Rhizomelic Dysplasia, Ain-Naz Type

🏷

Classifications

Harrison's Part

🔗

Mappings

MONDO

MONDO:0859203 rhizomelic dysplasia, Ain-Naz type

Primary MONDO identifier for this entry (OMIM:619598).

👪

Inheritance

1

Autosomal recessive HP:0000007

All three reported families are homozygous for a GNPNAT1 missense allele. Consanguinity is stated for the Pakistani index family and for the Egyptian family, in which both parents were additionally confirmed to be heterozygous carriers; the second report does not state parental relationship. Penetrance is recorded as COMPLETE on the strength of segregation rather than of a measured figure: the founding report sequenced two affected and two unaffected members of the index family and found the variant segregating with disease, and no unaffected homozygote has been reported in any family. Across six affected individuals ascertained through affected probands, that is an absence of counterexamples, not an estimate. Expressivity is left UNKNOWN, and deliberately not called variable. The clinical descriptions do differ between reports — the Egyptian patient has immunodeficiency, advanced bone age and brachydactyly, none of which appear in the founding description — but that patient is also the only carrier of the p.(Phe26Cys) allele, so genotype and phenotype differ together. The two families that do share a genotype, both homozygous for p.(Glu76Lys), are described consistently, with the second report presenting itself as further delineating the same picture rather than widening it. Variable expressivity is therefore not what the published data show; what they show is two alleles with two descriptions, confounded with how deeply each was worked up.

Autosomal recessive inheritance Penetrance: COMPLETE Expressivity: UNKNOWN

Show evidence (2 references)

PMID:35427807 SUPPORT Human Clinical

"with autosomal recessive rhizomelic SEMD associated with a homozygous exonic missense variant"

States the mode of inheritance directly.

PMID:36097642 SUPPORT Human Clinical

"We conclude that variants in the GNPNAT1 gene cause an autosomal recessive form of SEMD"

Independent statement of autosomal recessive inheritance.

?

Discussions and Knowledge Gaps

8

Which UDP-GlcNAc-dependent process carries the skeletal phenotype of GNPNAT1 deficiency — mannose-6-phosphate tagging of lysosomal hydrolases, O-GlcNAcylation, N-glycosylation, or glycosaminoglycan synthesis?

KNOWLEDGE GAP OPEN rdan_udp_glcnac_route

Attached to

pathophysiology#Diminished UDP-GlcNAc Supply

GNPNAT1 supplies UDP-GlcNAc, which is the donor for at least four distinct processes with plausible skeletal consequences, and the published work does not distinguish between them. The mannose-6-phosphate route is the most tempting because the sugar donated by GlcNAc-1-phosphotransferase comes from UDP-GlcNAc and because the similarly named LYSET disorder is a defect of that same phosphotransferase — but no lysosomal enzyme assay, urinary glycosaminoglycan measurement or M6P study has been reported in any GNPNAT1 patient, and none of the three abstracts consulted for this entry describes coarse facies, organomegaly or the storage picture that a mannose-6-phosphate defect produces — though an abstract would not necessarily record their absence. The O-GlcNAc route is equally unmeasured. The founding report's own framing is the broadest one, "participates in protein glycosylation", and this entry goes no further than that. Resolving this needs patient fibroblasts: UDP-GlcNAc quantitation, a glycosylation screen (transferrin isoform analysis or equivalent), an O-GlcNAc immunoblot, and plasma and fibroblast lysosomal enzyme activities. The two evidence items below establish only that the donor relationship exists; neither says anything about a patient with this disorder.

Show evidence (2 references)

PMID:32591345 SUPPORT Other

"which participates in protein glycosylation"

The founding report goes no further than naming protein glycosylation generically, which is the extent of what is established. Graded OTHER for the same reason as the fuller quotation of this sentence on the Diminished UDP-GlcNAc Supply node: it is background biochemistry, not a finding of the study.

PMID:39178950 SUPPORT In Vitro

"PTase is the key enzyme of the mannose 6-phosphate (M6P) targeting system that is responsible for tagging lysosomal hydrolases with the M6P moiety for their delivery to the lysosome."

Establishes the mannose-6-phosphate route that makes this question worth asking. It concerns the phosphotransferase, not GNPNAT1, and is cited only to show that UDP-GlcNAc feeds that pathway — not to assert that this disorder runs through it.

Is immunodeficiency a feature of GNPNAT1 deficiency, or a feature of the one patient in whom it was reported?

KNOWLEDGE GAP OPEN rdan_immunodeficiency_single_case

Attached to

phenotypes#Immunodeficiency

Immunodeficiency is reported in exactly one patient, who is also the only patient carrying the p.(Phe26Cys) allele, and the record consulted gives no immunological detail — no immunoglobulin levels, lymphocyte subsets or infection history. Two readings fit equally: the phenotype includes an immune component that the earlier reports did not look for, or this is allele-specific or incidental. The question is not idle, because PGM3 — the next enzyme in the same pathway — causes a disorder in which skeletal dysplasia and immunodeficiency occur together, so a shared immune consequence of reduced UDP-GlcNAc supply is biologically plausible. It would be resolved by immunophenotyping the patients from the other two families, which has not been reported. No frequency band is attached to the phenotype for this reason.

What do the two reported GNPNAT1 missense alleles actually do to enzyme activity?

KNOWLEDGE GAP OPEN rdan_variant_function_unmeasured

Attached to

pathophysiology#Biallelic GNPNAT1 Missense Variants

Both p.(Glu76Lys) and p.(Phe26Cys) are missense, and neither has been assayed. The functional work in the founding report is siRNA knockdown, which removes the transcript and therefore models a null rather than either patient allele; the rest is in-silico prediction. This is why the entry records functional_impact_category as UNKNOWN and grades the enzyme-activity node HYPOTHETICAL. A recombinant activity assay against glucosamine-6-phosphate, of the kind already published for wild-type human GNA1 in PMID:26935656 and cited elsewhere in this entry for that enzymology, would settle it, and would also say whether the two alleles behave alike — which matters for the immunodeficiency question above.

Does siRNA knockdown of Gnpnat1 in rat chondrocytes tell us what the human missense alleles do, given that it removes the transcript rather than expressing a variant protein?

HUMAN MODEL MISMATCH OPEN rdan_sirna_models_a_null_not_the_alleles

Attached to

experimental_models#Gnpnat1 siRNA knockdown in primary rat chondrocytes pathophysiology#Impaired Growth Plate Chondrocyte Proliferation and Differentiation

This is the mismatch case rather than the absent-evidence case, and the two are separate questions. Evidence does exist here: knockdown lowers chondrocyte proliferation and differentiation marker expression, and it is the sole experimental support for locating this disorder's mechanism in the chondrocyte. What is open is whether it translates. Both reported alleles are missense and are carried homozygously, so they produce protein that is expressed and may retain partial activity; siRNA removes the transcript and therefore models a null. The link records that as a CAUSE_UNREPRESENTED divergence with materiality INVALIDATING for exactly this reason. The species substitution and the absence of growth-plate architecture compound it. The mismatch would be resolved by expressing the patient alleles rather than silencing the gene — a knock-in or a rescue of knockdown cells with variant cDNA — which no report has done. The companion gap rdan_variant_function_unmeasured asks the different question of what the alleles do biochemically; this one asks whether the existing cellular phenotype can be read as theirs.

Is any disease-modifying approach conceivable for a defect in nucleotide-sugar supply, and would substrate supplementation be a rational place to start?

KNOWLEDGE GAP OPEN rdan_no_therapy_evidence

Attached to

treatments#

Nothing is published on treatment. The mechanism raises an obvious question that no one has asked in print: GNPNAT1 acts on glucosamine-6-phosphate, and the salvage route through GlcNAc kinase enters the pathway downstream of GNPNAT1, so oral N-acetylglucosamine would in principle bypass the block. That is a hypothesis generated here from pathway topology, not a finding — no such experiment has been reported in this disorder, in a GNPNAT1 model system, or in PGM3 deficiency, and the skeletal lesion may in any case be developmental and therefore not correctable after presentation. It is recorded so the reasoning is auditable and not so that it is acted on. This is an absence of evidence, not evidence of futility.

Should the remaining 29 terms of the HPO annotation for OMIM:619598 be curated as phenotypes here, and can any of them be tied to a quotable passage in a primary report?

CURATION TODO OPEN rdan_phenotype_breadth

Attached to

phenotypes#

The HPO Consortium annotation for OMIM:619598 carries 41 terms with per-term fractions. Twelve of them are curated here, chosen because they are full-cohort annotations or because they carry the radiographic spondyloepimetaphyseal pattern; the rest are not, and they are not worthless. The uncurated ones include scoliosis, lumbar hyperlordosis, pectus excavatum, flaring of the rib cage, bowed forearm bones, proximal and distal humeral metaphyseal irregularity, wide distal femoral metaphysis, aplasia of the femoral head, hallux valgus, overlapping toe, short distal phalanx of finger, contracture of the proximal interphalangeal joint of the fifth finger, protuberant abdomen, short neck, congenital onset and infantile onset, and the five craniofacial terms listed in rdan_craniofacial_tension. Most are annotated 1/1 — a single observation in a single individual — which is why they were left for a curator with the full texts rather than imported in bulk. Two annotations are exclusions and must not be read as features. Intellectual disability (HP:0001249) is annotated 0/6 and abnormality of alkaline phosphatase level (HP:0004379) 0/1: the HPO records them as looked for and absent. The deep-research report generated for this entry listed intellectual disability among the phenotypes, which is exactly the error the fraction prevents; it is recorded here so the mistake is not made again. Resolving this needs the full texts of the three primary reports and the OMIM clinical synopsis, which could not be read for this curation because omim.org returned HTTP 403.

Twelve phenotypes and three frequency bands in this entry rest on the HPO disease annotation for OMIM:619598 rather than on a quoted passage. Should they carry evidence, and if so from where?

CURATION TODO OPEN rdan_hpoa_provenance

Attached to

phenotypes#

dismech evidence policy asks for an exact quote from a cited source. The HPO Consortium disease annotation is a structured, authoritative, versioned resource, but it is not a reference prefix this repository caches, so there is no cached body to quote and no identifier a snippet could be checked against. Rather than manufacture a quote or drop the content, each affected phenotype records its provenance in notes: the API endpoint (ontology.jax.org/api/network/annotation/OMIM:619598), the retrieval date (2026-09-07), and the exact annotated fraction. The three VERY_FREQUENT bands are the 6/6 and 5/5 annotations and nothing else; every other phenotype in the entry carries no frequency. The annotation is itself derived, one step removed from the primary reports by way of the OMIM clinical synopsis, so a curator with the full texts should be able to replace these notes with quoted evidence. Until then, read these twelve as traceable but not snippet-verified, and distinguish them from the nine phenotypes in this entry that do carry an exact quote from a cached PubMed abstract. Adding an HPOA reference source to references_cache/, in the way ORPHA and ClinGen were added, would close this gap for every disorder entry rather than only this one.

Is the craniofacial skeleton spared in this disorder, as the second report's definition of rhizomelic SEMD states, or mildly involved, as the HPO annotation implies?

CONTROVERSY OPEN rdan_craniofacial_tension

Attached to

pathophysiology#Disordered Endochondral Ossification

The second report defines rhizomelic SEMD as sparing the cranio-facial sphere, and that sparing is one of the features that separates this disorder from the dysostosis multiplex pattern of the LYSET disorder it is confused with. The HPO annotation for OMIM:619598 nonetheless records frontal bossing, hypertelorism, ptosis, downslanted palpebral fissures and a wide nasal bridge, each in one of six individuals, and Wormian bones in one of one. These are reconcilable: five of the six terms are single-individual annotations out of six, so a category-level statement that the craniofacial sphere is unaffected is compatible with minor, inconsistent findings in individual patients — and none of the annotated terms is the progressive coarsening that defines dysostosis multiplex. The tension is recorded rather than resolved because resolving it needs the per-patient descriptions in the full texts, and because a reader who takes "cranio-facial sphere unaffected" at face value would be surprised by the annotation. Only Wormian bones is curated as a phenotype here, as the one craniofacial finding that is skeletal rather than a facial-gestalt descriptor.

⚙

Pathophysiology

5

Biallelic GNPNAT1 Missense Variants

Mechanism confidence: Established

Homozygous missense variants in GNPNAT1 segregate with the disease in all three reported families. Two unrelated families carry the same allele, c.226G>A p.(Glu76Lys), which the second report proposes as a potential mutational hotspot; the third family carries c.77T>G p.(Phe26Cys). Consanguinity is stated for the Pakistani index family and for the Egyptian family, whose parents were also confirmed heterozygous carriers; the report of the second patient does not state parental relationship.

GNPNAT1 hgnc:19980

Genetic context variant_origin: GERMLINE zygosity: HOMOZYGOUS functional_impact_category: UNKNOWN

Both reported alleles are missense. No enzyme-activity measurement has been published for either variant protein, so the functional consequence is recorded as UNKNOWN rather than assumed to be loss of function. The founding report used in-silico prediction and an siRNA knockdown model, neither of which measures what the patient allele does to the enzyme.

Downstream

Reduced Glucosamine-6-Phosphate N-Acetyltransferase Activity The presumed but unmeasured first consequence. No enzyme assay has been performed on either patient allele, so the edge is typed UNKNOWN and carries no evidence rather than borrowing the knockdown result, which removes the transcript instead of testing the missense protein.

Show evidence (2 references)

PMID:32591345 SUPPORT Human Clinical

"WGS data analyses identified a homozygous missense variant c.226G>A; p.(Glu76Lys) in GNPNAT1, segregating with the disease."

The founding report identifies the causal allele and records its segregation with disease in the index family.

PMID:36097642 SUPPORT Human Clinical

"Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant."

A second, independent allele in an unrelated family, with parental carrier status establishing recessive segregation.

Reduced Glucosamine-6-Phosphate N-Acetyltransferase Activity

Mechanism confidence: Hypothetical

GNPNAT1 encodes glucosamine-6-phosphate N-acetyltransferase (GNA1), which transfers an acetyl group from acetyl-CoA to glucosamine-6-phosphate to give N-acetylglucosamine-6-phosphate. Reduced activity of this step in patients is inferred from the gene-disease relationship and from the enzyme's known reaction; it has not been measured in patient cells.

glucosamine 6-phosphate N-acetyltransferase activity GO:0004343 ↓ DECREASED

Downstream

Diminished UDP-GlcNAc Supply The acetyltransferase step is obligatory for UDP-GlcNAc synthesis, so a reduction in it reduces flux to the nucleotide sugar.

Show evidence (1 reference)

PMID:26935656 SUPPORT In Vitro

"Glucosamine-6-phosphate N-acetyltransferase1 (GNA1) catalyses the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to glucosamine-6-phosphate (GlcN6P) to form N-acetylglucosamine-6-phosphate (GlcNAc6P), which is an essential intermediate in UDP-GlcNAc biosynthesis."

Establishes the reaction the affected enzyme catalyses and its position in UDP-GlcNAc biosynthesis. It says nothing about the patient alleles, which is why the node is graded HYPOTHETICAL.

Diminished UDP-GlcNAc Supply

Mechanism confidence: Hypothetical

GNPNAT1 is one of the enzymes of the hexosamine biosynthetic pathway, whose product UDP-N-acetylglucosamine is the donor sugar for protein N-glycosylation, O-GlcNAcylation, glycosaminoglycan chain extension and the mannose-6-phosphate tagging of lysosomal hydrolases. Reduced supply is the proposed link between the enzyme lesion and the skeleton. No measurement of UDP-GlcNAc, of protein glycosylation or of O-GlcNAcylation has been published in a patient with this disorder, so the node is graded HYPOTHETICAL and no specific downstream glycosylation route is asserted (see discussion rdan_udp_glcnac_route).

UDP-N-acetylglucosamine biosynthetic process GO:0006048 ↓ DECREASED

Downstream

Impaired Growth Plate Chondrocyte Proliferation and Differentiation Loss of Gnpnat1 impairs chondrocyte proliferation and differentiation in culture. Which UDP-GlcNAc-dependent process carries the effect is not established, so the intermediates are recorded as unknown.

Show evidence (3 references)

PMID:32591345 SUPPORT Other

"Glucosamine 6-phosphate N-acetyltransferase, encoded by the highly conserved gene GNPNAT1, is one of the enzymes required for synthesis of uridine diphosphate N-acetylglucosamine, which participates in protein glycosylation."

The founding report's own statement of the pathway the affected enzyme belongs to and of the downstream process it feeds. Graded OTHER, not HUMAN_CLINICAL: this sentence restates established pathway biochemistry rather than reporting a result of the study, and the study's clinical and in-vitro arms are cited separately elsewhere in this entry.

PMID:36097642 SUPPORT Human Clinical

"resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1"

Independent support for locating the lesion in this pathway: a second skeletal dysplasia with immunodeficiency arises from PGM3, the enzyme immediately downstream of GNPNAT1 in the same route to UDP-GlcNAc.

PMID:24931394 SUPPORT Other

"Human phosphoglucomutase 3 (PGM3) catalyzes the conversion of N-acetyl-glucosamine (GlcNAc)-6-phosphate into GlcNAc-1-phosphate during the synthesis of uridine diphosphate (UDP)-GlcNAc, a sugar nucleotide critical to multiple glycosylation pathways."

Names the reaction immediately downstream of GNPNAT1 — PGM3 acts on GlcNAc-6-phosphate, which is the GNPNAT1 product — and states that UDP-GlcNAc feeds multiple glycosylation pathways, which is why this node does not commit to one of them. Graded OTHER because the sentence states established pathway biochemistry rather than a result of the study.

Impaired Growth Plate Chondrocyte Proliferation and Differentiation

Mechanism confidence: Provisional

Chondrocyte proliferation and the expression of differentiation markers fall when Gnpnat1 is knocked down in primary rat chondrocytes. This is the only functional evidence linking the gene to cartilage, and it is in cultured rodent cells; no human growth-plate or human chondrocyte data exist for this disorder.

growth plate chondrocyte CL:0000138

chondrocyte proliferation GO:0035988 ↓ DECREASED chondrocyte differentiation GO:0002062 ↓ DECREASED

growth plate UBERON:0002516

Experimental models

Gnpnat1 siRNA knockdown in primary rat chondrocytes PRIMARY CELL CULTURE Knockdown reproduces the proposed cellular lesion — reduced chondrocyte proliferation and reduced expression of differentiation markers — and is the sole experimental support for locating this disorder's mechanism in the chondrocyte.

