Cystic Leukoencephalopathy Without Megalencephaly

Mendelian MONDO:0013058 Pathograph 17 Show in embeddings browser Leukodystrophy Lysosomal storage disorder Type I interferonopathy

Cystic leukoencephalopathy without megalencephaly is an autosomal recessive infantile white matter disorder caused by biallelic RNASET2 variants. RNASET2 is the only known acidic ribonuclease in humans; it sits in the lysosome and degrades RNA delivered there, ribosomal RNA in particular. Its defining clinical property is that it is not clinically distinguishable from something acquired. Anterior temporal subcortical cysts, multifocal lobar white matter lesions, cerebral atrophy and intracranial calcification, in an infant with psychomotor delay, spasticity and seizures, is the picture of in utero cytomegalovirus infection. A negative CMV PCR and a normal metabolic screen in a child with that MRI is the point at which RNASET2 should be sequenced. It also overlaps substantially with Aicardi-Goutieres syndrome, including CSF pleocytosis, raised CSF neopterin and an interferon signature in blood. Two accounts of the mechanism were offered separately and have now been joined up. Undegraded rRNA accumulates in lysosomes, which made the first case for reading this as a lysosomal storage disorder. The cell in which that matters is the microglion rather than the neuron: mutant microglia are engorged with undigested apoptotic cells during development, and replacing them rescues the phenotype in zebrafish. What connects the storage to the inflammation is an RNA-sensing Toll-like receptor sitting in the same endolysosomal compartment. In mice that receptor is TLR13, and deleting it reverses the whole inflammatory phenotype; a type I interferon response and early microglial pyroptosis follow, ahead of T cell infiltration and atrophy. Humans have no functional TLR13, so the human sensor is inferred rather than shown. The clinical course is characteristically non-progressive after the neonatal period. The active phase is fetal, which is why the disease sits with the congenital infections it mimics and why postnatal intervention has so far had nothing to modify.

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1
Inheritance
8
Pathophys.
9
Phenotypes
3
Gaps
17
Pathograph
1
Genes
3
Medical Actions
2
Differentials
3
Models
14
References
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Deep Research
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Inheritance

1
Autosomal recessive inheritance HP:0000007
Biallelic loss-of-function RNASET2 variants. Reported genotypes include homozygous nonsense alleles and a nonsense variant in trans with a 6q27 microdeletion spanning the gene, so copy-number analysis belongs in the workup alongside sequencing.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:19525954 SUPPORT Human Clinical
"Here we show that loss-of-function mutations in the gene encoding the RNASET2 glycoprotein lead to cystic leukoencephalopathy, an autosomal recessive disorder with an indistinguishable clinical and neuroradiological phenotype."
The gene-disease assignment and the inheritance mode, from the paper that established both.
PMID:29336640 SUPPORT Human Clinical
"We identified a novel nonsense variant c.128G>A (p. W43*) and a 430 Kb 6q27 microdeletion encompassing RNASET2."
A compound genotype in which one allele is a deletion, which is why the description above asks for copy-number analysis.
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Discussions and Knowledge Gaps

3
Is this a lysosomal storage disorder or a microglial interferonopathy?
INTERPRETATION rnaset2_storage_versus_immune
Attached to
pathophysiology#Lysosomal Accumulation of Undegraded RNA pathophysiology#Endolysosomal TLR Sensing of Accumulated Ribosomal RNA pathophysiology#Microglial Failure to Digest Apoptotic Cells
The question was live for a decade and the 2025 work has largely answered it: both, consecutively. The 2011 zebrafish study concluded the disease is a lysosomal storage disorder with rRNA as the storage material. The 2020 and 2024 zebrafish work located the earliest abnormality in microglia, tested it causally by depletion and rescue, and showed microglial replacement rescues behaviour. The missing link was how stored RNA becomes inflammation, and TLR13 supplies it - the accumulated RNA is a ligand for an endolysosomal RNA-sensing receptor sitting in the same compartment, and deleting that receptor reverses the whole inflammatory phenotype. The entry models the chain as storage, then sensing, then interferon, then microglial pyroptosis, then tissue damage. What remains genuinely unresolved is the relative weight of the two microglial routes - failed phagocytic clearance of apoptotic cells, established in zebrafish, versus TLR-driven autoinflammation, established in mouse - and whether they are the same defect seen through two model systems. Both are drawn from the same upstream node for that reason.
The receptor that drives the mouse phenotype does not exist in humans. Which sensor carries this mechanism in patients?
HUMAN MODEL MISMATCH rnaset2_tlr13_has_no_human_counterpart
Attached to
pathophysiology#Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
TLR13 is the receptor whose deletion reverses the Rnaset2-/- inflammatory phenotype, and the two 2025 studies that established it are both murine. Humans have no functional TLR13; TLR8 is its usual functional counterpart in the endolysosomal single-stranded-RNA-sensing role, and it is the inferred human sensor here. That inference is not a small step. It is a different receptor with a different ligand preference, expressed on a different set of human myeloid cells, and no patient study has shown that TLR8 carries this mechanism. Until it does, the interferon signature measurable in patients is the human evidence and the receptor identity is not. This matters therapeutically as well as descriptively: an inflammasome or TLR-directed intervention derived from the mouse would be aimed at a target the human disease may not use.
Proposed experiments
Test TLR8 dependence of the interferon response in RNASET2-deficient patient cells
rnaset2_tlr8_dependence_in_patient_cells
Derive macrophages or microglia-like cells from RNASET2-deficient patient induced pluripotent stem cells, and test whether TLR8 knockout or TLR8 antagonism abolishes the interferon-stimulated gene response that these cells show relative to isogenic controls.
Readouts
Interferon-stimulated gene expression
pathophysiology#Type I Interferon-Driven Neuroinflammation
Direction: ABOLISHED
Interpretation: Loss of the ISG response on TLR8 disruption would establish TLR8 as the human counterpart of the murine TLR13 mechanism.
If the active phase of the disease is fetal, can any postnatal intervention including microglial replacement change the outcome?
KNOWLEDGE GAP rnaset2_fetal_window
Attached to
treatments#Microglial replacement
The zebrafish rescue was performed by transplanting into embryonic hosts, and the human disease is described as already established at birth in severe cases with an apparently non-progressive course afterwards. Those two facts together are the central translational problem: the preclinical success happened inside a window that human treatment cannot currently reach. Whether a postnatal interferon-directed or cell-replacement therapy could still prevent accrued damage, or whether the damage is complete before diagnosis is possible, is unresolved and determines whether this disease has a treatable phase at all.
Proposed experiments
Post-hatching macrophage transplantation in rnaset2 mutant zebrafish
rnaset2_postnatal_transplant_window
Repeat the macrophage transplantation at successively later developmental stages, after the embryonic window in which the published rescue was performed, and test whether motor rescue and suppression of the antiviral transcriptional response are still obtained.
Readouts
Brain antiviral response transcript signature
pathophysiology#Type I Interferon-Driven Neuroinflammation
Direction: DECREASED
Interpretation: Suppression of the antiviral signature after late transplantation would indicate the therapeutic window extends beyond the embryonic period.
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Pathophysiology

8
Biallelic RNASET2 Loss-of-Function Variants
Nonsense, missense and whole-gene deletion alleles on both copies of RNASET2, a single-copy gene on chromosome 6 encoding a 256 amino acid protein.
Genetic context variant_origin: GERMLINE functional_impact_category: LOSS_OF_FUNCTION
Downstream
Loss of Lysosomal Acidic Ribonuclease Activity
Show evidence (2 references)
PMID:31349848 SUPPORT Human Clinical
"RNASET2 as a subtype of RNASEs is a 256 amino acid protein, encoded by RNASET2 gene located on chromosome six."
The gene and protein this node describes.
PMID:31349848 SUPPORT Human Clinical
"Molecular study revealed a novel homozygous variant of c.233C > A; p.Ser78Ter in exon 4 of RNASET2 gene compatible with the diagnosis of RNASET2-deficient leukoencephalopathy."
A worked homozygous nonsense genotype.
Loss of Lysosomal Acidic Ribonuclease Activity
RNASET2 is the only known acidic ribonuclease in humans. It is optimally active at pH 4 to 5, which places its activity inside the lysosome, where it degrades RNA arriving by autophagy and endocytosis. There is no redundant human enzyme for that compartment, which is why complete loss has a phenotype at all.
lysosomal acidic ribonuclease activity GO:0033897 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased lysosomal acidic ribonuclease activity, annotated with ribonuclease T2 activity (GO:0033897). GO:0033897 is a molecular function from the Gene Ontology. ↓ DECREASED
lysosome GO:0005764 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves lysosome (GO:0005764). GO:0005764 is a cellular component from the Gene Ontology.
Downstream
Lysosomal Accumulation of Undegraded RNA
Show evidence (2 references)
PMID:32295832 SUPPORT Model Organism
"RNASET2 is a single copy gene encoding the RNASET2 protein, the only known acidic ribonuclease in humans."
Establishes that there is no human paralogue for this activity, which the node's non-redundancy claim rests on. Graded by the publication, which is a zebrafish study, even though the biochemical fact quoted is general.
PMID:29752287 SUPPORT Model Organism
"Unlike other ribonuclease families, RNASET2 is optimally active in an acidic environment of pH4 to 5, which is consistent with its localization in lysosomes and vacuoles"
The pH optimum that localises the activity to the lysosome. Cited from a rodent-model paper's introduction, which is why it is graded as model-organism evidence even though the biochemistry is general.
Lysosomal Accumulation of Undegraded RNA
Mechanism confidence: Provisional
Undigested ribosomal RNA builds up inside lysosomes. This was demonstrated in rnaset2 mutant zebrafish and is the observation behind reading the disorder as a lysosomal storage disease with rRNA as the storage material. Whether the load itself is toxic, or matters mainly because it disables the lysosome for its other jobs, is the open question - and the microglial evidence points at the second.
lysosomal ribosomal RNA degradation GO:0016075 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased lysosomal ribosomal RNA degradation, annotated with rRNA catabolic process (GO:0016075). GO:0016075 is a biological process from the Gene Ontology. ↓ DECREASED
lysosome GO:0005764 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves lysosome (GO:0005764). GO:0005764 is a cellular component from the Gene Ontology.
Animal models
rnaset2 mutant zebrafish Zebrafish recapitulates Undigested rRNA accumulates within brain lysosomes, with white matter lesions on MR microimaging comparable to those in RNASET2-deficient infants.
Downstream
Microglial Failure to Digest Apoptotic Cells
Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
Show evidence (2 references)
PMID:21199949 SUPPORT Model Organism
"Further, we demonstrate that loss of rnaset2 in mutant zebrafish results in accumulation of undigested rRNA within lysosomes within neurons of the brain."
The primary demonstration of the accumulation, in the model that established it.
PMID:21199949 SUPPORT Model Organism
"Thus we conclude that familial cystic leukoencephalopathy is a lysosomal storage disorder in which rRNA is the best candidate for the noxious storage material."
The lysosomal-storage reading, quoted with the authors' own "best candidate" so the hedge is preserved.
Microglial Failure to Digest Apoptotic Cells
During normal brain development microglia clear the excess neurons produced by developmental apoptosis. In rnaset2 mutants they cannot: mutant microglia are increased in number, abnormal in morphology, engorged, and filled with undigested apoptotic cells and undigested substrate, while neurons and oligodendrocyte precursors are unaffected at the same stage. That cell-type-restricted early abnormality is the reason microglia are read as the driver rather than as a reactive population.
microglial cell CL:0000129 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves microglial cell (CL:0000129). CL:0000129 is a cell type from the Cell Ontology.
microglial clearance of developmental apoptotic cells GO:0043277 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased microglial clearance of developmental apoptotic cells, annotated with apoptotic cell clearance (GO:0043277). GO:0043277 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
rnaset2 mutant zebrafish Zebrafish recapitulates Microglia-specific depletion and rescue experiments identify microglia as the drivers of the embryonic phenotype, which is a causal test rather than an observation of correlation.
Downstream
Type I Interferon-Driven Neuroinflammation
Show evidence (2 references)
PMID:32212285 SUPPORT Model Organism
"Live imaging and electron microscopy identified that mutant microglia displayed an engorged morphology and were filled with undigested apoptotic cells and undigested substrate."
The direct observation of the failed clearance this node asserts.
PMID:32295832 SUPPORT Model Organism
"In contrast to wild-type brains, RNASET2-deficient larvae displayed increased numbers of microglia with altered morphology, often containing inclusions of neurons. Furthermore, lysosomes within distinct populations of the myeloid cell lineage including microglia showed increased lysosomal..."
An independent group's confirmation, with the crucial control that neurons and OPCs are spared at this stage.
Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
Mechanism confidence: Provisional
RNA-sensing Toll-like receptors sit in the endolysosome, the same compartment RNASET2 works in, and their normal job is to detect non-self RNA. RNASET2 processes long structured RNA into the short oligoribonucleotides those receptors read, and it also restricts recognition; without it, an RNA ligand accumulates and drives the receptor. In mice the receptor is TLR13, and the identification is genetic rather than inferential: the whole inflammatory phenotype of Rnaset2-/- mice is reversed when TLR13 is removed. The ligand is endogenous rather than microbial in the neuroinflammatory arm, because the phenotype persists in germ-free animals. This node is what connects the lysosomal storage account of the disease to the interferonopathy account - they are consecutive steps, not competing explanations.
endolysosomal RNA-sensing toll-like receptor activation GO:0002224 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased endolysosomal RNA-sensing toll-like receptor activation, annotated with toll-like receptor signaling pathway (GO:0002224). GO:0002224 is a biological process from the Gene Ontology. ↑ INCREASED
endolysosome GO:0036019 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves endolysosome (GO:0036019). GO:0036019 is a cellular component from the Gene Ontology.
Downstream
Type I Interferon-Driven Neuroinflammation
Show evidence (3 references)
PMID:39853306 SUPPORT Model Organism
"RNA-sensing TLRs are strategically positioned in the endolysosome to detect incoming nonself RNA. RNase T2 plays a critical role in processing long, structured RNA into short oligoribonucleotides that engage TLR7 or TLR8."
Establishes the compartment and the enzyme's normal relationship to these receptors, which is what makes its loss a sensing problem.
PMID:39853306 SUPPORT Model Organism
"Interestingly, this TLR13-driven inflammatory phenotype is also fully present in germ-free mice, suggesting a role for RNase T2 in limiting erroneous TLR13 activation by an as yet unidentified endogenous ligand."
The germ-free control that makes the ligand endogenous, which matters because the companion paper's liver phenotype runs on a microbiota-derived ligand instead.
PMID:39853307 SUPPORT Model Organism
"Here, we show that lysosomal RNA stress, caused by the lack of RNase T2, induces macrophage accumulation in multiple organs such as the spleen and liver through TLR13 activation by microbiota-derived ribosomal RNAs."
A second group reaching the same receptor by a different route. Note the ligand source differs from the neuroinflammatory arm above, which is why both are quoted rather than merged.
Microglial Pyroptosis
Inflammasome-mediated lytic cell death in microglia, and it arrives early. In Rnaset2-/- mice the pyroptosis markers ASC, caspase-1 and gasdermin D rise at three to six weeks and fall thereafter, while apoptotic markers stay flat throughout - so this is pyroptosis specifically, not general cell death. ASC co-localises with the microglial marker IBA-1, and T cell and TNF markers peak much later, which orders pyroptosis upstream of the adaptive infiltrate rather than alongside it.
microglial cell CL:0000129 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves microglial cell (CL:0000129). CL:0000129 is a cell type from the Cell Ontology.
microglial pyroptosis GO:0070269 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased microglial pyroptosis, annotated with pyroptotic inflammatory response (GO:0070269). GO:0070269 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Multifocal White Matter Lesions and Cystic Degeneration
Show evidence (2 references)
PMID:41453865 SUPPORT Model Organism
"Pyroptosis-related markers (ASC, CASP1, GSDMD) were significantly increased already at three to 6 weeks of age and decreased thereafter, whereas apoptotic markers such as Bax, Bad, Bid, CASP3, CASP8, and PARP were not differentially expressed compared to controls."
The timing and the apoptosis controls together, which is what makes this a pyroptosis claim rather than a cell-death claim.
PMID:41453865 SUPPORT Model Organism
"Taken together, these findings support the notion that pyroptosis is an early, disease-associated event restricted to microglia that likely contributes to establishing a proinflammatory milieu prior to T cell infiltration and brain atrophy."
The authors' ordering of pyroptosis relative to the adaptive infiltrate, quoted with their own "likely contributes" hedge.
Type I Interferon-Driven Neuroinflammation
An antiviral-pattern immune response follows in the brain: interferon-stimulated genes are upregulated, and in the mouse the resulting neuroinflammation is IFNAR1-dependent, with CD8+ effector memory T cells and inflammatory monocytes infiltrating grey and white matter. This is what places the disease among the type I interferonopathies and explains the biochemical overlap with Aicardi-Goutieres syndrome - raised CSF neopterin, CSF pleocytosis, a blood interferon signature.
microglial cell CL:0000129 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves microglial cell (CL:0000129). CL:0000129 is a cell type from the Cell Ontology.
type I interferon-mediated signaling in brain GO:0060337 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased type I interferon-mediated signaling in brain, annotated with type I interferon-mediated signaling pathway (GO:0060337). GO:0060337 is a biological process from the Gene Ontology. ↑ INCREASED
Animal models
Rnaset2 knockout mouse Mouse recapitulates Interferon-stimulated gene upregulation with IFNAR1-dependent neuroinflammation and T cell and monocyte infiltration of grey and white matter, matching the interferon signature found in patients.
Downstream
Microglial Pyroptosis
Multifocal White Matter Lesions and Cystic Degeneration
Show evidence (2 references)
PMID:34764281 SUPPORT Model Organism
"Rnaset2-/- mice demonstrate upregulation of interferon-stimulated genes and concurrent IFNAR1-dependent neuroinflammation, with infiltration of CD8+ effector memory T cells and inflammatory monocytes into the grey and white matter."
The interferon dependence, established genetically through IFNAR1, and the cellular infiltrate it drives.
PMID:27091087 SUPPORT Human Clinical
"We describe the clinical, biochemical and radiological findings of five patients demonstrating a phenotype reminiscent of AGS."
Five patients recruited on an Aicardi-Goutieres phenotype who all proved to carry biallelic RNASET2 variants. This is the human corroboration for placing the disease among the type I interferonopathies, and it comes from a human cohort rather than from a mouse paper's background section.
Multifocal White Matter Lesions and Cystic Degeneration
White matter lesions with neurodegeneration at their margins, accumulation of amyloid precursor protein and astrocytes at those sites, and anterior temporal subcortical cysts. Central white matter structures are characteristically spared, which is part of what makes the MRI pattern recognisable.
astrocyte CL:0000127 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves astrocyte (CL:0000127). CL:0000127 is a cell type from the Cell Ontology.
Animal models
RNaseT2 knockout rat Rat fails to recapitulate T1- and T2-weighted imaging showed no cystic lesions. The prefrontal cortex and hippocampal complex were enlarged rather than atrophic, which is the opposite direction from the human cerebral atrophy.
Downstream
Leukoencephalopathy
Global developmental delay
Show evidence (2 references)
PMID:21199949 SUPPORT Model Organism
"Further, by using high field intensity magnetic resonance microimaging, we reveal white matter lesions in these animals comparable to those observed in RNASET2-deficient infants. This correlates with accumulation of Amyloid precursor protein and astrocytes at sites of neurodegeneration."
The lesion pathology and its cellular correlates, with the model's own comparison to the human imaging.
PMID:27091087 SUPPORT Human Clinical
"Cystic leukoencephalopathy without megalencephaly is a disorder related in some cases to RNASET2 mutations and characterized by bilateral anterior temporal subcortical cysts and multifocal lobar white matter lesions with sparing of central white matter structures."
The human lesion distribution, including the central sparing that makes the pattern distinctive.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Cystic Leukoencephalopathy Without Megalencephaly Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

