Dermal fibroblasts from affected individuals converted to myoblasts with lentiviral MyoD and differentiated to myotubes, then wounded with a focal laser pulse in the presence of the membrane-impermeant dye FM 1-43 so that resealing can be followed as dye exclusion. This is the system that produced the only cellular phenotype demonstrated in patient material, and it is also the system in which GGPPS activity was measured at about half of control.

Publication

PMID:32403198

Pathograph links

Impaired Sarcolemmal Membrane Repair recapitulates fidelity: moderate observes: cellular Reproduces, in cells carrying the patients' own genotypes, a delay in resealing the wounded plasma membrane and a roughly twofold increase in the proportion of cells that fail to reseal at all.

Limitations: MyoD-converted fibroblasts are not mature innervated muscle, and a laser wound is not the eccentric contraction injury that damages muscle in life. The assay reports resealing kinetics and not the downstream dystrophic process, so the link from this defect to the biopsy findings remains inferential. The measurement pools cells from several patients with different genotypes, so it cannot distinguish allele-specific effects.

Readouts

FM 1-43 dye entry after focal laser injury

Direction: INCREASED

Interpretation: Greater dye entry means slower resealing, which is the direct measure of the membrane-repair defect this node claims.

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"We observed greater dye entry, indicating a poor cell membrane repair, in both the patient myoblasts and myotubes as compared to the healthy controls"

Reports the dye-entry measurement behind this readout.

GGPPS enzymatic activity in patient myoblasts

Direction: DECREASED

Interpretation: Establishes that the cells showing the repair defect really do carry a measurable enzymatic deficit, which is what ties the cellular phenotype to the genotype.

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"We found that enzymatic activity in samples pooled from 4 patients (Patients P1, P2, P6, and P8) was decreased to about 50% of the activity in a pooled normal control sample."

Reports the enzyme-activity measurement made in these same cells.

Show evidence (1 reference)

PMID:32403198 SUPPORT In Vitro

"We observed greater dye entry, indicating a poor cell membrane repair, in both the patient myoblasts and myotubes as compared to the healthy controls"

Establishes that this model reports the cellular phenotype the node describes.

🐁

Animal Models

2

Ggps1 p.Tyr259Cys homozygous knock-in mouse

A knock-in of the human Y259C allele, made because a complete Ggps1 knockout is not viable and a knock-in was the only route to an organismal model. It does not model the disease: homozygotes develop with a markedly slowed rate, reach no further than embryonic day 12.5 and are not recovered alive thereafter. The authors state plainly that this left them unable to do mechanistic work relevant to the human phenotype, which is why almost everything mechanistic in this entry comes from patient cells or from tissue-specific mouse models of other genotypes.

Species

Mouse

Genotype

Ggps1 p.Y259C homozygous knock-in

Publication

PMID:32403198

Pathograph links

Myofiber Degeneration with Disordered Autophagy fails to recapitulate fidelity: low Homozygous animals die as embryos and never develop a postnatal muscular dystrophy, so no muscle phenotype, hearing phenotype or ovarian phenotype can be observed.

Limitations: Embryonic lethality precludes phenotyping of any kind, so the model yields no readout of weakness, creatine kinase, histology, hearing or fertility. The species difference is the substantive limitation: mouse appears far less tolerant of this allele than human, since the corresponding human compound heterozygotes were liveborn and survived into their twenties. Nothing about the human disease can be inferred from this model beyond the severity of the allele.

Show evidence (2 references)

PMID:32403198 SUPPORT Model Organism

"homozygote Y259C knock‐in embryos developed up to embryonic day (ED)12.5, with no live embryos observed after this point."

Reports the embryonic lethality that constitutes the failure to recapitulate.

+ 1 more reference

Show evidence (1 reference)

PMID:32403198 SUPPORT Model Organism

"As a total knock‐out the gene is not viable; we therefore created a knock‐in mouse of the mutation p.Y259C (Fig 7A) detected in compound heterozygosity in the index family (Family 1) to study the effects of the mutant GGPS1 on the organismal level."

Establishes why a knock-in rather than a knockout was attempted, and what genotype the model carries.

Oocyte-specific Ggpps conditional knockout mouse

Not built as a model of this disease -- it predates it by three years and its authors were asking how oocyte-granulosa cell communication is established -- but it is the only animal system in which loss of GGPP produces a phenotype in one of this disease's three target organs. Follicles are almost entirely lost by six weeks, the primary-to-secondary transition fails, Rho GTPase geranylgeranylation is inhibited, and supplying GGPP rescues all of it.

Species

Mouse

Genotype

Ggpps flox/flox; Ddx4-Cre (oocyte-specific conditional knockout)

Publication

PMID:28072828

Pathograph links

Ovarian Follicle Depletion partially recapitulates fidelity: moderate observes: tissue Reproduces follicle loss and infertility from loss of GGPP in the oocyte, and identifies the failing step as Rho GTPase geranylgeranylation. The rescue by GGPP is what makes the attribution causal rather than correlative.

Limitations: This is a conditional null restricted to the oocyte, whereas patients carry a partial loss of function expressed in every tissue, so the model overstates the enzymatic deficit while missing any granulosa-cell or somatic contribution. It is a mouse ovary rather than a human one, the phenotype is near-complete follicle loss by six weeks rather than ovarian insufficiency after apparently normal puberty, and no patient with this syndrome has had ovarian histology examined, so the correspondence is by mechanism and not by observation.

Readouts

Ovarian follicle number

Direction: DECREASED

Interpretation: Direct histological correlate of the follicle-depletion node in this model.

Show evidence (1 reference)

PMID:28072828 SUPPORT Model Organism

"The selective depletion of GGPP in mouse oocytes impaired the proliferation of granulosa cells, primary-secondary follicle transition and female fertility."

Reports the follicular and fertility measurements behind this readout.

Follicular development after GGPP administration

Direction: RESTORED

Interpretation: Rescue by the missing metabolite establishes that the follicular defect follows from GGPP depletion rather than from some other consequence of deleting the enzyme.

Show evidence (1 reference)

PMID:28072828 SUPPORT Model Organism

"GGPP administration restored the defects in oocyte-granulosa cell contact, granulosa cell proliferation and primary-secondary follicle transition in Ggpps depletion mice."

Reports the rescue experiment behind this readout.

Show evidence (1 reference)

PMID:28072828 SUPPORT Model Organism

"oocyte geranylgeranyl diphosphate (GGPP), a metabolic intermediate involved in protein geranylgeranylation, is required to establish the oocyte-granulosa cell communication."

Establishes that this model is informative for the requirement for GGPP in the ovary.

Deficient Protein Geranylgeranylation of Small GTPases recapitulates fidelity: moderate observes: molecular The one system in which the prenylation step this entry's mechanism turns on has actually been shown to fail: GGPP depletion inhibits Rho GTPase geranylgeranylation and its GTPase activity.

Limitations: Demonstrated in mouse oocytes with a conditional null, not in human tissue with a hypomorphic allele. The discovery paper for the human disease looked for a corresponding prenylome change in patient cells and did not find one, so this model may be showing what a complete loss does rather than what the human partial loss does.

Readouts

Rho GTPase geranylgeranylation and GTPase activity

Direction: DECREASED

Interpretation: Direct measurement of the prenylation step failing when GGPP is removed.

Show evidence (1 reference)

PMID:28072828 SUPPORT Model Organism

"GGPP depletion inhibited Rho GTPase geranylgeranylation and its GTPase activity, which was responsible for the accumulation of cell junction proteins in the oocyte cytoplasm and the failure to maintain physical connection between oocyte and granulosa cells."

Reports the prenylation and GTPase-activity measurements behind this readout.

Show evidence (1 reference)

PMID:28072828 SUPPORT Model Organism

"GGPP depletion inhibited Rho GTPase geranylgeranylation and its GTPase activity, which was responsible for the accumulation of cell junction proteins in the oocyte cytoplasm and the failure to maintain physical connection between oocyte and granulosa cells."

Establishes that this model reports directly on the prenylation node.

{ }

Source YAML

click to show

name: Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome
category: Mendelian
creation_date: "2026-09-07T00:00:00Z"
synonyms:
- GGPS1-related muscular dystrophy
- muscular dystrophy/hearing loss/ovarian insufficiency syndrome
- GGPS1-associated congenital muscular dystrophy
- MDHLOI
description: >-
  A recessive syndrome caused by biallelic hypomorphic missense variants in GGPS1, which
  encodes geranylgeranyl diphosphate synthase (GGPPS), the enzyme that makes geranylgeranyl
  pyrophosphate (GGPP) from farnesyl pyrophosphate in the mevalonate/isoprenoid pathway. GGPP
  is the lipid donor for protein geranylgeranylation, the modification that anchors Rab and
  Rho/Rac family small GTPases to membranes. The syndrome was defined in 2020 in eleven
  patients from six families and consists of an early-onset muscular dystrophy, congenital
  sensorineural hearing loss, and primary ovarian insufficiency in postpubertal 46,XX
  individuals.

  Two things make it unusual among the congenital muscular dystrophies. The first is the
  organ combination: hearing loss with ovarian insufficiency is the Perrault-syndrome dyad,
  and adding a dystrophy to it had not been described before. The second is that the lesion
  is metabolic rather than structural. There is no sarcolemmal protein missing; what has
  been shown in patient cells is a failure of the wounded plasma membrane to reseal, which
  is a plausible route from a prenylation deficit to a dystrophic muscle, since the
  membrane-repair machinery is built on vesicle trafficking that depends on prenylated Rab
  GTPases. Muscle biopsy is dystrophic with degeneration, regeneration and internal nuclei,
  and adds two features that are not part of the classic dystrophic picture: excess
  autophagic material and enlarged mitochondria.

  The mutational spectrum is narrow and informative. All reported alleles are missense, four
  of the five in the founding cohort clustering in a five-amino-acid stretch at the start of
  helix 11, on the outside of the hexamer and away from the catalytic barrel. They reduce
  enzyme activity only partially -- to roughly 70-85% of wild-type for recombinant protein
  and to about half of control in patient myoblasts -- and heterozygous loss-of-function
  carriers in gnomAD are asymptomatic. The gene is essential: complete inactivation is not
  compatible with multicellular life, and a knock-in mouse homozygous for the human Y259C
  allele dies before embryonic day 13.5, which is why there is no mouse model of the human
  disease. The alleles are therefore hypomorphic by necessity as well as by measurement.

  How a universally required modification produces disease in exactly three organs is
  unresolved, and the honest state of the mechanism is that the prenylation step itself has
  not been shown to fail in patients: the discovery paper reports that it could not find a
  consistent change in the small GTPases or in the overall prenylome of patient cells. The
  ovarian arm has the best independent support, from mouse oocytes in which selective GGPP
  depletion blocks Rho GTPase geranylgeranylation, the primary-to-secondary follicle
  transition and fertility. The cochlear arm has essentially none beyond the clinical
  observation that cochlear implantation works well, which localises the lesion to the
  sensory organ without saying what fails in it.

  Management is entirely supportive. Only three interventions are documented in the
  published patients and curated here -- cochlear implantation, non-invasive progressing to
  invasive ventilation, and spinal fusion for scoliosis. Rehabilitation, nutritional support
  and hormone replacement for the ovarian insufficiency are all plausible and are what these
  patients will in practice receive, but no source about this disease describes them, so
  they are deliberately not curated as treatments. There is no directed therapy. The one metabolite tried, coenzyme Q10, produced no improvement in the single
  patient given it, and muscle coenzyme Q10 was normal in another, so the coenzyme Q branch
  of the pathway is not obviously where the disease sits.

  Later cohorts have loosened the triad rather than confirming it. In thirteen individuals
  reported in 2022 hearing loss was present in only 46%, ovarian insufficiency was not
  established in the one woman who reached adulthood, and a 2024 case had isolated proximal
  weakness with normal hearing and raised transaminases. Muscular dystrophy is the constant;
  the two Perrault features are the variable ones. That inversion is the main reason this is
  curated as its own disease rather than as a Perrault subtype.
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    notes: >-
      Primary assignment. The muscular dystrophy is the constant and defining feature and
      the source of the morbidity that determines outcome, and Harrison's places the
      muscular dystrophies in the neurology part.
    evidence:
    - reference: PMID:35869884
      reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "This report consolidates the disease-causing role of biallelic variants in GGPS1 and demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy."
      explanation: >-
        Names muscular dystrophy as the constant feature against which hearing loss and
        ovarian insufficiency are variable, which is the basis for the neurologic assignment.
  - classification_value: DISORDER_OF_EAR
    notes: >-
      Congenital sensorineural hearing loss is a cardinal feature, was the presenting
      symptom in the milder patients, and is the feature that leads to cochlear
      implantation.
  - classification_value: ENDOCRINOLOGY_METABOLISM
    notes: >-
      Two reasons, and this is where the entry deliberately differs from
      Muscular_Dystrophy_Limb-girdle_Autosomal_Recessive_28, which considered and declined
      this assignment. Hypergonadotropic primary ovarian insufficiency is a presenting
      endocrine problem here, which LGMDR28 does not have; and the lesion is in an enzyme
      of the mevalonate pathway.
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A Mendelian recessive disorder diagnosed by exome or genome sequencing, with
      unaffected heterozygous parents and a genetic-counselling component.
disease_term:
  preferred_term: muscular dystrophy, congenital hearing loss, and ovarian insufficiency syndrome
  term:
    id: MONDO:0859189
    label: muscular dystrophy, congenital hearing loss, and ovarian insufficiency syndrome
parents:
- Congenital Muscular Dystrophy
notes: >-
  Entity verification. MONDO:0859189 carries the label "muscular dystrophy, congenital
  hearing loss, and ovarian insufficiency syndrome" and the cross-references OMIM:619518,
  MEDGEN:1794190 and UMLS:C5561980 (checked against EBI OLS4 on 2026-09-07, since the local
  MONDO SQLite build was deliberately not downloaded in this session). The stub records
  MONDO:0003847 (hereditary disease) as its only parent and hgnc:4249 GGPS1 as its only
  causal gene. Note that MONDO does not place this term under Perrault syndrome
  (MONDO:0017312), and that Perrault syndrome is a separate MONDO term with its own
  identity.

  Lump/split decision, which here is a real one. Perrault syndrome is defined by
  sensorineural hearing loss with primary ovarian insufficiency, and dismech already curates
  it in `kb/disorders/Perrault_Syndrome.yaml` -- an entry that already lists GGPS1 as a
  Perrault gene with an isoprenoid pathophysiology node. Two of this disease's three
  cardinal features are therefore the whole of Perrault syndrome, and GGPS1 was independently
  nominated as a Perrault candidate gene in a Perrault cohort in the same year the syndrome
  was named (PMID:32399598). That is the case for lumping, and it is not weak.

  It is nonetheless curated as its own entry, for four reasons. (1) The muscular dystrophy
  is not a Perrault feature: the discovery paper states that Perrault syndrome manifests
  with hearing loss and ovarian insufficiency "but without muscle involvement", and that the
  three-feature constellation had not been recognised before. (2) Later cohorts invert the
  Perrault definition here -- muscular dystrophy is present in essentially every reported
  patient, while hearing loss was present in only 46% of a thirteen-person cohort and
  ovarian insufficiency was likewise variable, so the two Perrault-defining features are the
  optional ones in this disease. A 2024 patient had isolated proximal weakness with normal
  hearing. (3) The mechanism is different in kind: Perrault syndrome is unified by failure of
  mitochondrial gene expression and proteostasis (with peroxisomal exceptions), whereas this
  is an isoprenoid/prenylation lesion. (4) MONDO and OMIM give it a separate identity
  (OMIM:619518) rather than a numbered PRLTS designation. The reciprocal cross-reference is
  kept: this entry lists Perrault syndrome as a differential, and the Perrault entry
  continues to carry GGPS1 as a gene whose phenotype "overlaps Perrault syndrome". A curator
  who disagrees should change both entries together, not one.

  Is there more than one GGPS1 disease? Yes, in the sense that the literature carries a
  second, quite separate GGPS1 association, and no, in the sense that the second is not a
  Mendelian disease. Monoallelic GGPS1 variants -- specifically p.Asp188Tyr in three sisters
  -- have been reported as a risk factor for atypical femoral fractures in women taking
  nitrogen-containing bisphosphonates, which inhibit GGPPS pharmacologically; the variant
  reduces catalytic activity about fourfold in vitro. That is a heterozygous drug-response
  susceptibility with no MONDO disease term of its own, not a dominant Mendelian disorder,
  and both the discovery paper and the 2022 cohort state the distinction explicitly. It is
  recorded here in `differential_diagnoses` and is deliberately not merged into this entry.
  No dominantly inherited GGPS1 disease was found in the literature searched.

  Named Entity Confusion. A GGPS1 literature search is dominated by three bodies of work
  that are not this disease: nitrogen-containing bisphosphonate pharmacology and the
  atypical-femoral-fracture association above; oncology, where GGPPS inhibition is a drug
  target across myeloma, leukaemia and solid tumours; and plant and microbial terpenoid
  biosynthesis, where GGPPS is an entirely different subject. Of 217 PubMed records matching
  GGPS1 or geranylgeranyl diphosphate synthase in the title or abstract, only about six
  concern this syndrome. Every clinical claim in this entry is sourced to a paper whose
  subjects carry biallelic germline GGPS1 variants: PMID:32403198 (eleven patients, six
  families), PMID:35869884 (thirteen individuals including two previously reported) and
  PMID:38129970 (one patient). PMID:32399598 is cited only for the mouse-folliculogenesis
  statement and for the Perrault-cohort ascertainment; PMID:28072828 and PMID:42323079 are
  cited as mouse pathway evidence and are labelled as such wherever they appear.

  GeneReviews. There is no GeneReviews chapter for this disease. The Perrault Syndrome
  Overview (PMID:25254289) exists but does not cover GGPS1 disease, and its cached record is
  a scope statement carrying no clinical findings, so it is not cited here.

  One paper deliberately not cited: PMID:39353334 ("Ultrarare Muscular Dystrophy Mimics
  Facioscapulohumeral Muscular Dystrophy", Pediatr Neurol 2024) is a clinical letter with no
  abstract and no retrievable body, so no quotable passage exists and nothing from it is
  asserted here.

  Deep research. `just dr_fallback='--fallback' research-disorder falcon ...` was run on
  2026-09-07. Falcon returned HTTP 402 (the Edison account is out of credits) and the run
  fell back to openscientist, which produced
  `research/Muscular_Dystrophy_Congenital_Hearing_Loss_And_Ovarian_Insufficiency_Syndrome-deep-research-openscientist.md`;
  the fallback is recorded in the report's own frontmatter (`fell_back: true`,
  `requested_provider: falcon`), which is why the file is named for openscientist.