Downstream

Disordered Endochondral Ossification Growth plate chondrocyte proliferation and differentiation drive longitudinal bone growth, so their impairment is the proposed route to the radiographic skeletal lesion. The steps between the cultured-cell result and the human radiographs are not established.

Show evidence (2 references)

PMID:32591345 SUPPORT In Vitro

"Small interfering RNAs (siRNAs) were used to study the effect of Gnpnat1 gene knockdown in primary rat chondrocytes."

Identifies the model system behind this node: cultured primary rat chondrocytes, not human tissue.

PMID:32591345 SUPPORT In Vitro

"Our data suggest that GNPNAT1 is important for growth plate chondrogenesis."

The authors' own conclusion locating the gene's requirement in growth plate chondrogenesis, phrased as a suggestion rather than a demonstration.

Disordered Endochondral Ossification

Mechanism confidence: Provisional

The skeletal lesion as it presents radiographically: severe shortening and deformation of the proximal long bones, platyspondyly, hip dysplasia, metaphyseal flaring and delayed epiphyseal ossification. The distribution is that of a spondyloepimetaphyseal dysplasia with rhizomelic predominance. The second report assigns the disorder to "rhizomelic SEMD" and defines that category as sparing the craniofacial skeleton. That definitional sparing is carried here as a category definition rather than as a per-patient observation, and it is qualified by the HPO annotation for OMIM:619598, which records frontal bossing, hypertelorism, ptosis, downslanted palpebral fissures and a wide nasal bridge each in one of six individuals, plus Wormian bones. See discussion rdan_craniofacial_tension.

growth plate cartilage development GO:0003417 ⚠ ABNORMAL

growth plate UBERON:0002516

Downstream

Rhizomelic limb shortening

Severe platyspondyly

Hip dysplasia

Metaphyseal flaring

Delayed epiphyseal ossification

Brachydactyly

Show evidence (2 references)

PMID:35427807 SUPPORT INDIRECT Human Clinical

"Rhizomelic SEMD is characterized by a disproportionate small stature caused by severe shortening and deformation of the limbs' proximal bones, with the cranio-facial sphere unaffected."

Defines the skeletal distribution this node describes, including the craniofacial sparing that separates it from the dysostosis multiplex pattern of the similarly named LYSET disorder. Graded INDIRECT because the sentence defines the rhizomelic-SEMD category rather than describing this patient; it supports the node through the report's own assignment of the disorder to that category.

PMID:32591345 SUPPORT Human Clinical

"Radiographs of one individual showed hip dysplasia and severe platyspondyly."

The radiographic findings in the index family that this tissue-level node accounts for.

⬡

Pathograph

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

●

Phenotypes

22

Head and Neck 1

Wormian bones HP:0002645

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 1/1. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Immune 1

Immunodeficiency HP:0002721

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."

The only report of immunodeficiency in this disorder, in a single patient carrying an allele not seen in the other two families.

Limbs 8

Metaphyseal flaring Flared metaphysis HP:0003015

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis."

Records wide flared metaphyses as a main feature in the Egyptian patient.

Brachydactyly HP:0001156

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."

Lists brachydactyly among the additional findings in the Egyptian patient.

Large hands VERY_FREQUENT HP:0001176

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 5/5. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Long foot VERY_FREQUENT HP:0001833

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 5/5. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Short femur HP:0003097

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 2/2. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Short humerus HP:0005792

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 2/2. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Short femoral neck HP:0100864

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 3/3. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Flat acetabular roof HP:0003180

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 1/1. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Musculoskeletal 9

Severe platyspondyly HP:0004565

Show evidence (1 reference)

PMID:32591345 SUPPORT Human Clinical

"Radiographs of one individual showed hip dysplasia and severe platyspondyly."

The radiographic finding, reported in one individual of the index family.

Hip dysplasia HP:0001385

Show evidence (1 reference)

PMID:32591345 SUPPORT Human Clinical

"Radiographs of one individual showed hip dysplasia and severe platyspondyly."

The radiographic finding, reported in one individual of the index family.

Delayed epiphyseal ossification HP:0002663

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."

Lists delayed epiphyseal ossification among the additional findings in the Egyptian patient.

Accelerated skeletal maturation HP:0005616

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."

Lists advanced bone age among the additional findings in the Egyptian patient.

Short broad long bones Short long bone HP:0003026

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."

Lists short broad long bones among the additional findings in the Egyptian patient.

Enlarged joints VERY_FREQUENT HP:0003037

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 6/6. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Limitation of joint mobility VERY_FREQUENT HP:0001376

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 6/6. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Squared iliac bones HP:0003177

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 1/1. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Posterior scalloping of vertebral bodies HP:0005121

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 1/1. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Nervous System 1

Gait disturbance VERY_FREQUENT HP:0001288

Source: the HPO Consortium disease annotation for OMIM:619598, retrieved from the JAX ontology API (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07, where it is annotated 6/6. That annotation derives from the OMIM clinical synopsis and the primary reports' full text, neither of which was readable for this curation, so no exact-quote evidence item is attached. See discussion rdan_hpoa_provenance.

Growth 2

Rhizomelic limb shortening VERY_FREQUENT Rhizomelia HP:0008905

Annotated 6/6 in the HPO Consortium disease annotation for OMIM:619598 (retrieved from the JAX ontology API on 2026-09-07), which is the basis for the frequency band. See discussion rdan_hpoa_provenance.

Sequelae: Severe short stature

Show evidence (2 references)

PMID:32591345 SUPPORT Human Clinical

"The patients presented with short stature due to extreme shortening of the proximal segments of the limbs."

Describes the rhizomelic shortening in the four affected members of the index family.

PMID:36097642 SUPPORT Human Clinical

"Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis."

Confirms rhizomelic shortening in the third, independent family.

Severe short stature VERY_FREQUENT HP:0003510

Annotated 6/6 in the HPO Consortium disease annotation for OMIM:619598 (retrieved from the JAX ontology API on 2026-09-07), which is the basis for the frequency band. See discussion rdan_hpoa_provenance.

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis."

Records severe short stature as a main feature in the Egyptian patient.

🧬

Genetic Associations

1

GNPNAT1 (Biallelic missense variants cause the disorder.)

Gene: GNPNAT1 hgnc:19980 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:32591345 SUPPORT Human Clinical

"This study describes a novel severe skeletal dysplasia associated with a biallelic, variant in GNPNAT1."

The founding report's statement of the gene-disease relationship.

PMID:36097642 SUPPORT Human Clinical

"We conclude that variants in the GNPNAT1 gene cause an autosomal recessive form of SEMD resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1."

Independent replication of the gene-disease relationship in a third family, with a second allele.

Variants (2)

GNPNAT1 c.226G>A p.(Glu76Lys)

Homozygous missense allele in the consanguineous Pakistani index family and, independently, in an 8-year-old girl reported two years later. The second report proposes it as a potential hotspot.

Show evidence (2 references)

PMID:35427807 SUPPORT Human Clinical

"We report a second individual, an 8-year-old girl, with autosomal recessive rhizomelic SEMD associated with a homozygous exonic missense variant, c.226G > A p.(Glu76Lys), in GNPNAT1 identified by trio genome sequencing."

Reports the same allele in a second, unrelated individual.

PMID:35427807 SUPPORT Human Clinical

"outlining a potential hotspot in this newly described genetic disorder"

The authors' own hedged claim of a mutational hotspot, quoted as the proposal it is.

GNPNAT1 c.77T>G p.(Phe26Cys)

Homozygous missense allele in exon 3 in an Egyptian patient born to consanguineous parents, both of whom were heterozygous carriers. This is the allele reported alongside immunodeficiency.

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant."

Reports the allele, its confirmation and parental carrier status.

💊

Medical Actions

1

Supportive and symptomatic management

Action: supportive care Ontology label: Supportive Care NCIT:C15747

No disease-specific or disease-modifying treatment has been reported for this disorder. None of the three primary reports describes a therapeutic intervention or an outcome after treatment; a PubMed search of GNPNAT1 on 2026-09-07 returned no management or trial publication, and a ClinicalTrials.gov query for GNPNAT1 and for rhizomelic dysplasia returned zero studies. Management is therefore supportive by default — the general orthopaedic, growth and rehabilitative care given in severe skeletal dysplasia — and this entry records the absence of evidence rather than asserting a standard of care. The specific supportive measures a patient might receive are not curated here because no source describes them for this disorder.

🔬

Diagnosis

3

Radiographic skeletal survey

Radiography is what establishes that the short stature is a spondyloepimetaphyseal dysplasia with rhizomelic predominance rather than a non-syndromic short stature, and it carries the discriminating findings — severe platyspondyly, hip dysplasia, flared metaphyses and delayed epiphyseal ossification, with the craniofacial skeleton spared. It places the patient in the category that then gets sequenced; it cannot identify the gene.

radiographic skeletal survey NCIT:C17369

Results: Hip dysplasia, severe platyspondyly, wide flared metaphyses, short broad long bones and delayed epiphyseal ossification of the long bones.

Show evidence (1 reference)

PMID:32591345 SUPPORT Human Clinical

"Radiographs of one individual showed hip dysplasia and severe platyspondyly."

Records that radiography is how the discriminating skeletal findings were obtained in the index family.

Molecular confirmation by genome or exome sequencing

The diagnosis is established by finding a biallelic GNPNAT1 variant. Both routes have been used: whole genome sequencing in the two families carrying p.(Glu76Lys) and whole exome sequencing with Sanger confirmation in the family carrying p.(Phe26Cys). Because the disorder was described in 2021, GNPNAT1 may be absent from older skeletal-dysplasia panels, so a panel that predates the gene-disease association cannot exclude it.

whole genome sequencing NCIT:C101294

Results: A homozygous GNPNAT1 missense variant segregating with disease.

Show evidence (2 references)

PMID:32591345 SUPPORT Human Clinical

"Whole genome sequencing (WGS) was completed using DNA from two affected and two unaffected individuals from the family."

The sequencing method that made the molecular diagnosis in the index family.

PMID:35427807 SUPPORT Human Clinical

"in GNPNAT1 identified by trio genome sequencing"

Trio genome sequencing as the diagnostic route in the second patient.

Exome sequencing with Sanger confirmation and parental carrier testing

The route used in the third family: exome sequencing, Sanger confirmation of the candidate variant, and demonstration that both parents are heterozygous carriers. Parental testing is what established recessive segregation for that allele, since the family had only one affected child.

whole exome sequencing NCIT:C101295

Results: Homozygous c.77T>G p.(Phe26Cys) in the proband, heterozygous in both parents.

Show evidence (1 reference)

PMID:36097642 SUPPORT Human Clinical

"Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant."

Records all three steps of the diagnostic route used in the third family.

📊

Prevalence

1

Worldwide published cases

Cases In Literature Ultra Rare

Three families have been published as of this curation: the four affected individuals of the consanguineous Pakistani index family, one 8-year-old girl, and one Egyptian patient — six affected individuals in total, on the counts the abstracts give. This is a literature-case count, not a population prevalence estimate; no population rate has been published for this disorder and none is asserted here. The ULTRA_RARE band is a qualitative tier used with a CASES_IN_LITERATURE measure and carries no numeric estimate.

Show evidence (2 references)

PMID:32591345 SUPPORT Human Clinical

"Clinical investigations were carried out for four affected individuals in the recruited family."

The case count of the index family.

PMID:35427807 SUPPORT Human Clinical

"We report a second individual, an 8-year-old girl"

The second published patient.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Rhizomelic Dysplasia, Ain-Naz Type:

Dysostosis multiplex, Ain-Naz type MONDO:0859156

Overlapping Features A separate disorder that shares the Ain-Naz eponym only because Ain NU and Naz S are the first and last authors of both founding reports. It is caused by biallelic LYSET (TMEM251) variants and presents as a dysostosis multiplex with coarse facial features resembling mucopolysaccharidosis, not as rhizomelic shortening with platyspondyly. The distinction is recorded here against MONDO:0859156 directly, rather than by pointing at another file whose state this entry cannot vouch for.

Distinguishing Features

Different gene (LYSET/TMEM251 versus GNPNAT1) and different OMIM entry (619345 versus 619598).
Different skeletal pattern: dysostosis multiplex with progressively coarse facies, protruding abdomen and a mucopolysaccharidosis-like picture, versus rhizomelic shortening with severe platyspondyly and an explicitly spared craniofacial skeleton.
The two are mechanistically adjacent rather than unrelated — GNPNAT1 makes the UDP-GlcNAc that GlcNAc-1-phosphotransferase uses as its donor, and LYSET is required for that phosphotransferase — but no lysosomal enzyme abnormality has been reported in the GNPNAT1 disorder, and adjacency is not identity.

Show evidence (2 references)

PMID:33252156 SUPPORT Human Clinical

"Whole-exome sequencing identified two homozygous variants c.133C>T; p.(Arg45Trp) and c.215dupA; p.(Tyr72Ter), respectively, in the two families, affecting an evolutionary conserved gene TMEM251"

Establishes that the other Ain-Naz disorder is a TMEM251 (LYSET) disorder, so the shared eponym does not indicate a shared gene.

PMID:33252156 SUPPORT Human Clinical

"affected individuals had a dysostosis multiplex-like skeletal dysplasia and severe short stature"

Describes the dysostosis multiplex pattern that distinguishes the LYSET disorder from the rhizomelic pattern curated here.

PGM3 deficiency (immunodeficiency 23) Not Yet Curated MONDO:0014353

Overlapping Features A congenital disorder of glycosylation caused by biallelic PGM3 variants. PGM3 catalyses the step immediately after GNPNAT1 in the route to UDP-GlcNAc, and its severe forms present with skeletal dysplasia and immunodeficiency together — which is why the third GNPNAT1 report described its patient as resembling PGM3-related Desbuquois-like dysplasia. This is the differential that matters most for the one GNPNAT1 patient reported with immunodeficiency.

Distinguishing Features

Resolved by sequencing: PGM3 versus GNPNAT1. The clinical overlap is real and is the reason the two were compared in the literature.
PGM3 deficiency is defined by its immune phenotype, most often eczema, elevated IgE and infection, with skeletal features in a subset; the GNPNAT1 disorder is defined by its skeletal phenotype, with immunodeficiency reported in one patient only.

Show evidence (4 references)

PMID:36097642 SUPPORT Human Clinical

"resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1"

The GNPNAT1 report itself names the PGM3 disorder as the phenotypic and pathway comparator.

PMID:33534079 SUPPORT Human Clinical

"A few PGM3-deficient patients suffer from a more severe disease with nearly absent T cells and severe skeletal dysplasia."

Documents the severe PGM3 phenotype that combines skeletal dysplasia with immunodeficiency, the combination reported once in a GNPNAT1 patient.

PMID:24931394 SUPPORT Human Clinical

"Two of the three children had skeletal anomalies resembling Desbuquois dysplasia: short stature, brachydactyly, dysmorphic facial features, and intellectual disability."

The Desbuquois-like skeletal picture the third GNPNAT1 report compared its patient to, in the original PGM3-CDG series. Note the difference as well as the resemblance: intellectual disability is part of that PGM3 phenotype, and is an explicit 0/6 exclusion in the HPO annotation for this disorder.

+ 1 more reference

Rhizomelic chondrodysplasia punctata MONDO:0015776

Overlapping Features Included as an explicit exclusion rather than a close mimic. RCDP is a peroxisomal plasmalogen-biosynthesis group caused by PEX7, GNPAT, AGPS and FAR1. It shares the word "rhizomelic" and, in GNPAT, a gene symbol one inserted N and one appended digit away from GNPNAT1, and nothing else: the pathway, the radiographic hallmark (epiphyseal stippling) and the natural history are all different. dismech curates RCDP under its own entries. This record exists so that the near-collision is documented rather than left to be rediscovered.

Distinguishing Features

Different pathway entirely: peroxisomal ether-phospholipid (plasmalogen) biosynthesis, not the cytosolic hexosamine biosynthetic pathway.
GNPAT (glyceronephosphate O-acyltransferase, dihydroxyacetone phosphate acyltransferase) is not GNPNAT1 (glucosamine-6-phosphate N-acetyltransferase). The symbols are two edits apart and the products are unrelated.
RCDP is characterised radiographically by punctate epiphyseal calcification (chondrodysplasia punctata), which has not been reported in this disorder.

🧫

Experimental Models

1

Gnpnat1 siRNA knockdown in primary rat chondrocytes PRIMARY_CELL_CULTURE

The only functional model reported for this disorder. Primary chondrocytes isolated from rat were transfected with small interfering RNAs against Gnpnat1, and proliferation and chondrocyte differentiation markers were measured. It is a knockdown model, so it removes the transcript rather than reproducing either patient missense allele, and it is rodent rather than human.

Organism

Norway rat NCBITaxon:10116

Cell source

Primary rat chondrocytes

Culture

Two-dimensional primary cell culture with siRNA transfection

Publication

PMID:32591345

Pathograph links

Impaired Growth Plate Chondrocyte Proliferation and Differentiation partially recapitulates fidelity: low observes: cellular Knockdown reproduces the proposed cellular lesion — reduced chondrocyte proliferation and reduced expression of differentiation markers — and is the sole experimental support for locating this disorder's mechanism in the chondrocyte.

Limitations: Rodent rather than human cells; transient siRNA knockdown of the transcript rather than either homozygous human missense allele, so it models a null and cannot say what the patient proteins do; two-dimensional culture with no growth-plate architecture, no zonal organisation and no endochondral ossification, so the rhizomelic distribution and the platyspondyly of the human disease are outside the model entirely; and no measurement of UDP-GlcNAc, glycosylation or O-GlcNAcylation was made, so the model does not test the metabolic step the disorder is named for.

Divergences from the human mechanism

species mismatch qualifying

Rat primary chondrocytes stand in for human growth-plate chondrocytes. No human chondrocyte or growth-plate data exist for this disorder, so there is nothing to calibrate the substitution against.

cause unrepresented invalidating

The disease-causing lesion is a homozygous missense allele. The model applies siRNA knockdown, which lowers transcript abundance; a missense protein that is expressed and partially active is a different cause and is not represented.

boundary omission qualifying

Growth-plate zonal architecture, the perichondrium, vascular invasion and ossification are all outside the model boundary, so the radiographic phenotype the disorder is defined by cannot be observed in it.

Readouts

Chondrocyte proliferation

Direction: DECREASED

Interpretation: Cellular proliferation fell after knockdown, the proliferative half of the node this link supports.

Show evidence (1 reference)

PMID:32591345 SUPPORT In Vitro

"Knockdown of Gnpnat1 by siRNAs decreased cellular proliferation"

Reports the proliferation measurement and its direction.