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Ear 1
Sensorineural hearing impairment HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing loss, annotated with Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:31349848 SUPPORT Human Clinical
"These individuals may show other neurological features including sensorineural hearing loss, seizures, spasticity, abnormal movements, and nystagmus"
Lists sensorineural hearing loss among the recognised features, with the source's own "may show" preserved.
PMID:29336640 REFUTE Human Clinical
"Our patient did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features."
A genetically confirmed patient without hearing loss. Graded REFUTE against the claim that this phenotype is general, which is why the description says it is not present in every patient and no frequency is recorded.
Head and Neck 1
Microcephaly OCCASIONAL HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31349848 SUPPORT Human Clinical
"Most affected newborns were asymptomatic but psychomotor developmental delay with norm/microcephaly developed gradually during the first months of life."
Records that head size is normal or small in patients, which is the frequency claim this phenotype makes, from a human source.
Musculoskeletal 2
Spasticity HP:0001257 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spasticity (HP:0001257). HP:0001257 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31349848 SUPPORT Human Clinical
"These individuals may show other neurological features including sensorineural hearing loss, seizures, spasticity, abnormal movements, and nystagmus"
The recognised neurological features in patients, quoted for the spasticity component from a human source.
Cerebral calcification OCCASIONAL HP:0002514 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intracranial calcification, annotated with Cerebral calcification (HP:0002514). HP:0002514 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27091087 SUPPORT Human Clinical
"This phenotype significantly overlaps with the sequelae of in utero cytomegalovirus (CMV) infection, including the presence of intracranial calcification in some cases."
Records the calcification, its frequency qualifier, and the mimicry it contributes to.
Nervous System 5
Leukoencephalopathy OBLIGATE HP:0002352 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cystic leukoencephalopathy, annotated with Leukoencephalopathy (HP:0002352). HP:0002352 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31349848 SUPPORT Human Clinical
"Brain imaging showed white matter involvement, calcification and anterior temporal cysts."
The imaging phenotype in a genetically confirmed patient, from a human case report rather than an animal study's background section.
Global developmental delay VERY_FREQUENT HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Psychomotor delay, annotated with Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31349848 SUPPORT Human Clinical
"Most affected newborns were asymptomatic but psychomotor developmental delay with norm/microcephaly developed gradually during the first months of life."
The developmental course in patients, from a human case report and literature review rather than from an animal study's background section.
Seizure HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Epilepsy, annotated with Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31349848 SUPPORT Human Clinical
"Recurrent seizures, psychomotor delay and regression, microcephaly, spasticity, and truncal hypotinia were the main clinical findings."
The seizure phenotype in a genetically confirmed patient. Quoted verbatim including the source's own misspelling of hypotonia.
Cerebral atrophy HP:0002059 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebral atrophy (HP:0002059). HP:0002059 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34764281 SUPPORT Model Organism
"Brain magnetic resonance imaging (MRI) reveals frontal and temporal lobe cystic lesions, multifocal white matter alterations, and cerebral atrophy"
The sentence describes the human imaging phenotype but is the background section of a mouse-model paper, so it is graded by the publication rather than by the sentence, per the rule this entry applies elsewhere. The committed human case report does not carry a cleanly quotable atrophy sentence, so no human substitute was available for this phenotype.
Dystonia HP:0001332 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dystonia (HP:0001332). HP:0001332 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29336640 REFUTE Human Clinical
"Our patient did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features."
Records dystonia as part of the expected spectrum by naming its absence in this patient as notable. Graded REFUTE against generality for the same reason as the hearing-loss item.
🧬

Genetic Associations

1
RNASET2 (Causal biallelic variant)
Gene: RNASET2 hgnc:21686 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is RNASET2 (hgnc:21686). hgnc:21686 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:29336640 SUPPORT Human Clinical
"Our patient did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features."
A genetically confirmed patient lacking the features usually treated as characteristic, which is the basis for the caution above.
PMID:27091087 SUPPORT Human Clinical
"All patients were found to carry biallelic mutations of RNASET2."
Five patients presenting as Aicardi-Goutieres syndrome who all turned out to carry biallelic RNASET2 variants, which is the strongest statement in the cited literature that this gene reaches the AGS-like end of the spectrum.
💊

Medical Actions

3
Supportive and antiepileptic care
Action: Supportive CareNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. NCIT:C15747
Platform: Other
No disease-modifying treatment exists. Management is seizure control, spasticity management, and developmental and feeding support. The disease's own natural history sets the ceiling on what postnatal treatment could achieve: the active phase appears to be fetal and the clinical course afterwards is described as apparently non-progressive.
Target Phenotypes: Epilepsy HP:0001250 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Epilepsy, annotated with Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:32212285 SUPPORT Other
"There are no treatments available for this disease as our understanding of the cellular drivers of the pathology are still unknown."
States the absence of treatment and ties it to the mechanistic gap. Graded OTHER rather than HUMAN_CLINICAL or MODEL_ORGANISM because it is a statement about the treatment landscape in a zebrafish paper's introduction, not a result of any study.
Microglial replacement
Action: Hematopoietic Cell TransplantationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Hematopoietic Cell Transplantation (NCIT:C15431). NCIT:C15431 is a clinical intervention from the NCI Thesaurus. NCIT:C15431
Platform: Cell therapy
Not an available treatment. It is recorded because the preclinical result is unusually direct: transplanting macrophages into rnaset2 mutant zebrafish embryos produced cells that engrafted in the brain, expressed microglial markers, cleared apoptotic cells, reduced the antiviral response, and restored motor activity to wild-type levels. Hematopoietic stem cell transplantation is already established in several other leukodystrophies and is thought to act by replacing microglia, which is what makes this a plausible route rather than only a model finding. What is missing is any human data in this disease, and the fetal onset raises a real question about whether postnatal replacement could arrive in time.
Mechanism Target:
Microglial Failure to Digest Apoptotic Cells — Replacing the deficient microglial population with competent transplant-derived cells restores clearance at this node, which the zebrafish work then shows resolves the downstream interferon response.
Show evidence (2 references)
PMID:38753517 SUPPORT Model Organism
"Crucially, this reduction in neuroinflammation resulted in behavioral rescue-restoring rnaset2 mutant motor activity to wild-type (WT) levels in embryonic and juvenile stages."
The functional rescue endpoint. Graded model-organism, and the treatment description says explicitly that no human data exist.
PMID:38753517 SUPPORT Model Organism
"In addition, hematopoietic stem cell (HSC) transplantation—which may act to replace microglia—is a clinically established therapy in several leukodystrophies"
The clinical precedent in other leukodystrophies that makes this a translatable route rather than only a zebrafish result.
JAK inhibition
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Platform: Small molecule
Untried in this disease and recorded as a mechanistically rational candidate, not as practice. The entry models an IFNAR1-dependent type I interferon response, and JAK inhibitors act on exactly that axis: in the monogenic type I interferonopathies where they have been used, they improved clinical and laboratory parameters and reduced interferon-stimulated gene expression. No trial, case series or case report exists in RNASET2 deficiency, and the fetal onset of this disorder raises the same window problem recorded for microglial replacement. It is listed for the same reason that candidate is: the pathograph already names the target.
Mechanism Target:
Type I Interferon-Driven Neuroinflammation — JAK inhibition acts downstream of the type I interferon receptor, so it targets this node rather than the upstream RNA-sensing step that produces the interferon.
Show evidence (1 reference)
PMID:33856640 SUPPORT INDIRECT Human Clinical
"JAK inhibitors improved clinical and analytical parameters and decreased flare numbers, plasma inflammatory markers, and expression of IFN-stimulated genes."
Efficacy in other type I interferon-mediated monogenic disorders. Recorded as INDIRECT because none of the reviewed disorders is RNASET2 deficiency; the claim reaches this disease only through the shared interferon mechanism the entry models.
🔬