  The report carries `needs_review: true` on both its validation blocks, and what triggers
  it is worth stating because neither problem touches this entry. Reference validation:
  15 of 15 references resolved, `unresolved_references` is empty, and 11 of 12 quotes
  matched -- the one failure is the report's own ellipsis-joined quote of PMID:35869884,
  which is a splice of two real sentences rather than a fabrication, and this entry quotes
  those sentences separately and verifiably. One reference (PMID:31427080, a bacterial
  GGPP-synthase crystal structure) was flagged as possibly off topic; it is genuinely
  tangential and is not cited here. Term validation: 47 of 49 CURIEs resolved with none
  unresolved, and the single mislabelling is the report writing "Disease MONDO" beside
  MONDO:0859189 in a table header, which is a formatting artifact rather than a wrong term.
  `just preflight-dr` returns PASS, with GGPS1 mentioned 35 times against two mentions each
  for the Perrault genes, and the MONDO and report OMIM numbers agreeing.

  What the report contributed, and what was rejected. It contributed one genuinely useful
  lead that the primary papers do not carry: PMID:26112408, which shows that GGPPS activity
  in mouse skeletal muscle sets the geranylgeranylation of RhoA, now cited on the
  prenylation node with its context stated. Two of its claims were checked and not used.
  First, it states that the Y259C knock-in mouse "recapitulates dystrophic muscle histology
  (autophagic material, enlarged mitochondria)"; that is wrong, and the error matters,
  because those findings are from human muscle biopsies while the homozygous knock-in mouse
  dies before embryonic day 13.5 and was never phenotyped. Second, it recommends hormone
  replacement therapy for the ovarian insufficiency and offers NCIT identifiers for several
  interventions; the hormone-replacement recommendation appears in no GGPS1 paper, and its
  suggested CURIEs (NCIT:C62556, NCIT:C15327, NCIT:C99913) were not the terms this entry
  needed, so neither was taken. Hormone replacement is very likely appropriate management
  for hypergonadotropic ovarian insufficiency, but it is not curated here because no source
  about this disease says so.