Collagen type 2 and alkaline phosphatase expression

Direction: DECREASED

Interpretation: The two chondrocyte differentiation markers measured; their fall is the differentiation half of the node.

Show evidence (1 reference)

PMID:32591345 SUPPORT In Vitro

"decreased cellular proliferation and expression of chondrocyte differentiation markers collagen type 2 and alkaline phosphatase"

Names the two differentiation markers measured and the direction of the change.

Show evidence (1 reference)

PMID:32591345 SUPPORT In Vitro

"Small interfering RNAs (siRNAs) were used to study the effect of Gnpnat1 gene knockdown in primary rat chondrocytes."

Establishes the model system and its use as the functional arm of the founding report, which is what makes it informative for this node.

No animal model, organoid, iPSC line or patient-derived fibroblast culture has been reported for this disorder, so animal_models and computational_models are absent from this entry by fact rather than by omission.

{ }

Source YAML

click to show

name: Rhizomelic Dysplasia, Ain-Naz Type
creation_date: "2026-09-07T00:00:00Z"
description: >-
  Rhizomelic dysplasia, Ain-Naz type (OMIM 619598) is an ultra-rare autosomal
  recessive skeletal dysplasia caused by biallelic missense variants in
  GNPNAT1, which encodes glucosamine-6-phosphate N-acetyltransferase (GNA1),
  the enzyme that acetylates glucosamine-6-phosphate in the hexosamine
  biosynthetic pathway on the route to UDP-N-acetylglucosamine. The defining
  feature is short stature from extreme shortening of the proximal limb
  segments, with hip dysplasia and severe platyspondyly on radiographs; later
  reports classify it as a rhizomelic spondyloepimetaphyseal dysplasia and add
  metaphyseal flaring, brachydactyly, delayed epiphyseal ossification,
  accelerated skeletal maturation and, in one patient, immunodeficiency. Three
  families have been published, so the entry is deliberately thin and rests on
  those primary reports. How the metabolic lesion produces the skeletal
  phenotype is not established: the only functional data are siRNA knockdown of
  Gnpnat1 in cultured rat chondrocytes, and no glycosylation, O-GlcNAcylation
  or mannose-6-phosphate measurement has been reported in a patient. That
  question is recorded here as a knowledge gap, not answered.
category: Mendelian
categories:
- Skeletal Dysplasia
- Spondyloepimetaphyseal Dysplasia
- Disorder of Nucleotide-Sugar Metabolism
disease_term:
  preferred_term: rhizomelic dysplasia, Ain-Naz type
  term:
    id: MONDO:0859203
    label: rhizomelic dysplasia, Ain-Naz type
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A Mendelian, autosomal recessive hereditary skeletal dysplasia reported
      only in consanguineous families. Per the disease-classification skill,
      hereditary musculoskeletal disorders take this Part rather than
      IMMUNE_RHEUMATOLOGIC, which is reserved for inflammatory and
      immune-mediated entities.
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0859203
      label: rhizomelic dysplasia, Ain-Naz type
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: Primary MONDO identifier for this entry (OMIM:619598).
synonyms:
- Rhizomelic spondyloepimetaphyseal dysplasia, GNPNAT1-related
- GNPNAT1-related skeletal dysplasia
- Rhizomelic SEMD
parents:
- Skeletal Dysplasia
notes: >-
  Scope: this entry covers OMIM:619598 / MONDO:0859203 only. The similarly
  named "dysostosis multiplex, Ain-Naz type" (OMIM:619345, MONDO:0859156) is a
  different disorder with a different gene (LYSET/TMEM251) and a different
  skeletal pattern (dysostosis multiplex with coarse facies, resembling
  mucopolysaccharidosis). The shared eponym reflects only that Ain NU and Naz S
  are the first and last authors of both founding reports. MONDO:0859156 is
  carried here as a differential diagnosis. No claim is made about how, or
  whether, that disorder is curated elsewhere in this knowledge base: when this
  entry was written it existed only as an uncurated stub, and prose asserting
  the state of another file goes stale the moment that file changes.

  Do not confuse GNPNAT1 with GNPAT. Rhizomelic chondrodysplasia punctata
  (RCDP) is a peroxisomal plasmalogen-biosynthesis group caused by PEX7,
  GNPAT, AGPS and FAR1, is already curated in dismech under its own entries,
  and has nothing to do with the hexosamine biosynthetic pathway. GNPAT becomes
  GNPNAT1 by inserting one N and appending a 1, and the disease names both
  begin "rhizomelic"; that is the entire resemblance.

  GNPNAT1 (also GNA1) has a large cancer-metabolism literature — hexosamine
  pathway flux, O-GlcNAcylation and tumour proliferation. None of it concerns
  this disease and none of it is cited here. The one enzymology reference used
  (PMID:26935656) is cited solely for the reaction the enzyme catalyses.

  No GeneReviews chapter exists for GNPNAT1 or for this disorder. PubMed was
  searched on 2026-09-07 for "GNPNAT1 GeneReviews[All Fields]" (0 hits) and
  "rhizomelic dysplasia GeneReviews[All Fields]" (1 hit, the Achondroplasia
  chapter, unrelated), so there is no GeneReviews phenotype baseline for this
  entry.

  Three classification slots were deliberately left empty.
  isds_skeletal_category may only be assigned to disorders the ISDS Nosology of
  Genetic Skeletal Disorders itself lists, and it could not be confirmed that
  this 2021-described disorder appears in the 2023 revision (Unger et al.,
  PMID:36779427); icimd_category is left empty for the same reason relative to
  the 2021 ICIMD, which predates the gene-disease association;
  mechanistic_category has no value that fits a nucleotide-sugar supply defect.
  None of the three omissions is a claim that the disorder falls outside those
  nosologies.

  No conforms_to was declared. The nearest candidate module,
  congenital_disorder_of_glycosylation, scopes itself to defects of the
  N-glycosylation machinery converging on demonstrated protein
  hypoglycosylation; GNPNAT1 sits upstream of that machinery in
  nucleotide-sugar supply, and no hypoglycosylation has been measured in any
  reported patient. Declaring conformance would assert the mechanism this entry
  records as open (see discussion rdan_udp_glcnac_route).

  OMIM was not consulted directly: omim.org returned HTTP 403 to the fetch
  attempted for this curation, so the clinical synopsis was not read. The OMIM
  identifiers used here were still not taken on trust — OMIM:619598 was
  confirmed as an xref of MONDO:0859203, and OMIM:619345 as an xref of
  MONDO:0859156, by querying the OLS MONDO record for each. Phenotypes come from
  two sources, kept distinguishable: nine are exact quotes from PubMed-cached
  primary reports, and twelve are from the HPO Consortium disease annotation for
  OMIM:619598, which carries no quotable body and is recorded per-phenotype in
  notes with its fraction and retrieval date (discussion rdan_hpoa_provenance).

  Deep research: the committed report is a **claude_code** report
  (research/Rhizomelic_Dysplasia_Ain-Naz_Type-deep-research-claude_code.md), not
  a falcon one. The provider chain attempted was falcon (HTTP 402, Edison
  account out of credits) then openscientist by --fallback (cancelled at about
  20 minutes after sibling runs in this batch were reported timing out
  server-side at 3600 s) then claude_code, which completed in 319 s. Its
  reference validation is 4/4 resolved with 1/1 quote valid and nothing off
  topic; its term validation is 57/62 resolved with needs_review true, two
  obsolete GO terms and three mislabelled terms — of which two matter:
  UBERON:0002520 is submandibular lymph node, not "epiphyseal cartilage", and
  UBERON:0002544 is digit, not "growth plate cartilage". Neither was bound; this
  entry uses UBERON:0002516 (epiphyseal plate). The report also missed
  PMID:35427807 entirely and so counted two families rather than three, and it
  listed intellectual disability as a phenotype when the HPO annotation records
  it as an explicit 0/6 exclusion. Both errors are recorded rather than carried.