Diagnosis

1
RNASET2 sequencing after negative CMV testing
The diagnosis is made by not stopping at the obvious answer. An infant with anterior temporal cysts, multifocal white matter lesions and intracranial calcification will be worked up for congenital CMV; when serum and urine CMV PCR are negative and metabolic screening is normal, RNASET2 is the gene to sequence, with copy-number analysis alongside it because one reported allele is a 430 kb deletion. RMND1 is the other Mendelian mimic worth including on the same panel.
Show evidence (2 references)
PMID:31349848 SUPPORT Human Clinical
"Basic metabolic tests were normal and CMV PCR was negative."
The negative results that redirect the workup from acquired infection to the genetic diagnosis.
PMID:31349848 SUPPORT Human Clinical
"According to clinical and imaging findings, screening of RNASET2 and RMND1 genes were performed."
The two-gene panel this diagnostic advice recommends, as actually used in a reported case.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
No population estimate exists. Eight families had been reported by 2018 and the literature has grown by single cases and small series since. The count is likely an underestimate for a specific reason: the phenotype is indistinguishable from congenital CMV infection, so undiagnosed cases sit under that label.
Show evidence (1 reference)
PMID:29336640 SUPPORT Human Clinical
"Only eight families with RNASET2 mutation have been previously reported."
The published family count, standing in for a prevalence estimate that has never been made.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Cystic Leukoencephalopathy Without Megalencephaly:

Congenital cytomegalovirus brain infection Not Yet Curated MONDO:0017409
Overlapping Features The acquired disease this disorder is indistinguishable from. Congenital CMV without symptoms at birth produces a static encephalopathy with the same brain abnormality patterns, and it is the diagnosis these children usually receive first.
Distinguishing Features
  • Serum and urine CMV PCR are negative in RNASET2 deficiency.
  • Biallelic RNASET2 variants are present in the genetic disease.
  • There is no maternal infection history or neonatal CMV detection.
Show evidence (1 reference)
PMID:19525954 SUPPORT Human Clinical
"Congenital cytomegalovirus brain infection without symptoms at birth can cause a static encephalopathy with characteristic patterns of brain abnormalities."
Describes the acquired disorder whose pattern this genetic disease reproduces.
Aicardi-Goutieres syndrome MONDO:0018866
Overlapping Features The other Mendelian mimic of congenital infection, and the closer one mechanistically: both are type I interferonopathies driven by mishandled nucleic acid. Five patients presenting as AGS turned out to carry biallelic RNASET2 variants, so this is not a theoretical overlap.
Distinguishing Features
  • AGS is caused by variants in nucleic acid metabolism and sensing genes rather than RNASET2.
  • The RNASET2 disorder has bilateral anterior temporal subcortical cysts with sparing of central white matter, which is not the AGS pattern.
  • The clinical course in RNASET2 deficiency is characteristically non-progressive after the neonatal period.
Show evidence (1 reference)
PMID:27091087 SUPPORT Human Clinical
"We describe the clinical, biochemical and radiological findings of five patients demonstrating a phenotype reminiscent of AGS."
The cohort recruited as AGS-like, which the next quoted finding then reassigns to RNASET2.
🐁

Animal Models

3
rnaset2 mutant zebrafish
The model that carries most of the mechanistic weight in this disease. Its optical transparency and ex utero development allow the embryonic phase - the phase that matters in the human disease and is inaccessible in a human fetus - to be watched directly.
Species
Zebrafish
Genotype
rnaset2 loss-of-function mutant
Publication
PMID:21199949
Pathograph links
Lysosomal Accumulation of Undegraded RNA recapitulates fidelity: high observes: cellular Undigested rRNA accumulates within brain lysosomes, with white matter lesions on MR microimaging comparable to those in RNASET2-deficient infants.
Limitations: The lesion comparison is a resemblance on imaging rather than a histopathological match to human tissue, and zebrafish white matter is not organised as human white matter is.
Show evidence (1 reference)
PMID:21199949 SUPPORT Model Organism
"Further, by using high field intensity magnetic resonance microimaging, we reveal white matter lesions in these animals comparable to those observed in RNASET2-deficient infants."
The imaging correspondence on which the model's fidelity for this node rests.
Microglial Failure to Digest Apoptotic Cells recapitulates fidelity: high observes: cellular Microglia-specific depletion and rescue experiments identify microglia as the drivers of the embryonic phenotype, which is a causal test rather than an observation of correlation.
Limitations: The causal attribution is established in zebrafish only. No human tissue study has shown that microglia are the initiating cell type in patients, and the disease's fetal timing makes such a study difficult to obtain.
Readouts
Larval motor activity
Direction: DECREASED
Interpretation: Reduced locomotor activity in mutants, restored to wild-type levels by macrophage transplantation, is the functional endpoint linking the microglial defect to whole-animal impairment.
Show evidence (1 reference)
PMID:32212285 SUPPORT Model Organism
"Our zebrafish model also presented with reduced survival and locomotor defects, therefore recapitulating many aspects of the human disease."
The behavioural readout and the authors' own claim about what it recapitulates.
Show evidence (1 reference)
PMID:32212285 SUPPORT Model Organism
"Using microglia-specific depletion and rescue experiments, we identified microglia as drivers of this embryonic phenotype and potential key cellular player in the pathology of RNAseT2-deficient leukoencephalopathy."
The causal manipulation that makes this model informative for the node rather than merely consistent with it.
Rnaset2 knockout mouse
Generated to supply the neuroinflammatory encephalopathy that earlier mouse work had failed to produce. It is the model that establishes the interferon dependence genetically.
Species
Mouse
Genotype
Rnaset2-/- (CRISPR/Cas9)
Publication
PMID:34764281
Pathograph links
Type I Interferon-Driven Neuroinflammation recapitulates fidelity: high observes: tissue Interferon-stimulated gene upregulation with IFNAR1-dependent neuroinflammation and T cell and monocyte infiltration of grey and white matter, matching the interferon signature found in patients.
Limitations: The mouse shows hippocampal-accentuated atrophy and cognitive impairment rather than the cystic anterior temporal lesions that define the human disease, so the regional distribution of damage differs even though the immunological mechanism matches.
Show evidence (1 reference)
PMID:34764281 SUPPORT Model Organism
"Single nuclei RNA sequencing reveals homeostatic dysfunctions in glial cells and neurons and provide important insights into the mechanisms of hippocampal-accentuated brain atrophy and cognitive impairment."
The regional pattern the model actually produces, which is the basis for the limitation recorded above.
RNaseT2 knockout rat
A rodent model with hippocampal neuroinflammation, altered lysosomal function and object-recognition memory deficits, but no cystic lesions.
Species
Rat
Genotype
RNaseT2 knockout
Publication
PMID:29752287
Pathograph links
Multifocal White Matter Lesions and Cystic Degeneration fails to recapitulate fidelity: low observes: tissue T1- and T2-weighted imaging showed no cystic lesions. The prefrontal cortex and hippocampal complex were enlarged rather than atrophic, which is the opposite direction from the human cerebral atrophy.
Limitations: The rat does not develop the defining lesion of the human disease, and the authors say directly that patients show a more severe neurodegenerative phenotype. It remains informative for lysosomal function and hippocampal neuroinflammation and should not be used to model the white matter pathology.
Show evidence (2 references)
PMID:29752287 REFUTE Model Organism
"While T1- and T2-weighted images of RNaseT2 knockout rats exhibited no evidence of cystic lesions, the prefrontal cortex and hippocampal complex were enlarged in knockout animals."
The negative imaging result. Graded REFUTE because it contradicts the claim that this model reproduces the cystic white matter lesion.
+ 1 more reference
{ }

Source YAML

click to show 
name: Cystic Leukoencephalopathy Without Megalencephaly
creation_date: "2026-09-09T14:10:00Z"
category: Mendelian
synonyms:
- RNASET2-deficient cystic leukoencephalopathy
- RNASET2-deficient leukodystrophy
- RNase T2-deficient leukoencephalopathy
- leukoencephalopathy, cystic, without megalencephaly
- CLWM
description: >-
  Cystic leukoencephalopathy without megalencephaly is an autosomal recessive
  infantile white matter disorder caused by biallelic RNASET2 variants. RNASET2
  is the only known acidic ribonuclease in humans; it sits in the lysosome and
  degrades RNA delivered there, ribosomal RNA in particular.

  Its defining clinical property is that it is not clinically distinguishable
  from something acquired. Anterior temporal subcortical cysts, multifocal lobar
  white matter lesions, cerebral atrophy and intracranial calcification, in an
  infant with psychomotor delay, spasticity and seizures, is the picture of in
  utero cytomegalovirus infection. A negative CMV PCR and a normal metabolic
  screen in a child with that MRI is the point at which RNASET2 should be
  sequenced. It also overlaps substantially with Aicardi-Goutieres syndrome,
  including CSF pleocytosis, raised CSF neopterin and an interferon signature in
  blood.

  Two accounts of the mechanism were offered separately and have now been joined
  up. Undegraded rRNA accumulates in lysosomes, which made the first case for
  reading this as a lysosomal storage disorder. The cell in which that matters
  is the microglion rather than the neuron: mutant microglia are engorged with
  undigested apoptotic cells during development, and replacing them rescues the
  phenotype in zebrafish. What connects the storage to the inflammation is an
  RNA-sensing Toll-like receptor sitting in the same endolysosomal compartment.
  In mice that receptor is TLR13, and deleting it reverses the whole inflammatory
  phenotype; a type I interferon response and early microglial pyroptosis follow,
  ahead of T cell infiltration and atrophy. Humans have no functional TLR13, so
  the human sensor is inferred rather than shown.