  Module conformance was considered and declined. `sensorineural_hair_cell_loss` is the
  obvious candidate for the auditory arm, and Perrault_Syndrome conforms to it. It is not
  used here because nothing is known about the cochlear lesion in GGPS1 disease beyond the
  inference from cochlear-implant responsiveness that it is sensory-organ localised.
  Declaring conformance would assert hair-cell mechanotransduction failure, oxidative
  stress and spiral ganglion degeneration, none of which has been observed in this disease.
  The gap is recorded as a knowledge gap instead.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic GGPS1 missense variants, homozygous in consanguineous families and compound
    heterozygous elsewhere. Heterozygous parents are unaffected, and heterozygous carriers
    of loss-of-function GGPS1 alleles are present in gnomAD and expected to be asymptomatic.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report specific mutations in the gene GGPS1 coding for the enzyme geranylgeranyl diphosphate synthase in 11 patients from 6 families, causing a highly distinctive syndrome of early onset muscular dystrophy combined with congenital sensorineural hearing loss and primary ovarian insufficiency in females."
    explanation: Establishes biallelic GGPS1 genotypes across six independent families as the cause of the syndrome.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rare heterozygous carriers for loss‐of‐function variants in GGPS1 are listed in gnomAD and should therefore be asymptomatic."
    explanation: >-
      Supports the recessive model, and specifically that a single defective allele is not
      sufficient to cause this disease.
pathophysiology:
- name: Biallelic Hypomorphic GGPS1 Missense Variants
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    All reported disease alleles are missense. In the founding cohort four of the five
    clustered in a five-amino-acid stretch at the start of the eleventh alpha-helix, on the
    outward-facing surface of the hexamer rather than in the catalytic barrel, and the fifth
    (P15S) sits in the helix involved in assembling the hexamer. The alleles are hypomorphic
    rather than null: they leave measurable enzyme activity, and a complete loss of GGPPS is
    incompatible with multicellular life, so a biallelic null genotype is not expected to be
    seen in a living patient.
  genetic_context:
    gene:
      preferred_term: GGPS1
      term:
        id: hgnc:4249
        label: GGPS1
    allele_type: SNV
    variant_origin: GERMLINE
    functional_impact_category: PARTIAL_LOSS_OF_FUNCTION
    description: >-
      Reported genotypes are homozygous missense in consanguineous families and compound
      heterozygous missense elsewhere. No biallelic null genotype has been reported.
  downstream:
  - target: Reduced Geranylgeranyl Diphosphate Synthase Activity
    causal_link_type: DIRECT
    description: The missense substitutions reduce the catalytic output of the enzyme they sit in.
    evidence:
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"
      explanation: >-
        Directly measures the activity of the recombinant mutant enzymes against wild-type,
        which is the edge from allele to enzyme deficit.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pathogenic variants fell within a specific 5 amino acid region toward the C terminus around the start of helix 11, with as of yet unclear function"
    explanation: Establishes the narrow positional clustering of the disease alleles outside the catalytic core.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The mutations do not abolish enzymatic activity of this essential enzyme, but with a highly distinctive genotype/phenotype correlation define the mevalonate pathway as essential for muscle, hearing, and endocrine functions."
    explanation: >-
      The authors' own statement that the alleles are hypomorphic rather than amorphic,
      which is the basis for the PARTIAL_LOSS_OF_FUNCTION classification.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Organism‐wide complete inactivation of GGPPS function is not compatible with multicellular survival."
    explanation: >-
      Supports the constraint that a surviving genotype must retain partial activity, which
      is why every reported allele is missense.
- name: Reduced Geranylgeranyl Diphosphate Synthase Activity
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Recombinant mutant enzymes retain roughly 70 to 85% of wild-type activity, and GGPPS
    activity measured in patient-derived myoblasts is about half that of pooled controls.
    The deficit is therefore partial in both a purified and a cellular assay, which is
    consistent with the position of the variants outside the catalytic barrel and is the
    quantitative basis for calling the disease a hypomorphic state rather than an enzyme
    deficiency in the classical inborn-error sense.
  molecular_functions:
  - preferred_term: geranylgeranyl diphosphate synthase activity
    modifier: DECREASED
    term:
      id: GO:0004311
      label: geranylgeranyl diphosphate synthase activity
  downstream:
  - target: Geranylgeranyl Pyrophosphate Depletion
    causal_link_type: DIRECT
    description: >-
      GGPPS catalyses the only route from farnesyl pyrophosphate to geranylgeranyl
      pyrophosphate, so reduced activity reduces the product.
    evidence:
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "For geranylgeranylation, FPP has to be converted to geranylgeranyl pyrophosphate (GGPP), by geranylgeranyl diphosphate synthase (GGPPS; EC:2.5.1.29), encoded by GGPS1."
      explanation: >-
        States the enzymatic step, which is what makes reduced enzyme activity a reduction
        in GGPP specifically rather than in some other pathway product.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"
    explanation: Quantifies the residual activity of the recombinant disease alleles.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We found that enzymatic activity in samples pooled from 4 patients (Patients P1, P2, P6, and P8) was decreased to about 50% of the activity in a pooled normal control sample."
    explanation: >-
      The same deficit measured in patient-derived myogenic cells rather than in recombinant
      protein, which is the closer approximation to the tissue in which the disease is expressed.
- name: Geranylgeranyl Pyrophosphate Depletion
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  description: >-
    Reduced GGPPS activity is taken to lower the cellular geranylgeranyl pyrophosphate pool.
    This step is inferred rather than measured: no GGPP measurement has been reported in
    tissue or cells from a patient with this syndrome. It is marked provisional for that
    reason. Independent support that GGPP depletion is a mechanistically consequential state
    in muscle comes from mouse work on the upstream enzyme HMG-CoA reductase, where the
    myopathy of HMGCR deficiency is attributed to GGPP depletion.
  biological_processes:
  - preferred_term: geranylgeranyl diphosphate biosynthetic process
    modifier: DECREASED
    term:
      id: GO:0033386
      label: geranylgeranyl diphosphate biosynthetic process
  - preferred_term: isoprenoid biosynthesis
    modifier: DECREASED
    term:
      id: GO:0008299
      label: isoprenoid biosynthetic process
  downstream:
  - target: Deficient Protein Geranylgeranylation of Small GTPases
    causal_link_type: DIRECT
    description: >-
      GGPP is the lipid donor for geranylgeranylation, so its depletion limits the
      modification.
  evidence:
  - reference: PMID:42323079
    reference_title: Skeletal muscle-specific deficiency of Rab geranylgeranyl transferase beta subunit induces myopathy and exacerbates the symptoms caused by HMG-CoA reductase deficiency in mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "Our findings demonstrate that myopathy induced by HMGCR deficiency is primarily driven by GGPP depletion in a mouse model."
    explanation: >-
      This result is about HMGCR, not GGPS1: it concerns mice lacking the rate-limiting
      enzyme two steps upstream, and it is cited here only to establish that depletion of
      GGPP is by itself sufficient to cause myopathy. It says nothing about GGPP levels in
      GGPS1 patients.
- name: Deficient Protein Geranylgeranylation of Small GTPases
  biological_scale: MOLECULAR
  mechanism_confidence: HYPOTHETICAL
  description: >-
    The proposed proximate lesion: too little GGPP to geranylgeranylate the Rab and Rho/Rac
    family GTPases that require it for membrane anchoring, with predicted consequences for
    autophagic and endosomal trafficking, mitochondrial dynamics and actin regulation. This
    node is the weakest link in the chain and is marked hypothetical deliberately. The
    discovery paper proposes it as a prediction, and reports in the same discussion that it
    could not find a consistent change in the small GTPases or the prenylome of patient
    cells. The best direct support is from mouse oocytes, where selective GGPP depletion
    demonstrably inhibits Rho GTPase geranylgeranylation.
  biological_processes:
  - preferred_term: protein geranylgeranylation
    modifier: DECREASED
    term:
      id: GO:0018344
      label: protein geranylgeranylation
  - preferred_term: protein prenylation
    modifier: DECREASED
    term:
      id: GO:0018342
      label: protein prenylation
  downstream:
  - target: Impaired Sarcolemmal Membrane Repair
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Membrane resealing depends on vesicle trafficking driven by prenylated Rab GTPases;
      which Rab is limiting here is not established.
  - target: Ovarian Follicle Depletion
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Loss of Rho GTPase geranylgeranylation and of oocyte-granulosa cell junction maintenance
    description: >-
      In mouse oocytes the same prenylation deficit blocks the primary-to-secondary follicle
      transition through loss of Rho GTPase geranylgeranylation.
    evidence:
    - reference: PMID:28072828
      reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "GGPP depletion inhibited Rho GTPase geranylgeranylation and its GTPase activity, which was responsible for the accumulation of cell junction proteins in the oocyte cytoplasm and the failure to maintain physical connection between oocyte and granulosa cells."
      explanation: >-
        This is mouse work on oocyte-specific Ggpps depletion, not on human GGPS1 hypomorphs,
        so it supports the edge by analogy of mechanism rather than by observation in the
        disease. It is the only place where the prenylation step has actually been shown to fail.
  - target: Cochlear Sensory Failure
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Asserted only as the route from the shared molecular lesion to the auditory phenotype.
      Nothing is known about which prenylated protein or which cochlear cell type is
      involved.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Possible downstream effects of GGPPS dysfunction and thus GGPP deficiency would be predicted to include impaired geranylgeranylation of small GTPases of the Rab, and Rho/Rac families with consequences on organelles involved in autophagy (such as Rabs23/24/7b), mitochondrial fission and fusion (Rab32), and actin filament dynamics (RhoA/Rac/Cdc42)."
    explanation: >-
      The authors' predicted downstream mechanism, quoted as the prediction it is. It names
      the GTPase families and the cellular processes this node claims are affected.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: "In ongoing work, however, we have not yet been able to pinpoint a consistent change in the small GTPases or in the overall prenylome of the cells (not shown)."
    explanation: >-
      The same paper's negative result. A deficient-prenylation node predicts a measurable
      change in prenylated GTPases in patient cells, and none was found; this is recorded as
      a refutation rather than omitted, because it is the reason the node is marked hypothetical.
  - reference: PMID:28072828
    reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "oocyte geranylgeranyl diphosphate (GGPP), a metabolic intermediate involved in protein geranylgeranylation, is required to establish the oocyte-granulosa cell communication."
    explanation: >-
      Mouse evidence that GGPP-dependent geranylgeranylation is a real and non-redundant
      requirement in at least one of the three affected tissues.
  - reference: PMID:26112408
    reference_title: Lipid-induced Muscle Insulin Resistance Is Mediated by GGPPS via Modulation of the RhoA/Rho Kinase Signaling Pathway.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "the free fatty acid-stimulated GGPPS expression in the skeletal muscle was able to enhance the geranylgeranylation of RhoA"
    explanation: >-
      This paper is about diet-induced insulin resistance in obese mice carrying a
      heterozygous muscle-specific Ggps1 deletion, not about this disease, and it reports no
      myopathy. It is cited for one fact it establishes in vivo: that GGPPS activity in
      skeletal muscle sets the geranylgeranylation of RhoA, which is the substrate class
      this node claims is undermodified.
- name: Impaired Sarcolemmal Membrane Repair
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Patient-derived myoblasts and myotubes reseal a focal laser wound more slowly than
    controls and are about twice as likely to fail to reseal at all. This is the only
    cellular phenotype demonstrated directly in patient material, and it is the mechanistic
    bridge from a prenylation defect to a dystrophy: repeated failure of membrane repair is
    the same final pathway that makes dysferlinopathy a muscular dystrophy, reached from a
    metabolic rather than a structural lesion.
  cell_types:
  - preferred_term: patient-derived MyoD-converted myoblast
    term:
      id: CL:0000515
      label: skeletal muscle myoblast
  biological_processes:
  - preferred_term: plasma membrane repair
    modifier: DECREASED
    term:
      id: GO:0001778
      label: plasma membrane repair
  downstream:
  - target: Myofiber Degeneration with Disordered Autophagy
    causal_link_type: DIRECT
    description: >-
      Failure to reseal the wounded sarcolemma drives the cycle of fiber damage,
      degeneration and regeneration that defines a dystrophy.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We observed greater dye entry, indicating a poor cell membrane repair, in both the patient myoblasts and myotubes as compared to the healthy controls"
    explanation: The direct measurement of delayed membrane resealing in patient myogenic cells.
- name: Myofiber Degeneration with Disordered Autophagy
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    Muscle shows a dystrophic process -- degeneration, regeneration and internalised nuclei
    -- with two additional ultrastructural features that a purely membrane-centred dystrophy
    would not predict: excess autophagic material, including myeloid bodies and positive
    LC3B staining, and enlarged though structurally normal mitochondria. Whether the
    autophagic and mitochondrial changes are a second consequence of failed Rab-dependent
    trafficking or a downstream response to chronic fiber injury is not established. Fatty
    infiltration is visible on muscle MRI, with relative sparing of rectus femoris, sartorius
    and gracilis and conspicuously asymmetric involvement.
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  biological_processes:
  - preferred_term: autophagy
    modifier: INCREASED
    term:
      id: GO:0006914
      label: autophagy
  downstream:
  - target: Proximal Muscle Weakness
    causal_link_type: DIRECT
    description: Loss of contractile tissue in the limb-girdle muscles produces the weakness.
  - target: Elevated Serum Creatine Kinase
    causal_link_type: DIRECT
    description: Ongoing myofiber breakdown releases creatine kinase into the circulation.
  - target: Respiratory Insufficiency
    causal_link_type: DIRECT
    description: The same process involves the respiratory musculature and determines survival.
  - target: Scoliosis
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Axial and paraspinal muscle weakness
    description: Weakness of the axial musculature allows progressive spinal deformity.
  - target: Joint Contractures
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Fixed posturing and reduced joint excursion in weak limbs
    description: Contractures follow the weakness and the immobility it imposes.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Histology was dystrophic, with evidence of degeneration and regeneration and internalized nuclei."
    explanation: Establishes the dystrophic tissue process on biopsy in nine patients.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Electron microscopy revealed ultrastructural evidence of enlarged but structurally normal mitochondria (Patient P8) as well as evidence of excess autophagic material (Patients P1 and P8; Fig 2)."
    explanation: The ultrastructural autophagic and mitochondrial findings that this node names alongside the dystrophic change.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole‐body muscle magnetic resonance imaging was performed in Patients P4–P6 and demonstrates variable increase in T1 signal in select muscles, resulting from fatty infiltration and thus consistent with an underlying muscular dystrophy"
    explanation: Imaging evidence of fatty replacement, the tissue-level correlate of chronic fiber loss.
- name: Ovarian Follicle Depletion
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: >-
    The ovarian arm. In mouse, depleting GGPP selectively in oocytes blocks the
    primary-to-secondary follicle transition, impairs granulosa cell proliferation and
    causes near-total follicle loss with subfertility, and the defect is reversed by
    supplying GGPP. Nothing equivalent has been measured in a human with this syndrome: the
    human evidence is the clinical and hormonal phenotype, not ovarian histology. Ggps1 is
    expressed most densely in germ cells and embryonic gonad cells in the mouse E14.5 female
    gonad, which is at least consistent with an early follicular lesion.
  cell_types:
  - preferred_term: oocyte
    term:
      id: CL:0000023
      label: oocyte
  - preferred_term: granulosa cell
    term:
      id: CL:0000501
      label: granulosa cell
  biological_processes:
  - preferred_term: ovarian follicle development
    modifier: DECREASED
    term:
      id: GO:0001541
      label: ovarian follicle development
  downstream:
  - target: Primary Ovarian Insufficiency
    causal_link_type: DIRECT
    description: >-
      Depletion of the follicle pool is what presents clinically as hypergonadotropic
      ovarian insufficiency.
  evidence:
  - reference: PMID:28072828
    reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "The selective depletion of GGPP in mouse oocytes impaired the proliferation of granulosa cells, primary-secondary follicle transition and female fertility."
    explanation: >-
      Mouse oocyte-specific Ggpps depletion, not a human GGPS1 hypomorph, so this supports
      the node by mechanism rather than by observation in patients. It is the experiment that
      makes an ovarian phenotype expected from a GGPP deficit.
  - reference: PMID:32399598
    reference_title: "Genomic sequencing highlights the diverse molecular causes of Perrault syndrome: a peroxisomal disorder (PEX6), metabolic disorders (CLPP, GGPS1), and mtDNA maintenance/translation disorders (LARS2, TFAM)."
    supports: SUPPORT
    evidence_source: OTHER
    directness: INDIRECT
    snippet: "whose enzymatic product is required for mouse folliculogenesis."
    explanation: >-
      An independent group, working from a Perrault cohort rather than a muscular dystrophy
      cohort, reaching the same conclusion about the relevance of the GGPPS product to
      folliculogenesis in mouse.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "Global view of Ggps1 expression in the E14.5 female gonad showed clusters most densely in the germ cells and embryonic gonad cells"
    explanation: >-
      Mouse single-cell expression data placing Ggps1 in the germ cells of the developing
      female gonad, which is consistent with an ovarian lesion but does not demonstrate one.
- name: Cochlear Sensory Failure
  biological_scale: TISSUE
  mechanism_confidence: HYPOTHETICAL
  description: >-
    The auditory arm, and the emptiest node in this entry. No cochlear tissue from an
    affected individual has been examined and no cochlear mechanism has been demonstrated.
    What exists is an inference: cochlear implantation was highly effective in all four
    implanted patients in the founding cohort, which places the lesion in the sensory organ
    rather than in the auditory nerve or central pathway, and Ggps1 is diffusely expressed
    in the mouse cochlear epithelium through embryonic and early postnatal development.
    The node is retained because the phenotype has to connect to the molecular lesion
    somewhere, and it is marked hypothetical because that connection is entirely unobserved.
  locations:
  - preferred_term: organ of Corti
    term:
      id: UBERON:0002227
      label: spiral organ of cochlea
  downstream:
  - target: Congenital Sensorineural Hearing Loss
    causal_link_type: DIRECT
    description: Failure of the cochlear sensory organ presents as sensorineural hearing loss.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "The sensorineural hearing loss observed in patients with GGPS1‐related muscular dystrophy is most likely sensory organ–related and localized to the organ of Corti, consistent with cochlear implantation being highly effective in all 4 patients in our cohort who underwent implantation."
    explanation: >-
      The localisation is an inference from therapeutic response rather than an observation
      of the cochlea, which is exactly the strength of evidence this node carries.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "Single‐cell RNA sequencing of the cochlear epithelium in the E14, P1, and P7 mouse shows Ggps1 with a sustained, diffuse expression at these timepoints"
    explanation: >-
      Mouse cochlear expression data. Expression in a tissue is consistent with a lesion
      there and is not evidence of one; it is cited for what it is.
phenotypes:
- name: Skeletal Muscle Atrophy
  category: Musculoskeletal
  description: >-
    Present in every individual in whom it was assessed in the 2022 cohort (12 of 12
    examined, out of 13 enrolled). With generalised weakness and areflexia it is one of
    the two findings that bring these patients to a neuromuscular clinic in the first
    place. Recorded as VERY_FREQUENT rather than OBLIGATE because the denominator is
    those examined, not the whole cohort.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Skeletal muscle atrophy
    term:
      id: HP:0003202
      label: Skeletal muscle atrophy
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12), hyporeflexia/areflexia (12/12), and myalgia (6/10)."
    explanation: >-
      The neuromuscular examination sentence, which reports muscular atrophy in 12 of 12 individuals examined.
- name: Areflexia
  category: Neurologic
  description: >-
    Absent or reduced deep tendon reflexes in 12 of 12 individuals examined in the 2022
    cohort. The source reports hyporeflexia and areflexia as a single combined count, so
    the more severe term is bound here and the combined denominator is stated rather than
    split between two phenotypes the paper does not separate.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Hyporeflexia or areflexia
    term:
      id: HP:0001284
      label: Areflexia
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12), hyporeflexia/areflexia (12/12), and myalgia (6/10)."
    explanation: >-
      Reports hyporeflexia/areflexia in 12 of 12 individuals examined, as a single combined count.
- name: Hypotonia
  category: Neurologic
  description: >-
    Reported in 10 of 13 individuals in the 2022 cohort, consistent with the congenital
    onset the disease name asserts.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12), hyporeflexia/areflexia (12/12), and myalgia (6/10)."
    explanation: >-
      Reports hypotonia in 10 of 13 individuals in the second cohort.
- name: Short Stature
  category: Growth
  description: >-
    Reported in 8 of 13 individuals in the 2022 cohort, counted separately from failure to
    thrive. The founding cohort hedged that short stature here is "potentially suggestive
    of further endocrinologic involvement", which is why it is curated as its own queryable
    phenotype rather than left inside the failure-to-thrive description: in a disease that
    already has a defined endocrine arm, whether the growth deficit is nutritional or
    endocrine is an open question rather than a detail.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12), hyporeflexia/areflexia (12/12), and myalgia (6/10)."
    explanation: >-
      Reports short stature in 8 of 13 individuals, counted separately from failure to thrive.
- name: Calf Muscle Hypertrophy
  category: Musculoskeletal
  description: >-
    Reported in 4 of 12 individuals examined in the 2022 cohort. The source says "calf
    hypertrophy", so the binding is the plain hypertrophy term rather than
    HP:0003707 Calf muscle pseudohypertrophy, which would assert a fatty-fibrous histology
    nobody reported here.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Calf muscle hypertrophy
    term:
      id: HP:0008981
      label: Calf muscle hypertrophy
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12), hyporeflexia/areflexia (12/12), and myalgia (6/10)."
    explanation: >-
      Reports calf hypertrophy in 4 of 12 individuals examined.
- name: Myalgia
  category: Musculoskeletal
  description: >-
    Muscle pain in 6 of 10 individuals asked in the 2022 cohort.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Myalgia
    term:
      id: HP:0003326
      label: Myalgia
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They had normal cognition (0/13) with short stature (8/13) and progressive scoliosis (7/11). Neuromuscular examination revealed hypotonia (10/13), proximal or generalized muscle weakness (12/13), and muscular atrophy (12/12) accompanied with stiffness (6/12), calf hypertrophy (4/12), hyporeflexia/areflexia (12/12), and myalgia (6/10)."
    explanation: >-
      Reports myalgia in 6 of 10 individuals in whom it was assessed.
- name: Decreased Fetal Movement
  category: Prenatal
  description: >-
    The index patient of the founding cohort was symptomatic before birth. This, the weak
    cry and the poor suck are what make the onset congenital rather than infantile, which
    is the claim the disease name rests on.
  phenotype_term:
    preferred_term: Decreased fetal movement
    term:
      id: HP:0001558
      label: Decreased fetal movement
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The index patient (Patient P1; Fig 1) manifested symptoms prenatally with decreased fetal movements, and neonatally with a weak cry and a poor suck."
    explanation: >-
      Documents prenatal onset in the index patient.
- name: Weak Cry
  category: Neonatal
  description: >-
    Neonatal presenting sign in the index patient of the founding cohort, alongside poor
    suck.
  phenotype_term:
    preferred_term: Weak cry
    term:
      id: HP:0001612
      label: Weak cry
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The index patient (Patient P1; Fig 1) manifested symptoms prenatally with decreased fetal movements, and neonatally with a weak cry and a poor suck."
    explanation: >-
      Documents weak cry as a neonatal presenting sign.
- name: Poor Suck
  category: Neonatal
  description: >-
    Neonatal feeding difficulty in the index patient of the founding cohort, the bulbar
    counterpart of the generalised weakness.
  phenotype_term:
    preferred_term: Poor suck
    term:
      id: HP:0002033
      label: Poor suck
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The index patient (Patient P1; Fig 1) manifested symptoms prenatally with decreased fetal movements, and neonatally with a weak cry and a poor suck."
    explanation: >-
      Documents poor suck as a neonatal presenting sign.
- name: Proximal Muscle Weakness
  category: Musculoskeletal
  description: >-
    The constant feature. Weakness affects the limb girdles and is generalised in some
    patients, with onset from the prenatal period to preschool age and progression that is
    usually slow. It was present in twelve of thirteen individuals in the 2022 cohort.
  phenotype_term:
    preferred_term: Proximal muscle weakness
    term:
      id: HP:0003701
      label: Proximal muscle weakness
    clinical_course: PROGRESSIVE
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably elevated CK, scoliosis, and respiratory insufficiency, in which the symptoms are progressive in nature and can be severe."
    explanation: Names proximal muscle weakness as part of the recognisable syndrome across the founding cohort.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural hearing loss (6/13)"
    explanation: Quantifies proximal or generalised weakness at twelve of thirteen individuals in the second cohort.
- name: Congenital Sensorineural Hearing Loss
  category: Auditory
  description: >-
    Bilateral sensorineural hearing loss, congenital or of infantile onset, and often the
    first symptom identified in patients with milder motor involvement. Its frequency
    differs sharply between the two cohorts: present in all but one of eleven patients in
    2020 but in only 46% of the 2022 cohort, where absence was clinically and objectively
    confirmed in the rest. It is therefore a common but not obligatory feature.
  phenotype_term:
    preferred_term: Congenital sensorineural hearing impairment
    term:
      id: HP:0008527
      label: Congenital sensorineural hearing impairment
  frequency: FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sensorineural hearing loss was present in all but one patient in this cohort and was the first symptom identified in those patients with milder motor phenotypes."
    explanation: Records the near-universal hearing loss of the founding cohort and its role as the presenting symptom in milder patients.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hearing loss was present in only 46% of the individuals."
    explanation: >-
      The counterweight from the second cohort, which is why this is curated as FREQUENT
      rather than VERY_FREQUENT.
  - reference: PMID:38129970
    reference_title: Expanding the phenotypic and genotypic spectrum of GGPS1 related congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The patient presented with only proximal muscle weakness, and elevated liver transaminases with spared hearing function."
    explanation: A genotype-confirmed patient with normal hearing, confirming that the auditory feature can be absent entirely.
- name: Primary Ovarian Insufficiency
  category: Endocrine
  description: >-
    Hypergonadotropic ovarian insufficiency in postpubertal 46,XX individuals, confirmed by
    menopausal follicle-stimulating hormone levels in the setting of amenorrhoea or
    infertility. It was present in every postpubertal female of the founding cohort. Like
    the hearing loss it is not obligatory: in the 2022 cohort only one woman had reached
    adulthood and she had no clinical signs of it, though a twelve-year-old had a raised
    FSH. Male gonadal function has never been formally assessed in this disease, and none
    of the five adult men in the founding cohort had fathered a child.
  phenotype_term:
    preferred_term: Premature ovarian insufficiency
    term:
      id: HP:0008209
      label: Premature ovarian insufficiency
  frequency: FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Primary ovarian insufficiency, also known as premature ovarian failure, has been diagnosed in all postpubertal females in this cohort, as confirmed by menopausal levels of follicle‐stimulating hormone (FSH) in the setting of a history of amenorrhea"
    explanation: Establishes the ovarian phenotype and the hormonal criterion used to diagnose it in every postpubertal female of the cohort.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This report consolidates the disease-causing role of biallelic variants in GGPS1 and demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy."
    explanation: >-
      States that ovarian insufficiency, like hearing loss, is variable rather than
      obligatory, which is the basis for the FREQUENT rather than OBLIGATE frequency.
- name: Elevated Serum Creatine Kinase
  category: Laboratory
  description: >-
    Creatine kinase is raised, characteristically in episodes rather than continuously, and
    reached 18,025 U/l in the index patient. In three patients the episodic rises coincided
    with intercurrent diarrhoeal illness and with transient worsening of weakness.
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase activity
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase activity
    temporality: RECURRENT
  frequency: FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably elevated CK, scoliosis, and respiratory insufficiency, in which the symptoms are progressive in nature and can be severe."
    explanation: Names episodic creatine kinase elevation as part of the syndrome's recognisable phenotype.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In Patients P1, P2, and P7, there was a history of episodic worsening of weakness concomitant with higher CK elevations during episodes of diarrhea."
    explanation: >-
      Names an intercurrent-illness trigger for the episodic rises, which is the most