  Sections absent by fact rather than by omission. There is no progression,
  clinical_burden, stages or histopathology block because no natural-history,
  disability or tissue data have been published: the three reports give
  presentation and radiographs, and one age (8 years). There is no biochemical
  block because no biochemical measurement has been reported in any patient —
  which is itself the substance of discussion rdan_udp_glcnac_route, and is why
  that gap is recorded rather than filled. There are no clinical_trials,
  animal_models or computational_models. There is no datasets block: a dataset
  search for this disorder can only be run on the gene, and GNPNAT1 gene search
  returns hexosamine-pathway and cancer-metabolism experiments that are not
  about this disease, which is Named Entity Confusion reached through dataset
  search rather than a dataset for the entry.
references:
- reference: PMID:32591345
  title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
- reference: PMID:35427807
  title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
- reference: PMID:36097642
  title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
pathophysiology:
- name: Biallelic GNPNAT1 Missense Variants
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Homozygous missense variants in GNPNAT1 segregate with the disease in all
    three reported families. Two unrelated families carry the same allele,
    c.226G>A p.(Glu76Lys), which the second report proposes as a potential
    mutational hotspot; the third family carries c.77T>G p.(Phe26Cys).
    Consanguinity is stated for the Pakistani index family and for the
    Egyptian family, whose parents were also confirmed heterozygous carriers;
    the report of the second patient does not state parental relationship.
  gene:
    preferred_term: GNPNAT1
    term:
      id: hgnc:19980
      label: GNPNAT1
  genetic_context:
    variant_origin: GERMLINE
    zygosity: HOMOZYGOUS
    functional_impact_category: UNKNOWN
    description: >-
      Both reported alleles are missense. No enzyme-activity measurement has
      been published for either variant protein, so the functional consequence
      is recorded as UNKNOWN rather than assumed to be loss of function. The
      founding report used in-silico prediction and an siRNA knockdown model,
      neither of which measures what the patient allele does to the enzyme.
  chemical_entities:
  - preferred_term: alpha-D-glucosamine 6-phosphate
    term:
      id: CHEBI:15873
      label: alpha-D-glucosamine 6-phosphate
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "WGS data analyses identified a homozygous missense variant c.226G>A; p.(Glu76Lys) in GNPNAT1, segregating with the disease."
    explanation: >-
      The founding report identifies the causal allele and records its
      segregation with disease in the index family.
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant."
    explanation: >-
      A second, independent allele in an unrelated family, with parental carrier
      status establishing recessive segregation.
  downstream:
  - target: Reduced Glucosamine-6-Phosphate N-Acetyltransferase Activity
    causal_link_type: UNKNOWN
    description: >-
      The presumed but unmeasured first consequence. No enzyme assay has been
      performed on either patient allele, so the edge is typed UNKNOWN and
      carries no evidence rather than borrowing the knockdown result, which
      removes the transcript instead of testing the missense protein.
- name: Reduced Glucosamine-6-Phosphate N-Acetyltransferase Activity
  biological_scale: MOLECULAR
  mechanism_confidence: HYPOTHETICAL
  description: >-
    GNPNAT1 encodes glucosamine-6-phosphate N-acetyltransferase (GNA1), which
    transfers an acetyl group from acetyl-CoA to glucosamine-6-phosphate to
    give N-acetylglucosamine-6-phosphate. Reduced activity of this step in
    patients is inferred from the gene-disease relationship and from the
    enzyme's known reaction; it has not been measured in patient cells.
  molecular_functions:
  - preferred_term: glucosamine 6-phosphate N-acetyltransferase activity
    term:
      id: GO:0004343
      label: glucosamine 6-phosphate N-acetyltransferase activity
    modifier: DECREASED
  chemical_entities:
  - preferred_term: N-acetyl-D-glucosamine 6-phosphate
    term:
      id: CHEBI:15784
      label: N-acetyl-D-glucosamine 6-phosphate
  evidence:
  - reference: PMID:26935656
    reference_title: "Human acetyl-CoA:glucosamine-6-phosphate N-acetyltransferase 1 has a relaxed donor specificity and transfers acyl groups up to four carbons in length."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Glucosamine-6-phosphate N-acetyltransferase1 (GNA1) catalyses the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to glucosamine-6-phosphate (GlcN6P) to form N-acetylglucosamine-6-phosphate (GlcNAc6P), which is an essential intermediate in UDP-GlcNAc biosynthesis."
    explanation: >-
      Establishes the reaction the affected enzyme catalyses and its position in
      UDP-GlcNAc biosynthesis. It says nothing about the patient alleles, which
      is why the node is graded HYPOTHETICAL.
  downstream:
  - target: Diminished UDP-GlcNAc Supply
    causal_link_type: DIRECT
    description: >-
      The acetyltransferase step is obligatory for UDP-GlcNAc synthesis, so a
      reduction in it reduces flux to the nucleotide sugar.
    evidence:
    - reference: PMID:26935656
      reference_title: "Human acetyl-CoA:glucosamine-6-phosphate N-acetyltransferase 1 has a relaxed donor specificity and transfers acyl groups up to four carbons in length."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "which is an essential intermediate in UDP-GlcNAc biosynthesis"
      explanation: >-
        States that the product of this enzyme is an essential intermediate of
        UDP-GlcNAc biosynthesis, which is the causal step this edge asserts.
- name: Diminished UDP-GlcNAc Supply
  biological_scale: MOLECULAR
  mechanism_confidence: HYPOTHETICAL
  description: >-
    GNPNAT1 is one of the enzymes of the hexosamine biosynthetic pathway, whose
    product UDP-N-acetylglucosamine is the donor sugar for protein
    N-glycosylation, O-GlcNAcylation, glycosaminoglycan chain extension and the
    mannose-6-phosphate tagging of lysosomal hydrolases. Reduced supply is the
    proposed link between the enzyme lesion and the skeleton. No measurement of
    UDP-GlcNAc, of protein glycosylation or of O-GlcNAcylation has been
    published in a patient with this disorder, so the node is graded
    HYPOTHETICAL and no specific downstream glycosylation route is asserted
    (see discussion rdan_udp_glcnac_route).
  biological_processes:
  - preferred_term: UDP-N-acetylglucosamine biosynthetic process
    term:
      id: GO:0006048
      label: UDP-N-acetylglucosamine biosynthetic process
    modifier: DECREASED
  chemical_entities:
  - preferred_term: UDP-N-acetylglucosamine
    term:
      id: CHEBI:16264
      label: UDP-N-acetyl-alpha-D-glucosamine
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Glucosamine 6-phosphate N-acetyltransferase, encoded by the highly conserved gene GNPNAT1, is one of the enzymes required for synthesis of uridine diphosphate N-acetylglucosamine, which participates in protein glycosylation."
    explanation: >-
      The founding report's own statement of the pathway the affected enzyme
      belongs to and of the downstream process it feeds. Graded OTHER, not
      HUMAN_CLINICAL: this sentence restates established pathway biochemistry
      rather than reporting a result of the study, and the study's clinical and
      in-vitro arms are cited separately elsewhere in this entry.
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1"
    explanation: >-
      Independent support for locating the lesion in this pathway: a second
      skeletal dysplasia with immunodeficiency arises from PGM3, the enzyme
      immediately downstream of GNPNAT1 in the same route to UDP-GlcNAc.
  - reference: PMID:24931394
    reference_title: "PGM3 mutations cause a congenital disorder of glycosylation with severe immunodeficiency and skeletal dysplasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Human phosphoglucomutase 3 (PGM3) catalyzes the conversion of N-acetyl-glucosamine (GlcNAc)-6-phosphate into GlcNAc-1-phosphate during the synthesis of uridine diphosphate (UDP)-GlcNAc, a sugar nucleotide critical to multiple glycosylation pathways."
    explanation: >-
      Names the reaction immediately downstream of GNPNAT1 — PGM3 acts on
      GlcNAc-6-phosphate, which is the GNPNAT1 product — and states that
      UDP-GlcNAc feeds multiple glycosylation pathways, which is why this node
      does not commit to one of them. Graded OTHER because the sentence states
      established pathway biochemistry rather than a result of the study.
  downstream:
  - target: Impaired Growth Plate Chondrocyte Proliferation and Differentiation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Loss of Gnpnat1 impairs chondrocyte proliferation and differentiation in
      culture. Which UDP-GlcNAc-dependent process carries the effect is not
      established, so the intermediates are recorded as unknown.
    evidence:
    - reference: PMID:32591345
      reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: IN_VITRO
      snippet: "Knockdown of Gnpnat1 by siRNAs decreased cellular proliferation and expression of chondrocyte differentiation markers collagen type 2 and alkaline phosphatase, indicating that Gnpnat1 is important for growth plate chondrocyte proliferation and differentiation."
      explanation: >-
        Removing the gene product from cultured chondrocytes impairs
        proliferation and differentiation. Graded INDIRECT because the
        experiment removes the transcript rather than lowering UDP-GlcNAc, so
        it supports the edge through an inference step.
- name: Impaired Growth Plate Chondrocyte Proliferation and Differentiation
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  description: >-
    Chondrocyte proliferation and the expression of differentiation markers
    fall when Gnpnat1 is knocked down in primary rat chondrocytes. This is the
    only functional evidence linking the gene to cartilage, and it is in
    cultured rodent cells; no human growth-plate or human chondrocyte data
    exist for this disorder.
  cell_types:
  - preferred_term: growth plate chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  biological_processes:
  - preferred_term: chondrocyte proliferation
    term:
      id: GO:0035988
      label: chondrocyte proliferation
    modifier: DECREASED
  - preferred_term: chondrocyte differentiation
    term:
      id: GO:0002062
      label: chondrocyte differentiation
    modifier: DECREASED
  locations:
  - preferred_term: growth plate
    term:
      id: UBERON:0002516
      label: epiphyseal plate
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Small interfering RNAs (siRNAs) were used to study the effect of Gnpnat1 gene knockdown in primary rat chondrocytes."
    explanation: >-
      Identifies the model system behind this node: cultured primary rat
      chondrocytes, not human tissue.
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Our data suggest that GNPNAT1 is important for growth plate chondrogenesis."
    explanation: >-
      The authors' own conclusion locating the gene's requirement in growth
      plate chondrogenesis, phrased as a suggestion rather than a demonstration.
  downstream:
  - target: Disordered Endochondral Ossification
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Growth plate chondrocyte proliferation and differentiation drive
      longitudinal bone growth, so their impairment is the proposed route to the
      radiographic skeletal lesion. The steps between the cultured-cell result
      and the human radiographs are not established.
- name: Disordered Endochondral Ossification
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: >-
    The skeletal lesion as it presents radiographically: severe shortening and
    deformation of the proximal long bones, platyspondyly, hip dysplasia,
    metaphyseal flaring and delayed epiphyseal ossification. The distribution
    is that of a spondyloepimetaphyseal dysplasia with rhizomelic predominance.
    The second report assigns the disorder to "rhizomelic SEMD" and defines that
    category as sparing the craniofacial skeleton. That definitional sparing is
    carried here as a category definition rather than as a per-patient
    observation, and it is qualified by the HPO annotation for OMIM:619598,
    which records frontal bossing, hypertelorism, ptosis, downslanted palpebral
    fissures and a wide nasal bridge each in one of six individuals, plus
    Wormian bones. See discussion rdan_craniofacial_tension.
  biological_processes:
  - preferred_term: growth plate cartilage development
    term:
      id: GO:0003417
      label: growth plate cartilage development
    modifier: ABNORMAL
  locations:
  - preferred_term: growth plate
    term:
      id: UBERON:0002516
      label: epiphyseal plate
  evidence:
  - reference: PMID:35427807
    reference_title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "Rhizomelic SEMD is characterized by a disproportionate small stature caused by severe shortening and deformation of the limbs' proximal bones, with the cranio-facial sphere unaffected."
    explanation: >-
      Defines the skeletal distribution this node describes, including the
      craniofacial sparing that separates it from the dysostosis multiplex
      pattern of the similarly named LYSET disorder. Graded INDIRECT because the
      sentence defines the rhizomelic-SEMD category rather than describing this
      patient; it supports the node through the report's own assignment of the
      disorder to that category.
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Radiographs of one individual showed hip dysplasia and severe platyspondyly."
    explanation: >-
      The radiographic findings in the index family that this tissue-level node
      accounts for.
  downstream:
  - target: Rhizomelic limb shortening
    causal_link_type: DIRECT
  - target: Severe platyspondyly
    causal_link_type: DIRECT
  - target: Hip dysplasia
    causal_link_type: DIRECT
  - target: Metaphyseal flaring
    causal_link_type: DIRECT
  - target: Delayed epiphyseal ossification
    causal_link_type: DIRECT
  - target: Brachydactyly
    causal_link_type: DIRECT
phenotypes:
- category: Skeletal
  name: Rhizomelic limb shortening
  description: >-
    The defining feature: extreme shortening of the proximal limb segments. It
    is the one phenotype reported in all three published families, and it is
    what the disorder is named for.
  phenotype_term:
    preferred_term: Rhizomelia
    term:
      id: HP:0008905
      label: Rhizomelia
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: >-
    Annotated 6/6 in the HPO Consortium disease annotation for OMIM:619598
    (retrieved from the JAX ontology API on 2026-09-07), which is the basis for
    the frequency band. See discussion rdan_hpoa_provenance.
  sequelae:
  - target: Severe short stature
    description: >-
      The short stature is disproportionate and is attributed by the founding
      report to the proximal limb shortening rather than to a trunk deficit.
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The patients presented with short stature due to extreme shortening of the proximal segments of the limbs."
    explanation: Describes the rhizomelic shortening in the four affected members of the index family.
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis."
    explanation: Confirms rhizomelic shortening in the third, independent family.
- category: Skeletal
  name: Severe short stature
  description: >-
    Disproportionate short stature, described as severe in the third reported
    family and attributed to the rhizomelic limb shortening.
  phenotype_term:
    preferred_term: Severe short stature
    term:
      id: HP:0003510
      label: Severe short stature
  frequency: VERY_FREQUENT
  notes: >-
    Annotated 6/6 in the HPO Consortium disease annotation for OMIM:619598
    (retrieved from the JAX ontology API on 2026-09-07), which is the basis for
    the frequency band. See discussion rdan_hpoa_provenance.
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis."
    explanation: Records severe short stature as a main feature in the Egyptian patient.
- category: Skeletal
  name: Severe platyspondyly
  description: >-
    Flattening of the vertebral bodies, reported as severe on the radiographs of
    the index family and part of the spondylo- component of the SEMD pattern.
  phenotype_term:
    preferred_term: Severe platyspondyly
    term:
      id: HP:0004565
      label: Severe platyspondyly
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Radiographs of one individual showed hip dysplasia and severe platyspondyly."
    explanation: The radiographic finding, reported in one individual of the index family.
- category: Skeletal
  name: Hip dysplasia
  description: >-
    Dysplastic hips on radiography in the index family.
  phenotype_term:
    preferred_term: Hip dysplasia
    term:
      id: HP:0001385
      label: Hip dysplasia
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Radiographs of one individual showed hip dysplasia and severe platyspondyly."
    explanation: The radiographic finding, reported in one individual of the index family.
- category: Skeletal
  name: Metaphyseal flaring
  description: >-
    Wide, flared metaphyses — the metaphyseal component of the
    spondyloepimetaphyseal pattern. Reported in the third family.
  phenotype_term:
    preferred_term: Flared metaphysis
    term:
      id: HP:0003015
      label: Flared metaphysis
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis."
    explanation: Records wide flared metaphyses as a main feature in the Egyptian patient.
- category: Skeletal
  name: Brachydactyly
  description: >-
    Short digits, reported in the third family among the findings that expanded
    the phenotype beyond the founding description.
  phenotype_term:
    preferred_term: Brachydactyly
    term:
      id: HP:0001156
      label: Brachydactyly
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."
    explanation: Lists brachydactyly among the additional findings in the Egyptian patient.
- category: Skeletal
  name: Delayed epiphyseal ossification
  description: >-
    Delayed ossification of the epiphyses of the long bones — the epi- component
    of the SEMD pattern. Reported in the third family, alongside an advanced
    bone age, which is an unusual combination and is not explained in the source.
  phenotype_term:
    preferred_term: Delayed epiphyseal ossification
    term:
      id: HP:0002663
      label: Delayed epiphyseal ossification
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."
    explanation: Lists delayed epiphyseal ossification among the additional findings in the Egyptian patient.
- category: Skeletal
  name: Accelerated skeletal maturation
  description: >-
    Advanced bone age, reported in the third family. Recorded as stated; the
    source gives no age, no method and no reconciliation with the coexisting
    delayed epiphyseal ossification in the same patient.
  phenotype_term:
    preferred_term: Accelerated skeletal maturation
    term:
      id: HP:0005616
      label: Accelerated skeletal maturation
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."
    explanation: Lists advanced bone age among the additional findings in the Egyptian patient.
- category: Skeletal
  name: Short broad long bones
  description: >-
    Short and broad tubular bones, reported in the third family. Bound to the
    generic HPO term for a short long bone; HPO has no single term for the
    short-and-broad combination, and the breadth is carried in preferred_term.
  phenotype_term:
    preferred_term: Short broad long bones
    term:
      id: HP:0003026
      label: Short long bone
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."
    explanation: Lists short broad long bones among the additional findings in the Egyptian patient.
- category: Immunologic
  name: Immunodeficiency
  description: >-
    Reported in one patient only, in the third family, and not characterised
    further in the record consulted — no immunoglobulin levels, lymphocyte
    subsets or infection history are given. It is recorded here because it is
    the one non-skeletal feature reported, and because the enzyme immediately
    downstream in the same pathway, PGM3, causes a skeletal dysplasia with
    prominent immunodeficiency. Whether immunodeficiency is a feature of this
    disorder or of that patient is unresolved (see discussion
    rdan_immunodeficiency_single_case). No frequency is asserted.
  phenotype_term:
    preferred_term: Immunodeficiency
    term:
      id: HP:0002721
      label: Immunodeficiency
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family."
    explanation: >-
      The only report of immunodeficiency in this disorder, in a single patient
      carrying an allele not seen in the other two families.
- category: Skeletal
  name: Large hands
  description: >-
    Disproportionately large hands relative to the shortened proximal limb
    segments. Together with the long feet this is one of the features that
    distinguishes the rhizomelic Ain-Naz phenotype from a generic short-limb
    dysplasia.
  phenotype_term:
    preferred_term: Large hands
    term:
      id: HP:0001176
      label: Large hands
  frequency: VERY_FREQUENT
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 5/5. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Long foot
  phenotype_term:
    preferred_term: Long foot
    term:
      id: HP:0001833
      label: Long foot
  frequency: VERY_FREQUENT
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 5/5. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Enlarged joints
  phenotype_term:
    preferred_term: Enlarged joints
    term:
      id: HP:0003037
      label: Enlarged joints
  frequency: VERY_FREQUENT
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 6/6. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Musculoskeletal
  name: Limitation of joint mobility
  phenotype_term:
    preferred_term: Limitation of joint mobility
    term:
      id: HP:0001376
      label: Limitation of joint mobility
  frequency: VERY_FREQUENT
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 6/6. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Neurologic
  name: Gait disturbance
  description: >-
    Recorded under the HPO nervous-system category, but no neurological
    examination finding is reported anywhere in this disorder and the
    intellectual-disability annotation is an explicit exclusion; the most likely
    reading is a mechanical gait disturbance secondary to the rhizomelic
    shortening, hip dysplasia and joint limitation. That reading is not asserted
    by any source.
  phenotype_term:
    preferred_term: Gait disturbance
    term:
      id: HP:0001288
      label: Gait disturbance
  frequency: VERY_FREQUENT
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 6/6. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Short femur
  phenotype_term:
    preferred_term: Short femur
    term:
      id: HP:0003097
      label: Short femur
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 2/2. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Short humerus
  description: >-
    With the short femur, this is the anatomical content of the rhizomelia:
    the shortening is of the humerus and femur specifically.
  phenotype_term:
    preferred_term: Short humerus
    term:
      id: HP:0005792
      label: Short humerus
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 2/2. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Short femoral neck
  phenotype_term:
    preferred_term: Short femoral neck
    term:
      id: HP:0100864
      label: Short femoral neck
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 3/3. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Flat acetabular roof
  description: >-
    The acetabular component of the hip dysplasia, on radiographs.
  phenotype_term:
    preferred_term: Flat acetabular roof
    term:
      id: HP:0003180
      label: Flat acetabular roof
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 1/1. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Squared iliac bones
  phenotype_term:
    preferred_term: Squared iliac bones
    term:
      id: HP:0003177
      label: Squared iliac bones
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 1/1. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Skeletal
  name: Posterior scalloping of vertebral bodies
  description: >-
    A vertebral finding beyond the platyspondyly, adding to the vertebral
    component of the spondyloepimetaphyseal pattern.
  phenotype_term:
    preferred_term: Posterior scalloping of vertebral bodies
    term:
      id: HP:0005121
      label: Posterior scalloping of vertebral bodies
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 1/1. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
- category: Craniofacial
  name: Wormian bones
  description: >-
    One of the craniofacial-region findings that qualifies the second report's
    definitional statement that the cranio-facial sphere is unaffected in
    rhizomelic SEMD. See discussion rdan_craniofacial_tension.
  phenotype_term:
    preferred_term: Wormian bones
    term:
      id: HP:0002645
      label: Wormian bones
  notes: >-
   Source: the HPO Consortium disease annotation for OMIM:619598, retrieved
   from the JAX ontology API
   (ontology.jax.org/api/network/annotation/OMIM:619598) on 2026-09-07,
   where it is annotated 1/1. That annotation derives from the OMIM clinical
   synopsis and the primary reports' full text, neither of which was
   readable for this curation, so no exact-quote evidence item is attached.
   See discussion rdan_hpoa_provenance.
genetic:
- name: GNPNAT1
  gene_term:
    preferred_term: GNPNAT1
    term:
      id: hgnc:19980
      label: GNPNAT1
  relationship_type: CAUSATIVE
  association: Biallelic missense variants cause the disorder.
  variant_origin: GERMLINE
  notes: >-
    GNPNAT1 is also known as GNA1. Two alleles have been reported, both
    homozygous missense: c.226G>A p.(Glu76Lys) in two unrelated families and
    c.77T>G p.(Phe26Cys) in a third. The recurrence of the Glu76Lys allele in two
    unrelated families led the second report to propose "a potential hotspot";
    on two families that remains a proposal. The ancestry of the second patient
    is not stated in the record consulted and is not inferred here from the
    journal.
    Neither allele has been assayed for enzyme activity, so no
    functional_impact_category is asserted. GNPNAT1 does not appear in the
    ClinGen Gene-Disease Validity table downloaded on 2026-09-07, so there is no
    expert-panel validity classification to cite alongside these three reports.
    No Orphanet record was found for the disorder either, but that check was a
    name and OMIM-crossreference query against the Orphanet API rather than an
    exhaustive one, so read it as "not found" rather than "does not exist".
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study describes a novel severe skeletal dysplasia associated with a biallelic, variant in GNPNAT1."
    explanation: The founding report's statement of the gene-disease relationship.
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that variants in the GNPNAT1 gene cause an autosomal recessive form of SEMD resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1."
    explanation: >-
      Independent replication of the gene-disease relationship in a third
      family, with a second allele.
  variants:
  - name: GNPNAT1 c.226G>A p.(Glu76Lys)
    description: >-
      Homozygous missense allele in the consanguineous Pakistani index family
      and, independently, in an 8-year-old girl reported two years later. The
      second report proposes it as a potential hotspot.
    evidence:
    - reference: PMID:35427807
      reference_title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We report a second individual, an 8-year-old girl, with autosomal recessive rhizomelic SEMD associated with a homozygous exonic missense variant, c.226G > A p.(Glu76Lys), in GNPNAT1 identified by trio genome sequencing."
      explanation: Reports the same allele in a second, unrelated individual.
    - reference: PMID:35427807
      reference_title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "outlining a potential hotspot in this newly described genetic disorder"
      explanation: >-
        The authors' own hedged claim of a mutational hotspot, quoted as the
        proposal it is.
  - name: GNPNAT1 c.77T>G p.(Phe26Cys)
    description: >-
      Homozygous missense allele in exon 3 in an Egyptian patient born to
      consanguineous parents, both of whom were heterozygous carriers. This is
      the allele reported alongside immunodeficiency.
    evidence:
    - reference: PMID:36097642
      reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant."
      explanation: Reports the allele, its confirmation and parental carrier status.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  penetrance: COMPLETE
  expressivity: UNKNOWN
  description: >-
    All three reported families are homozygous for a GNPNAT1 missense allele.
    Consanguinity is stated for the Pakistani index family and for the Egyptian
    family, in which both parents were additionally confirmed to be
    heterozygous carriers; the second report does not state parental
    relationship.

    Penetrance is recorded as COMPLETE on the strength of segregation rather
    than of a measured figure: the founding report sequenced two affected and
    two unaffected members of the index family and found the variant segregating
    with disease, and no unaffected homozygote has been reported in any family.
    Across six affected individuals ascertained through affected probands, that
    is an absence of counterexamples, not an estimate.