  The clinical course is characteristically non-progressive after the neonatal
  period. The active phase is fetal, which is why the disease sits with the
  congenital infections it mimics and why postnatal intervention has so far had
  nothing to modify.
disease_term:
  preferred_term: cystic leukoencephalopathy without megalencephaly
  term:
    id: MONDO:0013058
    label: cystic leukoencephalopathy without megalencephaly
parents:
- Leukodystrophy
- Lysosomal storage disorder
- Type I interferonopathy
references:
- reference: PMID:19525954
  title: RNASET2-deficient cystic leukoencephalopathy resembles congenital cytomegalovirus brain infection.
- reference: PMID:21199949
  title: rnaset2 mutant zebrafish model familial cystic leukoencephalopathy and reveal a role for RNase T2 in degrading ribosomal RNA.
- reference: PMID:32295832
  title: Zebrafish disease model of human RNASET2-deficient cystic leukoencephalopathy displays abnormalities in early microglia.
- reference: PMID:32212285
  title: The failure of microglia to digest developmental apoptotic cells contributes to the pathology of RNASET2-deficient leukoencephalopathy.
- reference: PMID:34764281
  title: Interferon-driven brain phenotype in a mouse model of RNaseT2 deficient leukoencephalopathy.
- reference: PMID:38753517
  title: Macrophage transplantation rescues RNASET2-deficient leukodystrophy by replacing deficient microglia in a zebrafish model.
- reference: PMID:29752287
  title: RNaseT2 knockout rats exhibit hippocampal neuropathology and deficits in memory.
- reference: PMID:27091087
  title: "Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome."
- reference: PMID:31349848
  title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
- reference: PMID:29336640
  title: Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
- reference: PMID:39853306
  title: RNase T2 restricts TLR13-mediated autoinflammation in vivo.
- reference: PMID:39853307
  title: RNase T2 deficiency promotes TLR13-dependent replenishment of tissue-protective Kupffer cells.
- reference: PMID:41453865
  title: "Unlocking microglia pyroptosis in a model of type I interferon-driven neuroinflammation: lessons from Rnaset2(-/-) mice."
- reference: PMID:33856640
  title: "Efficacy and Safety of Janus Kinase Inhibitors in Type I Interferon-Mediated Monogenic Autoinflammatory Disorders: A Scoping Review."
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic loss-of-function RNASET2 variants. Reported genotypes include
    homozygous nonsense alleles and a nonsense variant in trans with a 6q27
    microdeletion spanning the gene, so copy-number analysis belongs in the
    workup alongside sequencing.
  evidence:
  - reference: PMID:19525954
    reference_title: RNASET2-deficient cystic leukoencephalopathy resembles congenital cytomegalovirus brain infection.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we show that loss-of-function mutations in the gene encoding the RNASET2 glycoprotein lead to cystic leukoencephalopathy, an autosomal recessive disorder with an indistinguishable clinical and neuroradiological phenotype.
    explanation: >-
      The gene-disease assignment and the inheritance mode, from the paper that
      established both.
  - reference: PMID:29336640
    reference_title: Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified a novel nonsense variant c.128G>A (p. W43*) and a 430 Kb 6q27 microdeletion encompassing RNASET2.
    explanation: >-
      A compound genotype in which one allele is a deletion, which is why the
      description above asks for copy-number analysis.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No population estimate exists. Eight families had been reported by 2018 and
    the literature has grown by single cases and small series since. The count
    is likely an underestimate for a specific reason: the phenotype is
    indistinguishable from congenital CMV infection, so undiagnosed cases sit
    under that label.
  evidence:
  - reference: PMID:29336640
    reference_title: Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Only eight families with RNASET2 mutation have been previously reported.
    explanation: >-
      The published family count, standing in for a prevalence estimate that has
      never been made.
pathophysiology:
- name: Biallelic RNASET2 Loss-of-Function Variants
  biological_scale: MOLECULAR
  description: >-
    Nonsense, missense and whole-gene deletion alleles on both copies of
    RNASET2, a single-copy gene on chromosome 6 encoding a 256 amino acid
    protein.
  genetic_context:
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
  downstream:
  - target: Loss of Lysosomal Acidic Ribonuclease Activity
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      RNASET2 as a subtype of RNASEs is a 256 amino acid protein, encoded by RNASET2 gene located on chromosome six.
    explanation: >-
      The gene and protein this node describes.
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Molecular study revealed a novel homozygous variant of c.233C > A; p.Ser78Ter in exon 4 of RNASET2 gene compatible with the diagnosis of RNASET2-deficient leukoencephalopathy.
    explanation: >-
      A worked homozygous nonsense genotype.
- name: Loss of Lysosomal Acidic Ribonuclease Activity
  biological_scale: MOLECULAR
  description: >-
    RNASET2 is the only known acidic ribonuclease in humans. It is optimally
    active at pH 4 to 5, which places its activity inside the lysosome, where it
    degrades RNA arriving by autophagy and endocytosis. There is no redundant
    human enzyme for that compartment, which is why complete loss has a
    phenotype at all.
  cellular_components:
  - preferred_term: lysosome
    term:
      id: GO:0005764
      label: lysosome
  molecular_functions:
  - preferred_term: lysosomal acidic ribonuclease activity
    modifier: DECREASED
    term:
      id: GO:0033897
      label: ribonuclease T2 activity
  downstream:
  - target: Lysosomal Accumulation of Undegraded RNA
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:32295832
    reference_title: Zebrafish disease model of human RNASET2-deficient cystic leukoencephalopathy displays abnormalities in early microglia.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      RNASET2 is a single copy gene encoding the RNASET2 protein, the only known acidic ribonuclease in humans.
    explanation: >-
      Establishes that there is no human paralogue for this activity, which the
      node's non-redundancy claim rests on. Graded by the publication, which is
      a zebrafish study, even though the biochemical fact quoted is general.
  - reference: PMID:29752287
    reference_title: RNaseT2 knockout rats exhibit hippocampal neuropathology and deficits in memory.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Unlike other ribonuclease families, RNASET2 is optimally active in an acidic environment of pH4 to 5, which is consistent with its localization in lysosomes and vacuoles
    explanation: >-
      The pH optimum that localises the activity to the lysosome. Cited from a
      rodent-model paper's introduction, which is why it is graded as
      model-organism evidence even though the biochemistry is general.
- name: Lysosomal Accumulation of Undegraded RNA
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  description: >-
    Undigested ribosomal RNA builds up inside lysosomes. This was demonstrated
    in rnaset2 mutant zebrafish and is the observation behind reading the
    disorder as a lysosomal storage disease with rRNA as the storage material.
    Whether the load itself is toxic, or matters mainly because it disables the
    lysosome for its other jobs, is the open question - and the microglial
    evidence points at the second.
  cellular_components:
  - preferred_term: lysosome
    term:
      id: GO:0005764
      label: lysosome
  biological_processes:
  - preferred_term: lysosomal ribosomal RNA degradation
    modifier: DECREASED
    term:
      id: GO:0016075
      label: rRNA catabolic process
  downstream:
  - target: Microglial Failure to Digest Apoptotic Cells
    causal_link_type: DIRECT
  - target: Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:39853306
      reference_title: RNase T2 restricts TLR13-mediated autoinflammation in vivo.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Here, we report that the inflammatory phenotype found in Rnaset2-/- mice is completely reversed in the absence of TLR13, suggesting aberrant accumulation of an RNA ligand for this receptor.
      explanation: >-
        The genetic epistasis result that makes this edge causal rather than
        correlative: removing the receptor abolishes the phenotype, so the
        accumulated RNA is acting through it.
  evidence:
  - reference: PMID:21199949
    reference_title: rnaset2 mutant zebrafish model familial cystic leukoencephalopathy and reveal a role for RNase T2 in degrading ribosomal RNA.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Further, we demonstrate that loss of rnaset2 in mutant zebrafish results in accumulation of undigested rRNA within lysosomes within neurons of the brain.
    explanation: >-
      The primary demonstration of the accumulation, in the model that
      established it.
  - reference: PMID:21199949
    reference_title: rnaset2 mutant zebrafish model familial cystic leukoencephalopathy and reveal a role for RNase T2 in degrading ribosomal RNA.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Thus we conclude that familial cystic leukoencephalopathy is a lysosomal storage disorder in which rRNA is the best candidate for the noxious storage material.
    explanation: >-
      The lysosomal-storage reading, quoted with the authors' own "best
      candidate" so the hedge is preserved.
- name: Microglial Failure to Digest Apoptotic Cells
  biological_scale: CELLULAR
  description: >-
    During normal brain development microglia clear the excess neurons produced
    by developmental apoptosis. In rnaset2 mutants they cannot: mutant microglia
    are increased in number, abnormal in morphology, engorged, and filled with
    undigested apoptotic cells and undigested substrate, while neurons and
    oligodendrocyte precursors are unaffected at the same stage. That
    cell-type-restricted early abnormality is the reason microglia are read as
    the driver rather than as a reactive population.
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  biological_processes:
  - preferred_term: microglial clearance of developmental apoptotic cells
    modifier: DECREASED
    term:
      id: GO:0043277
      label: apoptotic cell clearance
  downstream:
  - target: Type I Interferon-Driven Neuroinflammation
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:32212285
    reference_title: The failure of microglia to digest developmental apoptotic cells contributes to the pathology of RNASET2-deficient leukoencephalopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Live imaging and electron microscopy identified that mutant microglia displayed an engorged morphology and were filled with undigested apoptotic cells and undigested substrate.
    explanation: >-
      The direct observation of the failed clearance this node asserts.
  - reference: PMID:32295832
    reference_title: Zebrafish disease model of human RNASET2-deficient cystic leukoencephalopathy displays abnormalities in early microglia.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In contrast to wild-type brains, RNASET2-deficient larvae displayed increased numbers of microglia with altered morphology, often containing inclusions of neurons. Furthermore, lysosomes within distinct populations of the myeloid cell lineage including microglia showed increased lysosomal staining. Neurons and oligodendrocyte precursor cells remained unaffected.
    explanation: >-
      An independent group's confirmation, with the crucial control that neurons
      and OPCs are spared at this stage.
- name: Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  description: >-
    RNA-sensing Toll-like receptors sit in the endolysosome, the same compartment
    RNASET2 works in, and their normal job is to detect non-self RNA. RNASET2
    processes long structured RNA into the short oligoribonucleotides those
    receptors read, and it also restricts recognition; without it, an RNA ligand
    accumulates and drives the receptor.

    In mice the receptor is TLR13, and the identification is genetic rather than
    inferential: the whole inflammatory phenotype of Rnaset2-/- mice is reversed
    when TLR13 is removed. The ligand is endogenous rather than microbial in the
    neuroinflammatory arm, because the phenotype persists in germ-free animals.
    This node is what connects the lysosomal storage account of the disease to
    the interferonopathy account - they are consecutive steps, not competing
    explanations.
  cellular_components:
  - preferred_term: endolysosome
    term:
      id: GO:0036019
      label: endolysosome
  biological_processes:
  - preferred_term: endolysosomal RNA-sensing toll-like receptor activation
    modifier: INCREASED
    term:
      id: GO:0002224
      label: toll-like receptor signaling pathway
  downstream:
  - target: Type I Interferon-Driven Neuroinflammation
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:39853306
    reference_title: RNase T2 restricts TLR13-mediated autoinflammation in vivo.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      RNA-sensing TLRs are strategically positioned in the endolysosome to detect incoming nonself RNA. RNase T2 plays a critical role in processing long, structured RNA into short oligoribonucleotides that engage TLR7 or TLR8.
    explanation: >-
      Establishes the compartment and the enzyme's normal relationship to these
      receptors, which is what makes its loss a sensing problem.
  - reference: PMID:39853306
    reference_title: RNase T2 restricts TLR13-mediated autoinflammation in vivo.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Interestingly, this TLR13-driven inflammatory phenotype is also fully present in germ-free mice, suggesting a role for RNase T2 in limiting erroneous TLR13 activation by an as yet unidentified endogenous ligand.
    explanation: >-
      The germ-free control that makes the ligand endogenous, which matters
      because the companion paper's liver phenotype runs on a microbiota-derived
      ligand instead.
  - reference: PMID:39853307
    reference_title: RNase T2 deficiency promotes TLR13-dependent replenishment of tissue-protective Kupffer cells.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we show that lysosomal RNA stress, caused by the lack of RNase T2, induces macrophage accumulation in multiple organs such as the spleen and liver through TLR13 activation by microbiota-derived ribosomal RNAs.
    explanation: >-
      A second group reaching the same receptor by a different route. Note the
      ligand source differs from the neuroinflammatory arm above, which is why
      both are quoted rather than merged.
- name: Microglial Pyroptosis
  biological_scale: CELLULAR
  description: >-
    Inflammasome-mediated lytic cell death in microglia, and it arrives early.
    In Rnaset2-/- mice the pyroptosis markers ASC, caspase-1 and gasdermin D
    rise at three to six weeks and fall thereafter, while apoptotic markers stay
    flat throughout - so this is pyroptosis specifically, not general cell death.
    ASC co-localises with the microglial marker IBA-1, and T cell and TNF markers
    peak much later, which orders pyroptosis upstream of the adaptive infiltrate
    rather than alongside it.
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  biological_processes:
  - preferred_term: microglial pyroptosis
    modifier: INCREASED
    term:
      id: GO:0070269
      label: pyroptotic inflammatory response
  downstream:
  - target: Multifocal White Matter Lesions and Cystic Degeneration
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:41453865
    reference_title: "Unlocking microglia pyroptosis in a model of type I interferon-driven neuroinflammation: lessons from Rnaset2(-/-) mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Pyroptosis-related markers (ASC, CASP1, GSDMD) were significantly increased already at three to 6 weeks of age and decreased thereafter, whereas apoptotic markers such as Bax, Bad, Bid, CASP3, CASP8, and PARP were not differentially expressed compared to controls.
    explanation: >-
      The timing and the apoptosis controls together, which is what makes this a
      pyroptosis claim rather than a cell-death claim.
  - reference: PMID:41453865
    reference_title: "Unlocking microglia pyroptosis in a model of type I interferon-driven neuroinflammation: lessons from Rnaset2(-/-) mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Taken together, these findings support the notion that pyroptosis is an early, disease-associated event restricted to microglia that likely contributes to establishing a proinflammatory milieu prior to T cell infiltration and brain atrophy.
    explanation: >-
      The authors' ordering of pyroptosis relative to the adaptive infiltrate,
      quoted with their own "likely contributes" hedge.
- name: Type I Interferon-Driven Neuroinflammation
  biological_scale: TISSUE
  description: >-
    An antiviral-pattern immune response follows in the brain: interferon-stimulated
    genes are upregulated, and in the mouse the resulting neuroinflammation is
    IFNAR1-dependent, with CD8+ effector memory T cells and inflammatory
    monocytes infiltrating grey and white matter. This is what places the disease
    among the type I interferonopathies and explains the biochemical overlap with
    Aicardi-Goutieres syndrome - raised CSF neopterin, CSF pleocytosis, a blood
    interferon signature.
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  biological_processes:
  - preferred_term: type I interferon-mediated signaling in brain
    modifier: INCREASED
    term:
      id: GO:0060337
      label: type I interferon-mediated signaling pathway
  downstream:
  - target: Microglial Pyroptosis
    causal_link_type: DIRECT
  - target: Multifocal White Matter Lesions and Cystic Degeneration
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:34764281
    reference_title: Interferon-driven brain phenotype in a mouse model of RNaseT2 deficient leukoencephalopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Rnaset2-/- mice demonstrate upregulation of interferon-stimulated genes and concurrent IFNAR1-dependent neuroinflammation, with infiltration of CD8+ effector memory T cells and inflammatory monocytes into the grey and white matter.
    explanation: >-
      The interferon dependence, established genetically through IFNAR1, and the
      cellular infiltrate it drives.
  - reference: PMID:27091087
    reference_title: "Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We describe the clinical, biochemical and radiological findings of five patients demonstrating a phenotype reminiscent of AGS.
    explanation: >-
      Five patients recruited on an Aicardi-Goutieres phenotype who all proved
      to carry biallelic RNASET2 variants. This is the human corroboration for
      placing the disease among the type I interferonopathies, and it comes from
      a human cohort rather than from a mouse paper's background section.
- name: Multifocal White Matter Lesions and Cystic Degeneration
  biological_scale: TISSUE
  description: >-
    White matter lesions with neurodegeneration at their margins, accumulation
    of amyloid precursor protein and astrocytes at those sites, and anterior
    temporal subcortical cysts. Central white matter structures are
    characteristically spared, which is part of what makes the MRI pattern
    recognisable.
  cell_types:
  - preferred_term: astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  downstream:
  - target: Leukoencephalopathy
    causal_link_type: DIRECT
  - target: Global developmental delay
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:21199949
    reference_title: rnaset2 mutant zebrafish model familial cystic leukoencephalopathy and reveal a role for RNase T2 in degrading ribosomal RNA.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Further, by using high field intensity magnetic resonance microimaging, we reveal white matter lesions in these animals comparable to those observed in RNASET2-deficient infants. This correlates with accumulation of Amyloid precursor protein and astrocytes at sites of neurodegeneration.
    explanation: >-
      The lesion pathology and its cellular correlates, with the model's own
      comparison to the human imaging.
  - reference: PMID:27091087
    reference_title: "Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cystic leukoencephalopathy without megalencephaly is a disorder related in some cases to RNASET2 mutations and characterized by bilateral anterior temporal subcortical cysts and multifocal lobar white matter lesions with sparing of central white matter structures.
    explanation: >-
      The human lesion distribution, including the central sparing that makes
      the pattern distinctive.
phenotypes:
- name: Leukoencephalopathy
  category: Neurologic
  description: >-
    Multifocal lobar white matter alterations with bilateral anterior temporal
    subcortical cysts and cerebral atrophy on MRI.
  phenotype_term:
    preferred_term: Cystic leukoencephalopathy
    term:
      id: HP:0002352
      label: Leukoencephalopathy
  frequency: OBLIGATE
  diagnostic: true
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Brain imaging showed white matter involvement, calcification and anterior temporal cysts.
    explanation: >-
      The imaging phenotype in a genetically confirmed patient, from a human
      case report rather than an animal study's background section.
- name: Global developmental delay
  category: Neurologic
  description: >-
    Psychomotor delay, the presenting feature in most patients, apparent within
    the first year.
  phenotype_term:
    preferred_term: Psychomotor delay
    term:
      id: HP:0001263
      label: Global developmental delay
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most affected newborns were asymptomatic but psychomotor developmental delay with norm/microcephaly developed gradually during the first months of life.
    explanation: >-
      The developmental course in patients, from a human case report and
      literature review rather than from an animal study's background section.
- name: Spasticity
  category: Neurologic
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These individuals may show other neurological features including sensorineural hearing loss, seizures, spasticity, abnormal movements, and nystagmus
    explanation: >-
      The recognised neurological features in patients, quoted for the
      spasticity component from a human source.
- name: Seizure
  category: Neurologic
  phenotype_term:
    preferred_term: Epilepsy
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Recurrent seizures, psychomotor delay and regression, microcephaly, spasticity, and truncal hypotinia were the main clinical findings.
    explanation: >-
      The seizure phenotype in a genetically confirmed patient. Quoted verbatim
      including the source's own misspelling of hypotonia.
- name: Microcephaly
  category: Neurologic
  description: >-
    Head circumference is normal or reduced. It is never increased, which is
    what the "without megalencephaly" in the disease name exists to say, and it
    separates this disorder from the megalencephalic cystic leukodystrophies.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most affected newborns were asymptomatic but psychomotor developmental delay with norm/microcephaly developed gradually during the first months of life.
    explanation: >-
      Records that head size is normal or small in patients, which is the
      frequency claim this phenotype makes, from a human source.
- name: Cerebral calcification
  category: Neurologic
  description: >-
    Intracranial calcification is present in some cases and is a large part of
    why the imaging is read as congenital infection or as Aicardi-Goutieres
    syndrome.
  phenotype_term:
    preferred_term: Intracranial calcification
    term:
      id: HP:0002514
      label: Cerebral calcification
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:27091087
    reference_title: "Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This phenotype significantly overlaps with the sequelae of in utero cytomegalovirus (CMV) infection, including the presence of intracranial calcification in some cases.
    explanation: >-
      Records the calcification, its frequency qualifier, and the mimicry it
      contributes to.
- name: Cerebral atrophy
  category: Neurologic
  phenotype_term:
    preferred_term: Cerebral atrophy
    term:
      id: HP:0002059
      label: Cerebral atrophy
  evidence:
  - reference: PMID:34764281
    reference_title: Interferon-driven brain phenotype in a mouse model of RNaseT2 deficient leukoencephalopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Brain magnetic resonance imaging (MRI) reveals frontal and temporal lobe cystic lesions, multifocal white matter alterations, and cerebral atrophy
    explanation: >-
      The sentence describes the human imaging phenotype but is the background
      section of a mouse-model paper, so it is graded by the publication rather
      than by the sentence, per the rule this entry applies elsewhere. The
      committed human case report does not carry a cleanly quotable atrophy
      sentence, so no human substitute was available for this phenotype.
- name: Sensorineural hearing impairment
  category: Otologic
  description: >-
    Reported among the recognised neurological features, though not in every
    patient: one genetically confirmed case is explicitly recorded as lacking
    it. No frequency has been quantified.
  phenotype_term:
    preferred_term: Sensorineural hearing loss
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These individuals may show other neurological features including sensorineural hearing loss, seizures, spasticity, abnormal movements, and nystagmus
    explanation: >-
      Lists sensorineural hearing loss among the recognised features, with the
      source's own "may show" preserved.
  - reference: PMID:29336640
    reference_title: Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our patient did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features.
    explanation: >-
      A genetically confirmed patient without hearing loss. Graded REFUTE
      against the claim that this phenotype is general, which is why the
      description says it is not present in every patient and no frequency is
      recorded.
- name: Dystonia
  category: Neurologic
  description: >-
    Abnormal movements including dystonia are reported in the phenotype
    spectrum, and are explicitly absent in at least one confirmed case.
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  evidence:
  - reference: PMID:29336640
    reference_title: Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our patient did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features.
    explanation: >-
      Records dystonia as part of the expected spectrum by naming its absence in
      this patient as notable. Graded REFUTE against generality for the same
      reason as the hearing-loss item.
genetic:
- name: RNASET2
  association: Causal biallelic variant
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: RNASET2
    term:
      id: hgnc:21686
      label: RNASET2
  notes: >-
    Single-copy gene on chromosome 6q27, encoding a 256 amino acid secreted and
    lysosomal glycoprotein. It is the only acidic ribonuclease in the human
    genome, which is why loss of it is not buffered.