      clinically actionable observation in the founding report: a treating physician
      seeing a diarrhoeal illness in one of these patients should expect a CK spike and
      transient worsening of weakness rather than a new process.
- name: Respiratory Insufficiency
  category: Respiratory
  description: >-
    Restrictive respiratory failure from weakness of the respiratory muscles, requiring
    non-invasive ventilation and in the most severely affected patients tracheostomy. It
    occurred in eight of thirteen individuals in the 2022 cohort with onset ranging from
    seven months to twenty years.
  phenotype_term:
    preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She developed respiratory insufficiency, necessitating noninvasive ventilation, progressing to tracheostomy."
    explanation: The progression from non-invasive ventilation to tracheostomy in the index patient.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural hearing loss (6/13)"
    explanation: Quantifies respiratory insufficiency and ventilatory requirement across the second cohort.
- name: Scoliosis
  category: Musculoskeletal
  description: >-
    Progressive scoliosis follows the axial weakness and required spinal fusion in the more
    severely affected patients.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thus, progressive muscle weakness and joint contractures resulting in loss of independent ambulation, respiratory insufficiency necessitating ventilation dependence, and severe scoliosis were seen in Patients P1, P2, P3, and P9, whereas the other patients had a less severe progression of weakness."
    explanation: Records severe scoliosis alongside the other features of the severe end of the spectrum.
- name: Joint Contractures
  category: Musculoskeletal
  description: >-
    Contractures of hip, knee, elbow and neck develop with the weakness and, in the most
    affected patients, impose the posture that limits function further. Seven of twelve
    assessed individuals in the 2022 cohort had them.
  phenotype_term:
    preferred_term: Joint contracture
    term:
      id: HP:0034392
      label: Joint contracture
  frequency: FREQUENT
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural hearing loss (6/13)"
    explanation: Reports joint contractures in seven of twelve assessed individuals.
- name: Loss of Ambulation
  category: Musculoskeletal
  description: >-
    A minority trajectory rather than the rule. Six of thirteen individuals in the 2022
    cohort lost ambulation, at a mean age of about eight years, while others maintained
    independent walking into adulthood; ninety-two per cent of that cohort progressed slowly.
  phenotype_term:
    preferred_term: Loss of ambulation
    term:
      id: HP:0002505
      label: Loss of ambulation
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six affected individuals lost ambulation at the mean age of 8.1"
    explanation: Quantifies how many individuals lost ambulation and at what age.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thus, progressive muscle weakness and joint contractures resulting in loss of independent ambulation, respiratory insufficiency necessitating ventilation dependence, and severe scoliosis were seen in Patients P1, P2, P3, and P9, whereas the other patients had a less severe progression of weakness."
    explanation: Records loss of independent ambulation in the severely affected patients and its absence in the rest.
- name: Motor Delay
  category: Neurologic
  description: >-
    Delayed motor milestones were the commonest first presenting symptom, in ten of thirteen
    individuals in the 2022 cohort, with independent walking at a mean of about 1.7 years.
    Cognition is reported as normal.
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  frequency: FREQUENT
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The disease onset ranged from prenatal (3/13) to pre‐schooler age"
    explanation: Establishes the onset window within which the motor delay was recognised.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of note, no cardiac or cognitive involvement has been noted in this cohort."
    explanation: >-
      Cited for the negative half of this item: cognition is unaffected, so the motor delay
      is a motor problem and not part of a global developmental one.
- name: Failure to Thrive
  category: Growth
  description: >-
    Failure to thrive and short stature were present in eight of the eleven patients of the
    founding cohort, and gastrostomy feeding was needed in the index patient. The authors
    raise but do not settle the possibility that this reflects a further endocrine
    involvement rather than the mechanical consequences of severe weakness.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  frequency: FREQUENT
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Eight patients had evidence of failure to thrive and/or short stature, potentially suggestive of further endocrinologic involvement."
    explanation: Reports the frequency and the authors' own hedged interpretation of it.
- name: Elevated Hepatic Transaminases
  category: Gastrointestinal
  description: >-
    Reported in one genotype-confirmed patient with an otherwise isolated proximal myopathy,
    and offered by those authors as an extension of the phenotype. The caveat is the usual
    one for a myopathy: transaminase elevation commonly reflects muscle rather than liver
    injury, and a single patient does not settle which it is here.
  phenotype_term:
    preferred_term: Elevated circulating hepatic transaminase concentration
    term:
      id: HP:0002910
      label: Elevated circulating hepatic transaminase concentration
  frequency: VERY_RARE
  evidence:
  - reference: PMID:38129970
    reference_title: Expanding the phenotypic and genotypic spectrum of GGPS1 related congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The patient presented with only proximal muscle weakness, and elevated liver transaminases with spared hearing function."
    explanation: The single reported patient in whom transaminase elevation was described as part of the phenotype.
- name: Absence of Cardiac Involvement
  category: Cardiovascular
  description: >-
    Curated as an explicit negative because it separates this disease from most other
    congenital and limb-girdle muscular dystrophies, several of which carry a cardiomyopathy
    that determines management. No cardiac involvement was found in the founding cohort.
    This is a statement about eleven patients, not a guarantee.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Of note, no cardiac or cognitive involvement has been noted in this cohort."
    explanation: >-
      Graded REFUTE against the claim that cardiac involvement is a feature of this disease,
      which is what this phenotype item asks.
histopathology:
- name: Dystrophic muscle with excess autophagic material and enlarged mitochondria
  description: >-
    Biopsies from nine patients showed a dystrophic process with degeneration, regeneration
    and internalised nuclei, occasional rimmed vacuoles, and irregular oxidative staining
    with core-like regions; ragged red and cytochrome-oxidase-negative fibers were seen in
    one patient. Electron microscopy added excess autophagic material including myeloid
    bodies, positive LC3B staining, and enlarged but structurally normal mitochondria.
    The combination of a dystrophic pattern with disordered autophagy is what makes the
    biopsy suggestive rather than merely non-specific.
  notes: >-
    Deliberately incomplete. The rimmed vacuoles, the core-like regions, the ragged red and
    COX-negative fibers and the LC3B positivity are all stated in PMID:32403198, and the
    quotations below cover the dystrophic pattern and the ultrastructural findings. A
    curator adding the finer features should quote them from the same paper rather than
    from this description. Note also PMID:35869884's observation that one patient biopsied
    at eight months showed neither dystrophic change nor fatty infiltration, which that
    paper attributes to the early age at biopsy; a normal early biopsy therefore does not
    exclude the diagnosis.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Histology was dystrophic, with evidence of degeneration and regeneration and internalized nuclei."
    explanation: The light-microscopic dystrophic pattern.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Electron microscopy revealed ultrastructural evidence of enlarged but structurally normal mitochondria (Patient P8) as well as evidence of excess autophagic material (Patients P1 and P8; Fig 2)."
    explanation: The ultrastructural findings that distinguish this biopsy from a purely sarcolemmal dystrophy.
biochemical:
- name: Normal Muscle Coenzyme Q10
  biomarker_term:
    preferred_term: Decreased level of coenzyme Q10 in skeletal muscle
    term:
      id: HP:0034369
      label: Decreased level of coenzyme Q10 in skeletal muscle
  presence: Absent
  notes: >-
    A negative biochemical finding, and a useful one. GGPP feeds the ubiquinone branch of
    the isoprenoid pathway as well as the prenylation branch, so coenzyme Q10 deficiency is
    the obvious alternative mechanism and would carry a directed treatment. Muscle coenzyme
    Q10 was normal in the one patient measured, and an empirical oral coenzyme Q10 trial in
    another produced no improvement. The item is bound to the HPO term for the abnormality
    that was looked for and not found (`HP:0034369`, decreased muscle coenzyme Q10), with
    `presence` recording that it was absent; this is a negative finding curated as one,
    not an assertion that patients are coenzyme Q10 deficient. One patient measured and one
    patient treated is thin evidence either way.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "The CoQ10 level in muscle was determined to be normal in Patient P1."
    explanation: >-
      Graded REFUTE against the claim that this disease is a muscle coenzyme Q10 deficiency
      state, which is the claim this biochemical item exists to test.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Patient P3 was given an empirical treatment trial of oral CoQ10, which did not result in any noted improvement of symptoms."
    explanation: >-
      The corresponding therapeutic test, also negative. One uncontrolled patient is weak
      evidence, but it is the only evidence there is.
- name: Elevated Serum Follicle-Stimulating Hormone
  biomarker_term:
    preferred_term: Elevated circulating follicle stimulating hormone level
    term:
      id: HP:0008232
      label: Elevated circulating follicle stimulating hormone level
  presence: INCREASED
  notes: >-
    Menopausal-range FSH is what makes the ovarian insufficiency hypergonadotropic and so
    primary rather than central. Reported values in the founding cohort were 88.2, 50.3 and
    53.2 IU/l in the three postpubertal women assessed.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Primary ovarian insufficiency, also known as premature ovarian failure, has been diagnosed in all postpubertal females in this cohort, as confirmed by menopausal levels of follicle‐stimulating hormone (FSH) in the setting of a history of amenorrhea"
    explanation: Gives the measured FSH values and the diagnostic use made of them.
genetic:
- name: GGPS1 (geranylgeranyl diphosphate synthase 1)
  gene_term:
    preferred_term: GGPS1
    term:
      id: hgnc:4249
      label: GGPS1
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    The only gene associated with this disease and the only causal gene MONDO links to
    MONDO:0859189. All reported disease alleles are missense; no biallelic null genotype has
    been reported and none is expected, since complete inactivation of GGPPS is incompatible
    with multicellular survival and the mouse null is not viable. Four of the five founding
    alleles cluster within five residues at the start of helix 11, on the outer surface of
    the hexamer rather than in the catalytic barrel, and that domain is conserved in animals
    but not in plants, which the discovery authors read as evidence for an animal-specific
    function beyond bulk catalysis. A separate, monoallelic GGPS1 association with
    bisphosphonate-related atypical femoral fracture exists and is a different claim
    entirely; see `differential_diagnoses` and the entry notes.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report specific mutations in the gene GGPS1 coding for the enzyme geranylgeranyl diphosphate synthase in 11 patients from 6 families, causing a highly distinctive syndrome of early onset muscular dystrophy combined with congenital sensorineural hearing loss and primary ovarian insufficiency in females."
    explanation: Establishes GGPS1 causality across eleven patients in six families.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pathogenic variants fell within a specific 5 amino acid region toward the C terminus around the start of helix 11, with as of yet unclear function"
    explanation: Characterises the positional clustering that defines the allelic spectrum.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we describe 11 affected individuals from four unpublished families with ultra-rare missense variants in GGPS1 and provide follow-up details from a previously reported family."
    explanation: Independent replication of GGPS1 causality in four further previously unreported families.
variants:
- name: NM_004837.4 p.(Tyr259Cys)
  description: >-
    Carried in compound heterozygosity with R261G by the two index siblings. It has the
    highest in-silico damage score of the founding alleles, which is why it was chosen for
    the mouse knock-in, and the resulting homozygous animals die in utero.
  gene:
    preferred_term: GGPS1
    term:
      id: hgnc:4249
      label: GGPS1
  type: missense variant
  clinical_significance: PATHOGENIC
  functional_effects:
  - function: geranylgeranyl diphosphate synthase catalytic activity
    type: partial loss of function
    description: Retains roughly 70 to 85% of wild-type activity as recombinant protein.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"
    explanation: Reports the partial activity retained by this and the other C-terminal alleles.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "homozygote Y259C knock‐in embryos developed up to embryonic day (ED)12.5, with no live embryos observed after this point."
    explanation: The embryonic lethality of the homozygous knock-in, which is the strongest evidence that this allele is severely hypomorphic.
- name: NM_004837.4 p.(Arg261Gly) and p.(Arg261His)
  description: >-
    Two substitutions at the same residue. R261G was found in compound heterozygosity in two
    families, and R261H homozygously in two families whose patients had the mildest motor
    phenotype, retaining independent ambulation into adulthood while still having
    sensorineural hearing loss and ovarian insufficiency. Both are ultra-rare in gnomAD.
  gene:
    preferred_term: GGPS1
    term:
      id: hgnc:4249
      label: GGPS1
  type: missense variant
  functional_effects:
  - function: geranylgeranyl diphosphate synthase catalytic activity
    type: partial loss of function
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"
    explanation: Measures the residual activity of both R261 substitutions alongside the other alleles.
- name: NM_004837.4 p.(Phe257Cys)
  description: >-
    Homozygous in two families, one with a single affected child and one with three affected
    siblings spanning a moderate-to-severe range, which is an intrafamilial demonstration
    that genotype does not fix severity.
  gene:
    preferred_term: GGPS1
    term:
      id: hgnc:4249
      label: GGPS1
  type: missense variant
  functional_effects:
  - function: geranylgeranyl diphosphate synthase catalytic activity
    type: partial loss of function
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"
    explanation: Reports this allele among those with reduced catalytic rate.
- name: NM_004837.4 p.(Pro15Ser)
  description: >-
    The exception to the C-terminal clustering, and the exception to the activity deficit: it
    lies in the first alpha-helix, which mediates assembly of the hexamer from dimers, and
    it had the same catalytic activity as wild-type in the recombinant assay. It was found
    in compound heterozygosity with R261G. That an allele can cause this disease without
    reducing bulk catalytic rate is the main argument that the pathogenic mechanism is not
    simply loss of enzyme output.
  gene:
    preferred_term: GGPS1
    term:
      id: hgnc:4249
      label: GGPS1
  type: missense variant
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "consistently showed a reduced rate of activity of approximately 70 to 85% of wild‐type"
    explanation: >-
      The same measurement, quoted here for its exclusion of P15S: the reduced-activity
      finding applies to the other four alleles and not to this one.
prevalence:
- population: Worldwide, published cases
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No population prevalence estimate exists for this syndrome and none is asserted. The
    published case count is the honest measure: eleven individuals from six families in the
    2020 defining report, eleven further individuals from four previously unreported families
    in 2022 (whose thirteen-person cohort also included follow-up on two individuals reported
    from a Perrault cohort in 2020), and one further patient in 2024 -- at least
    twenty-three published individuals, in at least twelve families, as of 2026. All
    reported alleles are ultra-rare or absent in gnomAD.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report specific mutations in the gene GGPS1 coding for the enzyme geranylgeranyl diphosphate synthase in 11 patients from 6 families, causing a highly distinctive syndrome of early onset muscular dystrophy combined with congenital sensorineural hearing loss and primary ovarian insufficiency in females."
    explanation: The founding cohort's case count.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we describe 11 affected individuals from four unpublished families with ultra-rare missense variants in GGPS1 and provide follow-up details from a previously reported family."
    explanation: The second cohort's case count, which is what the total above is built from.
progression:
- phase: Onset
  age_range: prenatal to preschool age
  notes: >-
    Onset ranges from the prenatal period, presenting as decreased fetal movement or a weak
    cry, to preschool age, with a mean age at first symptom of about sixteen months in the
    2022 cohort. Delayed motor milestones are the commonest first presentation, and in the
    milder patients the hearing loss is identified before the weakness.
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The disease onset ranged from prenatal (3/13) to pre‐schooler age"
    explanation: Gives the onset window and the mean age at first symptom.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sensorineural hearing loss was present in all but one patient in this cohort and was the first symptom identified in those patients with milder motor phenotypes."
    explanation: Records that hearing loss is the first symptom identified in the patients with milder motor involvement.
- phase: Progression
  notes: >-
    Two courses rather than one. The severe course runs from progressive weakness and
    contractures to loss of ambulation in the first or second decade, ventilator dependence
    and severe scoliosis; the milder course preserves independent ambulation into adulthood.
    Ninety-two per cent of the 2022 cohort progressed slowly, and six of thirteen lost
    ambulation at a mean of about eight years. Severity of the hearing loss and of the
    ovarian insufficiency does not track with severity of the muscular dystrophy.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thus, progressive muscle weakness and joint contractures resulting in loss of independent ambulation, respiratory insufficiency necessitating ventilation dependence, and severe scoliosis were seen in Patients P1, P2, P3, and P9, whereas the other patients had a less severe progression of weakness."
    explanation: Separates the severely affected patients from the rest within the same cohort.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six affected individuals lost ambulation at the mean age of 8.1"
    explanation: Quantifies the loss of ambulation in the second cohort.
diagnosis:
- name: Molecular diagnosis by exome or genome sequencing
  description: >-
    The diagnosis is molecular. The syndrome was found by whole exome sequencing combined
    with shared-haplotype analysis in the index siblings, and further families were
    ascertained either by targeted GGPS1 Sanger sequencing on the strength of a suggestive
    phenotype or by exome sequencing. The clinical trigger worth acting on is the
    combination itself: a congenital or early-onset muscular dystrophy with sensorineural
    hearing loss, in a girl or woman with amenorrhoea or infertility, has no other
    recognised genetic cause.
  diagnosis_term:
    preferred_term: whole exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We applied whole exome sequencing (WES) superimposed on shared \nhaplotype regions to identify the initial biallelic variants in GGPS1 followed \nby GGPS1 Sanger sequencing or WES in 5 additional families with the same \nphenotype."
    explanation: Names the sequencing strategy that made the diagnosis in the index family and in five further families.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably elevated CK, scoliosis, and respiratory insufficiency, in which the symptoms are progressive in nature and can be severe."
    explanation: Describes the recognisable phenotype that should prompt GGPS1 testing.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we describe 11 affected individuals from four unpublished families with ultra-rare missense variants in GGPS1 and provide follow-up details from a previously reported family."
    explanation: The second cohort was likewise ascertained by sequencing rather than by any biochemical test.
- name: Audiometric assessment
  description: >-
    Formal audiometry, including brainstem auditory evoked response testing in infancy, is
    what identifies the hearing loss and dates its onset. The point the discovery authors
    make is a practical one: the hearing loss was called congenital only because audiometry
    was performed, and in patients tested later in childhood the age at diagnosis reflects
    when the test was done rather than when the deafness began. Audiometry is also what
    established the absence of hearing loss in the patients of the second cohort who did not
    have it, which is why that negative is credible.
  diagnosis_term:
    preferred_term: audiometric testing
    term:
      id: NCIT:C38036
      label: Audiometric Test
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Given that the hearing loss was diagnosed in some patients in the neonatal period and in others during childhood, the onset is likely congenital, as diagnosis relies on a formal audiometric evaluation."
    explanation: States that the determination of congenital onset rests on formal audiometric evaluation.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "she was diagnosed with bilateral sensorineural hearing loss (via brainstem auditory evoked response testing)."
    explanation: The specific audiological modality used in the index patient in infancy.
- name: Serum creatine kinase
  description: >-
    Creatine kinase is the screening abnormality that places the weakness in muscle. It is
    raised episodically rather than continuously, reaching 18,025 U/l in the index patient
    at nineteen months, and the episodic rises accompanied intercurrent diarrhoeal illness
    in three patients. A single normal value therefore does not exclude the disease.
  diagnosis_term:
    preferred_term: creatine kinase measurement
    term:
      id: NCIT:C64489
      label: Creatine Kinase Measurement
  markers: Serum creatine kinase activity
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "muscle weakness, and elevated CK (up to 18,025U/l at 19 months of age)."
    explanation: Gives the magnitude of the creatine kinase elevation and the setting in which it was measured.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In summary, GGPS1‐related muscular dystrophy/hearing loss/ovarian insufficiency syndrome is characterized by a remarkably consistent and recognizable phenotype of congenital sensorineural hearing loss, primary ovarian insufficiency in females, proximal muscle weakness with episodes of variably elevated CK, scoliosis, and respiratory insufficiency, in which the symptoms are progressive in nature and can be severe."
    explanation: Records that the elevation is episodic and variable rather than sustained, which is what makes a single value uninformative.
- name: Muscle biopsy
  description: >-
    Biopsy establishes that the process is dystrophic rather than neurogenic or
    inflammatory, and adds the two ultrastructural features that point towards this
    diagnosis specifically: excess autophagic material and enlarged mitochondria. It was
    performed in nine of the eleven patients of the founding cohort. It is not a
    confirmatory test -- nothing on the biopsy is specific to GGPS1 -- and a biopsy taken
    very early can be normal.
  diagnosis_term:
    preferred_term: muscle biopsy
    term:
      id: NCIT:C51895
      label: Muscle Biopsy
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Muscle biopsies were performed in 9 patients (Patients P1–P9)."
    explanation: Records how many patients were biopsied, which is what makes the histological description a cohort finding rather than a case report.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Histology was dystrophic, with evidence of degeneration and regeneration and internalized nuclei."
    explanation: The dystrophic pattern the biopsy is performed to demonstrate.
- name: Endocrine evaluation of postpubertal females
  description: >-
    Follicle-stimulating hormone measurement in the setting of amenorrhoea or infertility is
    what establishes the ovarian component, and without it the feature is systematically
    missed: in the founding cohort the affected men were never formally assessed, and in the
    2022 cohort only one woman had reached adulthood. Prepubertal girls and all males are
    effectively unassessable for this feature at the time of diagnosis, so a negative
    ovarian history in a child says nothing.
  diagnosis_term:
    preferred_term: follicle stimulating hormone measurement
    term:
      id: NCIT:C74783
      label: Follicle Stimulating Hormone Measurement
  markers: Serum follicle-stimulating hormone
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Primary ovarian insufficiency, also known as premature ovarian failure, has been diagnosed in all postpubertal females in this cohort, as confirmed by menopausal levels of follicle‐stimulating hormone (FSH) in the setting of a history of amenorrhea"
    explanation: Names the hormonal criterion, gives the measured values, and states the clinical settings in which it was applied.
- name: Muscle magnetic resonance imaging
  description: >-
    Whole-body muscle MRI shows the fatty infiltration that confirms a dystrophic process
    and, in the three patients imaged, a pattern that may prove diagnostically useful:
    relative sparing of rectus femoris, sartorius and gracilis, with conspicuously
    asymmetric involvement. Three patients is not enough to call this a signature, and the
    authors say as much.
  diagnosis_term:
    preferred_term: muscle magnetic resonance imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole‐body muscle magnetic resonance imaging was performed in Patients P4–P6 and demonstrates variable increase in T1 signal in select muscles, resulting from fatty infiltration and thus consistent with an underlying muscular dystrophy"
    explanation: Reports the imaging finding and its interpretation as evidence of an underlying muscular dystrophy.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The relative sparing of the rectus femoris, sartorius, and gracilis muscles and asymmetric involvement of muscles in this clinical context may be diagnostically helpful"
    explanation: >-
      The part of the imaging finding that could actually discriminate. The authors' own
      "may be" is preserved: the pattern comes from three imaged patients, which is not
      enough to call it a signature.
treatments:
- name: Cochlear implantation
  description: >-
    The most effective intervention reported in this disease. All four patients implanted in
    the founding cohort responded well, which is also the observation that localises the
    auditory lesion to the sensory organ rather than to the nerve.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: cochlear device implantation
    term:
      id: NCIT:C15329
      label: Surgical Procedure
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: cochlear implant
        term:
          id: NCIT:C157820
          label: Cochlear Implant
  target_mechanisms:
  - target: Cochlear Sensory Failure
    description: >-
      Bypasses the failed cochlear sensory transduction by stimulating the auditory nerve
      directly; it does not modify the underlying metabolic lesion.
    evidence:
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The sensorineural hearing loss observed in patients with GGPS1‐related muscular dystrophy is most likely sensory organ–related and localized to the organ of Corti, consistent with cochlear implantation being highly effective in all 4 patients in our cohort who underwent implantation."
      explanation: >-
        Reports the implant response and the authors' inference from it about where the
        lesion sits, which is the rationale for this intervention.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The sensorineural hearing loss observed in patients with GGPS1‐related muscular dystrophy is most likely sensory organ–related and localized to the organ of Corti, consistent with cochlear implantation being highly effective in all 4 patients in our cohort who underwent implantation."
    explanation: The clinical outcome of implantation in the four patients who received it.
- name: Non-invasive and invasive ventilatory support
  description: >-
    Nocturnal non-invasive ventilation progressing to tracheostomy in the severely affected.
    This is the supportive measure that determines survival, as it is in every congenital
    muscular dystrophy with respiratory involvement.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: mechanical ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  target_mechanisms:
  - target: Respiratory Insufficiency
    description: Substitutes for the failing respiratory musculature without modifying the myopathy.
    evidence:
    - reference: PMID:35869884
      reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Proximal or generalized muscle weakness (12/13) with the mean onset age of 2.7 ± 2.7 years (range 0.6–11), respiratory insufficiency (8/13) requiring non‐invasive ventilation (6/13) and tracheostomy (2/13), joint contractures (7/12), congenital or infantile‐onset bilateral severe sensorineural hearing loss (6/13)"
      explanation: Ties the ventilatory requirement to the measured respiratory insufficiency across the cohort.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "She developed respiratory insufficiency, necessitating noninvasive ventilation, progressing to tracheostomy."
    explanation: Documents the escalation from non-invasive ventilation to tracheostomy.
- name: Spinal fusion for progressive scoliosis
  description: >-
    Orthopaedic stabilisation of the neuromuscular scoliosis. Reported in the index patient
    at eleven years; no series and no outcome data exist for this disease specifically.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: spinal fusion
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure
  target_mechanisms:
  - target: Scoliosis
    description: Corrects and stabilises the spinal deformity produced by axial weakness.
    evidence:
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Progressive scoliosis necessitated spinal fusion at age 11 years."
      explanation: The single reported instance, quoted rather than generalised.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Progressive scoliosis necessitated spinal fusion at age 11 years."
    explanation: Records that spinal fusion was performed for the progressive scoliosis.
differential_diagnoses:
- name: Perrault syndrome
  disease_term:
    preferred_term: Perrault syndrome
    term:
      id: MONDO:0017312
      label: Perrault syndrome
  description: >-
    The closest differential and the reason the lump/split decision for this entry is a real
    one. Perrault syndrome is sensorineural hearing loss with primary ovarian insufficiency
    in 46,XX individuals -- two of this disease's three cardinal features -- and GGPS1 was
    independently nominated as a Perrault candidate gene from a Perrault cohort in the same
    year this syndrome was named. dismech curates Perrault syndrome separately in
    `kb/disorders/Perrault_Syndrome.yaml`, where GGPS1 appears as a gene whose phenotype
    overlaps Perrault syndrome. The two entries are deliberately cross-referenced rather
    than merged.
  distinguishing_features:
  - "Perrault syndrome does not include muscle disease; the discovery paper for this syndrome states that Perrault syndrome manifests with hearing loss and ovarian insufficiency but without muscle involvement."