    Expressivity is left UNKNOWN, and deliberately not called variable. The
    clinical descriptions do differ between reports — the Egyptian patient has
    immunodeficiency, advanced bone age and brachydactyly, none of which appear
    in the founding description — but that patient is also the only carrier of
    the p.(Phe26Cys) allele, so genotype and phenotype differ together. The two
    families that do share a genotype, both homozygous for p.(Glu76Lys), are
    described consistently, with the second report presenting itself as further
    delineating the same picture rather than widening it. Variable expressivity
    is therefore not what the published data show; what they show is two alleles
    with two descriptions, confounded with how deeply each was worked up.
  evidence:
  - reference: PMID:35427807
    reference_title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with autosomal recessive rhizomelic SEMD associated with a homozygous exonic missense variant"
    explanation: States the mode of inheritance directly.
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that variants in the GNPNAT1 gene cause an autosomal recessive form of SEMD"
    explanation: Independent statement of autosomal recessive inheritance.
prevalence:
- population: Worldwide published cases
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Three families have been published as of this curation: the four affected
    individuals of the consanguineous Pakistani index family, one 8-year-old
    girl, and one Egyptian patient — six affected individuals in total, on the
    counts the abstracts give. This is a literature-case count, not a population
    prevalence estimate; no population rate has been published for this disorder
    and none is asserted here. The ULTRA_RARE band is a qualitative tier used
    with a CASES_IN_LITERATURE measure and carries no numeric estimate.
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical investigations were carried out for four affected individuals in the recruited family."
    explanation: The case count of the index family.
  - reference: PMID:35427807
    reference_title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a second individual, an 8-year-old girl"
    explanation: The second published patient.
diagnosis:
- name: Radiographic skeletal survey
  description: >-
    Radiography is what establishes that the short stature is a
    spondyloepimetaphyseal dysplasia with rhizomelic predominance rather than a
    non-syndromic short stature, and it carries the discriminating findings —
    severe platyspondyly, hip dysplasia, flared metaphyses and delayed
    epiphyseal ossification, with the craniofacial skeleton spared. It places
    the patient in the category that then gets sequenced; it cannot identify the
    gene.
  diagnosis_term:
    preferred_term: radiographic skeletal survey
    term:
      id: NCIT:C17369
      label: Imaging Procedure
  results: >-
    Hip dysplasia, severe platyspondyly, wide flared metaphyses, short broad
    long bones and delayed epiphyseal ossification of the long bones.
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Radiographs of one individual showed hip dysplasia and severe platyspondyly."
    explanation: >-
      Records that radiography is how the discriminating skeletal findings were
      obtained in the index family.
- name: Molecular confirmation by genome or exome sequencing
  description: >-
    The diagnosis is established by finding a biallelic GNPNAT1 variant. Both
    routes have been used: whole genome sequencing in the two families carrying
    p.(Glu76Lys) and whole exome sequencing with Sanger confirmation in the
    family carrying p.(Phe26Cys). Because the disorder was described in 2021,
    GNPNAT1 may be absent from older skeletal-dysplasia panels, so a panel that
    predates the gene-disease association cannot exclude it.
  diagnosis_term:
    preferred_term: whole genome sequencing
    term:
      id: NCIT:C101294
      label: Whole Genome Sequencing
  results: >-
    A homozygous GNPNAT1 missense variant segregating with disease.
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole genome sequencing (WGS) was completed using DNA from two affected and two unaffected individuals from the family."
    explanation: The sequencing method that made the molecular diagnosis in the index family.
  - reference: PMID:35427807
    reference_title: "A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "in GNPNAT1 identified by trio genome sequencing"
    explanation: Trio genome sequencing as the diagnostic route in the second patient.
- name: Exome sequencing with Sanger confirmation and parental carrier testing
  description: >-
    The route used in the third family: exome sequencing, Sanger confirmation of
    the candidate variant, and demonstration that both parents are heterozygous
    carriers. Parental testing is what established recessive segregation for
    that allele, since the family had only one affected child.
  diagnosis_term:
    preferred_term: whole exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  results: >-
    Homozygous c.77T>G p.(Phe26Cys) in the proband, heterozygous in both parents.
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant."
    explanation: Records all three steps of the diagnostic route used in the third family.
differential_diagnoses:
- name: Dysostosis multiplex, Ain-Naz type
  disease_term:
    preferred_term: dysostosis multiplex, Ain-Naz type
    term:
      id: MONDO:0859156
      label: dysostosis multiplex, Ain-Naz type
  description: >-
    A separate disorder that shares the Ain-Naz eponym only because Ain NU and
    Naz S are the first and last authors of both founding reports. It is caused
    by biallelic LYSET (TMEM251) variants and presents as a dysostosis multiplex
    with coarse facial features resembling mucopolysaccharidosis, not as
    rhizomelic shortening with platyspondyly. The distinction is recorded here
    against MONDO:0859156 directly, rather than by pointing at another file
    whose state this entry cannot vouch for.
  distinguishing_features:
  - >-
    Different gene (LYSET/TMEM251 versus GNPNAT1) and different OMIM entry
    (619345 versus 619598).
  - >-
    Different skeletal pattern: dysostosis multiplex with progressively coarse
    facies, protruding abdomen and a mucopolysaccharidosis-like picture, versus
    rhizomelic shortening with severe platyspondyly and an explicitly spared
    craniofacial skeleton.
  - >-
    The two are mechanistically adjacent rather than unrelated — GNPNAT1 makes
    the UDP-GlcNAc that GlcNAc-1-phosphotransferase uses as its donor, and LYSET
    is required for that phosphotransferase — but no lysosomal enzyme
    abnormality has been reported in the GNPNAT1 disorder, and adjacency is not
    identity.
  evidence:
  - reference: PMID:33252156
    reference_title: "Biallelic TMEM251 variants in patients with severe skeletal dysplasia and extreme short stature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole-exome sequencing identified two homozygous variants c.133C>T; p.(Arg45Trp) and c.215dupA; p.(Tyr72Ter), respectively, in the two families, affecting an evolutionary conserved gene TMEM251"
    explanation: >-
      Establishes that the other Ain-Naz disorder is a TMEM251 (LYSET) disorder,
      so the shared eponym does not indicate a shared gene.
  - reference: PMID:33252156
    reference_title: "Biallelic TMEM251 variants in patients with severe skeletal dysplasia and extreme short stature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "affected individuals had a dysostosis multiplex-like skeletal dysplasia and severe short stature"
    explanation: >-
      Describes the dysostosis multiplex pattern that distinguishes the LYSET
      disorder from the rhizomelic pattern curated here.
- name: PGM3 deficiency (immunodeficiency 23)
  disease_term:
    preferred_term: immunodeficiency 23
    term:
      id: MONDO:0014353
      label: immunodeficiency 23
  description: >-
    A congenital disorder of glycosylation caused by biallelic PGM3 variants.
    PGM3 catalyses the step immediately after GNPNAT1 in the route to
    UDP-GlcNAc, and its severe forms present with skeletal dysplasia and
    immunodeficiency together — which is why the third GNPNAT1 report described
    its patient as resembling PGM3-related Desbuquois-like dysplasia. This is
    the differential that matters most for the one GNPNAT1 patient reported with
    immunodeficiency.
  distinguishing_features:
  - >-
    Resolved by sequencing: PGM3 versus GNPNAT1. The clinical overlap is real
    and is the reason the two were compared in the literature.
  - >-
    PGM3 deficiency is defined by its immune phenotype, most often eczema,
    elevated IgE and infection, with skeletal features in a subset; the GNPNAT1
    disorder is defined by its skeletal phenotype, with immunodeficiency
    reported in one patient only.
  evidence:
  - reference: PMID:36097642
    reference_title: "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1"
    explanation: >-
      The GNPNAT1 report itself names the PGM3 disorder as the phenotypic and
      pathway comparator.
  - reference: PMID:33534079
    reference_title: "Two Novel Homozygous Mutations in Phosphoglucomutase 3 Leading to Severe Combined Immunodeficiency, Skeletal Dysplasia, and Malformations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A few PGM3-deficient patients suffer from a more severe disease with nearly absent T cells and severe skeletal dysplasia."
    explanation: >-
      Documents the severe PGM3 phenotype that combines skeletal dysplasia with
      immunodeficiency, the combination reported once in a GNPNAT1 patient.
  - reference: PMID:24931394
    reference_title: "PGM3 mutations cause a congenital disorder of glycosylation with severe immunodeficiency and skeletal dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two of the three children had skeletal anomalies resembling Desbuquois dysplasia: short stature, brachydactyly, dysmorphic facial features, and intellectual disability."
    explanation: >-
      The Desbuquois-like skeletal picture the third GNPNAT1 report compared its
      patient to, in the original PGM3-CDG series. Note the difference as well
      as the resemblance: intellectual disability is part of that PGM3
      phenotype, and is an explicit 0/6 exclusion in the HPO annotation for this
      disorder.
  - reference: PMID:24931394
    reference_title: "PGM3 mutations cause a congenital disorder of glycosylation with severe immunodeficiency and skeletal dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two children received hematopoietic stem cell transplantation of cord blood and bone marrow from matched related donors; both had successful engraftment and correction of neutropenia and lymphopenia."
    explanation: >-
      The one therapeutic result anywhere in this pathway. It corrected the
      haematological phenotype of PGM3-CDG; it says nothing about a skeletal
      outcome and nothing at all about GNPNAT1, which is why it is cited on the
      differential rather than in treatments.
- name: Rhizomelic chondrodysplasia punctata
  disease_term:
    preferred_term: rhizomelic chondrodysplasia punctata
    term:
      id: MONDO:0015776
      label: rhizomelic chondrodysplasia punctata
  description: >-
    Included as an explicit exclusion rather than a close mimic. RCDP is a
    peroxisomal plasmalogen-biosynthesis group caused by PEX7, GNPAT, AGPS and
    FAR1. It shares the word "rhizomelic" and, in GNPAT, a gene symbol one
    inserted N and one appended digit away from GNPNAT1, and nothing else: the
    pathway, the
    radiographic hallmark (epiphyseal stippling) and the natural history are all
    different. dismech curates RCDP under its own entries. This record exists so
    that the near-collision is documented rather than left to be rediscovered.
  distinguishing_features:
  - >-
    Different pathway entirely: peroxisomal ether-phospholipid (plasmalogen)
    biosynthesis, not the cytosolic hexosamine biosynthetic pathway.
  - >-
    GNPAT (glyceronephosphate O-acyltransferase, dihydroxyacetone phosphate
    acyltransferase) is not GNPNAT1 (glucosamine-6-phosphate
    N-acetyltransferase). The symbols are two edits apart and the products are
    unrelated.
  - >-
    RCDP is characterised radiographically by punctate epiphyseal calcification
    (chondrodysplasia punctata), which has not been reported in this disorder.
  notes: >-
    No evidence item is attached. This is a curation guardrail recording a
    known confusion risk, not a clinical claim about either disorder, and the
    RCDP entries carry their own cited content.
experimental_models:
- name: Gnpnat1 siRNA knockdown in primary rat chondrocytes
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: >-
    The only functional model reported for this disorder. Primary chondrocytes
    isolated from rat were transfected with small interfering RNAs against
    Gnpnat1, and proliferation and chondrocyte differentiation markers were
    measured. It is a knockdown model, so it removes the transcript rather than
    reproducing either patient missense allele, and it is rodent rather than
    human.
  organism:
    preferred_term: Norway rat
    term:
      id: NCBITaxon:10116
      label: Rattus norvegicus
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  cell_source: Primary rat chondrocytes
  culture_system: Two-dimensional primary cell culture with siRNA transfection
  publication: PMID:32591345
  modeled_mechanisms:
  - target: Impaired Growth Plate Chondrocyte Proliferation and Differentiation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    model_scale: CELLULAR
    description: >-
      Knockdown reproduces the proposed cellular lesion — reduced chondrocyte
      proliferation and reduced expression of differentiation markers — and is
      the sole experimental support for locating this disorder's mechanism in
      the chondrocyte.
    limitations: >-
      Rodent rather than human cells; transient siRNA knockdown of the
      transcript rather than either homozygous human missense allele, so it
      models a null and cannot say what the patient proteins do; two-dimensional
      culture with no growth-plate architecture, no zonal organisation and no
      endochondral ossification, so the rhizomelic distribution and the
      platyspondyly of the human disease are outside the model entirely; and no
      measurement of UDP-GlcNAc, glycosylation or O-GlcNAcylation was made, so
      the model does not test the metabolic step the disorder is named for.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: QUALIFYING
      description: >-
        Rat primary chondrocytes stand in for human growth-plate chondrocytes.
        No human chondrocyte or growth-plate data exist for this disorder, so
        there is nothing to calibrate the substitution against.
    - divergence_type: CAUSE_UNREPRESENTED
      materiality: INVALIDATING
      description: >-
        The disease-causing lesion is a homozygous missense allele. The model
        applies siRNA knockdown, which lowers transcript abundance; a missense
        protein that is expressed and partially active is a different cause and
        is not represented.
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: >-
        Growth-plate zonal architecture, the perichondrium, vascular invasion
        and ossification are all outside the model boundary, so the radiographic
        phenotype the disorder is defined by cannot be observed in it.
    readouts:
    - name: Chondrocyte proliferation
      target: Impaired Growth Plate Chondrocyte Proliferation and Differentiation
      direction: DECREASED
      interpretation: >-
        Cellular proliferation fell after knockdown, the proliferative half of
        the node this link supports.
      evidence:
      - reference: PMID:32591345
        reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Knockdown of Gnpnat1 by siRNAs decreased cellular proliferation"
        explanation: Reports the proliferation measurement and its direction.
    - name: Collagen type 2 and alkaline phosphatase expression
      target: Impaired Growth Plate Chondrocyte Proliferation and Differentiation
      direction: DECREASED
      interpretation: >-
        The two chondrocyte differentiation markers measured; their fall is the
        differentiation half of the node.
      evidence:
      - reference: PMID:32591345
        reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "decreased cellular proliferation and expression of chondrocyte differentiation markers collagen type 2 and alkaline phosphatase"
        explanation: >-
          Names the two differentiation markers measured and the direction of
          the change.
    evidence:
    - reference: PMID:32591345
      reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Small interfering RNAs (siRNAs) were used to study the effect of Gnpnat1 gene knockdown in primary rat chondrocytes."
      explanation: >-
        Establishes the model system and its use as the functional arm of the
        founding report, which is what makes it informative for this node.
  notes: >-
    No animal model, organoid, iPSC line or patient-derived fibroblast culture
    has been reported for this disorder, so animal_models and computational_models
    are absent from this entry by fact rather than by omission.
treatments:
- name: Supportive and symptomatic management
  description: >-
    No disease-specific or disease-modifying treatment has been reported for
    this disorder. None of the three primary reports describes a therapeutic
    intervention or an outcome after treatment; a PubMed search of GNPNAT1 on
    2026-09-07 returned no management or trial publication, and a
    ClinicalTrials.gov query for GNPNAT1 and for rhizomelic dysplasia returned
    zero studies. Management is therefore supportive by default —
    the general orthopaedic, growth and rehabilitative care given in severe
    skeletal dysplasia — and this entry records the absence of evidence rather
    than asserting a standard of care. The specific supportive measures a
    patient might receive are not curated here because no source describes them
    for this disorder.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  notes: >-
    Deliberately uncited. There is nothing to cite: a search of the three
    primary reports found no treatment content, and quoting a management
    statement from a different skeletal dysplasia would attribute to this
    disorder a claim no source makes about it. See discussion
    rdan_no_therapy_evidence. therapeutic_modality is deliberately omitted:
    Supportive Care is a generic action term whose modality depends on the
    specific intervention, and no specific intervention is described for this
    disorder anywhere.
discussions:
- discussion_id: rdan_udp_glcnac_route
  kind: KNOWLEDGE_GAP
  prompt: >-
    Which UDP-GlcNAc-dependent process carries the skeletal phenotype of
    GNPNAT1 deficiency — mannose-6-phosphate tagging of lysosomal hydrolases,
    O-GlcNAcylation, N-glycosylation, or glycosaminoglycan synthesis?
  attaches_to:
  - pathophysiology#Diminished UDP-GlcNAc Supply
  rationale: >-
    GNPNAT1 supplies UDP-GlcNAc, which is the donor for at least four distinct
    processes with plausible skeletal consequences, and the published work does
    not distinguish between them. The mannose-6-phosphate route is the most
    tempting because the sugar donated by GlcNAc-1-phosphotransferase comes from
    UDP-GlcNAc and because the similarly named LYSET disorder is a defect of
    that same phosphotransferase — but no lysosomal enzyme assay, urinary
    glycosaminoglycan measurement or M6P study has been reported in any GNPNAT1
    patient, and none of the three abstracts consulted for this entry describes
    coarse facies, organomegaly or the storage picture that a
    mannose-6-phosphate defect produces — though an abstract would not
    necessarily record their absence. The
    O-GlcNAc route is equally unmeasured. The founding report's own framing is
    the broadest one, "participates in protein glycosylation", and this entry
    goes no further than that. Resolving this needs patient fibroblasts:
    UDP-GlcNAc quantitation, a glycosylation screen (transferrin isoform
    analysis or equivalent), an O-GlcNAc immunoblot, and plasma and fibroblast
    lysosomal enzyme activities. The two evidence items below establish only
    that the donor relationship exists; neither says anything about a patient
    with this disorder.
  evidence:
  - reference: PMID:32591345
    reference_title: "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "which participates in protein glycosylation"
    explanation: >-
      The founding report goes no further than naming protein glycosylation
      generically, which is the extent of what is established. Graded OTHER for
      the same reason as the fuller quotation of this sentence on the
      Diminished UDP-GlcNAc Supply node: it is background biochemistry, not a
      finding of the study.
  - reference: PMID:39178950
    reference_title: "Structure of a truncated human GlcNAc-1-phosphotransferase variant reveals the basis for its hyperactivity."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "PTase is the key enzyme of the mannose 6-phosphate (M6P) targeting system that is responsible for tagging lysosomal hydrolases with the M6P moiety for their delivery to the lysosome."
    explanation: >-
      Establishes the mannose-6-phosphate route that makes this question worth
      asking. It concerns the phosphotransferase, not GNPNAT1, and is cited only
      to show that UDP-GlcNAc feeds that pathway — not to assert that this
      disorder runs through it.
  status: OPEN
- discussion_id: rdan_immunodeficiency_single_case
  kind: KNOWLEDGE_GAP
  prompt: >-
    Is immunodeficiency a feature of GNPNAT1 deficiency, or a feature of the one
    patient in whom it was reported?
  attaches_to:
  - phenotypes#Immunodeficiency
  rationale: >-
    Immunodeficiency is reported in exactly one patient, who is also the only
    patient carrying the p.(Phe26Cys) allele, and the record consulted gives no
    immunological detail — no immunoglobulin levels, lymphocyte subsets or
    infection history. Two readings fit equally: the phenotype includes an
    immune component that the earlier reports did not look for, or this is
    allele-specific or incidental. The question is not idle, because PGM3 — the
    next enzyme in the same pathway — causes a disorder in which skeletal
    dysplasia and immunodeficiency occur together, so a shared immune
    consequence of reduced UDP-GlcNAc supply is biologically plausible. It would
    be resolved by immunophenotyping the patients from the other two families,
    which has not been reported. No frequency band is attached to the phenotype
    for this reason.
  status: OPEN
- discussion_id: rdan_variant_function_unmeasured
  kind: KNOWLEDGE_GAP
  prompt: >-
    What do the two reported GNPNAT1 missense alleles actually do to enzyme
    activity?
  attaches_to:
  - pathophysiology#Biallelic GNPNAT1 Missense Variants
  rationale: >-
    Both p.(Glu76Lys) and p.(Phe26Cys) are missense, and neither has been
    assayed. The functional work in the founding report is siRNA knockdown,
    which removes the transcript and therefore models a null rather than either
    patient allele; the rest is in-silico prediction. This is why the entry
    records functional_impact_category as UNKNOWN and grades the enzyme-activity
    node HYPOTHETICAL. A recombinant activity assay against
    glucosamine-6-phosphate, of the kind already published for wild-type human
    GNA1 in PMID:26935656 and cited elsewhere in this entry for that enzymology,
    would settle it, and would also say whether the two alleles behave alike —
    which matters for the immunodeficiency question above.
  status: OPEN
- discussion_id: rdan_sirna_models_a_null_not_the_alleles
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    Does siRNA knockdown of Gnpnat1 in rat chondrocytes tell us what the human
    missense alleles do, given that it removes the transcript rather than
    expressing a variant protein?
  attaches_to:
  - experimental_models#Gnpnat1 siRNA knockdown in primary rat chondrocytes
  - pathophysiology#Impaired Growth Plate Chondrocyte Proliferation and Differentiation
  rationale: >-
    This is the mismatch case rather than the absent-evidence case, and the two
    are separate questions. Evidence does exist here: knockdown lowers
    chondrocyte proliferation and differentiation marker expression, and it is
    the sole experimental support for locating this disorder's mechanism in the
    chondrocyte. What is open is whether it translates. Both reported alleles
    are missense and are carried homozygously, so they produce protein that is
    expressed and may retain partial activity; siRNA removes the transcript and
    therefore models a null. The link records that as a CAUSE_UNREPRESENTED divergence
    with materiality INVALIDATING for exactly this reason. The species
    substitution and the absence of growth-plate architecture compound it. The
    mismatch would be resolved by expressing the patient alleles rather than
    silencing the gene — a knock-in or a rescue of knockdown cells with variant
    cDNA — which no report has done. The companion gap
    rdan_variant_function_unmeasured asks the different question of what the
    alleles do biochemically; this one asks whether the existing cellular
    phenotype can be read as theirs.
  status: OPEN
- discussion_id: rdan_no_therapy_evidence
  kind: KNOWLEDGE_GAP
  prompt: >-
    Is any disease-modifying approach conceivable for a defect in
    nucleotide-sugar supply, and would substrate supplementation be a rational
    place to start?
  attaches_to:
  - treatments#
  rationale: >-
    Nothing is published on treatment. The mechanism raises an obvious question
    that no one has asked in print: GNPNAT1 acts on glucosamine-6-phosphate, and
    the salvage route through GlcNAc kinase enters the pathway downstream of
    GNPNAT1, so oral N-acetylglucosamine would in principle bypass the block.
    That is a hypothesis generated here from pathway topology, not a finding —
    no such experiment has been reported in this disorder, in a GNPNAT1 model
    system, or in PGM3 deficiency, and the skeletal lesion may in any case be
    developmental and therefore not correctable after presentation. It is
    recorded so the reasoning is auditable and not so that it is acted on. This
    is an absence of evidence, not evidence of futility.
  status: OPEN
- discussion_id: rdan_phenotype_breadth
  kind: CURATION_TODO
  prompt: >-
    Should the remaining 29 terms of the HPO annotation for OMIM:619598 be
    curated as phenotypes here, and can any of them be tied to a quotable
    passage in a primary report?
  attaches_to:
  - phenotypes#
  rationale: >-
    The HPO Consortium annotation for OMIM:619598 carries 41 terms with
    per-term fractions. Twelve of them are curated here, chosen because they are
    full-cohort annotations or because they carry the radiographic
    spondyloepimetaphyseal pattern; the rest are not, and they are not
    worthless. The uncurated ones include scoliosis, lumbar hyperlordosis,
    pectus excavatum, flaring of the rib cage, bowed forearm bones, proximal and
    distal humeral metaphyseal irregularity, wide distal femoral metaphysis,
    aplasia of the femoral head, hallux valgus, overlapping toe, short distal
    phalanx of finger, contracture of the proximal interphalangeal joint of the
    fifth finger, protuberant abdomen, short neck, congenital onset and
    infantile onset, and the five craniofacial terms listed in
    rdan_craniofacial_tension. Most are annotated 1/1 — a single observation in
    a single individual — which is why they were left for a curator with the
    full texts rather than imported in bulk.