    Two points for a diagnostic laboratory. Reported alleles include a 430 kb
    6q27 microdeletion spanning the gene, so sequencing alone can leave a case
    apparently heterozygous; copy-number analysis is needed. And the reported
    phenotype is not uniform even within the cystic-leukoencephalopathy label -
    one reported patient had neither the anterior temporal cysts nor the hearing
    loss usually described, so their absence does not exclude the gene.

    RNASET2 has also been associated by common-variant studies with inflammatory
    bowel disease, autoimmune thyroid disease, vitiligo and rheumatoid arthritis.
    Those are population associations at the locus and are not the Mendelian
    disease modelled here; this entry makes no claim that patients develop them.
  evidence:
  - reference: PMID:29336640
    reference_title: Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our patient did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features.
    explanation: >-
      A genetically confirmed patient lacking the features usually treated as
      characteristic, which is the basis for the caution above.
  - reference: PMID:27091087
    reference_title: "Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All patients were found to carry biallelic mutations of RNASET2.
    explanation: >-
      Five patients presenting as Aicardi-Goutieres syndrome who all turned out
      to carry biallelic RNASET2 variants, which is the strongest statement in
      the cited literature that this gene reaches the AGS-like end of the
      spectrum.
treatments:
- name: Supportive and antiepileptic care
  description: >-
    No disease-modifying treatment exists. Management is seizure control,
    spasticity management, and developmental and feeding support. The disease's
    own natural history sets the ceiling on what postnatal treatment could
    achieve: the active phase appears to be fetal and the clinical course
    afterwards is described as apparently non-progressive.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Epilepsy
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:32212285
    reference_title: The failure of microglia to digest developmental apoptotic cells contributes to the pathology of RNASET2-deficient leukoencephalopathy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      There are no treatments available for this disease as our understanding of the cellular drivers of the pathology are still unknown.
    explanation: >-
      States the absence of treatment and ties it to the mechanistic gap. Graded
      OTHER rather than HUMAN_CLINICAL or MODEL_ORGANISM because it is a
      statement about the treatment landscape in a zebrafish paper's
      introduction, not a result of any study.
- name: Microglial replacement
  description: >-
    Not an available treatment. It is recorded because the preclinical result is
    unusually direct: transplanting macrophages into rnaset2 mutant zebrafish
    embryos produced cells that engrafted in the brain, expressed microglial
    markers, cleared apoptotic cells, reduced the antiviral response, and
    restored motor activity to wild-type levels. Hematopoietic stem cell
    transplantation is already established in several other leukodystrophies and
    is thought to act by replacing microglia, which is what makes this a
    plausible route rather than only a model finding. What is missing is any
    human data in this disease, and the fetal onset raises a real question about
    whether postnatal replacement could arrive in time.
  therapeutic_modality: CELL_THERAPY
  treatment_term:
    preferred_term: Hematopoietic Cell Transplantation
    term:
      id: NCIT:C15431
      label: Hematopoietic Cell Transplantation
  target_mechanisms:
  - target: Microglial Failure to Digest Apoptotic Cells
    description: >-
      Replacing the deficient microglial population with competent
      transplant-derived cells restores clearance at this node, which the
      zebrafish work then shows resolves the downstream interferon response.
  evidence:
  - reference: PMID:38753517
    reference_title: Macrophage transplantation rescues RNASET2-deficient leukodystrophy by replacing deficient microglia in a zebrafish model.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Crucially, this reduction in neuroinflammation resulted in behavioral rescue-restoring rnaset2 mutant motor activity to wild-type (WT) levels in embryonic and juvenile stages.
    explanation: >-
      The functional rescue endpoint. Graded model-organism, and the treatment
      description says explicitly that no human data exist.
  - reference: PMID:38753517
    reference_title: Macrophage transplantation rescues RNASET2-deficient leukodystrophy by replacing deficient microglia in a zebrafish model.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In addition, hematopoietic stem cell (HSC) transplantation—which may act to replace microglia—is a clinically established therapy in several leukodystrophies
    explanation: >-
      The clinical precedent in other leukodystrophies that makes this a
      translatable route rather than only a zebrafish result.
- name: JAK inhibition
  description: >-
    Untried in this disease and recorded as a mechanistically rational
    candidate, not as practice. The entry models an IFNAR1-dependent type I
    interferon response, and JAK inhibitors act on exactly that axis: in the
    monogenic type I interferonopathies where they have been used, they improved
    clinical and laboratory parameters and reduced interferon-stimulated gene
    expression. No trial, case series or case report exists in RNASET2
    deficiency, and the fetal onset of this disorder raises the same
    window problem recorded for microglial replacement. It is listed for the
    same reason that candidate is: the pathograph already names the target.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: Type I Interferon-Driven Neuroinflammation
    description: >-
      JAK inhibition acts downstream of the type I interferon receptor, so it
      targets this node rather than the upstream RNA-sensing step that produces
      the interferon.
  evidence:
  - reference: PMID:33856640
    reference_title: "Efficacy and Safety of Janus Kinase Inhibitors in Type I Interferon-Mediated Monogenic Autoinflammatory Disorders: A Scoping Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      JAK inhibitors improved clinical and analytical parameters and decreased flare numbers, plasma inflammatory markers, and expression of IFN-stimulated genes.
    explanation: >-
      Efficacy in other type I interferon-mediated monogenic disorders. Recorded
      as INDIRECT because none of the reviewed disorders is RNASET2 deficiency;
      the claim reaches this disease only through the shared interferon
      mechanism the entry models.
diagnosis:
- name: RNASET2 sequencing after negative CMV testing
  description: >-
    The diagnosis is made by not stopping at the obvious answer. An infant with
    anterior temporal cysts, multifocal white matter lesions and intracranial
    calcification will be worked up for congenital CMV; when serum and urine CMV
    PCR are negative and metabolic screening is normal, RNASET2 is the gene to
    sequence, with copy-number analysis alongside it because one reported allele
    is a 430 kb deletion. RMND1 is the other Mendelian mimic worth including on
    the same panel.
  evidence:
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Basic metabolic tests were normal and CMV PCR was negative.
    explanation: >-
      The negative results that redirect the workup from acquired infection to
      the genetic diagnosis.
  - reference: PMID:31349848
    reference_title: "RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      According to clinical and imaging findings, screening of RNASET2 and RMND1 genes were performed.
    explanation: >-
      The two-gene panel this diagnostic advice recommends, as actually used in
      a reported case.
differential_diagnoses:
- name: Congenital cytomegalovirus brain infection
  disease_term:
    preferred_term: fetal cytomegalovirus syndrome
    term:
      id: MONDO:0017409
      label: fetal cytomegalovirus syndrome
  description: >-
    The acquired disease this disorder is indistinguishable from. Congenital CMV
    without symptoms at birth produces a static encephalopathy with the same
    brain abnormality patterns, and it is the diagnosis these children usually
    receive first.
  distinguishing_features:
  - Serum and urine CMV PCR are negative in RNASET2 deficiency.
  - Biallelic RNASET2 variants are present in the genetic disease.
  - There is no maternal infection history or neonatal CMV detection.
  evidence:
  - reference: PMID:19525954
    reference_title: RNASET2-deficient cystic leukoencephalopathy resembles congenital cytomegalovirus brain infection.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Congenital cytomegalovirus brain infection without symptoms at birth can cause a static encephalopathy with characteristic patterns of brain abnormalities.
    explanation: >-
      Describes the acquired disorder whose pattern this genetic disease
      reproduces.
- name: Aicardi-Goutieres syndrome
  disease_term:
    preferred_term: Aicardi-Goutieres syndrome
    term:
      id: MONDO:0018866
      label: Aicardi-Goutieres syndrome
  description: >-
    The other Mendelian mimic of congenital infection, and the closer one
    mechanistically: both are type I interferonopathies driven by mishandled
    nucleic acid. Five patients presenting as AGS turned out to carry biallelic
    RNASET2 variants, so this is not a theoretical overlap.
  distinguishing_features:
  - AGS is caused by variants in nucleic acid metabolism and sensing genes rather than RNASET2.
  - The RNASET2 disorder has bilateral anterior temporal subcortical cysts with sparing of central white matter, which is not the AGS pattern.
  - The clinical course in RNASET2 deficiency is characteristically non-progressive after the neonatal period.
  evidence:
  - reference: PMID:27091087
    reference_title: "Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We describe the clinical, biochemical and radiological findings of five patients demonstrating a phenotype reminiscent of AGS.
    explanation: >-
      The cohort recruited as AGS-like, which the next quoted finding then
      reassigns to RNASET2.
animal_models:
- name: rnaset2 mutant zebrafish
  species: Zebrafish
  genotype: rnaset2 loss-of-function mutant
  publication: PMID:21199949
  description: >-
    The model that carries most of the mechanistic weight in this disease. Its
    optical transparency and ex utero development allow the embryonic phase - the
    phase that matters in the human disease and is inaccessible in a human fetus
    - to be watched directly.
  modeled_mechanisms:
  - target: Lysosomal Accumulation of Undegraded RNA
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      Undigested rRNA accumulates within brain lysosomes, with white matter
      lesions on MR microimaging comparable to those in RNASET2-deficient
      infants.
    limitations: >-
      The lesion comparison is a resemblance on imaging rather than a
      histopathological match to human tissue, and zebrafish white matter is not
      organised as human white matter is.
    evidence:
    - reference: PMID:21199949
      reference_title: rnaset2 mutant zebrafish model familial cystic leukoencephalopathy and reveal a role for RNase T2 in degrading ribosomal RNA.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Further, by using high field intensity magnetic resonance microimaging, we reveal white matter lesions in these animals comparable to those observed in RNASET2-deficient infants.
      explanation: >-
        The imaging correspondence on which the model's fidelity for this node
        rests.
  - target: Microglial Failure to Digest Apoptotic Cells
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      Microglia-specific depletion and rescue experiments identify microglia as
      the drivers of the embryonic phenotype, which is a causal test rather than
      an observation of correlation.
    limitations: >-
      The causal attribution is established in zebrafish only. No human tissue
      study has shown that microglia are the initiating cell type in patients,
      and the disease's fetal timing makes such a study difficult to obtain.
    readouts:
    - name: Larval motor activity
      target: Microglial Failure to Digest Apoptotic Cells
      direction: DECREASED
      interpretation: >-
        Reduced locomotor activity in mutants, restored to wild-type levels by
        macrophage transplantation, is the functional endpoint linking the
        microglial defect to whole-animal impairment.
      evidence:
      - reference: PMID:32212285
        reference_title: The failure of microglia to digest developmental apoptotic cells contributes to the pathology of RNASET2-deficient leukoencephalopathy.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Our zebrafish model also presented with reduced survival and locomotor defects, therefore recapitulating many aspects of the human disease.
        explanation: >-
          The behavioural readout and the authors' own claim about what it
          recapitulates.
    evidence:
    - reference: PMID:32212285
      reference_title: The failure of microglia to digest developmental apoptotic cells contributes to the pathology of RNASET2-deficient leukoencephalopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Using microglia-specific depletion and rescue experiments, we identified microglia as drivers of this embryonic phenotype and potential key cellular player in the pathology of RNAseT2-deficient leukoencephalopathy.
      explanation: >-
        The causal manipulation that makes this model informative for the node
        rather than merely consistent with it.
- name: Rnaset2 knockout mouse
  species: Mouse
  genotype: Rnaset2-/- (CRISPR/Cas9)
  publication: PMID:34764281
  description: >-
    Generated to supply the neuroinflammatory encephalopathy that earlier mouse
    work had failed to produce. It is the model that establishes the interferon
    dependence genetically.
  modeled_mechanisms:
  - target: Type I Interferon-Driven Neuroinflammation
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: TISSUE
    description: >-
      Interferon-stimulated gene upregulation with IFNAR1-dependent
      neuroinflammation and T cell and monocyte infiltration of grey and white
      matter, matching the interferon signature found in patients.
    limitations: >-
      The mouse shows hippocampal-accentuated atrophy and cognitive impairment
      rather than the cystic anterior temporal lesions that define the human
      disease, so the regional distribution of damage differs even though the
      immunological mechanism matches.
    evidence:
    - reference: PMID:34764281
      reference_title: Interferon-driven brain phenotype in a mouse model of RNaseT2 deficient leukoencephalopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Single nuclei RNA sequencing reveals homeostatic dysfunctions in glial cells and neurons and provide important insights into the mechanisms of hippocampal-accentuated brain atrophy and cognitive impairment.
      explanation: >-
        The regional pattern the model actually produces, which is the basis for
        the limitation recorded above.
- name: RNaseT2 knockout rat
  species: Rat
  genotype: RNaseT2 knockout
  publication: PMID:29752287
  description: >-
    A rodent model with hippocampal neuroinflammation, altered lysosomal
    function and object-recognition memory deficits, but no cystic lesions.
  modeled_mechanisms:
  - target: Multifocal White Matter Lesions and Cystic Degeneration
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: TISSUE
    description: >-
      T1- and T2-weighted imaging showed no cystic lesions. The prefrontal
      cortex and hippocampal complex were enlarged rather than atrophic, which is
      the opposite direction from the human cerebral atrophy.
    limitations: >-
      The rat does not develop the defining lesion of the human disease, and the
      authors say directly that patients show a more severe neurodegenerative
      phenotype. It remains informative for lysosomal function and hippocampal
      neuroinflammation and should not be used to model the white matter
      pathology.
    evidence:
    - reference: PMID:29752287
      reference_title: RNaseT2 knockout rats exhibit hippocampal neuropathology and deficits in memory.
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: >-
        While T1- and T2-weighted images of RNaseT2 knockout rats exhibited no evidence of cystic lesions, the prefrontal cortex and hippocampal complex were enlarged in knockout animals.
      explanation: >-
        The negative imaging result. Graded REFUTE because it contradicts the
        claim that this model reproduces the cystic white matter lesion.
    - reference: PMID:29752287
      reference_title: RNaseT2 knockout rats exhibit hippocampal neuropathology and deficits in memory.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Overall, patients with RNASET2 deficiency exhibited a more severe neurodegeneration phenotype than was observed in the RNaseT2 knockout rats.
      explanation: >-
        The authors' own assessment of the gap between their model and the human
        disease, which supports recording this link as a failure to recapitulate.
discussions:
- discussion_id: rnaset2_storage_versus_immune
  kind: INTERPRETATION
  prompt: >-
    Is this a lysosomal storage disorder or a microglial interferonopathy?
  attaches_to:
  - pathophysiology#Lysosomal Accumulation of Undegraded RNA
  - pathophysiology#Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
  - pathophysiology#Microglial Failure to Digest Apoptotic Cells
  rationale: >-
    The question was live for a decade and the 2025 work has largely answered
    it: both, consecutively. The 2011 zebrafish study concluded the disease is a
    lysosomal storage disorder with rRNA as the storage material. The 2020 and
    2024 zebrafish work located the earliest abnormality in microglia, tested it
    causally by depletion and rescue, and showed microglial replacement rescues
    behaviour. The missing link was how stored RNA becomes inflammation, and
    TLR13 supplies it - the accumulated RNA is a ligand for an endolysosomal
    RNA-sensing receptor sitting in the same compartment, and deleting that
    receptor reverses the whole inflammatory phenotype.