  - "Here the muscular dystrophy is the constant feature and the two Perrault features are the variable ones, which inverts the Perrault definition: hearing loss was present in only 46% of one cohort and a 2024 patient had normal hearing."
  - "The mechanisms are different in kind. Perrault syndrome is unified by failure of mitochondrial gene expression and proteostasis, with peroxisomal exceptions; this is an isoprenoid and protein-prenylation lesion."
  - "MONDO and OMIM assign a separate identity (MONDO:0859189, OMIM:619518) rather than a numbered PRLTS designation, and MONDO does not place this term under Perrault syndrome."
  - "The practical discriminator is a creatine kinase and a muscle examination in anyone presenting with the Perrault dyad, since the dystrophy is what changes management."
  - "The case against this separation should be stated too: a 2026 review lists GGPS1 among the fifteen principal Perrault syndrome genes, so a reader who takes that classification is entitled to regard this disease as a Perrault subtype with muscle involvement."
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Perrault syndrome, caused by mutations in various mitochondrial and peroxisomal genes, clinically manifests with sensorineural hearing loss and primary ovarian insufficiency but without muscle involvement"
    explanation: States the nosological boundary this differential draws, that Perrault syndrome lacks muscle involvement.
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a constellation of all these three features had not been previously recognized prior to the Foley"
    explanation: Confirms independently that the three-feature constellation was not a recognised entity before 2020.
  - reference: PMID:42283975
    reference_title: "Comprehensive Insights into Perrault Syndrome: Genetic Diversity and Clinical Implications."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "highlighting mutations in fifteen principal genes: HSD17B4, HARS2, CLPP, LARS2, TWNK, ERAL1, RMND1, DAP3, PRORP, MRPL50, MRPL49, MRPS7, PEX6, GGPS1, and TFAM."
    explanation: >-
      The counter-argument, curated rather than omitted: a recent Perrault review counts
      GGPS1 among the Perrault genes, which is the strongest published statement of the
      lumping position this entry declines. Note that the same review characterises all
      fifteen genes as acting in mitochondrial or peroxisomal processes, which is not true
      of GGPS1.
- name: Muscular dystrophy, limb-girdle, autosomal recessive 28 (HMGCR-related)
  disease_term:
    preferred_term: muscular dystrophy, limb-girdle, autosomal recessive 28
    term:
      id: MONDO:0957270
      label: muscular dystrophy, limb-girdle, autosomal recessive 28
  description: >-
    The other Mendelian muscular dystrophy of the mevalonate pathway, curated in
    `kb/disorders/Muscular_Dystrophy_Limb-girdle_Autosomal_Recessive_28.yaml`. HMGCR
    catalyses the rate-limiting step at the head of the pathway; GGPS1 catalyses a committed
    step in the isoprenoid branch several steps below it. The two entries agree
    mechanistically rather than competing: the LGMDR28 entry argues from mouse rescue
    experiments that the myopathy of HMGCR deficiency is caused by depletion of the
    geranylgeranyl branch rather than of sterol, and this disease is what a lesion placed
    directly in that branch looks like. Both are hypomorphic-missense diseases of an
    essential enzyme whose complete loss is lethal.
  distinguishing_features:
  - "LGMDR28 is a limb-girdle dystrophy with markedly raised creatine kinase and no hearing or ovarian involvement; this syndrome adds congenital sensorineural hearing loss and primary ovarian insufficiency."
  - "The LGMDR28 biopsy is characteristically unremarkable, without necrosis, fibrosis or inflammation; the biopsy here is frankly dystrophic and adds excess autophagic material and enlarged mitochondria."
  - "LGMDR28 onset spans birth to the fourth decade and is often adult; this syndrome is congenital to preschool in onset."
  - "LGMDR28 has a directed metabolite-replacement candidate, oral mevalonolactone, which supplies the pathway product below the block; there is no equivalent for GGPS1, since the block is below the branch point and mevalonate would not bypass it."
  evidence:
  - reference: PMID:42323079
    reference_title: Skeletal muscle-specific deficiency of Rab geranylgeranyl transferase beta subunit induces myopathy and exacerbates the symptoms caused by HMG-CoA reductase deficiency in mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "Our findings demonstrate that myopathy induced by HMGCR deficiency is primarily driven by GGPP depletion in a mouse model."
    explanation: >-
      This result is about HMGCR-deficient mice, not GGPS1. It is cited to show that the two
      diseases are placed on one pathway by the same argument, since the HMGCR myopathy is
      attributed to depletion of the very metabolite GGPS1 makes.
- name: GGPS1-associated bisphosphonate-related atypical femoral fracture
  description: >-
    Not a disease entry and deliberately not merged into this one. Monoallelic GGPS1
    variants, notably p.Asp188Tyr in three sisters, have been reported as a risk factor for
    atypical femoral fractures in women on nitrogen-containing bisphosphonates, which
    inhibit GGPPS pharmacologically; the variant reduces catalytic activity roughly fourfold
    in vitro. This is a heterozygous drug-response susceptibility with no disease phenotype
    in the absence of the drug, and it has no MONDO term. It is recorded here because it is
    the single largest source of GGPS1 literature that is not about this syndrome, and
    because both the discovery paper and the replication cohort take care to distinguish the
    two.
  distinguishing_features:
  - "Monoallelic, and expressed only under bisphosphonate exposure; this syndrome is biallelic and expressed without any drug."
  - "The phenotype is a fracture in an adult on treatment, not a congenital muscular dystrophy with hearing and ovarian involvement."
  - "Heterozygous GGPS1 loss-of-function carriers are present in gnomAD and are expected to be asymptomatic, so a single defective allele does not produce this syndrome."
  evidence:
  - reference: PMID:35869884
    reference_title: GGPS1-associated muscular dystrophy with and without hearing loss.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "While monoallelic variants in GGPS1 have been identified as a risk factor for atypical femoral bone fractures in females exposed to bisphosphonates, ultra‐rare biallelic pathogenic missense variants in GGPS1 have recently been associated with muscular dystrophy/hearing loss/ovarian insufficiency syndrome."
    explanation: Draws the monoallelic-versus-biallelic distinction between the two GGPS1 associations in a single sentence.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although thus far there has been no human monogenic disease linked to mutations in GGPS1, it has been identified as a risk factor for atypical femoral bone fractures in females exposed to bisphosphonates."
    explanation: Records that before 2020 the only GGPS1 disease association was the bisphosphonate fracture risk factor.
  - reference: PMID:30275041
    reference_title: Reduced Activity of Geranylgeranyl Diphosphate Synthase Mutant Is Involved in Bisphosphonate-Induced Atypical Fractures.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "the D188Y mutation leads to ∼4-fold catalytic activity decrease."
    explanation: >-
      This is about the atypical-femoral-fracture allele D188Y, not about any allele in this
      syndrome. It is cited to show that the fracture-associated variant is also a partial
      loss-of-function allele, which is why the two associations are easy to conflate.
- name: Facioscapulohumeral muscular dystrophy
  disease_term:
    preferred_term: facioscapulohumeral muscular dystrophy
    term:
      id: MONDO:0001347
      label: facioscapulohumeral muscular dystrophy
  description: >-
    The other muscular dystrophy in which sensorineural hearing loss is an accepted feature,
    specifically in the early-onset infantile form. It is curated in
    `kb/disorders/Facioscapulohumeral_Muscular_Dystrophy.yaml`.
  distinguishing_features:
  - "FSHD is dominantly inherited and caused by D4Z4 contraction or SMCHD1 variants, not by a recessive metabolic-enzyme genotype."
  - "FSHD has a characteristic facial, scapular and humeral distribution with marked asymmetry; the weakness here is limb-girdle or generalised."
  - "Retinal vasculopathy accompanies the hearing loss in infantile FSHD, and primary ovarian insufficiency is not a feature."
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Congenital sensorineural hearing loss rarely manifests in association with muscular dystrophy but has been reported in early onset facioscapulohumeral muscular dystrophy."
    explanation: >-
      Names early-onset facioscapulohumeral muscular dystrophy as the other muscular dystrophy
      in which congenital sensorineural hearing loss occurs, which is what makes it a
      differential for this syndrome.
- name: Vici syndrome
  disease_term:
    preferred_term: Vici syndrome
    term:
      id: MONDO:0009452
      label: Vici syndrome
  description: >-
    An EPG5-related multisystem disorder combining a vacuolar myopathy with sensorineural
    hearing loss, which the discovery authors raise because it makes the same connection
    between disordered autophagy, myopathy and deafness that the ultrastructural findings
    here suggest. It is the differential most worth knowing about mechanistically rather
    than clinically.
  distinguishing_features:
  - "Vici syndrome has agenesis of the corpus callosum, cataracts, hypopigmentation, cardiomyopathy and immunodeficiency; none of these occurs in GGPS1 disease, which has no cardiac or cognitive involvement."
  - "Ovarian insufficiency is not a feature of Vici syndrome."
  - "The autophagy defect in Vici syndrome is a primary lesion in an autophagy regulator; here disordered autophagy is an ultrastructural finding whose place in the mechanism is unresolved."
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of note, no cardiac or cognitive involvement has been noted in this cohort."
    explanation: Records the absence of cardiac and cognitive involvement, which is the clearest clinical separation from Vici syndrome.
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Vici syndrome, a complex congenital multisystemic disorder caused by recessive mutations in autophagy regulator EPG5 gene, which can also be associated with sensorineural hearing loss,"
    explanation: >-
      Identifies Vici syndrome and its cause, and names the hearing loss that it shares with
      this syndrome, which is why the discovery authors raise it.
animal_models:
- name: Ggps1 p.Tyr259Cys homozygous knock-in mouse
  species: Mouse
  genotype: Ggps1 p.Y259C homozygous knock-in
  publication: PMID:32403198
  description: >-
    A knock-in of the human Y259C allele, made because a complete Ggps1 knockout is not
    viable and a knock-in was the only route to an organismal model. It does not model the
    disease: homozygotes develop with a markedly slowed rate, reach no further than
    embryonic day 12.5 and are not recovered alive thereafter. The authors state plainly
    that this left them unable to do mechanistic work relevant to the human phenotype, which
    is why almost everything mechanistic in this entry comes from patient cells or from
    tissue-specific mouse models of other genotypes.
  modeled_mechanisms:
  - target: Myofiber Degeneration with Disordered Autophagy
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Homozygous animals die as embryos and never develop a postnatal muscular dystrophy, so
      no muscle phenotype, hearing phenotype or ovarian phenotype can be observed.
    limitations: >-
      Embryonic lethality precludes phenotyping of any kind, so the model yields no readout
      of weakness, creatine kinase, histology, hearing or fertility. The species difference
      is the substantive limitation: mouse appears far less tolerant of this allele than
      human, since the corresponding human compound heterozygotes were liveborn and survived
      into their twenties. Nothing about the human disease can be inferred from this model
      beyond the severity of the allele.
    evidence:
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "homozygote Y259C knock‐in embryos developed up to embryonic day (ED)12.5, with no live embryos observed after this point."
      explanation: Reports the embryonic lethality that constitutes the failure to recapitulate.
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Thus, detailed mechanistic studies relevant to the human phenotype were not possible in this mouse strain."
      explanation: The authors' own statement that the model could not be used for mechanism.
  evidence:
  - reference: PMID:32403198
    reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "As a total knock‐out the gene is not viable; we therefore created a knock‐in mouse of the mutation p.Y259C (Fig 7A) detected in compound heterozygosity in the index family (Family 1) to study the effects of the mutant GGPS1 on the organismal level."
    explanation: Establishes why a knock-in rather than a knockout was attempted, and what genotype the model carries.
- name: Oocyte-specific Ggpps conditional knockout mouse
  species: Mouse
  genotype: Ggpps flox/flox; Ddx4-Cre (oocyte-specific conditional knockout)
  publication: PMID:28072828
  description: >-
    Not built as a model of this disease -- it predates it by three years and its authors
    were asking how oocyte-granulosa cell communication is established -- but it is the only
    animal system in which loss of GGPP produces a phenotype in one of this disease's three
    target organs. Follicles are almost entirely lost by six weeks, the primary-to-secondary
    transition fails, Rho GTPase geranylgeranylation is inhibited, and supplying GGPP
    rescues all of it.
  modeled_mechanisms:
  - target: Ovarian Follicle Depletion
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      Reproduces follicle loss and infertility from loss of GGPP in the oocyte, and
      identifies the failing step as Rho GTPase geranylgeranylation. The rescue by GGPP is
      what makes the attribution causal rather than correlative.
    limitations: >-
      This is a conditional null restricted to the oocyte, whereas patients carry a partial
      loss of function expressed in every tissue, so the model overstates the enzymatic
      deficit while missing any granulosa-cell or somatic contribution. It is a mouse ovary
      rather than a human one, the phenotype is near-complete follicle loss by six weeks
      rather than ovarian insufficiency after apparently normal puberty, and no patient with
      this syndrome has had ovarian histology examined, so the correspondence is by mechanism
      and not by observation.
    readouts:
    - name: Ovarian follicle number
      target: Ovarian Follicle Depletion
      direction: DECREASED
      interpretation: Direct histological correlate of the follicle-depletion node in this model.
      evidence:
      - reference: PMID:28072828
        reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The selective depletion of GGPP in mouse oocytes impaired the proliferation of granulosa cells, primary-secondary follicle transition and female fertility."
        explanation: Reports the follicular and fertility measurements behind this readout.
    - name: Follicular development after GGPP administration
      target: Ovarian Follicle Depletion
      direction: RESTORED
      interpretation: >-
        Rescue by the missing metabolite establishes that the follicular defect follows from
        GGPP depletion rather than from some other consequence of deleting the enzyme.
      evidence:
      - reference: PMID:28072828
        reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "GGPP administration restored the defects in oocyte-granulosa cell contact, granulosa cell proliferation and primary-secondary follicle transition in Ggpps depletion mice."
        explanation: Reports the rescue experiment behind this readout.
    evidence:
    - reference: PMID:28072828
      reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "oocyte geranylgeranyl diphosphate (GGPP), a metabolic intermediate involved in protein geranylgeranylation, is required to establish the oocyte-granulosa cell communication."
      explanation: Establishes that this model is informative for the requirement for GGPP in the ovary.
  - target: Deficient Protein Geranylgeranylation of Small GTPases
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      The one system in which the prenylation step this entry's mechanism turns on has
      actually been shown to fail: GGPP depletion inhibits Rho GTPase geranylgeranylation and
      its GTPase activity.
    limitations: >-
      Demonstrated in mouse oocytes with a conditional null, not in human tissue with a
      hypomorphic allele. The discovery paper for the human disease looked for a
      corresponding prenylome change in patient cells and did not find one, so this model may
      be showing what a complete loss does rather than what the human partial loss does.
    readouts:
    - name: Rho GTPase geranylgeranylation and GTPase activity
      target: Deficient Protein Geranylgeranylation of Small GTPases
      direction: DECREASED
      interpretation: Direct measurement of the prenylation step failing when GGPP is removed.
      evidence:
      - reference: PMID:28072828
        reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "GGPP depletion inhibited Rho GTPase geranylgeranylation and its GTPase activity, which was responsible for the accumulation of cell junction proteins in the oocyte cytoplasm and the failure to maintain physical connection between oocyte and granulosa cells."
        explanation: Reports the prenylation and GTPase-activity measurements behind this readout.
    evidence:
    - reference: PMID:28072828
      reference_title: GGPP-Mediated Protein Geranylgeranylation in Oocyte Is Essential for the Establishment of Oocyte-Granulosa Cell Communication and Primary-Secondary Follicle Transition in Mouse Ovary.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "GGPP depletion inhibited Rho GTPase geranylgeranylation and its GTPase activity, which was responsible for the accumulation of cell junction proteins in the oocyte cytoplasm and the failure to maintain physical connection between oocyte and granulosa cells."
      explanation: Establishes that this model reports directly on the prenylation node.
experimental_models:
- name: Patient-derived MyoD-converted myoblasts and myotubes with laser membrane injury
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: >-
    Dermal fibroblasts from affected individuals converted to myoblasts with lentiviral
    MyoD and differentiated to myotubes, then wounded with a focal laser pulse in the
    presence of the membrane-impermeant dye FM 1-43 so that resealing can be followed as
    dye exclusion. This is the system that produced the only cellular phenotype demonstrated
    in patient material, and it is also the system in which GGPPS activity was measured at
    about half of control.
  publication: PMID:32403198
  modeled_mechanisms:
  - target: Impaired Sarcolemmal Membrane Repair
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Reproduces, in cells carrying the patients' own genotypes, a delay in resealing the
      wounded plasma membrane and a roughly twofold increase in the proportion of cells that
      fail to reseal at all.
    limitations: >-
      MyoD-converted fibroblasts are not mature innervated muscle, and a laser wound is not
      the eccentric contraction injury that damages muscle in life. The assay reports
      resealing kinetics and not the downstream dystrophic process, so the link from this
      defect to the biopsy findings remains inferential. The measurement pools cells from
      several patients with different genotypes, so it cannot distinguish allele-specific
      effects.
    readouts:
    - name: FM 1-43 dye entry after focal laser injury
      target: Impaired Sarcolemmal Membrane Repair
      direction: INCREASED
      interpretation: >-
        Greater dye entry means slower resealing, which is the direct measure of the
        membrane-repair defect this node claims.
      evidence:
      - reference: PMID:32403198
        reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "We observed greater dye entry, indicating a poor cell membrane repair, in both the patient myoblasts and myotubes as compared to the healthy controls"
        explanation: Reports the dye-entry measurement behind this readout.
    - name: GGPPS enzymatic activity in patient myoblasts
      target: Impaired Sarcolemmal Membrane Repair
      direction: DECREASED
      interpretation: >-
        Establishes that the cells showing the repair defect really do carry a measurable
        enzymatic deficit, which is what ties the cellular phenotype to the genotype.
      evidence:
      - reference: PMID:32403198
        reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "We found that enzymatic activity in samples pooled from 4 patients (Patients P1, P2, P6, and P8) was decreased to about 50% of the activity in a pooled normal control sample."
        explanation: Reports the enzyme-activity measurement made in these same cells.
    evidence:
    - reference: PMID:32403198
      reference_title: GGPS1 Mutations Cause Muscular Dystrophy/Hearing Loss/Ovarian Insufficiency Syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We observed greater dye entry, indicating a poor cell membrane repair, in both the patient myoblasts and myotubes as compared to the healthy controls"
      explanation: Establishes that this model reports the cellular phenotype the node describes.
discussions:
- discussion_id: tissue_selectivity_of_prenylation_failure
  kind: KNOWLEDGE_GAP
  prompt: >-
    Why does a partial deficit of a universally required lipid modification produce disease
    in skeletal muscle, cochlea and ovary and spare everything else?
  attaches_to:
  - pathophysiology#Deficient Protein Geranylgeranylation of Small GTPases
  - pathophysiology#Cochlear Sensory Failure
  rationale: >-
    Protein geranylgeranylation is required in every cell, and more than a hundred human
    proteins are predicted substrates, yet these patients have no cardiac, cognitive,
    haematological or immune phenotype at all. Three explanations are on the table and none
    has been tested. The first is threshold: muscle, cochlear hair cells and oocytes may
    simply have the highest demand for prenylated Rab and Rho GTPases, so a 50% deficit
    crosses a threshold there and nowhere else. The second is that the disease alleles do
    not act through bulk catalytic output at all -- P15S has wild-type activity and still
    causes the disease, all the alleles sit outside the catalytic barrel, and the affected
    domain is conserved in animals but not plants -- so what fails may be a specific
    protein-protein interaction or a subcellular localisation of GGPPS in those tissues.
    The third is developmental timing, since Ggps1 is most densely expressed in the
    embryonic gonad and diffusely in the developing cochlea. Distinguishing these would
    change what a therapy should aim at.
  proposed_experiments:
  - experiment_id: ggps1_tissue_prenylome
    name: Comparative prenylome and GGPP quantification across affected and unaffected tissues
    description: >-
      Quantify geranylgeranyl pyrophosphate and the prenylated proteome in myotubes,
      cochlear organoids or hair-cell-like cells, oocytes or granulosa cells, and an
      unaffected control tissue such as fibroblasts or cardiomyocytes, all derived from
      patient induced pluripotent stem cells alongside isogenic corrected controls.
    would_support:
    - pathophysiology#Deficient Protein Geranylgeranylation of Small GTPases
    supporting_outcome:
    - >-
      A prenylation deficit that is selectively larger, or affects a distinct substrate set,
      in the three affected lineages than in unaffected ones, which would support the
      threshold or substrate-specificity model.
    refuting_outcome:
    - >-
      An equal prenylation deficit across affected and unaffected lineages, which would
      move the explanation away from prenylation stoichiometry entirely and towards a
      non-catalytic function of GGPPS.
- discussion_id: unconfirmed_prenylation_deficit_in_patients
  kind: KNOWLEDGE_GAP
  prompt: >-
    Has the prenylation defect that this entry's mechanism depends on ever been demonstrated
    in a patient with this syndrome?
  attaches_to:
  - pathophysiology#Geranylgeranyl Pyrophosphate Depletion
  - pathophysiology#Deficient Protein Geranylgeranylation of Small GTPases
  rationale: >-
    No. This is the most important caveat in the entry and it is easy to lose, because the
    biochemistry is so tidy. No geranylgeranyl pyrophosphate measurement has been reported
    in any tissue or cell from an affected individual, and the discovery paper states in its
    own discussion that it could not find a consistent change in the small GTPases or in the
    overall prenylome of patient cells. The chain from reduced enzyme activity to deficient
    prenylation is therefore an inference from enzymology and from mouse work in a different
    genotype, which is why those two nodes carry `mechanism_confidence: PROVISIONAL` and
    `HYPOTHETICAL` and why the negative result is curated as a REFUTE evidence item rather
    than left out. The alternative it leaves open -- that the disease alleles disrupt a
    localised or interaction-dependent function of GGPPS rather than the cell's bulk GGPP
    supply -- is supported by the P15S allele, which has normal catalytic activity.
  proposed_experiments:
  - experiment_id: ggps1_patient_ggpp_assay
    name: Direct measurement of GGPP and Rab prenylation in patient muscle
    description: >-
      Measure geranylgeranyl pyrophosphate, farnesyl pyrophosphate and the unprenylated
      fraction of Rab and Rho GTPases by mass spectrometry and by in-vitro prenylation
      assay in muscle biopsy tissue from genotyped patients against age-matched controls,
      with sufficient replication to detect the modest deficit the enzymology predicts.
    would_support:
    - pathophysiology#Geranylgeranyl Pyrophosphate Depletion
    supporting_outcome:
    - >-
      Reduced GGPP and an increased unprenylated fraction of Rab and Rho GTPases in patient
      muscle, which would convert the central nodes of this mechanism from inference to
      observation.
    refuting_outcome:
    - >-
      Normal GGPP pools and normal prenylation in patient muscle, which would refute the
      bulk-depletion model outright and redirect the mechanism towards a non-catalytic or
      localisation-dependent function of the enzyme.
- discussion_id: no_viable_animal_model
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    Can any animal model reproduce this syndrome, given that the mouse dies in utero from an
    allele a human tolerates into adulthood?
  attaches_to:
  - animal_models#Ggps1 p.Tyr259Cys homozygous knock-in mouse
  - pathophysiology#Myofiber Degeneration with Disordered Autophagy
  rationale: >-
    The mismatch is stark and quantitative. Homozygous Y259C mice are developmentally delayed
    from embryonic day 10.5 and are dead by 13.5, while the human compound heterozygotes
    carrying that same allele walked independently at eighteen months and survived into their
    twenties. The mouse is therefore not merely a poor model but an inverted one, and the
    authors say directly that it left them unable to do mechanistic work relevant to the
    human phenotype. Everything that is known about mechanism in this disease consequently
    comes from patient-derived cells or from mouse models of a different genotype in a
    different tissue. What is missing is a milder allelic series -- a knock-in of R261H,
    which produces the mildest human phenotype, or a hypomorphic allele engineered to leave
    more residual activity -- and tissue-restricted conditional deletions in muscle and
    cochlea to match the ovarian one that already exists.
  proposed_experiments:
  - experiment_id: ggps1_mild_allele_and_conditional_series
    name: Milder Ggps1 knock-in allele plus muscle- and cochlea-restricted conditional knockouts
    description: >-
      Generate homozygous knock-in mice carrying the human R261H allele, and separately cross
      the existing floxed Ggps1 allele to muscle-restricted and hair-cell-restricted Cre
      drivers, then phenotype for the human-relevant endpoints: strength and creatine kinase,
      muscle histology including autophagic and mitochondrial ultrastructure, auditory
      brainstem responses, and ovarian follicle counts.
    would_support:
    - pathophysiology#Myofiber Degeneration with Disordered Autophagy
    supporting_outcome:
    - >-
      Viable R261H homozygotes with a slowly progressive dystrophy and hearing loss, or
      tissue-restricted knockouts reproducing the muscle and cochlear phenotypes, either of
      which would give the field a system in which mechanism and therapy can be tested.
    refuting_outcome:
    - >-
      R261H homozygotes that are again embryonic lethal or, at the other extreme, entirely
      unaffected, which would suggest the mouse cannot be made to occupy the narrow window
      the human disease sits in and would push modelling towards human stem-cell systems.
- discussion_id: unexamined_male_reproductive_involvement
  kind: KNOWLEDGE_GAP
  prompt: >-
    Does GGPS1 deficiency impair male reproductive function, as the ovarian arm and the
    mouse expression data would predict?
  attaches_to:
  - phenotypes#Primary Ovarian Insufficiency
  rationale: >-
    The disease is defined in part by primary ovarian insufficiency, so the symmetric
    question in males is the obvious one, and nobody has asked it. The founding cohort
    reports that none of its five adult male patients has had children, but states in the
    same breath that no andrological examination was obtained -- so the observation is
    consistent with an unrecognised gonadal arm and equally consistent with five men who
    have not tried. It cannot presently distinguish the two. This is recorded as a gap
    rather than as a phenotype because curating childlessness as evidence of infertility
    would be exactly the inference the authors declined to make.
  proposed_experiments:
  - experiment_id: ggps1_male_gonadal_assessment
    name: Andrological assessment of adult male patients
    description: >-
      Semen analysis, testicular ultrasound, and gonadotrophin and testosterone measurement
      in postpubertal male patients, compared against the age-matched normal ranges, with
      the same follicle-equivalent endpoints the ovarian arm uses where an analogue exists.
    would_support:
    - phenotypes#Primary Ovarian Insufficiency
    supporting_outcome:
    - >-
      Impaired spermatogenesis or a hypergonadotropic pattern in affected males, which
      would recast the ovarian phenotype as one arm of a general gonadal involvement.
    refuting_outcome:
    - >-
      Normal semen parameters and normal gonadotrophins, which would make the ovarian
      involvement genuinely sex-specific and sharpen the tissue-selectivity question the
      entry already carries.
- discussion_id: no_directed_therapy
  kind: KNOWLEDGE_GAP
  prompt: >-
    Is there a metabolite or pathway intervention that could bypass the GGPS1 block, and has
    anything been tried?
  attaches_to:
  - treatments#
  - pathophysiology#Geranylgeranyl Pyrophosphate Depletion
  rationale: >-
    Very little has been tried, and the arithmetic of the pathway is discouraging in a
    specific way. The block here sits below the branch point, so supplying mevalonate -- the
    approach that produced measurable benefit in the one treated patient with the upstream
    HMGCR disease -- would not bypass it. The obvious candidate is geranylgeraniol, the
    alcohol precursor of GGPP, which reverses the fiber-type loss of muscle-specific Hmgcr
    knockout mice and is the exact metabolite this enzyme fails to make enough of; it has
    never been tested in a GGPS1 patient or model. The one metabolite that has been tried,
    coenzyme Q10, produced no improvement in the single patient given it, and muscle coenzyme
    Q10 was normal in another patient, so the ubiquinone branch is probably not where the
    disease sits. Any trial would also have to confront the fact that the prenylation deficit
    it is meant to correct has not yet been demonstrated in a patient.
  proposed_experiments:
  - experiment_id: ggps1_geranylgeraniol_preclinical
    name: Geranylgeraniol rescue in patient-derived myotubes and in a conditional Ggps1 model
    description: >-
      Test whether geranylgeraniol supplementation restores membrane resealing kinetics in
      the patient-derived MyoD-converted myotube laser-injury assay, and whether it rescues
      the muscle phenotype of a muscle-restricted conditional Ggps1 knockout, before any
      consideration of human use.
    would_support:
    - pathophysiology#Geranylgeranyl Pyrophosphate Depletion
    supporting_outcome:
    - >-
      Normalisation of membrane resealing in patient myotubes and of the muscle phenotype in
      the conditional knockout, which would both confirm GGPP depletion as the operative
      lesion and identify a candidate therapy.
    refuting_outcome:
    - >-
      No rescue by geranylgeraniol despite adequate cellular uptake, which would argue that
      the disease alleles act through something other than the cell's bulk GGPP supply and
      would close off the most obvious therapeutic route.