    Two annotations are exclusions and must not be read as features. Intellectual
    disability (HP:0001249) is annotated 0/6 and abnormality of alkaline
    phosphatase level (HP:0004379) 0/1: the HPO records them as looked for and
    absent. The deep-research report generated for this entry listed intellectual
    disability among the phenotypes, which is exactly the error the fraction
    prevents; it is recorded here so the mistake is not made again.

    Resolving this needs the full texts of the three primary reports and the
    OMIM clinical synopsis, which could not be read for this curation because
    omim.org returned HTTP 403.
  status: OPEN
- discussion_id: rdan_hpoa_provenance
  kind: CURATION_TODO
  prompt: >-
    Twelve phenotypes and three frequency bands in this entry rest on the HPO
    disease annotation for OMIM:619598 rather than on a quoted passage. Should
    they carry evidence, and if so from where?
  attaches_to:
  - phenotypes#
  rationale: >-
    dismech evidence policy asks for an exact quote from a cited source. The HPO
    Consortium disease annotation is a structured, authoritative, versioned
    resource, but it is not a reference prefix this repository caches, so there
    is no cached body to quote and no identifier a snippet could be checked
    against. Rather than manufacture a quote or drop the content, each affected
    phenotype records its provenance in notes: the API endpoint
    (ontology.jax.org/api/network/annotation/OMIM:619598), the retrieval date
    (2026-09-07), and the exact annotated fraction. The three VERY_FREQUENT
    bands are the 6/6 and 5/5 annotations and nothing else; every other
    phenotype in the entry carries no frequency.

    The annotation is itself derived, one step removed from the primary reports
    by way of the OMIM clinical synopsis, so a curator with the full texts
    should be able to replace these notes with quoted evidence. Until then, read
    these twelve as traceable but not snippet-verified, and distinguish them
    from the nine phenotypes in this entry that do carry an exact quote from a
    cached PubMed abstract. Adding an HPOA reference source to
    references_cache/, in the way ORPHA and ClinGen were added, would close this
    gap for every disorder entry rather than only this one.
  status: OPEN
- discussion_id: rdan_craniofacial_tension
  kind: CONTROVERSY
  prompt: >-
    Is the craniofacial skeleton spared in this disorder, as the second report's
    definition of rhizomelic SEMD states, or mildly involved, as the HPO
    annotation implies?
  attaches_to:
  - pathophysiology#Disordered Endochondral Ossification
  rationale: >-
    The second report defines rhizomelic SEMD as sparing the cranio-facial
    sphere, and that sparing is one of the features that separates this disorder
    from the dysostosis multiplex pattern of the LYSET disorder it is confused
    with. The HPO annotation for OMIM:619598 nonetheless records frontal bossing,
    hypertelorism, ptosis, downslanted palpebral fissures and a wide nasal
    bridge, each in one of six individuals, and Wormian bones in one of one.

    These are reconcilable: five of the six terms are single-individual
    annotations out of six, so a category-level statement that the craniofacial
    sphere is unaffected is compatible with minor, inconsistent findings in
    individual patients — and none of the annotated terms is the progressive
    coarsening that defines dysostosis multiplex. The tension is recorded rather
    than resolved because resolving it needs the per-patient descriptions in the
    full texts, and because a reader who takes "cranio-facial sphere unaffected"
    at face value would be surprised by the annotation. Only Wormian bones is
    curated as a phenotype here, as the one craniofacial finding that is
    skeletal rather than a facial-gestalt descriptor.
  status: OPEN

📚

References & Deep Research

References

3

PMID:32591345

Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1.

No top-level findings curated for this source.

PMID:35427807

A second individual with rhizomelic spondyloepimetaphyseal dysplasia and homozygous variant in GNPNAT1.

No top-level findings curated for this source.

PMID:36097642

A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia.

No top-level findings curated for this source.

Deep Research

1

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

Evaluations and curation notes (2)

Record notes

Scope: this entry covers OMIM:619598 / MONDO:0859203 only. The similarly named "dysostosis multiplex, Ain-Naz type" (OMIM:619345, MONDO:0859156) is a different disorder with a different gene (LYSET/TMEM251) and a different skeletal pattern (dysostosis multiplex with coarse facies, resembling mucopolysaccharidosis). The shared eponym reflects only that Ain NU and Naz S are the first and last authors of both founding reports. MONDO:0859156 is carried here as a differential diagnosis. No claim is made about how, or whether, that disorder is curated elsewhere in this knowledge base: when this entry was written it existed only as an uncurated stub, and prose asserting the state of another file goes stale the moment that file changes. Do not confuse GNPNAT1 with GNPAT. Rhizomelic chondrodysplasia punctata (RCDP) is a peroxisomal plasmalogen-biosynthesis group caused by PEX7, GNPAT, AGPS and FAR1, is already curated in dismech under its own entries, and has nothing to do with the hexosamine biosynthetic pathway. GNPAT becomes GNPNAT1 by inserting one N and appending a 1, and the disease names both begin "rhizomelic"; that is the entire resemblance. GNPNAT1 (also GNA1) has a large cancer-metabolism literature — hexosamine pathway flux, O-GlcNAcylation and tumour proliferation. None of it concerns this disease and none of it is cited here. The one enzymology reference used (PMID:26935656) is cited solely for the reaction the enzyme catalyses. No GeneReviews chapter exists for GNPNAT1 or for this disorder. PubMed was searched on 2026-09-07 for "GNPNAT1 GeneReviews[All Fields]" (0 hits) and "rhizomelic dysplasia GeneReviews[All Fields]" (1 hit, the Achondroplasia chapter, unrelated), so there is no GeneReviews phenotype baseline for this entry. Three classification slots were deliberately left empty. isds_skeletal_category may only be assigned to disorders the ISDS Nosology of Genetic Skeletal Disorders itself lists, and it could not be confirmed that this 2021-described disorder appears in the 2023 revision (Unger et al., PMID:36779427); icimd_category is left empty for the same reason relative to the 2021 ICIMD, which predates the gene-disease association; mechanistic_category has no value that fits a nucleotide-sugar supply defect. None of the three omissions is a claim that the disorder falls outside those nosologies. No conforms_to was declared. The nearest candidate module, congenital_disorder_of_glycosylation, scopes itself to defects of the N-glycosylation machinery converging on demonstrated protein hypoglycosylation; GNPNAT1 sits upstream of that machinery in nucleotide-sugar supply, and no hypoglycosylation has been measured in any reported patient. Declaring conformance would assert the mechanism this entry records as open (see discussion rdan_udp_glcnac_route). OMIM was not consulted directly: omim.org returned HTTP 403 to the fetch attempted for this curation, so the clinical synopsis was not read. The OMIM identifiers used here were still not taken on trust — OMIM:619598 was confirmed as an xref of MONDO:0859203, and OMIM:619345 as an xref of MONDO:0859156, by querying the OLS MONDO record for each. Phenotypes come from two sources, kept distinguishable: nine are exact quotes from PubMed-cached primary reports, and twelve are from the HPO Consortium disease annotation for OMIM:619598, which carries no quotable body and is recorded per-phenotype in notes with its fraction and retrieval date (discussion rdan_hpoa_provenance). Deep research: the committed report is a **claude_code** report (research/Rhizomelic_Dysplasia_Ain-Naz_Type-deep-research-claude_code.md), not a falcon one. The provider chain attempted was falcon (HTTP 402, Edison account out of credits) then openscientist by --fallback (cancelled at about 20 minutes after sibling runs in this batch were reported timing out server-side at 3600 s) then claude_code, which completed in 319 s. Its reference validation is 4/4 resolved with 1/1 quote valid and nothing off topic; its term validation is 57/62 resolved with needs_review true, two obsolete GO terms and three mislabelled terms — of which two matter: UBERON:0002520 is submandibular lymph node, not "epiphyseal cartilage", and UBERON:0002544 is digit, not "growth plate cartilage". Neither was bound; this entry uses UBERON:0002516 (epiphyseal plate). The report also missed PMID:35427807 entirely and so counted two families rather than three, and it listed intellectual disability as a phenotype when the HPO annotation records it as an explicit 0/6 exclusion. Both errors are recorded rather than carried. Sections absent by fact rather than by omission. There is no progression, clinical_burden, stages or histopathology block because no natural-history, disability or tissue data have been published: the three reports give presentation and radiographs, and one age (8 years). There is no biochemical block because no biochemical measurement has been reported in any patient — which is itself the substance of discussion rdan_udp_glcnac_route, and is why that gap is recorded rather than filled. There are no clinical_trials, animal_models or computational_models. There is no datasets block: a dataset search for this disorder can only be run on the gene, and GNPNAT1 gene search returns hexosamine-pathway and cancer-metabolism experiments that are not about this disease, which is Named Entity Confusion reached through dataset search rather than a dataset for the entry.

Create: Rhizomelic_Dysplasia_Ain-Naz_Type · 2026-09-07T22:21:33Z · View source

New entry for rhizomelic dysplasia, Ain-Naz type (MONDO:0859203, OMIM:619598), the GNPNAT1 disorder. LUMP/SPLIT. Curated as entry_type DISEASE. The stub carried one MONDO parent (MONDO:0018230 skeletal dysplasia) and no MONDO descendants — the leaf signature — and the literature supports a single entity: three families, two homozygous missense alleles in one gene, one skeletal pattern. No subtypes were created; the third family's expanded phenotype is recorded as phenotypes plus two open discussions, not as a subtype. GENE AND SCOPE, VERIFIED INDEPENDENTLY. GNPNAT1 was confirmed from the cached abstract of PMID:32591345, which states 'WGS data analyses identified a homozygous missense variant c.226G>A; p.(Glu76Lys) in GNPNAT1, segregating with the disease' — not taken from the task prompt. The distinction from MONDO:0859156 (dysostosis multiplex, Ain-Naz type) was verified the same way: PMID:33252156 identifies TMEM251 (LYSET) and describes a dysostosis multiplex-like phenotype with coarse facies, a different gene and a different skeletal pattern. OMIM identifiers were not taken on trust either: OMIM:619598 was confirmed as an xref of MONDO:0859203 and OMIM:619345 as an xref of MONDO:0859156 by querying the OLS MONDO records, since omim.org returned HTTP 403. The GNPAT/GNPNAT1 confusion risk (rhizomelic chondrodysplasia punctata, a peroxisomal group) is recorded both in notes and as an explicit differential-diagnosis record with no evidence item, flagged as a curation guardrail rather than a clinical claim. THIRD FAMILY FOUND BY PUBMED SEARCH, NOT BY THE REPORT. A PubMed query for 'GNPNAT1 AND (skeletal OR dysplasia OR chondrocyte OR bone OR stature)' surfaced PMID:35427807 (a second individual with the same c.226G>A p.(Glu76Lys) allele) and PMID:36097642 (an Egyptian patient with a second allele, c.77T>G p.(Phe26Cys), plus immunodeficiency). The deep-research report missed PMID:35427807 and counted two families; this entry curates three, six affected individuals. MECHANISM: A GAP, NOT AN ASSERTION. The pathophysiology is a five-node chain from the biallelic missense variants through reduced glucosamine-6-phosphate N-acetyltransferase activity and diminished UDP-GlcNAc supply to impaired growth-plate chondrocyte proliferation/differentiation and disordered endochondral ossification. Which UDP-GlcNAc-dependent process carries the phenotype — mannose-6-phosphate tagging, O-GlcNAcylation, N-glycosylation or glycosaminoglycan synthesis — is deliberately NOT asserted; it is discussion rdan_udp_glcnac_route, a KNOWLEDGE_GAP, with the M6P route named as tempting and unmeasured. The two mid-chain nodes are graded mechanism_confidence HYPOTHETICAL, the two downstream ones PROVISIONAL, and genetic_context.functional_impact_category is UNKNOWN because neither missense allele has been assayed (discussion rdan_variant_function_unmeasured). No conforms_to was declared: congenital_disorder_of_glycosylation scopes itself to the N-glycosylation machinery converging on demonstrated hypoglycosylation, and no hypoglycosylation has been measured in any patient, so declaring conformance would assert the route the entry records as open. PHENOTYPES FROM TWO SOURCES, KEPT DISTINGUISHABLE. Nine phenotypes carry exact quotes from cached PubMed abstracts. Twelve more come from the HPO Consortium disease annotation for OMIM:619598, retrieved and verified independently from ontology.jax.org on 2026-09-07 (41 terms with per-term fractions). Those twelve carry no evidence item — HPOA has no cached quotable body in this repository — and instead record the endpoint, retrieval date and exact fraction in per-phenotype notes, with discussion rdan_hpoa_provenance explaining the choice and recommending an HPOA reference source as the general fix. Three VERY_FREQUENT frequency bands are the 6/6 and 5/5 annotations and nothing else. Two HPOA annotations are exclusions and were NOT curated as features: intellectual disability HP:0001249 is 0/6 and abnormality of alkaline phosphatase level HP:0004379 is 0/1. The deep-research report listed intellectual disability as a phenotype; that error is recorded in discussion rdan_phenotype_breadth rather than carried. The HPO craniofacial annotations conflict with the second report's definition of rhizomelic SEMD as sparing the cranio-facial sphere; that tension is discussion rdan_craniofacial_tension (CONTROVERSY) and only Wormian bones was curated from that group. DEEP RESEARCH. The committed report is a claude_code report, not a falcon one. Provider chain attempted: falcon (HTTP 402, Edison account out of credits), then openscientist via --fallback (cancelled at about 20 minutes after sibling runs in this batch were reported timing out server-side at 3600 s), then claude_code, which completed in 319 s over 18 web searches and 34 turns. Report validation: references 4/4 resolved, 0 unresolved, 1/1 quote valid, 0 off topic; terms 57/62 resolved, 0 unresolved, 2 obsolete, 3 mislabelled, needs_review true. Nothing under unresolved_references or unresolved_terms was cited or bound. Two mislabelled terms mattered and were avoided: UBERON:0002520 is submandibular lymph node, not epiphyseal cartilage, and UBERON:0002544 is digit, not growth plate cartilage; this entry binds UBERON:0002516 (epiphyseal plate). just preflight-dr returned SKIP because MONDO records no causal gene for MONDO:0859203, so the manual preflight was done instead: the report's dominant gene is GNPNAT1 (30 mentions) against PGM3 (9, the pathway comparator) and TMEM251 (4, an explicit exclusion), and its OMIM set includes 619598. DIAGNOSIS AND DIFFERENTIALS. Three diagnosis records: radiographic skeletal survey (NCIT:C17369), whole genome sequencing (NCIT:C101294) and whole exome sequencing with Sanger confirmation and parental carrier testing (NCIT:C101295). Three differentials: the LYSET Ain-Naz disorder, PGM3 deficiency / immunodeficiency 23 (MONDO:0014353, the enzyme immediately downstream of GNPNAT1, cited from PMID:24931394 and PMID:33534079), and rhizomelic chondrodysplasia punctata as an explicit exclusion. MODEL. The siRNA Gnpnat1 knockdown in primary rat chondrocytes is curated as an experimental_models PRIMARY_CELL_CULTURE record with modeled_mechanisms (PARTIALLY_RECAPITULATES, fidelity LOW, model_scale CELLULAR, two readouts) and three typed divergences: CAUSE_UNREPRESENTED (INVALIDATING — knockdown models a null, not either missense allele), SPECIES_MISMATCH and BOUNDARY_OMISSION. WHAT WAS DELIBERATELY LEFT EMPTY. isds_skeletal_category and icimd_category (could not confirm the disorder appears in the 2023 ISDS revision or the 2021 ICIMD, and both may only be assigned to listed disorders); mechanistic_category (no value fits a nucleotide-sugar supply defect); progression, clinical_burden, stages, histopathology, biochemical, datasets, clinical_trials, animal_models and computational_models (no published data — the biochemical absence is itself the substance of rdan_udp_glcnac_route); therapeutic_modality on the supportive-care treatment. No GeneReviews chapter exists (PubMed searched 2026-09-07: 'GNPNAT1 GeneReviews[All Fields]' 0 hits; 'rhizomelic dysplasia GeneReviews[All Fields]' 1 hit, the Achondroplasia chapter). GNPNAT1 is absent from the ClinGen Gene-Disease Validity table downloaded 2026-09-07. No Orphanet record was found by name and OMIM query against the Orphanet API, recorded as not-found rather than as absent. No clinical trials: ClinicalTrials.gov queries for GNPNAT1 and for rhizomelic dysplasia returned zero studies. VALIDATION RUN TO COMPLETION. just validate-disorders passed with 47/47 snippets verified. just validate, just validate-terms, check-duplicate-keys, check-entity-refs, check-causal-targets, check-qualifier-terms, check-enum-values, check-title-snippets, check-snippet-length, check-snippet-grading, check-reference-titles, check-folded-hyphens, check-environmental-evidence, check-not4curation, check-term-cache-integrity and check-cache-order all pass. just qc as a whole was not run: it exceeds the available command timeout, so the individual gates were run instead. model-scale-audit --strict reports no scale gap for this entry's single model link. The cache diff is additive only (17 rows across 10 files), and only the eight references_cache files this entry cites are staged; two DOI caches written by the report's own validation step are left unstaged.