    The entry models the chain as storage, then sensing, then interferon, then
    microglial pyroptosis, then tissue damage. What remains genuinely unresolved
    is the relative weight of the two microglial routes - failed phagocytic
    clearance of apoptotic cells, established in zebrafish, versus
    TLR-driven autoinflammation, established in mouse - and whether they are the
    same defect seen through two model systems. Both are drawn from the same
    upstream node for that reason.
- discussion_id: rnaset2_tlr13_has_no_human_counterpart
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    The receptor that drives the mouse phenotype does not exist in humans. Which
    sensor carries this mechanism in patients?
  attaches_to:
  - pathophysiology#Endolysosomal TLR Sensing of Accumulated Ribosomal RNA
  rationale: >-
    TLR13 is the receptor whose deletion reverses the Rnaset2-/- inflammatory
    phenotype, and the two 2025 studies that established it are both murine.
    Humans have no functional TLR13; TLR8 is its usual functional counterpart in
    the endolysosomal single-stranded-RNA-sensing role, and it is the inferred
    human sensor here. That inference is not a small step. It is a different
    receptor with a different ligand preference, expressed on a different set of
    human myeloid cells, and no patient study has shown that TLR8 carries this
    mechanism. Until it does, the interferon signature measurable in patients is
    the human evidence and the receptor identity is not.

    This matters therapeutically as well as descriptively: an inflammasome or
    TLR-directed intervention derived from the mouse would be aimed at a target
    the human disease may not use.
  proposed_experiments:
  - experiment_id: rnaset2_tlr8_dependence_in_patient_cells
    name: Test TLR8 dependence of the interferon response in RNASET2-deficient patient cells
    description: >-
      Derive macrophages or microglia-like cells from RNASET2-deficient patient
      induced pluripotent stem cells, and test whether TLR8 knockout or TLR8
      antagonism abolishes the interferon-stimulated gene response that these
      cells show relative to isogenic controls.
    readouts:
    - name: Interferon-stimulated gene expression
      target: pathophysiology#Type I Interferon-Driven Neuroinflammation
      direction: ABOLISHED
      interpretation: >-
        Loss of the ISG response on TLR8 disruption would establish TLR8 as the
        human counterpart of the murine TLR13 mechanism.
- discussion_id: rnaset2_fetal_window
  kind: KNOWLEDGE_GAP
  prompt: >-
    If the active phase of the disease is fetal, can any postnatal intervention
    including microglial replacement change the outcome?
  attaches_to:
  - treatments#Microglial replacement
  rationale: >-
    The zebrafish rescue was performed by transplanting into embryonic hosts,
    and the human disease is described as already established at birth in severe
    cases with an apparently non-progressive course afterwards. Those two facts
    together are the central translational problem: the preclinical success
    happened inside a window that human treatment cannot currently reach.
    Whether a postnatal interferon-directed or cell-replacement therapy could
    still prevent accrued damage, or whether the damage is complete before
    diagnosis is possible, is unresolved and determines whether this disease has
    a treatable phase at all.
  proposed_experiments:
  - experiment_id: rnaset2_postnatal_transplant_window
    name: Post-hatching macrophage transplantation in rnaset2 mutant zebrafish
    description: >-
      Repeat the macrophage transplantation at successively later developmental
      stages, after the embryonic window in which the published rescue was
      performed, and test whether motor rescue and suppression of the antiviral
      transcriptional response are still obtained.
    readouts:
    - name: Brain antiviral response transcript signature
      target: pathophysiology#Type I Interferon-Driven Neuroinflammation
      direction: DECREASED
      interpretation: >-
        Suppression of the antiviral signature after late transplantation would
        indicate the therapeutic window extends beyond the embryonic period.
notes: >-
  Where the human evidence stops and the model evidence starts. Almost
  everything mechanistic in this entry comes from zebrafish, mouse and rat. The
  human contribution is the gene assignment, the imaging and clinical phenotype,
  and the interferon findings in CSF and blood. Every mechanistic node carries
  MODEL_ORGANISM-graded evidence for that reason, and the two nodes with human
  corroboration (the interferon response and the lesion distribution) carry a
  human-graded item alongside. A reader should not take the microglial account as
  established in patients; it is established in zebrafish and consistent with
  what is measurable in patients.

  The rat model is recorded as FAILS_TO_RECAPITULATE against the white matter
  node, with a REFUTE-graded evidence item. That is deliberate rather than
  incidental: a negative model result is the kind of thing that otherwise
  survives only as prose, and the rat is still a useful model for lysosomal
  function and hippocampal neuroinflammation, so deleting it would lose more than
  it saved.

  A correction worth recording, because the reasoning that produced it is a
  trap. The molecular-function binding was first made to GO:0004523, RNA-DNA
  hybrid ribonuclease activity, on the stated grounds that GO had no RNase
  T2-family term. That was wrong on both counts: GO:0004523 is RNase H, which
  cleaves the RNA strand of an RNA:DNA hybrid and is a different enzyme class
  with a different substrate, and GO:0033897 ribonuclease T2 activity exists and
  is exact. The mistake came from searching the committed cache/go/terms.csv
  rather than the ontology; those CSVs are stale snapshots, and a term absent
  from them is not a term absent from GO. The binding is now GO:0033897.

  RNASET2 has a second identity that this entry does not model. Outside the
  lysosome it is a secreted, evolutionarily conserved extracellular RNase with
  described roles as an alarmin and as a tumour suppressor, and it carries
  common-variant associations with inflammatory bowel disease, autoimmune
  thyroid disease, vitiligo and rheumatoid arthritis. None of that is part of
  the Mendelian disease curated here, no patient has been reported to develop
  those conditions, and the entry makes no claim either way. It is scoped out
  explicitly so a reader meeting that literature is not left to infer a
  connection.

  Two identifiers the schema has no home for. OMIM #612951 and ORPHA:210141 both
  name this disease, and DiseaseMappings carries slots only for ICD-10-CM,
  ICD-11, MONDO and NCIT, so neither could be fielded. They are recorded here
  instead.

  No disease-specific GeneReviews chapter exists. PubMed was searched for
  "RNASET2 GeneReviews[All Fields]", which returned one result: the retired
  Leukodystrophy Overview chapter, not a chapter for this disease. The phenotype
  baseline is therefore the primary case series and the 2016 AGS-overlap cohort.
📚

References & Deep Research

References

14
PMID:19525954
RNASET2-deficient cystic leukoencephalopathy resembles congenital cytomegalovirus brain infection.
No top-level findings curated for this source.
PMID:21199949
rnaset2 mutant zebrafish model familial cystic leukoencephalopathy and reveal a role for RNase T2 in degrading ribosomal RNA.
No top-level findings curated for this source.
PMID:32295832
Zebrafish disease model of human RNASET2-deficient cystic leukoencephalopathy displays abnormalities in early microglia.
No top-level findings curated for this source.
PMID:32212285
The failure of microglia to digest developmental apoptotic cells contributes to the pathology of RNASET2-deficient leukoencephalopathy.
No top-level findings curated for this source.
PMID:34764281
Interferon-driven brain phenotype in a mouse model of RNaseT2 deficient leukoencephalopathy.
No top-level findings curated for this source.
PMID:38753517
Macrophage transplantation rescues RNASET2-deficient leukodystrophy by replacing deficient microglia in a zebrafish model.
No top-level findings curated for this source.
PMID:29752287
RNaseT2 knockout rats exhibit hippocampal neuropathology and deficits in memory.
No top-level findings curated for this source.
PMID:27091087
Clinical, radiological and possible pathological overlap of cystic leukoencephalopathy without megalencephaly and Aicardi-Goutières syndrome.
No top-level findings curated for this source.
PMID:31349848
RNASET2-deficient leukoencephalopathy mimicking congenital CMV infection and Aicardi-Goutieres syndrome: a case report with a novel pathogenic variant.
No top-level findings curated for this source.
PMID:29336640
Novel RNASET2 Pathogenic Variants in an East Asian Child with Delayed Psychomotor Development.
No top-level findings curated for this source.
PMID:39853306
RNase T2 restricts TLR13-mediated autoinflammation in vivo.
No top-level findings curated for this source.
PMID:39853307
RNase T2 deficiency promotes TLR13-dependent replenishment of tissue-protective Kupffer cells.
No top-level findings curated for this source.
PMID:41453865
Unlocking microglia pyroptosis in a model of type I interferon-driven neuroinflammation: lessons from Rnaset2(-/-) mice.
No top-level findings curated for this source.
PMID:33856640
Efficacy and Safety of Janus Kinase Inhibitors in Type I Interferon-Mediated Monogenic Autoinflammatory Disorders: A Scoping Review.
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 (1)

Create: Cystic Leukoencephalopathy Without Megalencephaly (RNASET2, MONDO:0013058) · 2026-09-09T14:17:34Z · View source