📚

References & Deep Research

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 (2)

Record notes

Entity verification. MONDO:0859189 carries the label "muscular dystrophy, congenital hearing loss, and ovarian insufficiency syndrome" and the cross-references OMIM:619518, MEDGEN:1794190 and UMLS:C5561980 (checked against EBI OLS4 on 2026-09-07, since the local MONDO SQLite build was deliberately not downloaded in this session). The stub records MONDO:0003847 (hereditary disease) as its only parent and hgnc:4249 GGPS1 as its only causal gene. Note that MONDO does not place this term under Perrault syndrome (MONDO:0017312), and that Perrault syndrome is a separate MONDO term with its own identity. Lump/split decision, which here is a real one. Perrault syndrome is defined by sensorineural hearing loss with primary ovarian insufficiency, and dismech already curates it in `kb/disorders/Perrault_Syndrome.yaml` -- an entry that already lists GGPS1 as a Perrault gene with an isoprenoid pathophysiology node. Two of this disease's three cardinal features are therefore the whole of Perrault syndrome, and GGPS1 was independently nominated as a Perrault candidate gene in a Perrault cohort in the same year the syndrome was named (PMID:32399598). That is the case for lumping, and it is not weak. It is nonetheless curated as its own entry, for four reasons. (1) The muscular dystrophy is not a Perrault feature: the discovery paper states that Perrault syndrome manifests with hearing loss and ovarian insufficiency "but without muscle involvement", and that the three-feature constellation had not been recognised before. (2) Later cohorts invert the Perrault definition here -- muscular dystrophy is present in essentially every reported patient, while hearing loss was present in only 46% of a thirteen-person cohort and ovarian insufficiency was likewise variable, so the two Perrault-defining features are the optional ones in this disease. A 2024 patient had isolated proximal weakness with normal hearing. (3) The mechanism is different in kind: Perrault syndrome is unified by failure of mitochondrial gene expression and proteostasis (with peroxisomal exceptions), whereas this is an isoprenoid/prenylation lesion. (4) MONDO and OMIM give it a separate identity (OMIM:619518) rather than a numbered PRLTS designation. The reciprocal cross-reference is kept: this entry lists Perrault syndrome as a differential, and the Perrault entry continues to carry GGPS1 as a gene whose phenotype "overlaps Perrault syndrome". A curator who disagrees should change both entries together, not one. Is there more than one GGPS1 disease? Yes, in the sense that the literature carries a second, quite separate GGPS1 association, and no, in the sense that the second is not a Mendelian disease. Monoallelic GGPS1 variants -- specifically p.Asp188Tyr in three sisters -- have been reported as a risk factor for atypical femoral fractures in women taking nitrogen-containing bisphosphonates, which inhibit GGPPS pharmacologically; the variant reduces catalytic activity about fourfold in vitro. That is a heterozygous drug-response susceptibility with no MONDO disease term of its own, not a dominant Mendelian disorder, and both the discovery paper and the 2022 cohort state the distinction explicitly. It is recorded here in `differential_diagnoses` and is deliberately not merged into this entry. No dominantly inherited GGPS1 disease was found in the literature searched. Named Entity Confusion. A GGPS1 literature search is dominated by three bodies of work that are not this disease: nitrogen-containing bisphosphonate pharmacology and the atypical-femoral-fracture association above; oncology, where GGPPS inhibition is a drug target across myeloma, leukaemia and solid tumours; and plant and microbial terpenoid biosynthesis, where GGPPS is an entirely different subject. Of 217 PubMed records matching GGPS1 or geranylgeranyl diphosphate synthase in the title or abstract, only about six concern this syndrome. Every clinical claim in this entry is sourced to a paper whose subjects carry biallelic germline GGPS1 variants: PMID:32403198 (eleven patients, six families), PMID:35869884 (thirteen individuals including two previously reported) and PMID:38129970 (one patient). PMID:32399598 is cited only for the mouse-folliculogenesis statement and for the Perrault-cohort ascertainment; PMID:28072828 and PMID:42323079 are cited as mouse pathway evidence and are labelled as such wherever they appear. GeneReviews. There is no GeneReviews chapter for this disease. The Perrault Syndrome Overview (PMID:25254289) exists but does not cover GGPS1 disease, and its cached record is a scope statement carrying no clinical findings, so it is not cited here. One paper deliberately not cited: PMID:39353334 ("Ultrarare Muscular Dystrophy Mimics Facioscapulohumeral Muscular Dystrophy", Pediatr Neurol 2024) is a clinical letter with no abstract and no retrievable body, so no quotable passage exists and nothing from it is asserted here. Deep research. `just dr_fallback='--fallback' research-disorder falcon ...` was run on 2026-09-07. Falcon returned HTTP 402 (the Edison account is out of credits) and the run fell back to openscientist, which produced `research/Muscular_Dystrophy_Congenital_Hearing_Loss_And_Ovarian_Insufficiency_Syndrome-deep-research-openscientist.md`; the fallback is recorded in the report's own frontmatter (`fell_back: true`, `requested_provider: falcon`), which is why the file is named for openscientist. The report carries `needs_review: true` on both its validation blocks, and what triggers it is worth stating because neither problem touches this entry. Reference validation: 15 of 15 references resolved, `unresolved_references` is empty, and 11 of 12 quotes matched -- the one failure is the report's own ellipsis-joined quote of PMID:35869884, which is a splice of two real sentences rather than a fabrication, and this entry quotes those sentences separately and verifiably. One reference (PMID:31427080, a bacterial GGPP-synthase crystal structure) was flagged as possibly off topic; it is genuinely tangential and is not cited here. Term validation: 47 of 49 CURIEs resolved with none unresolved, and the single mislabelling is the report writing "Disease MONDO" beside MONDO:0859189 in a table header, which is a formatting artifact rather than a wrong term. `just preflight-dr` returns PASS, with GGPS1 mentioned 35 times against two mentions each for the Perrault genes, and the MONDO and report OMIM numbers agreeing. What the report contributed, and what was rejected. It contributed one genuinely useful lead that the primary papers do not carry: PMID:26112408, which shows that GGPPS activity in mouse skeletal muscle sets the geranylgeranylation of RhoA, now cited on the prenylation node with its context stated. Two of its claims were checked and not used. First, it states that the Y259C knock-in mouse "recapitulates dystrophic muscle histology (autophagic material, enlarged mitochondria)"; that is wrong, and the error matters, because those findings are from human muscle biopsies while the homozygous knock-in mouse dies before embryonic day 13.5 and was never phenotyped. Second, it recommends hormone replacement therapy for the ovarian insufficiency and offers NCIT identifiers for several interventions; the hormone-replacement recommendation appears in no GGPS1 paper, and its suggested CURIEs (NCIT:C62556, NCIT:C15327, NCIT:C99913) were not the terms this entry needed, so neither was taken. Hormone replacement is very likely appropriate management for hypergonadotropic ovarian insufficiency, but it is not curated here because no source about this disease says so. Module conformance was considered and declined. `sensorineural_hair_cell_loss` is the obvious candidate for the auditory arm, and Perrault_Syndrome conforms to it. It is not used here because nothing is known about the cochlear lesion in GGPS1 disease beyond the inference from cochlear-implant responsiveness that it is sensory-organ localised. Declaring conformance would assert hair-cell mechanotransduction failure, oxidative stress and spiral ganglion degeneration, none of which has been observed in this disease. The gap is recorded as a knowledge gap instead.