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-sonnet-5 6 citations 2026-09-07T22:07:59.610617

1. Disease Information

Overview. Rhizomelic Dysplasia, Ain-Naz Type (RHZDAN) is an ultra-rare, autosomal recessive skeletal dysplasia first delineated in 2020–2021, characterized by severe short stature from extreme shortening of the proximal (rhizomelic) limb segments, platyspondyly, hip dysplasia, and disproportionately large hands and feet. It is caused by biallelic loss-of-function-type missense variants in GNPNAT1, which encodes an enzyme in the UDP-N-acetylglucosamine (UDP-GlcNAc) biosynthesis pathway required for protein glycosylation. To date the literature contains two independently ascertained kindreds: the original consanguineous Pakistani family (4 affected sibs) and a single Egyptian patient with an overlapping but expanded, more severe phenotype (spondylo-epi-metaphyseal dysplasia [SEMD]-like, with immunodeficiency).

Key identifiers: | Resource | Identifier | |---|---| | OMIM (phenotype) | #619598 — RHIZOMELIC DYSPLASIA, AIN-NAZ TYPE; RHZDAN | | OMIM (gene) | 616510 — GLUCOSAMINE-PHOSPHATE N-ACETYLTRANSFERASE 1; GNPNAT1 | | MONDO | MONDO:0859203 | | MedGen | CUI C5562013 (UID 1794223) | | UniProt disease | DI-06238 | | HGNC | 19980 (GNPNAT1) | | NCBI Gene | 64841 | | Locus | 14q22.1 | | Orphanet | No dedicated ORPHA code identified* in searches performed for this report — the entity appears to postdate or fall below current Orphanet indexing; this should be verified directly against Orphadata before curation and flagged as "not yet documented" if confirmed absent. | | ICD-10/ICD-11 | No disease-specific code identified; would fall under a generic short-limb skeletal dysplasia / osteochondrodysplasia category (e.g., ICD-10 Q77.8, unverified — not independently confirmed). |

Synonyms: RHZDAN (OMIM abbreviation); "Novel form of rhizomelic skeletal dysplasia associated with GNPNAT1 variant" (as first titled in the discovery report); GNPNAT1-related skeletal dysplasia; note that the second reported case is described in its own publication title as resembling a "spondylo-epi-metaphyseal dysplasia (SEMD), PGM3–Desbuquois-like" phenotype — authors treat this as an expansion of the RHZDAN allelic spectrum rather than a separate entity, but curators should note the phenotypic (and possibly nosological) heterogeneity.

Evidence basis: All clinical/genetic information in the literature derives from two published aggregated case series/case reports (not large-cohort or EHR-derived data): a 4-affected-sibling consanguineous Pakistani family (Ain et al. 2021) and a single Egyptian proband (Elhossini et al. 2022). This is disease-level literature synthesis, not population/EHR-level data — sample size is n=5 total reported affected individuals across two publications.

2. Etiology

Disease causal factor: Purely monogenic/genetic. RHZDAN is caused by biallelic (homozygous, in both reported families — consistent with consanguinity) pathogenic variants in GNPNAT1 (glucosamine-6-phosphate N-acetyltransferase). No environmental, infectious, or multifactorial contribution has been reported or is mechanistically plausible given the described autosomal recessive enzymatic-deficiency model.

Genetic risk factors: - Consanguinity is the dominant risk factor identified in both reported families: the index Pakistani family was consanguineous, and the Egyptian proband was likewise "offspring of consanguineous parents" (Elhossini et al. 2022, PMID pending direct retrieval — see §Citations note below; abstract confirmed via Semantic Scholar record for DOI 10.1002/ajmg.a.62933). - Two variants reported to date: - c.226G>A; p.(Glu76Lys) (E76K) — Pakistani family, homozygous, segregating with disease; absent from 380 ethnically matched control chromosomes and public variant databases (Ain et al. 2021, PMID:32591345 — quote: "identified a homozygous missense variant c.226G>A; p.(Glu76Lys) in GNPNAT1, segregating with the disease"; risk-factor context per web search: "was not found in 380 ethnically matched controls or in public variant databases"). - c.77T>G; p.(Phe26Cys) — exon 3, Egyptian proband, homozygous, confirmed by Sanger sequencing; both parents heterozygous carriers (Elhossini et al. 2022, DOI:10.1002/ajmg.a.62933 — quote: "Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous"). - No modifier genes, susceptibility loci, or founder-effect data have been reported (only two unrelated families; insufficient data to establish a founder allele). - gnomAD/population-frequency data for GNPNAT1 constraint (pLI/LOEUF) could not be independently retrieved in this session (tool access to the gnomAD browser did not return machine-readable content); this must be pulled directly from gnomAD before KB entry to characterize LOF intolerance — flagged as a gap, not asserted.

Environmental/lifestyle risk factors: None reported; not applicable to a purely Mendelian enzymatic disorder of this kind.

Protective factors: None reported in the literature.

Gene-environment interaction: None described; not applicable.

3. Phenotypes

The HPO Consortium's official annotation set for OMIM:619598 (retrieved directly from the HPO ontology API, 2026-09-07) provides the authoritative, structured phenotype list with HPO IDs. This is the single richest source for phenotype curation and should be used as the primary term-binding reference (cross-check each term's frequency/onset against the two primary reports where possible, since the HPO annotation file does not itself encode per-term frequency for this entry).

Onset/course: Congenital or infantile onset (HP:0003577 Congenital onset; HP:0003593 Infantile onset); course is not explicitly described as progressive vs. stable in the retrieved abstracts, though the skeletal features (metaphyseal irregularity, delayed epiphyseal ossification) imply an evolving radiographic picture through childhood, consistent with other growth-plate chondrodysplasias.

Skeletal / growth phenotypes: | Phenotype | HPO ID | |---|---| | Severe short stature | HP:0003510 | | Rhizomelia | HP:0008905 | | Short femur | HP:0003097 | | Short humerus | HP:0005792 | | Short femoral neck | HP:0100864 | | Aplasia of the femoral head | HP:0100862 | | Flat acetabular roof | HP:0003180 | | Hip dysplasia | HP:0001385 | | Squared iliac bones | HP:0003177 | | Platyspondyly | HP:0000926 | | Posterior scalloping of vertebral bodies | HP:0005121 | | Scoliosis | HP:0002650 | | Lumbar hyperlordosis | HP:0002938 | | Pectus excavatum | HP:0000767 | | Flaring of rib cage | HP:0000904 | | Wormian bones | HP:0002645 | | Bowed forearm bones | HP:0003956 | | Distal humeral metaphyseal irregularity | HP:0003951 | | Proximal humeral metaphyseal irregularity | HP:0005043 | | Wide distal femoral metaphysis | HP:0006387 | | Large hands | HP:0001176 | | Long foot | HP:0001833 | | Hallux valgus | HP:0001822 | | Overlapping toe | HP:0001845 | | Short distal phalanx of finger | HP:0009882 | | Contracture of the PIP joint of the 5th finger | HP:0009185 | | Enlarged joints | HP:0003037 | | Limitation of joint mobility | HP:0001376 |

Craniofacial: | Phenotype | HPO ID | |---|---| | Frontal bossing | HP:0002007 | | Downslanted palpebral fissures | HP:0000494 | | Hypertelorism | HP:0000316 | | Ptosis | HP:0000508 | | Short neck | HP:0000470 | | Wide nasal bridge | HP:0000431 |

Other systemic/functional: | Phenotype | HPO ID | |---|---| | Protuberant abdomen | HP:0001538 | | Gait disturbance | HP:0001288 | | Intellectual disability | HP:0001249 | | Abnormality of alkaline phosphatase level | HP:0004379 | | Autosomal recessive inheritance | HP:0000007 |

Phenotype expansion in the second (Egyptian) case (Elhossini et al. 2022): Beyond the original Pakistani-family phenotype, this proband displayed features that broadened the spectrum toward a spondylo-epi-metaphyseal dysplasia resembling PGM3-related (Desbuquois-like) disease: "Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family" (direct quote, DOI:10.1002/ajmg.a.62933). The immunodeficiency finding is mechanistically notable — it parallels PGM3-CDG (a related UDP-GlcNAc-pathway disorder with immunologic involvement, see §6) and suggests the GNPNAT1 phenotypic spectrum may extend beyond a pure skeletal dysplasia, but this is based on a single additional case and should be flagged as tentative/unreplicated.

Frequency and severity data: No systematic percentage-frequency table has been published (consistent with n=5 reported cases across 2 families); severity should be recorded qualitatively as "severe" per both reports' own characterization ("severe skeletal dysplasia," "severe short stature," "severe form of unclassified SEMD").

Quality of life: Not formally measured (no EQ-5D/SF-36 data); qualitatively, gait disturbance, joint mobility limitation, and intellectual disability (reported in the Pakistani family) imply substantial functional impact, but no validated instrument has been applied.

4. Genetic/Molecular Information

Causal gene: GNPNAT1 (Glucosamine-Phosphate N-Acetyltransferase 1; HGNC:19980; NCBI Gene 64841; OMIM 616510; locus 14q22.1). Encodes a 184-amino-acid protein (GNA1) of the GCN5-related N-acetyltransferase (GNAT) superfamily, carrying all four GNAT-family conserved motifs; the enzyme forms homodimers, with the substrate glucosamine-6-phosphate (GlcN6P) binding at the dimer interface (source: web search synthesis of GeneCards/OMIM gene entry 616510 content — structural claim about dimerization and crystal structure not independently re-verified against the primary crystallography paper in this session; treat as a secondary-source claim pending direct citation check).

Pathogenic variants (both classified as biallelic, homozygous, autosomal recessive):

Variant	Protein change	Family	Zygosity	Classification basis
c.226G>A	p.(Glu76Lys) / E76K	Pakistani (4 sibs)	Homozygous	Segregates with disease; absent in 380 ethnic-matched controls and public databases (PMID:32591345)
c.77T>G	p.(Phe26Cys)	Egyptian (1 proband)	Homozygous	Confirmed by Sanger sequencing; both parents heterozygous carriers (DOI:10.1002/ajmg.a.62933)

Both are missense variants (no frameshift, nonsense, or splice-site variants reported for RHZDAN). No formal ACMG/AMP classification tier (e.g., "Pathogenic" vs. "Likely Pathogenic") was stated verbatim in the retrieved abstracts; ClinVar-hosted classification for these specific variants could not be independently confirmed in this session (a search for the E76K variant surfaced only an unrelated PTPN11 c.226G>A variant with the coincidentally identical nucleotide/codon position — do not conflate these two distinct genes/variants; this is exactly the kind of Named Entity Confusion risk the KB's evidence SOP warns about).

Population allele frequency: Not established; both variants are reported as absent from population databases at the time of publication (functionally, ultra-rare/private variants).

Functional consequences: Both reports interpret the variants as loss-of-function/hypomorphic for the enzyme's role in UDP-GlcNAc synthesis, based on functional (siRNA knockdown) data rather than direct enzymatic assay of the mutant protein (see §6). No formal LOF vs. GOF vs. dominant-negative distinction beyond "reduces enzyme's role in chondrocyte glycosylation" was established biochemically for the mutant proteins themselves.

Modifier genes: None reported.

Epigenetics: No epigenetic data (methylation, histone modification) reported for this disorder.

Chromosomal abnormalities: None; this is a single-gene missense disorder, not a copy-number/structural variant disease.

Related gene (for nosological clarity — do NOT bind to this entry): TMEM251 (now LYSET), locus 14q32, causes the phenotypically distinct Dysostosis Multiplex, Ain-Naz Type (DMAN, OMIM #619345) — a more severe, "dysostosis multiplex"/metabolic-disease-like phenotype with coarse facies and early death, described in the same 2021 publication series by overlapping authors but is a molecularly and clinically separate entity from RHZDAN.

5. Environmental Information

No environmental factors, lifestyle factors, or infectious triggers have been reported or are mechanistically implicated for RHZDAN; it is a purely monogenic enzymatic-deficiency skeletal dysplasia. This section should likely be left with a review_notes: waiver in the KB (per dismech evidence policy) rather than populated with speculative content, since no search for environmental modifiers returned relevant literature.

6. Mechanism / Pathophysiology

Causal chain (numbered, from molecular lesion to clinical phenotype)

Biallelic missense variants in GNPNAT1 (p.Glu76Lys or p.Phe26Cys) reduce or impair the function of glucosamine-6-phosphate N-acetyltransferase (GNA1) — inferred from disease segregation and from siRNA-knockdown phenocopy experiments, not from direct biochemical assay of the mutant enzyme itself (PMID:32591345).
Reduced GNA1 activity leads to decreased conversion of glucosamine-6-phosphate (GlcN6P) to N-acetylglucosamine-6-phosphate — the terminal, rate-limiting acetylation step of the hexosamine biosynthesis pathway (HBP) that generates the donor nucleotide sugar UDP-N-acetylglucosamine (UDP-GlcNAc). This step is established general GNPNAT1 enzymology (well-supported prior biochemical literature), applied here by inference to the disease mechanism rather than measured directly in patient tissue.
Diminished UDP-GlcNAc availability results in impaired protein N-linked glycosylation and O-GlcNAcylation broadly, since UDP-GlcNAc is an obligate donor substrate for the dolichol-linked oligosaccharide precursor of N-glycosylation and for O-GlcNAc modification of cytosolic/nuclear proteins (general pathway biology, not disease-specific measurement).
In growth-plate chondrocytes specifically, siRNA-mediated knockdown of Gnpnat1 in primary rat chondrocytes caused decreased cellular proliferation and decreased expression of the chondrocyte differentiation markers collagen type II (COL2) and alkaline phosphatase (ALP) — direct experimental (IN_VITRO) evidence from the discovery paper (PMID:32591345; direct quote: "Knockdown of Gnpnat1 by siRNAs decreased cellular proliferation and expression of chondrocyte differentiation markers collagen type 2 and alkaline phosphatase, indicating that Gnpnat1 is important for growth plate chondrocyte proliferation and differentiation").
Impaired chondrocyte proliferation and differentiation at the growth plate leads to disordered endochondral ossification, producing the radiographic/clinical picture of metaphyseal irregularity, delayed epiphyseal ossification, and shortened long bones — this step is an inference bridging the in vitro rat-chondrocyte data to the human skeletal phenotype (not itself directly imaged in patient growth-plate biopsy tissue).
The proximal long bones (femur, humerus) manifest the most pronounced shortening (rhizomelia) and metaphyseal/epiphyseal abnormality, producing the disproportionate short stature, hip dysplasia, and platyspondyly that define the clinical phenotype (clinical/radiographic observation, PMID:32591345).
Branch (severe/expanded phenotype, Egyptian case): in at least one reported individual, the same pathway disruption is additionally associated with immunodeficiency, paralleling the known immunologic phenotype of PGM3-CDG (a biosynthetically adjacent UDP-GlcNAc pathway disorder) — this branch is based on a single case and is explicitly framed by its authors as "resembling PGM3–Desbuquois-like dysplasia" rather than as an established, replicated mechanistic link (DOI:10.1002/ajmg.a.62933).

Molecular pathway

Hexosamine biosynthesis pathway (HBP): fructose-6-phosphate + glutamine → glucosamine-6-phosphate (GFPT1) → N-acetylglucosamine-6-phosphate (GNPNAT1, the RHZDAN gene) → N-acetylglucosamine-1-phosphate (PGM3) → UDP-GlcNAc (UAP1). GNPNAT1 catalyzes the specific step: acetyl-CoA + GlcN6P → GlcNAc6P + CoA (EC 2.3.1.4).
This pathway is the shared biosynthetic route disrupted in several allelic/pathway-adjacent congenital disorders of glycosylation: GFPT1 (congenital myasthenic syndrome), PGM3 (PGM3-CDG: severe immunodeficiency + Desbuquois-like skeletal dysplasia, PMID:24931394 — "PGM3 catalyzes the conversion of N-acetyl-glucosamine (GlcNAc)-6-phosphate into GlcNAc-1-phosphate during the synthesis of uridine diphosphate (UDP)-GlcNAc... Two of the three children had skeletal anomalies resembling Desbuquois dysplasia"), and GNE (GNE myopathy, sialic-acid pathway). RHZDAN/GNPNAT1 is mechanistically the direct upstream neighbor of PGM3 in this same pathway, which explains and predicts the phenotypic overlap (skeletal dysplasia ± immunodeficiency) observed between the two disorders.

Cellular process

Growth-plate chondrocyte proliferation and differentiation (GO:0035988 chondrocyte proliferation; GO:0002062 chondrocyte differentiation are plausible GO term candidates — not independently ontology-validated in this session and should be checked with OAK/just validate-terms before binding). Reduced N-glycosylation is expected to secondarily impair extracellular matrix protein maturation/secretion (e.g., collagen processing), consistent with the observed COL2 reduction, though this specific ECM-trafficking link was not directly tested in the cited experiments.

Protein dysfunction

Missense substitutions (E76K, F26C) are hypothesized to destabilize the GNAT-fold catalytic domain or the GlcN6P-binding dimer interface, but no crystal structure, thermal-stability assay, or direct enzymatic-activity assay of either mutant protein was reported in the retrieved sources — this is an inferred mechanism from variant location and phenocopy data, not a directly demonstrated biochemical defect.

Immune involvement

Only in the expanded (Egyptian) phenotype; mechanistically plausible via the shared UDP-GlcNAc pathway with PGM3-CDG (glycosylation is essential for lymphocyte receptor maturation and function), but not directly studied for GNPNAT1 in this case beyond clinical observation of immunodeficiency.

Molecular profiling / advanced technologies

No transcriptomic, proteomic, metabolomic, single-cell, or spatial data specific to GNPNAT1/RHZDAN patient tissue were identified in this search. The only functional-genomics data available is the bulk siRNA knockdown experiment in primary rat chondrocytes described above (COL2/ALP expression by presumed qPCR/immunostaining — exact assay method not confirmed from the abstract alone).

Suggested ontology terms for pathway/mechanism curation (to be validated via OAK before binding, per dismech term policy — not pre-verified here): - GO:0006048 (UDP-N-acetylglucosamine biosynthetic process) — candidate - GO:0016410 (N-acyltransferase activity) / GO:0004342 (glucosamine-6-phosphate N-acetyltransferase activity) — candidate, likely exact EC 2.3.1.4 match - GO:0006486 (protein glycosylation) - CL:0000138 (chondrocyte) - CL:1001608 or similar for growth-plate chondrocyte subtype (verify)

7. Anatomical Structures Affected

Organ/system level: Primarily the skeletal system — long bones (femur, humerus most severely — rhizomelic pattern), axial skeleton/spine (vertebral bodies — platyspondyly, posterior scalloping), pelvis (iliac bones, acetabulum, hip joint), rib cage, skull (frontal bone — bossing; cranial sutures — Wormian bones), hands/feet (phalanges, digits). Secondary/associated systems: craniofacial structures (orbits, nose), central nervous system (intellectual disability reported in the index family — CNS involvement not radiographically or mechanistically characterized beyond the clinical phenotype), gastrointestinal (protuberant abdomen — likely secondary to axial/postural skeletal change rather than primary GI pathology), and in the expanded phenotype, the immune system.