De novo curation of RNASET2-deficient cystic leukoencephalopathy, claimed on issue #11523. Deep research: one OpenScientist run (research/Cystic_Leukoencephalopathy_Without_Megalencephaly-deep-research-openscientist.md, 38 min, 14 citations). The report had no reference_validation or term_validation frontmatter block, so both sections were retro-fitted with 'just validate-research-reference' and are committed with the report. Results: 14/14 references resolved, 0 unresolved, 0 off topic; 23/25 terms resolved, 0 unresolved, 0 mislabelled, 3 name variations that are all recorded ontology synonyms (microglia/microglial cell, type I IFN signaling, pyroptosis). Nothing in the report was excluded on validation grounds. The report contributed the mechanistic step this entry would otherwise have lacked: endolysosomal RNA-sensing TLR activation as the link between lysosomal rRNA accumulation and the type I interferon response, from two 2025 companion papers (PMID:39853306, PMID:39853307), plus early microglial pyroptosis (PMID:41453865). Those three references were fetched and cited on the strength of the report. Before reading it, the entry modelled storage and interferonopathy as two competing framings in a CONTROVERSY discussion; the TLR13 epistasis result connects them into one chain, so that discussion was rewritten as INTERPRETATION and the chain now runs storage -> TLR sensing -> interferon -> microglial pyroptosis -> tissue damage. GeneReviews baseline: none exists. PubMed searched for 'RNASET2 GeneReviews[All Fields]', which returned only the retired Leukodystrophy Overview chapter (PMID:24501781), not a chapter for this disease. Phenotype baseline is therefore the primary case series and the 2016 AGS-overlap cohort. Evidence discipline. Almost all mechanism evidence here is model-organism (zebrafish, mouse, rat) and is graded as such; the two nodes with human corroboration carry a HUMAN_CLINICAL item alongside, and the notes say explicitly where human evidence stops. The rat model is recorded as FAILS_TO_RECAPITULATE against the white-matter node with a REFUTE-graded evidence item, because it does not develop the cystic lesion. A HUMAN_MODEL_MISMATCH discussion records that TLR13 has no human counterpart and TLR8 is inferred rather than shown. mechanism_confidence: PROVISIONAL is set on the storage and TLR-sensing nodes, because their supporting quotes are hedged by their own authors. Validation run in this worktree: just validate (schema + terms + references) passes, 43/43 snippets verified against cached references; just check-entity-refs and just check-causal-targets pass. Known binding limitation, recorded in the entry notes: GO has no term for lysosomal acidic ribonuclease or RNase T2-family activity, so the molecular_functions binding uses GO:0004523 (RNA-DNA hybrid ribonuclease activity) with a preferred_term stating the intended activity. This is flagged rather than left for a reader to find.

OpenScientist ▸
Cystic Leukoencephalopathy Without Megalencephaly (RNASET2-Deficient Cystic Leukoencephalopathy) — Comprehensive Disease Report
openscientist-autonomous 14 citations 2026-09-09T14:08:01.590654

Cystic Leukoencephalopathy Without Megalencephaly (RNASET2-Deficient Cystic Leukoencephalopathy) — Comprehensive Disease Report

Disease: Cystic Leukoencephalopathy Without Megalencephaly MONDO ID: MONDO:0013058 · OMIM: #612951 · Orphanet: ORPHA:210141 Causal gene: RNASET2 (6q27; HGNC:14015; alias RNASE6PL; NCBI Gene 8635; UniProt O00584) · Inheritance: Autosomal recessive Category: Mendelian, ultra-rare leukoencephalopathy / type I interferonopathy / lysosomal storage disorder

Summary

Cystic Leukoencephalopathy Without Megalencephaly is an ultra-rare, autosomal-recessive infantile leukoencephalopathy caused by biallelic loss-of-function variants in RNASET2 on chromosome 6q27, which encodes a conserved, glycosylated lysosomal T2-family acid ribonuclease. It was first defined molecularly by Henneke and colleagues in 2009, who recognized that the disorder produces a clinical and neuroradiological picture indistinguishable from congenital cytomegalovirus (CMV) brain infection — yet with negative CMV testing — making it a striking Mendelian mimic of an acquired congenital infection (PMID: 19525954).

The disease sits at the intersection of three mechanistic classes. It is a lysosomal storage disorder: RNase T2 normally degrades ribosomal RNA (rRNA) inside lysosomes, and its loss causes undigested rRNA to accumulate in neuronal lysosomes (demonstrated in zebrafish, PMID: 21199949). It is also a type I interferonopathy: the stored lysosomal RNA aberrantly engages endolysosomal RNA-sensing Toll-like receptors (TLR13 in mice, TLR8 inferred in humans), igniting an IFNAR1-dependent type I interferon response with microglial pyroptosis and infiltration of CD8+ T cells and inflammatory monocytes into brain parenchyma (mouse models, PMID: 34764281; PMID: 39853306; PMID: 41453865). This places it in clinical and pathological overlap with Aicardi–Goutières syndrome (AGS) (PMID: 27091087).

Clinically, the disorder presents in infancy with a largely static, severe encephalopathy — profound psychomotor impairment, spasticity, epilepsy, and sometimes microcephaly, hearing loss, or dystonia. The neuroradiological hallmarks are bilateral anterior temporal subcortical cysts, multifocal lobar white-matter lesions with sparing of central white matter, and intracranial calcification. Diagnosis is molecular, since imaging alone cannot separate it from congenital CMV or AGS. There is no disease-specific therapy; management is supportive, though the interferonopathy mechanism nominates JAK1/2 inhibition (baricitinib, ruxolitinib) as a biologically rational but as-yet-untrialed candidate. Fewer than a few dozen families have been reported worldwide.

Key Findings

1. RNASET2 biallelic loss-of-function is the sole known cause and produces a CMV-mimic phenotype

The founding study (Henneke et al., 2009) mapped and identified homozygous and compound heterozygous loss-of-function mutations in RNASET2 at chromosome 6q27 as the cause of an autosomal-recessive cystic leukoencephalopathy whose clinical and neuroradiological phenotype is indistinguishable from congenital CMV brain infection. The verbatim conclusion: "loss-of-function mutations in the gene encoding the RNASET2 glycoprotein lead to cystic leukoencephalopathy, an autosomal recessive disorder with an indistinguishable clinical and neuroradiological phenotype" (PMID: 19525954). The disorder carries OMIM #612951 and MONDO:0013058. Multiple subsequent families have confirmed the gene–disease relationship, including Tonduti et al. 2016 (PMID: 27091087) and Sun et al. 2018 (PMID: 29336640). (Evidence: human clinical/genetic.)

2. The disease is a lysosomal storage disorder in which rRNA is the stored material

Haud et al. (2011) generated rnaset2 mutant zebrafish and showed that RNase T2 localizes within lysosomes and that its loss causes accumulation of undigested rRNA inside neuronal lysosomes: "loss of rnaset2 in mutant zebrafish results in accumulation of undigested rRNA within lysosomes within neurons of the brain." High-field MR microimaging revealed white-matter lesions comparable to those in RNASET2-deficient infants, together with amyloid precursor protein accumulation and astrogliosis at sites of neurodegeneration. The authors concluded that "familial cystic leukoencephalopathy is a lysosomal storage disorder in which rRNA is the best candidate for the noxious storage material" (PMID: 21199949). This finding establishes both the subcellular site (lysosome, GO:0005764) and the initiating molecular lesion. (Evidence: model organism — zebrafish.)

3. RNASET2 deficiency is a type I interferonopathy driven by endolysosomal RNA-sensing TLR activation

Two 2025 companion studies converge on TLR13 as the driver of RNase T2-deficient autoinflammation in mice. Gomez-Diaz et al. showed that Rnaset2-/- mice develop interferon-dependent neuroinflammation, impaired hematopoiesis, and splenomegaly, and that "the inflammatory phenotype found in Rnaset2-/- mice is completely reversed in the absence of TLR13, suggesting aberrant accumulation of an RNA ligand for this receptor" (PMID: 39853306). Crucially, the phenotype persists in germ-free mice, indicating an endogenous rRNA-derived ligand. Sato et al. showed that "lysosomal RNA stress, caused by the lack of RNase T2, induces macrophage accumulation in multiple organs such as the spleen and liver through TLR13 activation by microbiota-derived ribosomal RNAs" (PMID: 39853307). Because humans lack functional TLR13, TLR8 is the inferred orthologous endolysosomal RNA sensor in patients. (Evidence: model organism — mouse.)

4. Microglial pyroptosis and ISG upregulation precede T-cell infiltration and brain atrophy

Wendland et al. (2025) charted the temporal cascade in Rnaset2-/- mice. Interferon-stimulated genes (IRF9, RIG-I) are sustainedly upregulated across 3–28 weeks; chemokines Ccl2, Ccl5, Cxcl10 peak early; and pyroptosis markers ASC, CASP1, and GSDMD are significantly increased at 3–6 weeks (declining thereafter) while apoptotic markers (Bax, CASP3/8, PARP) remain unchanged. ASC co-localizes with the microglial marker IBA-1, and Cd3e/Tnf peak later (~17 weeks). The authors conclude that "pyroptosis is an early, disease-associated event restricted to microglia that likely contributes to establishing a proinflammatory milieu prior to T cell infiltration and brain atrophy" (PMID: 41453865). This positions microglial pyroptosis as an early, upstream driver of neurodegeneration and nominates inflammasome/pyroptosis inhibition as a therapeutic node. (Evidence: model organism — mouse.)

5. IFNAR1 dependence proves type I interferon causality

Kettwig et al. (2021) generated CRISPR/Cas9 Rnaset2-/- mice and demonstrated that neuroinflammation is IFNAR1-dependent: "Rnaset2-/- mice demonstrate upregulation of interferon-stimulated genes and concurrent IFNAR1-dependent neuroinflammation, with infiltration of CD8+ effector memory T cells and inflammatory monocytes into the grey and white matter." Single-nuclei RNA sequencing revealed "homeostatic dysfunctions in glial cells and neurons," and the mice showed hippocampal-accentuated brain atrophy with cognitive impairment (PMID: 34764281). Genetic removal of the type I interferon receptor abrogating the phenotype provides the causal proof that type I IFN signaling — not merely storage — drives the neuropathology. (Evidence: model organism — mouse.)

6. Characteristic clinical and neuroradiological phenotype

Across reported families, the disorder is an infantile-onset, largely static encephalopathy with severe psychomotor impairment/developmental delay (the cardinal feature), spasticity, epilepsy/seizures, occasional neurological regression, and microcephaly — explicitly NOT megalencephaly. The signature MRI triad is bilateral anterior temporal subcortical cysts, multifocal lobar white-matter lesions with sparing of central white matter, and intracranial calcification: Tonduti et al. describe "bilateral anterior temporal subcortical cysts and multifocal lobar white matter lesions with sparing of central white matter structures" (PMID: 27091087), and Kameli et al. report "white matter involvement, calcification and anterior temporal cysts" (PMID: 31349848). CMV PCR is negative and metabolic screening is normal, distinguishing the disorder from its acquired mimic. Suggested HPO terms: intellectual disability (HP:0001249), global developmental delay (HP:0001263), spasticity (HP:0001257), seizure (HP:0001250), microcephaly (HP:0000252), cerebral white matter atrophy/leukoencephalopathy (HP:0002352), intracranial calcification (HP:0002514), sensorineural hearing impairment (HP:0000407), dystonia (HP:0001332). (Evidence: human clinical.)

7. Gene, protein, and representative pathogenic variants

RNASET2 encodes a 256-amino-acid acidic ribonuclease of the conserved T2 family — a glycoprotein located on chromosome 6q27 (PMID: 31349848: "RNASET2 as a subtype of RNASEs is a 256 amino acid protein, encoded by RNASET2 gene located on chromosome six"). Inheritance is autosomal recessive with biallelic loss-of-function variants. Reported pathogenic variants include the nonsense variants c.233C>A p.(Ser78Ter) (PMID: 31349848) and c.128G>A p.(Trp43Ter) (PMID: 29336640), plus a 430-kb 6q27 microdeletion encompassing RNASET2 and the compound-heterozygous/homozygous LoF alleles of the founding study (PMID: 19525954). The protein (UniProt O00584; alias RNASE6PL) carries two catalytic active-site histidines (CAS I/CAS II). (Evidence: human clinical/genetic.)

8. RNASET2 is a conserved alarmin and tumor suppressor beyond its housekeeping role

Beyond lysosomal rRNA turnover, human RNASET2 is a secreted "alarmin" and oncosuppressor that recruits and activates monocyte/macrophage-lineage innate immune cells. Rosini et al. describe that "the human RNASET2 protein (hRNASET2) has been reported as an extracellular tumor suppressor protein, endowed with the ability to act as an 'alarmin' signalling molecule" (PMID: 32450138), and Lualdi et al. document its role in "inducing a sustained recruitment of immune-competent cells belonging to the monocyte/macrophage lineage within a growing tumor mass" (PMID: 25797262). This dual identity — housekeeping lysosomal RNase and innate-immune signaling molecule — helps explain why its loss produces both storage pathology and inflammation. (Evidence: in vitro / cell biology.)

9. Phenotypic spectrum is variable; anterior temporal cysts are not obligate

The RNASET2-deficiency spectrum is broader than the classic triad. Sun et al. explicitly note that their patient "did not show anterior temporal lobe subcortical cysts, hearing loss, dystonia or extra-neurological features" (PMID: 29336640) — implying that sensorineural hearing loss and dystonia occur in other patients and that the hallmark anterior temporal cysts are variably present. Core features (delayed psychomotor development, intellectual disability, seizures) are consistent, but severity and the full imaging picture vary, indicating variable expressivity. (Evidence: human clinical.)

10. Ultra-rare, consanguinity-enriched, reported across diverse populations

As of 2018, "Only eight families with RNASET2 mutation have been previously reported" (PMID: 29336640), with additional families reported since (e.g., Tonduti 2016, 5 patients; Kameli 2019). Cases span European, East Asian/Chinese, and Iranian populations. Consanguinity contributes homozygous LoF alleles and structural microdeletions. Orphanet lists prevalence as unknown/<1 per 1,000,000. (Evidence: human epidemiological.)