Create: Muscular_Dystrophy_Congenital_Hearing_Loss_And_Ovarian_Insufficiency_Syndrome · 2026-09-07T21:52:37Z · View source

New entry for MONDO:0859189 (OMIM:619518), GGPS1-related muscular dystrophy / congenital hearing loss / ovarian insufficiency syndrome. LUMP/SPLIT: curated as its own disease rather than as a Perrault syndrome subtype, and the decision is argued explicitly in the entry notes and in a Perrault differential that carries the counter-evidence. Reasons for splitting: the discovery paper states Perrault syndrome manifests with hearing loss and ovarian insufficiency but without muscle involvement; later cohorts invert the Perrault definition here, with muscular dystrophy constant and hearing loss present in only 46 percent of one cohort; the mechanism is isoprenoid/prenylation rather than mitochondrial gene expression; and MONDO/OMIM assign a separate identity not placed under Perrault syndrome. The lumping case (Tucker 2020 nominating GGPS1 from a Perrault cohort, and a 2026 Perrault review listing GGPS1 among fifteen Perrault genes) is curated as evidence rather than omitted. The existing kb/disorders/Perrault_Syndrome.yaml keeps GGPS1 as a gene whose phenotype overlaps Perrault syndrome; the two entries cross-reference each other and were deliberately not merged. SECOND GGPS1 ASSOCIATION: monoallelic GGPS1 (p.Asp188Tyr) and bisphosphonate-related atypical femoral fracture is a heterozygous drug-response susceptibility with no MONDO term, not a dominant Mendelian disease. It is curated as a differential and explicitly not merged. CONSISTENCY WITH LGMDR28: this entry does not contradict kb/disorders/Muscular_Dystrophy_Limb-girdle_Autosomal_Recessive_28.yaml. That entry argues from mouse geranylgeraniol-rescue data that the HMGCR myopathy is caused by depletion of the geranylgeranyl branch rather than of sterol; this disease is a lesion placed directly in that branch, and PMID:42323079 is cited in both entries for the same claim. The LGMDR28 differential states the relation and the therapeutic asymmetry (mevalonolactone bypasses an HMGCR block but not a GGPS1 one). DEEP RESEARCH: 'just dr_fallback=--fallback research-disorder falcon ...' was run; falcon returned HTTP 402 (Edison account out of credits) and the run fell back to openscientist, recorded in the report frontmatter (fell_back: true, requested_provider: falcon) and reflected in the report filename. The report carries needs_review: true on both validation blocks: 15/15 references resolved with none unresolved, 11/12 quotes matched (the failure is the report's own ellipsis-joined splice of two real sentences from PMID:35869884), one reference flagged off topic (PMID:31427080, a bacterial GGPP-synthase structure, not cited here), and 47/49 CURIEs resolved with none unresolved. just preflight-dr returns PASS. The report contributed one lead used here (PMID:26112408, muscle GGPPS setting RhoA geranylgeranylation, cited with its context stated). Two of its claims were checked and rejected: it wrongly states the Y259C knock-in mouse recapitulates dystrophic muscle histology (those findings are human biopsies; the homozygous mouse dies before E13.5), and it recommends hormone replacement therapy with NCIT CURIEs that no GGPS1 source supports. Both rejections are recorded in the entry notes. EVIDENCE: every snippet was extracted programmatically from the reference cache rather than retyped, because the cached full text contains non-breaking hyphens and thin spaces. Two nodes carry REFUTE evidence for negative results that the mechanism predicts and the sources do not show: the discovery paper found no consistent prenylome change in patient cells, and muscle coenzyme Q10 was normal with an empirical CoQ10 trial producing no benefit. mechanism_confidence marks the inferred nodes PROVISIONAL/HYPOTHETICAL accordingly. MODULE CONFORMANCE considered and declined: sensorineural_hair_cell_loss would assert hair-cell mechanotransduction failure and spiral ganglion degeneration, none of which has been observed in GGPS1 disease. Recorded as a knowledge gap instead. VALIDATION: just validate-disorders passed (schema, terms, references); 101/101 snippets verified; check-duplicate-keys, check-entity-refs, check-causal-targets, check-qualifier-terms (offline and online), check-enum-values, check-snippet-length, check-title-snippets, check-snippet-grading, check-folded-hyphens, check-reference-titles, normalize-cache and check-term-cache-integrity all clean.

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Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome (MDHLOV): A Comprehensive Disease Report

openscientist-autonomous 7 citations 2026-09-07T18:09:30.155139

Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome (MDHLOV): A Comprehensive Disease Report

Disease: Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome MONDO ID: MONDO:0859189 · OMIM: #619518 (MDHLOV) · Gene: GGPS1 (1q42.3) Category: Mendelian (autosomal recessive)

Summary

Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome (MDHLOV; also abbreviated MDHLO/MUDHLOV) is an ultra-rare autosomal-recessive multisystem disorder caused by biallelic hypomorphic missense variants in GGPS1, the gene on chromosome 1q42.3 encoding geranylgeranyl diphosphate synthase (GGPPS/GGDPS). This enzyme sits in the mevalonate/isoprenoid pathway and produces geranylgeranyl pyrophosphate (GGPP, C20), the lipid donor used to geranylgeranylate small GTPases (the Rab and Rho families). The syndrome was first defined by Foley et al. in 2020, who identified 5 different biallelic pathogenic GGPS1 variants in 11 patients from 6 families, and has since been expanded by additional cohorts.

The core clinical picture is a fully penetrant, congenital-onset, progressive proximal muscular dystrophy (elevated creatine kinase; dystrophic histology with centrally nucleated fibers and rimmed vacuoles) accompanied by two variable extra-muscular features: congenital sensorineural hearing loss and, in post-pubertal females, primary/premature ovarian insufficiency. The combination of sensorineural hearing loss plus ovarian insufficiency overlaps clinically with Perrault syndrome, and GGPS1 is now counted among the Perrault-syndrome gene set. Later reports have shown the two non-muscle features are variable — hearing loss was present in only 46% of one cohort, and at least one patient had isolated proximal weakness with hepatic transaminase elevation and spared hearing — expanding the phenotypic spectrum.

Mechanistically, reduced GGPP supply is inferred to impair prenylation-dependent membrane anchoring of small GTPases (particularly Rab proteins), degrading vesicle trafficking and the Ca²⁺-dependent sarcolemmal membrane-repair machinery. Direct functional support comes from delayed membrane healing after laser injury in patient-derived myogenic cells and a disease-specific Y259C knock-in mouse. There is no disease-specific therapy; management is supportive (respiratory care, hearing rehabilitation, hormone replacement for ovarian insufficiency, physical therapy, orthopedic management of scoliosis). This report consolidates 10 confirmed findings and 25 reviewed papers across all 15 requested sections.

Key Findings

Finding 1 — Biallelic GGPS1 variants cause the muscle–ear–ovary triad

The foundational discovery (Foley et al., 2020) used whole exome sequencing superimposed on shared-haplotype mapping to identify biallelic GGPS1 variants as the cause of this syndrome. Eleven patients across six families carried five distinct biallelic pathogenic variants. The gene product, geranylgeranyl diphosphate synthase, catalyzes the synthesis of geranylgeranyl pyrophosphate, the lipid precursor of geranylgeranylated proteins including small GTPases. The clinical triad was: proximal muscular dystrophy in all 11 patients (100%), congenital sensorineural hearing loss in 10 of 11, and primary ovarian insufficiency in all post-pubertal females. Inheritance is autosomal recessive.

"We applied whole exome sequencing (WES) superimposed on shared haplotype regions to identify the initial biallelic variants in GGPS1." — PMID: 32403198 "In addition to proximal weakness, all but one patient presented with congenital sensorineural hearing loss, and all postpubertal females had primary ovarian insufficiency." — PMID: 32403198

Finding 2 — Hearing loss and ovarian insufficiency are variable; the spectrum includes hepatic involvement

Two subsequent reports broadened the phenotype. Kaiyrzhanov et al. (2022) described 11 additional individuals from 4 families with missense GGPS1 variants in whom hearing loss was present in only 46%, and concluded the data "demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy." Altassan et al. (2024) reported a patient who "presented with only proximal muscle weakness, and elevated liver transaminases with spared hearing function," adding hepatic involvement to the recognized spectrum and confirming that hearing can be spared.

"hearing loss was present in only 46% of the individuals … demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy." — PMID: 35869884 "The patient presented with only proximal muscle weakness, and elevated liver transaminases with spared hearing function." — PMID: 38129970

Interpretation: Myopathy is the obligate, fully penetrant feature; sensorineural hearing loss and ovarian insufficiency show variable expressivity. This variable expressivity is why the disorder is sometimes ascertained as "Perrault-syndrome-like" and sometimes as an isolated congenital muscular dystrophy.

Finding 3 — Mechanism: reduced GGPP impairs Rab/small-GTPase geranylgeranylation and sarcolemmal membrane repair

Foley et al. demonstrated delayed membrane healing after laser injury in patient-derived myogenic cells and generated a Y259C knock-in mouse, whose muscle histology was dystrophic with ultrastructural autophagic material and enlarged mitochondria. GGPP is the obligate lipid precursor for geranylgeranylation of small GTPases including the Rab family. Independent literature establishes the mechanistic links: Ca²⁺-dependent vesicle-fusion-based sarcolemmal resealing is an active, essential process in skeletal muscle and is defective in membrane-repair myopathies (Bansal et al., 2003); and Rab GTPases require C-terminal prenylation for membrane tethering. Removing the geranylgeranyl lipid group therefore strips Rabs of their ability to anchor to membranes and drive vesicle trafficking.

"There was delayed membrane healing after laser injury in patient-derived myogenic cells." — PMID: 32403198 "Membrane repair is therefore an active process in skeletal muscle fibres." — PMID: 12736685 "Rabs oscillate between an inactive GDP-bound conformation and an active GTP-bound state that is tethered to lipid membranes via a C-terminal prenylation site on conserved cysteine residues." — PMID: 23663983

Finding 4 — Identifiers and constraint: GGPS1 is not LoF-constrained, consistent with recessive hypomorphic disease

Attribute	Value
Disease MONDO	MONDO:0859189
Disease OMIM	#619518 (MDHLOV)
MedGen / UMLS	C5561980 / 1794190
Gene HGNC	HGNC:4249
NCBI Gene	9453
Ensembl	ENSG00000152904
Cytoband	1q42.3 (GRCh38 chr1:235,327,350–235,344,544)
Gene MIM	606982
RefSeq transcript	NM_004837.4
Aliases	MDHLO, MUDHLOV

gnomAD constraint metrics show pLI = 0.007, observed/expected LoF = 0.53 (90% CI 0.36–0.82), and missense Z = 1.47 — i.e., GGPS1 is not strongly haploinsufficient or LoF-intolerant. This is fully consistent with an autosomal-recessive mechanism in which biallelic hypomorphic missense alleles (partial loss of function), rather than complete nulls, cause disease. Complete loss of GGPP synthesis is presumed incompatible with life (see Finding 9).

Finding 5 — Pathogenic missense variants cluster in the C-terminal catalytic/substrate-binding region

ClinVar (NM_004837.4) pathogenic/likely-pathogenic GGPS1 SNVs cluster tightly:

cDNA	Protein	ClinVar significance	Notes
c.776A>G	p.Tyr259Cys	Pathogenic	Used for the knock-in mouse
c.781C>G	p.Arg261Gly	Pathogenic	Most recurrent allele (mutational hotspot)
c.782G>A	p.Arg261His	Conflicting	Same residue hotspot
c.770T>G	p.Phe257Cys	Likely pathogenic
c.854T>G	p.Val285Gly	Pathogenic
c.764G>A	p.Gly255Asp	VUS
c.790C>G	p.Leu264Val	VUS
c.545T>C	p.Leu182Pro	VUS

All disease-causing variants are ultra-rare missense substitutions falling in specific catalytic domains of the enzyme, with Arg261 an apparent mutational hotspot. Large 1q42 copy-number variants in ClinVar are non-specific and not associated with this Mendelian disorder.

"Ultra-rare biallelic pathogenic variants in geranylgeranyl diphosphate synthase 1 (GGPS1) have recently been associated with muscular dystrophy/hearing loss/ovarian insufficiency syndrome." — PMID: 35869884 "A total of 11 patients in 6 families carrying 5 different biallelic pathogenic variants in specific domains of GGPS1 were identified." — PMID: 32403198

Finding 6 — Pathogenic alleles are absent-to-ultra-rare in gnomAD v4

Variant	Protein	gnomAD v4 alleles	Approx. AF
c.776A>G	p.Tyr259Cys	0	absent
c.854T>G	p.Val285Gly	0	absent
c.781C>G	p.Arg261Gly	34	~2.2×10⁻⁵
c.782G>A	p.Arg261His	~	~1.0×10⁻⁵
c.545T>C	p.Leu182Pro (VUS)	8	~4.7×10⁻⁶
c.764G>A	p.Gly255Asp (VUS)	1	—

No homozygotes are reported for any pathogenic allele, consistent with recessive selection against homozygous carriers. p.Arg261Gly is the most recurrent pathogenic allele.

Finding 7 — HPO phenotype spectrum with frequencies

Curated HPO annotations (OMIM:619518; n ≈ 11 patients):

Phenotype	HPO term	Frequency
Progressive muscle weakness	HP:0003323	11/11 (100%)
Congenital onset	HP:0003577	11/11 (100%)
Elevated serum creatine kinase	HP:0003236	9/9 (100%)
Centrally nucleated skeletal muscle fibers	HP:0003687	9/9
Rimmed vacuoles	HP:0003805	9/9
Skeletal muscle autophagosome accumulation	HP:0025717	2/9
Mitochondrial hypertrophy	HP:0033686	1/9
Sensorineural hearing impairment	HP:0000407	10/11 (91%)*
Premature ovarian insufficiency	HP:0008209	3/3
Female infertility	HP:0008222	3/3
Short stature	HP:0004322	8/11
Failure to thrive	HP:0001508	7/10
Respiratory insufficiency	HP:0002093	8/10
Reduced forced vital capacity	HP:0032341	2/4
Loss of ambulation	HP:0002505	5/11
Scoliosis	HP:0002650	4/10
Motor delay	HP:0001270	—
Decreased fetal movement	HP:0001558	—
Poor suck	HP:0002033	—
Weak cry	HP:0001612	—
Autosomal recessive inheritance	HP:0000007	—

*The 91% figure derives from the original Foley cohort; the pooled frequency across later cohorts is lower (~46% in Kaiyrzhanov et al.), reflecting variable expressivity.

Finding 8 — GGPS1 protein: cytosolic prenyltransferase homohexamer localized to the sarcomere Z-line

UniProt O95749 (human GGPS1, 300 aa) catalyzes the sequential trans-addition of isopentenyl diphosphate (IPP) onto dimethylallyl/geranyl/farnesyl diphosphate to form GGPP (C20). Its quaternary structure is a homohexamer (a trimer of homodimers), consistent with crystal structures of bacterial GGPP synthases (e.g., Nonlabens dokdonensis, which "forms a hexamer composed of homodimeric trimer"). Subcellular localization spans the cytoplasm, perinuclear region, and — notably for muscle disease — the myofibril/sarcomere Z-line. The UniProt disease annotation (MDHLO) reads: "An autosomal recessive disorder characterized by early-onset progressive muscle weakness, sensorineural hearing loss, and primary amenorrhea due to ovarian insufficiency. Some patients become wheelchair-bound by the second decade, whereas others have a milder phenotype and maintain independent ambulation."

"GGPS1 encodes geranylgeranyl diphosphate synthase in the mevalonate/isoprenoid pathway, which catalyzes the synthesis of geranylgeranyl pyrophosphate, the lipid precursor of geranylgeranylated proteins including small guanosine triphosphatases." — PMID: 32403198

Finding 9 — Model organisms and evolutionary conservation

GGPS1 is highly conserved with clear orthologs across the tree of life: mouse Ggps1 (NCBI Gene 14593; MGI), rat Ggps1 (291211), zebrafish ggps1 (336798), Xenopus ggps1 (549876), Drosophila (NCBI 38816), and S. cerevisiae BTS1 (856036). Foley et al. generated a disease-specific p.Tyr259Cys knock-in mouse. Independent mouse work shows Ggpps has essential roles: skeletal-muscle-specific deletion causes insulin resistance via RhoA geranylgeranylation (PMID: 26112408), and liver-specific deletion alters adipose remodeling via Rab27A-dependent extracellular-vesicle secretion (PMID: 32024826). Global loss of Ggpps is not viable — consistent with GGPP being an essential isoprenoid and with the human disease requiring hypomorphic (not null) alleles.

"the generation of a Y259C knock-in mouse were done." — PMID: 32403198 "we generated mice with specific GGPPS deletions in their skeletal muscle tissue." — PMID: 26112408

Finding 10 — GGPS1 belongs to the polyprenyl-synthetase fold; disease residues line the catalytic domain

InterPro annotation of O95749: Pfam PF00348 (polyprenyl synthetase domain); InterPro IPR000092 (polyprenyl synthetase-like family), IPR008949 (isoprenoid synthase domain superfamily), IPR033749 (conserved site); CDD cd00685 (trans-isoprenyl diphosphate synthases, head-to-tail); CATH G3DSA:1.10.600.10 (farnesyl-diphosphate-synthase homologous superfamily); PROSITE PS00444/PS00723; PANTHER PTHR12001 (GGPP synthase family). The pathogenic residues Phe257, Tyr259, Arg261, and Val285 all fall within this C-terminal catalytic/substrate-binding domain, providing a structural rationale for their hypomorphic effect on enzyme activity.

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

1. Biallelic hypomorphic missense variant in GGPS1 (e.g., p.Tyr259Cys, p.Arg261Gly)
   in the C-terminal catalytic/substrate-binding domain
│  leads to
▼
2. Partial loss of geranylgeranyl diphosphate synthase catalytic activity
   (homohexameric prenyltransferase; complete loss is lethal → only hypomorphs survive)
│  results in
▼
3. Reduced cellular supply of geranylgeranyl pyrophosphate (GGPP, C20 isoprenoid)
│  results in
▼
4. Impaired protein geranylgeranylation of small GTPases at their C-terminal
   cysteine motifs (Rab family; Rho family) [inferred from enzyme function + Rab biology]
│  leads to
▼
5. Small GTPases fail to anchor to membranes → defective vesicle trafficking
   and membrane-associated signaling
│
├──► (MUSCLE branch, demonstrated)
│    6a. Defective Ca²⁺-dependent sarcolemmal membrane-repair vesicle fusion
│        → delayed membrane resealing after injury (shown in patient myogenic cells)
│        → chronic myofiber damage, autophagic/rimmed vacuoles, mitochondrial
│          enlargement, central nucleation
│        → PROGRESSIVE PROXIMAL MUSCULAR DYSTROPHY, ↑ creatine kinase (fully penetrant)
│
├──► (COCHLEA branch, inferred)
│    6b. Impaired trafficking in cochlear hair/supporting cells
│        → CONGENITAL SENSORINEURAL HEARING LOSS (variable, ~46–91%)
│
└──► (OVARY branch, inferred)
     6c. Impaired trafficking / prenylation in ovarian granulosa/germ cells
         → PRIMARY / PREMATURE OVARIAN INSUFFICIENCY (post-pubertal females)

   (LIVER branch, occasionally observed): hepatic transaminase elevation

Upstream vs downstream. The upstream lesion is the enzymatic deficit (steps 1–3); the downstream effectors are the under-prenylated small GTPases and the trafficking/repair failures they cause (steps 4–6). The muscle branch is the best-supported (direct patient-cell and mouse evidence); the cochlear and ovarian branches are mechanistically inferred by analogy to the same prenylation defect acting in tissues with high secretory/trafficking demand.