Tissue/cell level: Growth-plate cartilage and chondrocytes are the direct experimentally implicated cell population (CL:0000138 chondrocyte; more specifically proliferative and hypertrophic growth-plate zone chondrocytes). Candidate UBERON terms: UBERON:0002520 (epiphyseal cartilage) / UBERON:0002544 (growth plate cartilage) — not independently validated in this session.

Subcellular level: GNA1/GNPNAT1 is a cytosolic enzyme (GO Cellular Component: cytosol, GO:0005829) acting early in the hexosamine pathway before nucleotide-sugar transport into the endoplasmic reticulum/Golgi for glycosylation; downstream glycosylation machinery operates in the ER (UBERON/GO: endoplasmic reticulum, GO:0005783) and Golgi apparatus (GO:0005794).

Localization/laterality: Skeletal involvement is bilateral and symmetric, consistent with a systemic metabolic/enzymatic defect rather than a focal or lateralized process (standard expectation for this disease class; not separately confirmed per-patient in the retrieved abstracts).

8. Temporal Development

Onset: Congenital to infantile (HP:0003577, HP:0003593, both HPO-annotated to OMIM:619598). Short stature and limb disproportion are apparent from birth or early infancy, as is typical for rhizomelic skeletal dysplasias.

Progression: Radiographic descriptions (delayed epiphyseal ossification, advanced bone age in the Egyptian case, metaphyseal irregularity) imply an evolving skeletal picture through childhood, but no formal staging system or longitudinal natural-history study has been published — only cross-sectional case descriptions of affected sibs/probands at the time of ascertainment. Progression rate, remission, and long-term trajectory into adulthood are not documented in the available literature (both reports are relatively recent, 2020/2022, so long-term follow-up data may not yet exist).

Course pattern: Best characterized as a static/structural congenital skeletal dysplasia (analogous to other chondrodysplasias) rather than an episodic or relapsing-remitting condition, though this is inferred from disease-class analogy rather than directly documented longitudinal data for RHZDAN specifically.

Critical periods: By analogy to other growth-plate chondrodysplasias, the fetal/perinatal and childhood growth periods (active endochondral ossification) represent the biologically critical window during which the GNPNAT1 defect exerts its skeletal effect; this is inferred from the mechanism (growth-plate chondrocyte proliferation/differentiation defect) rather than explicitly stated as a "critical period" in the source papers.

9. Inheritance and Population

Epidemiology: RHZDAN is ultra-rare — only two published kindreds (one Pakistani family, 4 affected sibs; one Egyptian singleton proband), totaling 5 reported affected individuals as of the literature identified in this search (through 2022). No formal prevalence or incidence estimate exists; this should be curated as prevalence_class: NOT_YET_DOCUMENTED (Orphanet-aligned band) with measure_type: CASES_IN_LITERATURE given the absence of a population-based estimate, per dismech's Prevalence modeling conventions — do not apply a qualitative COMMON/RARE/ULTRA_RARE tier without a numeric or Orphanet-sourced anchor; "cases in literature" (n≈5) is the honest characterization here.

Inheritance pattern: Autosomal recessive (HP:0000007, directly HPO-annotated to OMIM:619598); confirmed by homozygosity in both reported families and heterozygous unaffected parents (explicitly reported for the Egyptian family).

Penetrance: Appears complete among homozygotes in both reported families (all homozygous individuals reported as affected), but sample size (n=5) is too small to formally establish penetrance statistics.

Expressivity: Variable — the Egyptian proband displays an expanded phenotype (immunodeficiency, more severe SEMD features, advanced bone age) relative to the original Pakistani family, suggesting variable expressivity and/or an emerging genotype-phenotype spectrum, though with only two families this cannot be statistically disentangled from simple inter-family/inter-variant variation.

Genetic anticipation, germline mosaicism: Not reported/not applicable (not a repeat-expansion disorder).

Founder effects: Not established; the two reported variants (E76K in the Pakistani family, F26C in the Egyptian proband) are distinct, private, population-specific missense changes — no shared founder haplotype has been reported between the two families.

Consanguinity: A central feature of both reported families — both are explicitly described as consanguineous unions, consistent with autosomal recessive segregation of a private, ultra-rare variant.

Population demographics: Affected individuals reported to date are of Pakistani (index family) and Egyptian (second case) ancestry — both populations with relatively high rates of consanguinity, which likely facilitated ascertainment of this recessive ultra-rare disorder. No data on sex ratio (the Pakistani family reportedly comprised siblings of unspecified/mixed sex distribution based on available search snippets — exact composition not independently confirmed here) or broader geographic distribution beyond these two reports.

Carrier frequency: Not established/not reported in population databases (gnomAD carrier frequency for either variant was not independently retrievable in this session — flagged as a gap).

10. Diagnostics

Genetic testing (primary diagnostic modality used in both reports): - Whole-genome sequencing (WGS) was the method used to identify the causal variant in the index Pakistani family (PMID:32591345: "Whole genome sequencing (WGS) was completed using DNA from two affected and two unaffected individuals from the family"). - Whole-exome sequencing (WES) was used in the Egyptian case (DOI:10.1002/ajmg.a.62933: "Whole exome sequencing identified a novel homozygous variant in exon 3..."). - Sanger sequencing was used for confirmatory/segregation testing in both families. - No gene panel, chromosomal microarray, karyotype, or targeted single-gene testing pathway has yet been formally established for RHZDAN specifically, given its very recent delineation (2020/2022) — clinically, it would currently only be identifiable via exome/genome sequencing in the context of an undiagnosed skeletal dysplasia, not via a pre-existing skeletal-dysplasia gene panel (RHZDAN is too newly described to be reliably included on all commercial panels; curators should verify current panel content directly with testing labs rather than assume inclusion).

Clinical/radiographic criteria: Diagnosis is currently based on the combination of characteristic radiographic findings (rhizomelic long-bone shortening, platyspondyly, metaphyseal irregularity, hip dysplasia) plus confirmatory biallelic GNPNAT1 variants — there is no independent, non-genetic "clinical diagnostic criteria" set (e.g., no consensus/society diagnostic checklist), consistent with an entity defined by only two published families.

Laboratory/biomarker findings: Alkaline phosphatase abnormality is HPO-annotated to this disease (HP:0004379) — implying a reported serum ALP finding in at least one family, though the precise direction (elevated/decreased) and its diagnostic utility were not confirmed from the abstracts retrieved. No specific biochemical/enzymatic assay (e.g., direct GNA1 enzyme activity assay in patient fibroblasts) has been reported as a diagnostic test, in contrast to some other CDGs where transferrin isoform analysis or specific enzyme assays are used.

Differential diagnosis: Based on the second case report's own framing, the key differential is PGM3-CDG / Desbuquois-like dysplasia (pathway-adjacent, overlapping skeletal + immunodeficiency phenotype), as well as other rhizomelic skeletal dysplasias more broadly (e.g., Rhizomelic Chondrodysplasia Punctata types 1–5 [PEX7, GNPAT, AGPS, FAR1, PEX5], which are mechanistically and genetically distinct — peroxisomal, not glycosylation-pathway, disorders — and should not be confused with RHZDAN despite the shared "rhizomelic" descriptor).

Screening: No newborn screening, carrier screening, or population screening program exists for this ultra-rare, recently described disorder.

11. Outcome/Prognosis

No formal survival, mortality, or long-term morbidity data have been published for RHZDAN specifically (in contrast to the phenotypically related but molecularly distinct DMAN/TMEM251 disorder, for which OMIM notes "early death has been observed in some patients" — that mortality statement applies to DMAN, not RHZDAN, and must not be transferred across entries). Given the recency of description (2020/2022) and small case count, no 5-/10-year survival statistics, disability registries, or quality-of-life instrument data exist. Prognostic factors and biomarkers predicting disease course have not been studied. This is an honest, disclosed evidence gap rather than an absence to paper over.

12. Treatment

No disease-specific or targeted therapy exists. No pharmacotherapy, gene therapy, enzyme-replacement, or other molecularly targeted treatment has been reported, trialed, or proposed for RHZDAN in the literature identified. Management, by analogy to other skeletal dysplasias with hip dysplasia/scoliosis/joint contracture features, would be expected to be supportive and orthopedic — but no orthopedic intervention, physical therapy protocol, or outcome data specific to RHZDAN patients was found in this search.

Suggested (inferred, not literature-confirmed for this specific disease) NCIT treatment-term candidates for a supportive-care framework, to be populated only if/when case reports describe actual interventions: - NCIT:C16186 Orthopedic Surgical Procedure (candidate — e.g., for hip dysplasia management, not yet reported for this disease) - NCIT:C15302 Physical Therapy (candidate) - NCIT:C15240 Genetic Counseling (appropriate given autosomal recessive inheritance and consanguinity) - NCIT:C15747 Supportive Care

No clinical trials (ClinicalTrials.gov, WHO ICTRP) for RHZDAN were identified — consistent with its status as an ultra-rare, recently described monogenic disorder with no established therapeutic pipeline.

13. Prevention

Primary prevention: Given the autosomal recessive inheritance and prominent role of consanguinity in both reported families, genetic counseling for consanguineous couples and carrier testing within affected families (once the familial variant is known) represent the only applicable prevention strategies — inferred by standard AR-disease logic, not separately documented as a formal recommendation for RHZDAN in the literature.

Secondary prevention (prenatal/preimplantation): No specific prenatal diagnosis or preimplantation genetic diagnosis (PGD) protocol has been reported for RHZDAN, though it would be technically feasible once a familial pathogenic variant is identified (standard recessive-disease logic; not literature-confirmed for this entity specifically).

Screening/carrier testing: No population or targeted carrier-screening panel currently includes GNPNAT1 for this indication, to our knowledge from this search.

Public health/behavioral: Not applicable — this is not an environmentally or behaviorally modifiable disease.

14. Other Species / Natural Disease

No naturally occurring GNPNAT1-associated disease in non-human species was identified in this search (no veterinary case reports, no OMIA entries located).

Orthologs: Gnpnat1 has a mouse ortholog (MGI:1858963, Gnpnat1, glucosamine-phosphate N-acetyltransferase 1) confirmed via MGI search-result indexing, but no mouse phenotype/knockout data specific to a skeletal or chondrodysplasia phenotype could be retrieved in this session — this is a genuine literature/database gap that should be checked directly against MGI/IMPC records before curation (do not assume absence of a mouse model; only that this search did not surface one).

Comparative biology: The enzyme (GNA1) and the broader hexosamine biosynthesis pathway are highly evolutionarily conserved (yeast to human), consistent with the disease report's own framing of GNPNAT1 as "highly conserved" (PMID:32591345), but no comparative-pathology or cross-species disease-mechanism study specific to this skeletal phenotype was found.

Zoonotic potential: Not applicable — this is a non-infectious, purely genetic disorder.

15. Model Organisms

In vitro/cellular model (the only functional model system reported to date): Primary rat chondrocytes with siRNA-mediated Gnpnat1 knockdown — used in the discovery paper (PMID:32591345) to functionally validate the gene-disease relationship. This is an IN_VITRO (not MODEL_ORGANISM) evidence source per dismech's evidence-source classification rules (cultured primary cells, not a whole-organism model), despite being rat-derived tissue. Key findings: knockdown → decreased proliferation, decreased COL2 and ALP expression (chondrocyte differentiation markers) — directly supporting a growth-plate chondrogenesis mechanism.

Whole-organism genetic models: None identified in this search — no mouse knockout, zebrafish morphant/mutant, or other whole-animal Gnpnat1 loss-of-function model with skeletal phenotyping was found. Given the gene's broader essential role in glycosylation (a pathway generally required for viability), a complete germline knockout might be expected to be embryonic lethal in mice (as is common for core HBP/glycosylation genes), which could explain the absence of a viable whole-body knockout model in the literature — but this is a plausibility inference, not a documented finding, and should be explicitly flagged as such (HUMAN_MODEL_MISMATCH-relevant gap: no animal model yet demonstrates in vivo recapitulation of the human skeletal phenotype).

Model limitations: The only existing functional evidence (rat primary chondrocyte siRNA knockdown) captures cell-autonomous proliferation/differentiation defects but cannot address whole-organism skeletal patterning, growth-plate architecture in situ, or the immunodeficiency phenotype seen in the expanded (Egyptian) clinical case — representing a clear translational gap between available model data and the full human phenotypic spectrum.

Research applications going forward (not yet realized): A conditional/chondrocyte-specific Gnpnat1 knockout mouse, or a zebrafish CRISPR model, would be the logical next model-system step to directly test in vivo recapitulation of rhizomelic shortening and growth-plate histology — this is an unmet need identified by the gap in current literature, not a described ongoing effort.

Summary of Evidence Quality and Key Gaps

Category	Status
Causal gene/variant evidence	Strong — 2 independent families, segregation + functional (in vitro) data
Mechanistic evidence	Moderate — pathway-level inference well supported by general GNPNAT1 biochemistry; disease-specific mechanism supported by one in vitro (rat chondrocyte) experiment; no direct enzymatic assay of mutant protein; no in vivo model
Phenotype delineation	Good — official HPO-curated annotation set exists (41 terms) tied to OMIM:619598
Epidemiology	Essentially absent (n≈5 cases; no prevalence estimate; no ORPHA code confirmed)
Prognosis/natural history	Essentially absent — no long-term follow-up published
Treatment	Absent — no disease-specific or trialed therapy
Animal models	Absent — no whole-organism model identified in this search
Nosological risk	High — must be kept distinct from Dysostosis Multiplex, Ain-Naz Type (TMEM251/LYSET, OMIM #619345), a different disease using the same author-derived naming convention

Primary Sources Cited

Ain N, Baroncelli M, Costantini A, Ishaq T, Taylan F, Nilsson O, Mäkitie O, Naz S. "Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1." J Med Genet. 2021;58(5):351–356. PMID:32591345. doi:10.1136/jmedgenet-2020-106929.
Elhossini R, Ahmed HA, Otaify G, Ghorab RM, Amr K, Aglan M. "A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3–Desbuquois like dysplasia." Am J Med Genet A. 2022;188A:2861–2868. doi:10.1002/ajmg.a.62933.
OMIM #619598 — RHIZOMELIC DYSPLASIA, AIN-NAZ TYPE; RHZDAN. https://www.omim.org/entry/619598
OMIM *616510 — GLUCOSAMINE-PHOSPHATE N-ACETYLTRANSFERASE 1; GNPNAT1. https://www.omim.org/entry/616510
OMIM #619345 — DYSOSTOSIS MULTIPLEX, AIN-NAZ TYPE; DMAN (cited only to distinguish from RHZDAN). https://www.omim.org/entry/619345
HPO/Monarch phenotype annotation set for OMIM:619598, retrieved via ontology.jax.org API, 2026-09-07.
UniProt Diseases — DI-06238, Rhizomelic dysplasia, Ain-Naz type. https://www.uniprot.org/diseases/DI-06238
MedGen — C5562013 / UID 1794223. https://www.ncbi.nlm.nih.gov/medgen/1794223
Winckler B, et al. "PGM3 mutations cause a congenital disorder of glycosylation with severe immunodeficiency and skeletal dysplasia." Am J Hum Genet. 2014. PMID:24931394 (cited for pathway-adjacent mechanistic context).
MalaCards — Rhizomelic Dysplasia, Ain-Naz Type (RHZDAN). https://www.malacards.org/card/rhizomelic_dysplasia_ain_naz_type

Caveat on citation completeness: Several claims in this report are sourced from search-engine-synthesized summaries of the above pages rather than from directly fetched, verbatim full-text content (multiple direct WebFetch attempts to OMIM, UniProt, MalaCards, and PubMed itself were blocked or returned only page chrome in this session). Two claims (abstract text of PMID:32591345 and DOI:10.1002/ajmg.a.62933) were retrieved as verbatim quotes via the Semantic Scholar API and can be treated as exact-quote-grade evidence; all other content should be re-verified against primary sources (direct OMIM clinical synopsis, ClinVar variant records, gnomAD constraint metrics) before being committed to a knowledge-base entry, per standard curation practice for this disease.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

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

All extracted references resolved successfully.

Term Validation

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

Outcome	Count
Terms checked	62
Resolved	57
Unresolved (possible confabulation)	0
Obsolete	2
Unverifiable	3
Terms whose name was checked	47
Terms named correctly	40
Terms named as a different term	3
Terms whose name is worth a second look	4

Terms the report names something else

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

MONDO:0859203 (2 mentions) - the report calls it "MONDO"; MONDO calls it rhizomelic dysplasia, Ain-Naz type
UBERON:0002520 (1 mention) - the report calls it "epiphyseal cartilage"; UBERON calls it submandibular lymph node
UBERON:0002544 (1 mention) - the report calls it "growth plate cartilage"; UBERON calls it digit

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

GO:0016410 (obsolete N-acyltransferase activity) (1 mention) - replaced by GO:0016747
GO:0006486 (obsolete protein glycosylation) (1 mention) - replaced by GO:0009101

Terms whose name is worth a second look

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

HP:0009185 (1 mention) - the report calls it "Contracture of the PIP joint of the 5th finger"; HP calls it Contracture of the proximal interphalangeal joint of the 5th finger
GO:0016410 (1 mention) - the report calls it "N-acyltransferase activity"; GO calls it obsolete N-acyltransferase activity
GO:0004342 (1 mention) - the report calls it "glucosamine-6-phosphate N-acetyltransferase activity"; GO calls it glucosamine-6-phosphate deaminase activity, and lists "glucosamine-6-phosphate isomerase activity" among its other names
GO:0006486 (1 mention) - the report calls it "protein glycosylation"; GO calls it obsolete protein glycosylation

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, MGI.

Ask OpenScientist

OpenScientist Report

Classifications

Mappings

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Differential Diagnoses

Experimental Models

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal chain (numbered, from molecular lesion to clinical phenotype)

Molecular pathway

Cellular process

Protein dysfunction

Immune involvement

Molecular profiling / advanced technologies

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Evidence Quality and Key Gaps

Primary Sources Cited

Reference Validation

Term Validation

Terms the report names something else

Obsolete terms

Terms whose name is worth a second look

Prefixes with no resolver