Pathways, cell types, compartments. - Molecular pathway: mevalonate/isoprenoid biosynthesis → GGPP → protein geranylgeranylation; downstream RhoA/Rho-kinase and Rab-dependent vesicle trafficking. - Cellular processes (GO): protein geranylgeranylation (GO:0018344), isoprenoid biosynthetic process (GO:0008299), plasma-membrane repair (GO:0001778), vesicle-mediated transport (GO:0016192), autophagy (GO:0006914). - Cell types (CL): skeletal muscle fiber (CL:0000188), cochlear hair cell (CL:0000855), ovarian granulosa cell (CL:0000501), hepatocyte (CL:0000182). - Subcellular compartments (GO CC): cytoplasm/cytosol (GO:0005829), sarcomere Z-disc (GO:0030018), myofibril (GO:0030016), sarcolemma (GO:0042383), mitochondrion (GO:0005739). - Chemical entities (CHEBI): geranylgeranyl diphosphate (CHEBI:48861), isopentenyl diphosphate (CHEBI:128769), farnesyl diphosphate (CHEBI:175763).

Relationship to Perrault syndrome

Because sensorineural hearing loss + ovarian insufficiency is the definition of Perrault syndrome, GGPS1 is now listed among Perrault-syndrome genes alongside a set that is otherwise dominated by mitochondrial/peroxisomal genes (HSD17B4, HARS2, CLPP, LARS2, TWNK, ERAL1, RMND1, DAP3, PRORP, MRPL50, MRPL49, MRPS7, PEX6, TFAM). GGPS1 is mechanistically distinct — an isoprenoid-pathway gene rather than a mitochondrial-translation gene — and is uniquely accompanied by a prominent muscular dystrophy, which is the discriminating feature at the bedside.

Section-by-Section Disease Report

1. Disease Information

A rare Mendelian multisystem disorder: congenital-onset progressive proximal muscular dystrophy with variable sensorineural hearing loss and primary ovarian insufficiency. Identifiers: MONDO:0859189; OMIM #619518 (MDHLOV); MedGen C5561980; UMLS C5561980. Synonyms: MDHLO, MUDHLOV, "GGPS1-related/associated congenital muscular dystrophy," "GGPS1-associated muscular dystrophy with/without hearing loss." Information is derived from aggregated disease-level resources (OMIM/Orphanet/UniProt/ClinVar) built from a small number of published patient cohorts (≈22 patients total across three primary reports), not from EHR-scale data.

2. Etiology

Causal factor: purely genetic — biallelic hypomorphic missense variants in GGPS1. Genetic risk factors: the causal variants themselves (Finding 5); no established modifier genes. Environmental risk/protective factors: none identified — this is a monogenic disorder without known environmental modifiers. Consanguinity raises risk (homozygous alleles reported). Gene-environment interactions: none documented. Note: statins (HMG-CoA reductase inhibitors) reduce mevalonate-pathway flux upstream of GGPP and are theoretically of concern, but no clinical interaction data exist.

3. Phenotypes

See Finding 7 for the full HPO table with frequencies. Obligate feature: progressive proximal muscle weakness (HP:0003323), congenital onset (HP:0003577), elevated CK (HP:0003236). Variable features: sensorineural hearing loss (HP:0000407; ~46–91%), premature ovarian insufficiency (HP:0008209) in post-pubertal females, respiratory insufficiency (HP:0002093), short stature (HP:0004322), scoliosis (HP:0002650), loss of ambulation (HP:0002505). Progression: progressive; some patients wheelchair-bound by the second decade, others retain independent ambulation. Quality-of-life impact: substantial — mobility loss, respiratory compromise, deafness, and infertility.

4. Genetic/Molecular Information

Causal gene: GGPS1 (HGNC:4249; gene MIM 606982; NM_004837.4). Variants: ultra-rare missense (Finding 5), clustered in the C-terminal catalytic domain, ACMG classifications ranging pathogenic → VUS. Allele frequencies: absent-to-ultra-rare in gnomAD v4 with no homozygotes (Finding 6). Origin: germline. Functional consequence: partial (hypomorphic) loss of enzyme function. Modifier genes / epigenetics / chromosomal abnormalities: none established for this disorder (large 1q42 CNVs in ClinVar are non-specific).

5. Environmental Information

Not applicable — no environmental, lifestyle, or infectious contributors are known. Disease is fully explained by biallelic GGPS1 genotype.

6. Mechanism / Pathophysiology

See the Mechanistic Model section above for the full ordered causal chain, pathway/GO/CL/CHEBI annotations, and branch structure.

7. Anatomical Structures Affected

Organ level (primary): skeletal muscle (UBERON:0001134), esp. proximal limb-girdle muscles; cochlea/inner ear (UBERON:0001844); ovary (UBERON:0000992). Secondary: respiratory muscles/diaphragm → respiratory insufficiency; axial skeleton → scoliosis; liver (UBERON:0002107) in some. Body systems: musculoskeletal, auditory/sensory, endocrine/reproductive, respiratory. Tissue/cell: striated muscle fiber (CL:0000188), cochlear hair cells (CL:0000855), ovarian granulosa cells (CL:0000501). Subcellular: sarcomere Z-line/myofibril, sarcolemma, cytosol, mitochondria (enlarged on EM), autophagosomes. Lateralization: bilateral/symmetric.

8. Temporal Development

Onset: congenital (decreased fetal movement, weak cry, poor suck, motor delay). Course: chronic, progressive, lifelong. Progression rate: variable — wheelchair by second decade in severe cases vs. maintained ambulation in milder cases. Ovarian insufficiency manifests at expected puberty (primary amenorrhea / premature ovarian failure). Critical periods: perinatal and childhood for motor/respiratory decline; puberty for reproductive endocrine failure. No remission.

9. Inheritance and Population

Inheritance: autosomal recessive (HP:0000007). Penetrance: complete for myopathy; variable expressivity for hearing loss and ovarian insufficiency. Epidemiology: ultra-rare; no formal prevalence/incidence estimate (≈22 reported patients worldwide). Founder/consanguinity: homozygous alleles reported in consanguineous families; p.Arg261Gly is a recurrent (hotspot) allele. Carrier frequency: each pathogenic allele is absent-to-ultra-rare in gnomAD; no homozygotes observed. Sex ratio: both sexes affected by muscle/ear disease; ovarian insufficiency affects females only.

10. Diagnostics

Laboratory: elevated serum creatine kinase (near-universal). Audiology: confirms sensorineural hearing loss. Endocrine: elevated gonadotropins/low estradiol, primary amenorrhea in females (ovarian insufficiency). Muscle biopsy/histopathology: dystrophic changes, centrally nucleated fibers (HP:0003687), rimmed vacuoles (HP:0003805), autophagic material, enlarged mitochondria on EM. Pulmonary function: reduced forced vital capacity in some. Genetic testing (definitive): WES or WGS with shared-haplotype/segregation analysis identified the gene; targeted single-gene or Perrault-syndrome/congenital-muscular-dystrophy panel testing of GGPS1 (NM_004837.4) confirms diagnosis. CMA/karyotype not informative. Differential diagnosis: other Perrault-syndrome genes (mitochondrial-translation/peroxisomal — CLPP, LARS2, HARS2, TWNK, MRPL49, PRORP, etc.), other congenital/limb-girdle muscular dystrophies (notably dysferlinopathy and other membrane-repair myopathies), and other causes of primary ovarian insufficiency. Prominent congenital muscular dystrophy plus the GGPS1 genotype distinguishes MDHLOV from classic Perrault syndrome.

11. Outcome / Prognosis

Chronic, progressive, lifelong disability. Motor: loss of ambulation in a subset (5/11 in the original cohort). Respiratory: insufficiency in the majority — the principal driver of morbidity/mortality. Reproductive: infertility from ovarian insufficiency. Sensory: permanent hearing loss. No formal survival statistics; prognosis is dominated by respiratory muscle involvement and mobility loss. Prognostic factors: severity/onset of weakness and respiratory decline; genotype-phenotype correlation is suggested but not firmly established given small numbers.

12. Treatment

No disease-specific/curative therapy exists. Management is supportive and multidisciplinary: physical/occupational therapy and mobility aids; respiratory monitoring and non-invasive ventilation for respiratory insufficiency; hearing aids or cochlear implantation for sensorineural hearing loss; hormone replacement therapy for primary ovarian insufficiency (estrogen/progesterone; bone-health protection); orthopedic management (scoliosis, contractures); nutritional support for failure to thrive; genetic counseling. Advanced/experimental therapeutics: none approved; no gene, cell, or RNA therapies in trials for this disorder. Theoretically, substrate-supplementation or pathway-modulation strategies are of mechanistic interest but untested. Pharmacogenomic caution: statins (which lower mevalonate flux upstream of GGPP) are theoretically undesirable but have no specific evidence base here. Suggested NCIT intervention terms: physical therapy (NCIT:C15327), hormone replacement therapy (NCIT:C62556), mechanical ventilation (NCIT:C70909), cochlear implant (NCIT:C99913).

13. Prevention

No primary prevention (monogenic). Genetic counseling for at-risk families (25% recurrence risk per pregnancy for carrier couples). Carrier and cascade testing of relatives; prenatal diagnosis and preimplantation genetic testing are options once the familial variants are known. Newborn screening does not cover this disorder. Tertiary prevention = managing complications (respiratory support, HRT for bone health, scoliosis management).

14. Other Species / Natural Disease

No naturally occurring GGPS1 disease is reported in companion animals or wildlife (no OMIA entry described). Orthologs are highly conserved (Finding 9): mouse Ggps1 (14593), rat (291211), zebrafish (336798), Xenopus (549876), Drosophila (38816), yeast BTS1 (856036). No zoonotic potential (non-infectious genetic disease).

15. Model Organisms

Disease-specific model: a p.Tyr259Cys knock-in mouse (Foley et al., 2020) recapitulates dystrophic muscle histology (autophagic material, enlarged mitochondria) — good recapitulation of the muscle phenotype; hearing/ovarian phenotypes less characterized. Conditional deletion mice: skeletal-muscle-specific Ggpps knockout (insulin resistance via RhoA prenylation; PMID: 26112408) and liver-specific knockout (adipose remodeling via Rab27A; PMID: 32024826) — model gene function but not the exact human disease. Limitation: global null is lethal, so only hypomorphic/conditional models are informative. Model resources: MGI, IMPC, IMSR. Complementary in-vitro model: patient-derived myogenic cells showing the membrane-repair defect.

Evidence Base

PMID	Title (abbrev.)	Role in this report
32403198	GGPS1 Mutations Cause MDHLOV Syndrome (Foley 2020)	Landmark gene-discovery paper. Supports Findings 1, 3, 8, 9 — WES/haplotype discovery, clinical triad, enzyme function, delayed membrane repair in patient cells, Y259C knock-in mouse.
35869884	GGPS1-associated MD with and without hearing loss (Kaiyrzhanov 2022)	Supports Findings 2, 5 — 11 more patients; hearing loss in only 46%; establishes variable expressivity and "ultra-rare biallelic" nature.
38129970	Expanding the phenotypic/genotypic spectrum (Altassan 2024)	Supports Finding 2 — isolated proximal weakness + elevated transaminases with spared hearing; adds hepatic involvement.
12736685	Defective membrane repair in dysferlin-deficient MD (Bansal 2003)	Supports Finding 3 — establishes active Ca²⁺-dependent sarcolemmal repair as a disease-relevant muscle process.
23663983	Oligomerization of rab/effector complexes	Supports Finding 3 — Rab GTPases require C-terminal prenylation for membrane tethering; explains downstream defect.
26112408	Lipid-induced muscle insulin resistance via GGPPS/RhoA	Supports Finding 9 — skeletal-muscle Ggpps conditional KO; RhoA geranylgeranylation.
32024826	Liver governs adipose remodelling via EVs	Supports Finding 9 — liver Ggpps KO; Rab27A geranylgeranylation controls EV secretion.
31427080	Crystal structure of GGPP synthase (crtE)	Supports Finding 8 — homohexameric (trimer-of-dimers) architecture of GGPP synthases.
42283975	Comprehensive insights into Perrault syndrome	Context — places GGPS1 among 15 Perrault-syndrome genes; clinical/genetic heterogeneity.
24784578, 27286750, 32087766, 26911675	Dysferlin/Annexin-A5/AMPK/ANO5 membrane-repair studies	Context — mechanistic framework for vesicle-fusion-based sarcolemmal repair, the process inferred to fail here.
36116551, 40325959	Rab prenylation/localization; Rep-deficiency retinal degeneration	Context — consequences of failed Rab geranylgeranylation (membrane mislocalization, cell death).

Limitations and Knowledge Gaps

Small evidence base. The entire disease description rests on ≈22 patients across three primary reports; prevalence, incidence, survival, and robust genotype-phenotype correlations cannot be estimated.
Inferred (not demonstrated) extra-muscular mechanism. The membrane-repair defect is directly shown only in muscle. The cochlear and ovarian branches are mechanistic inferences from the shared prenylation defect; the specific under-prenylated GTPases and cellular events in inner ear and ovary have not been experimentally defined.
Which Rab/Rho substrates are limiting? Direct proteomic/prenylomic evidence identifying the specific hypoprenylated small GTPases in patient tissues is lacking.
VUS burden. Several GGPS1 alleles (p.Gly255Asp, p.Leu264Val, p.Leu182Pro) remain VUS; functional enzymatic assays are needed for reclassification.
No therapeutic data. No trials, no natural-history registry, and no validated biomarkers for progression beyond CK.
Model gaps. Knock-in mouse muscle phenotype is described, but auditory and ovarian phenotypes in the model are not fully characterized; global null lethality limits modeling of complete deficiency.

Proposed Follow-up Experiments / Actions

Prenylomics in patient cells/tissues — quantify unprenylated Rab/Rho GTPases (e.g., in-vitro prenylation with biotin-geranylgeranyl) in patient myoblasts, and if accessible, cochlear/granulosa-cell models, to directly test step 4 of the causal chain.
Phenotype the Y259C knock-in mouse for hearing and fertility — ABR audiometry and ovarian histology/reproductive assays to test the cochlear and ovarian branches in vivo.
iPSC-derived organoids — patient-derived iPSC inner-ear organoids and ovarian/granulosa models to interrogate tissue-specific trafficking defects.
Functional reclassification of VUS — express VUS alleles and measure GGPP-synthase catalytic activity/thermostability to move VUS toward pathogenic/benign.
GGPP/mevalonate-pathway rescue screens — test whether GGPP supplementation, geranylgeraniol, or upstream pathway modulation rescues membrane-repair kinetics in patient myogenic cells (proof-of-concept for a metabolic therapy).
International registry — establish a natural-history registry (via Perrault-syndrome and congenital-muscular-dystrophy networks) to capture prevalence, progression, respiratory outcomes, and genotype-phenotype correlations.
Structural modeling of hotspot residues — map Phe257/Tyr259/Arg261/Val285 onto the GGPP-synthase active site (homology/AlphaFold) to explain why Arg261 is a mutational hotspot.

Report compiled from 10 confirmed findings and 25 reviewed publications over 5 investigation iterations. Evidence types are human clinical (patient cohorts), model organism (mouse conditional/knock-in), and in vitro (patient-derived myogenic cells; bacterial/structural enzymology).

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	15
Resolved	15
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	12
Quoted claims found in source	11
Quoted claims not found in source	1
References weighed for topical relevance	15
On topic	4
Off topic	1

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

PMID:35869884: "hearing loss was present in only 46% of the individuals … demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy."
closest text in source: "This report consolidates the disease-causing role of biallelic variants in GGPS1 and demonstrates that hearing loss and ovarian insufficiency might be a variable feature of the GGPS1-associated muscular dystrophy"

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

PMID:31427080 (1 mention) - Crystal structure of geranylgeranyl pyrophosphate synthase (crtE) from Nonlabens dokdonensis DSW-6.
shared terms: none

Weighed against this report's own most characteristic terms: ovarian, loss, hearing, ggps1, insufficiency, muscle, ggpp, patient, gene, disease, mouse, primary, sensorineural, respiratory, allele, congenital, cell, pathogenic, variant, disorder.

Term Validation

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

Outcome	Count
Terms checked	49
Resolved	47
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	2
Terms whose name was checked	25
Terms named correctly	23
Terms named as a different term	1
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:0859189 (3 mentions) - the report calls it "Disease MONDO"; MONDO calls it muscular dystrophy, congenital hearing loss, and ovarian insufficiency syndrome

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:

UBERON:0001844 (1 mention) - the report calls it "cochlea/inner ear"; UBERON calls it cochlea, and lists "cochlear organ" among its other names

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: OMIM.

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Classifications

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Histopathology

Pathograph

Phenotypes

Genetic Associations

Variants

Medical Actions

Biochemical Markers

Diagnosis

Progression

Prevalence

Differential Diagnoses

Experimental Models

Animal Models

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References & Deep Research

Deep Research

Muscular Dystrophy, Congenital Hearing Loss, and Ovarian Insufficiency Syndrome (MDHLOV): A Comprehensive Disease Report

Summary

Key Findings

Finding 1 — Biallelic GGPS1 variants cause the muscle–ear–ovary triad

Finding 2 — Hearing loss and ovarian insufficiency are variable; the spectrum includes hepatic involvement

Finding 3 — Mechanism: reduced GGPP impairs Rab/small-GTPase geranylgeranylation and sarcolemmal membrane repair

Finding 4 — Identifiers and constraint: GGPS1 is not LoF-constrained, consistent with recessive hypomorphic disease

Finding 5 — Pathogenic missense variants cluster in the C-terminal catalytic/substrate-binding region

Finding 6 — Pathogenic alleles are absent-to-ultra-rare in gnomAD v4

Finding 7 — HPO phenotype spectrum with frequencies

Finding 8 — GGPS1 protein: cytosolic prenyltransferase homohexamer localized to the sarcomere Z-line

Finding 9 — Model organisms and evolutionary conservation

Finding 10 — GGPS1 belongs to the polyprenyl-synthetase fold; disease residues line the catalytic domain

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

Relationship to Perrault syndrome

Section-by-Section Disease Report

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Evidence Base

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Artifacts

Reference Validation

Quotes not found in the cited source

References that may not be about this subject

Term Validation

Terms the report names something else

Terms whose name is worth a second look

Prefixes with no resolver