11. Deep evolutionary conservation and three engineered animal models

The T2/Rh ribonuclease family is ancient and ubiquitous: "T2-family acidic endoribonucleases are represented in all genomes" (PMID: 21199949). Verified orthologs include human RNASET2 (GeneID 8635; Taxon 9606), mouse Rnaset2a/Rnaset2b (GeneIDs 100037283/68195; Taxon 10090), rat Rnaset2 (GeneID 292306; Taxon 10116), and zebrafish rnaset2 (GeneID 791890; Taxon 7955). Three engineered models exist — zebrafish (lysosomal rRNA storage + white-matter lesions), mouse (IFNAR1-dependent neuroinflammation, cystic/white-matter lesions, atrophy), and rat (hippocampal neuroinflammation and memory deficits but no cystic lesions; PMID: 29752287). No naturally occurring RNASET2 disease is documented in OMIA. (Evidence: model organism / comparative.)

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

  1. Biallelic loss-of-function variants in RNASET2 (6q27; nonsense, deletion, or microdeletion) result in absent/nonfunctional lysosomal T2-family acid ribonuclease. (Demonstrated — human genetics, PMID 19525954.)
  2. Loss of RNase T2 catalytic activity leads to failure of lysosomal ribosomal RNA degradation, so undigested rRNA accumulates within neuronal lysosomes — a lysosomal storage state. (Demonstrated — zebrafish, PMID 21199949.)
  3. Accumulated lysosomal rRNA acts as a ligand for endolysosomal RNA-sensing Toll-like receptors — TLR13 in mice (genetically proven), TLR8 inferred in humans. (Demonstrated in mouse; human step inferred — PMID 39853306, 39853307.)
  4. TLR activation drives type I interferon production and signaling, which is IFNAR1-dependent: removing IFNAR1 abrogates neuroinflammation. (Demonstrated — mouse, PMID 34764281.)
  5. Type I IFN signaling results in sustained interferon-stimulated gene (ISG) upregulation and early microglial pyroptosis (ASC/CASP1/GSDMD), establishing a proinflammatory milieu. (Demonstrated — mouse, PMID 41453865.)
  6. The proinflammatory milieu leads to infiltration of CD8+ effector-memory T cells and inflammatory monocytes into grey and white matter (branch: also splenomegaly, impaired hematopoiesis, emergency myelopoiesis systemically). (Demonstrated — mouse, PMID 34764281, 39853307.)
  7. Glial/neuronal homeostatic dysfunction and neuroinflammation cause white-matter injury, anterior temporal subcortical cysts, intracranial calcification, and cerebral (hippocampal-accentuated) atrophy. (Demonstrated across models + human imaging.)
  8. These structural lesions produce the clinical phenotype: severe, largely static infantile encephalopathy with psychomotor impairment, spasticity, epilepsy, ± microcephaly/hearing loss/dystonia. (Demonstrated — human clinical, PMID 19525954, 27091087.)
 RNASET2 biallelic LoF (6q27)
    │  loss of lysosomal acid RNase
    ▼
 Undigested rRNA storage in neuronal lysosomes  ── lysosomal storage disorder
    │  endogenous RNA ligand
    ▼
 Endolysosomal RNA-sensing TLR (TLR13 mouse / TLR8 human inferred)
    │
    ▼
 Type I interferon production ──► IFNAR1-dependent signaling ── type I interferonopathy
    │
    ├──► ISG upregulation (IRF9, RIG-I)
    ├──► EARLY microglial pyroptosis (ASC/CASP1/GSDMD)  [3–6 wk peak]
    │
    ▼
 CD8+ T-cell + inflammatory monocyte infiltration [~17 wk]
    │                                   └─(systemic: splenomegaly, myelopoiesis)
    ▼
 White-matter injury · anterior temporal cysts · calcification · atrophy
    │
    ▼
 Severe static infantile encephalopathy (CMV/AGS mimic)

Upstream vs downstream: The lysosomal storage defect (steps 1–2) is upstream and cell-intrinsic; the TLR→IFN axis (steps 3–5) is the amplifying inflammatory core; T-cell/monocyte infiltration and tissue injury (steps 6–7) are downstream effectors. The IFNAR1-knockout rescue (step 4) and TLR13-knockout rescue (step 3) identify two genetically validated intervention points.

Cell types involved (CL terms): neurons (CL:0000540), oligodendrocytes/myelin (CL:0000128), astrocytes/astrogliosis (CL:0000127), microglia (CL:0000129), infiltrating CD8+ T cells, inflammatory monocytes/macrophages. Biological processes (GO terms): lysosomal RNA catabolism (rRNA degradation), Toll-like receptor signaling pathway (GO:0002224), type I interferon-mediated signaling pathway (GO:0060337), pyroptosis (GO:0070269) / inflammasome activation, neuroinflammatory response (GO:0150076). Subcellular compartment (GO CC): lysosome (GO:0005764) — the site of the primary storage lesion.

Comparison of the three axes of pathogenesis

Mechanistic class Evidence Key node Therapeutic implication
Lysosomal storage disorder Zebrafish rRNA accumulation (PMID: 21199949) Failed rRNA degradation Substrate reduction / enzyme replacement (theoretical)
Type I interferonopathy IFNAR1-dependence (PMID: 34764281); TLR13 rescue (PMID: 39853306) TLR→IFN axis JAK1/2 inhibition; TLR blockade
Innate-immune / pyroptotic Microglial pyroptosis (PMID: 41453865) Inflammasome (ASC/CASP1/GSDMD) Inflammasome/pyroptosis inhibitors

Anatomical, Temporal, and Population Summary

Anatomy (Section 7 of template): Primary organ — brain (UBERON:0000955), nervous system. Sites — bilateral cerebral/lobar white matter (UBERON:0002316) with central white-matter sparing, anterior temporal lobe subcortical cysts (temporal lobe UBERON:0001871), basal ganglia/intracranial calcification, and cerebral atrophy including hippocampus (UBERON:0002421). Lateralization — bilateral/symmetric. Kettwig et al. confirm "cystic brain lesions, multifocal white matter alterations, cerebral atrophy" (PMID: 34764281).

Temporal development (Section 8): Onset is congenital/infantile; course is largely static (non- or slowly progressive) rather than relentlessly degenerative, though regression is described in some patients. Mouse data reveal a defined temporal order — ISGs and chemokines early, microglial pyroptosis peaking at 3–6 weeks, T-cell infiltration ~17 weeks — suggesting an early critical window for anti-inflammatory intervention before irreversible atrophy.

Inheritance & population (Section 9): Autosomal recessive; ultra-rare (<1/1,000,000). Consanguinity-enriched; founder-type homozygous LoF and microdeletions occur. Reported in European, Chinese/East Asian, and Iranian families. No strong sex bias reported. Penetrance appears high for biallelic LoF; expressivity is variable (see Finding 9). No genetic anticipation, mosaicism, or repeat-expansion mechanism is implicated.

Diagnostics (Section 10): Diagnosis is molecular (single-gene RNASET2 testing, leukodystrophy gene panels, WES, or WGS; chromosomal microarray detects the 6q27 microdeletion), because MRI cannot distinguish the disorder from congenital CMV or AGS. Supportive workup: negative CMV PCR, normal metabolic screening, characteristic MRI triad. Differential diagnosis — congenital CMV infection, Aicardi–Goutières syndrome, and other cystic leukoencephalopathies (e.g., megalencephalic leukoencephalopathy, which by contrast features macrocephaly). A blood interferon signature (ISG score) would be expected to support the interferonopathy classification, though it is not yet validated as a routine test in this disorder.

Prognosis (Section 11): Severe neurodevelopmental disability; course largely static with lifelong dependency. Morbidity is high (spasticity, epilepsy, cognitive impairment). Formal survival statistics are not established given rarity.

Treatment (Section 12): No disease-specific therapy. Care is symptomatic/supportive — antiepileptics (NCIT anticonvulsant agents), spasticity management (e.g., baclofen), physiotherapy/occupational/speech therapy, developmental support. JAK1/2 inhibitors (baricitinib, ruxolitinib, tofacitinib) are a mechanistically rational, untrialed candidate given the interferonopathy classification; a scoping review of type I interferonopathies found that "JAK inhibitors improved clinical and analytical parameters and decreased flare numbers, plasma inflammatory markers, and expression of IFN-stimulated genes" (PMID: 33856640). Preclinical work additionally nominates inflammasome/pyroptosis inhibition (PMID: 41453865).

Prevention (Section 13): No primary prevention exists. Relevant measures are genetic counseling, carrier testing in consanguineous families, cascade testing, and prenatal/preimplantation genetic testing where a familial variant is known.

Other species / models (Sections 14–15): No naturally occurring animal disease documented in OMIA. Three engineered models — zebrafish (faithful lysosomal storage + white-matter lesions), mouse (best recapitulation: interferonopathy, cystic/white-matter pathology, atrophy, cognitive deficits), and rat (hippocampal neuroinflammation and memory deficits, but lacks cystic lesions). A 2024 review documents zebrafish as a leukodystrophy model (PMID: 38239149).

Evidence Base

PMID Title (abbrev.) Evidence type Supports
19525954 RNASET2-deficient cystic leukoencephalopathy resembles congenital CMV Human genetics/clinical Gene–disease causality; CMV mimic (F001, F005, F006)
21199949 rnaset2 mutant zebrafish model familial cystic leukoencephalopathy… Model organism (zebrafish) Lysosomal rRNA storage mechanism; conservation (F002, F011, F013)
27091087 Clinical, radiological and pathological overlap … and AGS Human clinical MRI triad; AGS overlap (F005, F008)
29336640 Novel RNASET2 pathogenic variants in an East Asian child Human genetics/clinical Variants; rarity; phenotypic variability (F006, F009, F010)
31349848 Kameli et al., RNASET2 case Human clinical/genetic Protein size/location; variant; imaging (F005, F006)
34764281 Kettwig et al., Rnaset2-/- mice Model organism (mouse) IFNAR1-dependence; cellular infiltrate (F011, F012, F014)
39853306 Gomez-Diaz et al., TLR13 Model organism (mouse) TLR13 as driver; interferonopathy (F003, F014)
39853307 Sato et al., lysosomal RNA stress Model organism (mouse) TLR13/rRNA link; myelopoiesis (F003)
41453865 Wendland et al., microglial pyroptosis Model organism (mouse) Early pyroptosis cascade (F004)
29752287 Sinkevicius et al., RNaseT2 KO rat Model organism (rat) Rat model characteristics (F011)
25797262 Lualdi et al., RNASET2 alarmin In vitro Alarmin/immune recruitment (F007)
32450138 Rosini et al., hRNASET2 tumor suppressor In vitro Alarmin/tumor-suppressor identity (F007)
33856640 Gómez-Arias et al., JAK inhibitors in interferonopathies Human clinical (scoping review) Rational therapy (F008)
38239149 Review — zebrafish leukodystrophy models Review Model relevance (F014)

How the evidence coheres: Human genetics (PMID 19525954) established causality; zebrafish (PMID 21199949) defined the storage mechanism; and a series of rodent models (PMID 34764281, 39853306/07, 41453865) built the inflammatory arc, culminating in two genetically validated intervention points (TLR13, IFNAR1). No study contradicts the consolidated model; the primary uncertainty is translational (the human TLR8-vs-mouse-TLR13 inference).

Limitations and Knowledge Gaps

  • Human TLR identity unproven. The TLR13 dependence is established only in mice; humans lack functional TLR13, so the orthologous sensor (TLR8 is the leading candidate) has not been experimentally confirmed in patient cells. This is the single most important translational gap.
  • No human trial data for any disease-modifying therapy. JAK inhibition and inflammasome/pyroptosis inhibition are mechanistically rational but entirely untrialed in this disease; efficacy, blood–brain-barrier penetration, and timing (early critical window) are unknown.
  • Small evidence base for epidemiology and natural history. With only a few dozen reported families, prevalence, penetrance, expressivity, sex ratio, and survival statistics are imprecise. No formal registry or natural-history cohort exists.
  • Genotype–phenotype correlations are undefined. It is unclear why some patients lack anterior temporal cysts or develop hearing loss/dystonia while others do not; modifier genes and environmental modifiers are unexplored.
  • Static-vs-progressive course. The relative contributions of a fixed developmental lesion versus ongoing inflammation to the "static" clinical picture are not fully resolved, which matters for whether late anti-inflammatory therapy could help.
  • Human neuropathology is limited. Most cellular/mechanistic detail derives from animal models; direct confirmation of microglial pyroptosis and the ISG signature in human brain tissue is sparse.
  • No epigenetic, proteomic, or metabolomic patient datasets were identified for this disease; molecular profiling remains model-based.

Proposed Follow-up Experiments / Actions

  1. Confirm the human sensor. Test whether patient-derived macrophages/microglia (iPSC-derived) or RNASET2-knockout human cells show TLR8-dependent type I IFN induction; use TLR8 antagonists and CRISPR knockout to establish the human ortholog of the mouse TLR13 axis.
  2. Preclinical JAK-inhibitor trial in Rnaset2-/- mice. Test whether baricitinib/ruxolitinib started within the early critical window (before the 3–6-week pyroptosis peak) prevents ISG upregulation, T-cell infiltration, and hippocampal atrophy, with dose–timing arms to define the intervention window.
  3. Inflammasome/pyroptosis blockade. Evaluate GSDMD or CASP1/NLRP3 inhibitors (or genetic Gsdmd deletion) in Rnaset2-/- mice to test whether interrupting microglial pyroptosis is sufficient to blunt downstream neuroinflammation.
  4. Interferon signature as a biomarker. Measure a blood ISG score (IFI27, IFI44L, IFIT1, ISG15, etc.) in RNASET2-deficient patients to confirm the human interferonopathy signature and provide a pharmacodynamic readout for future trials.
  5. Establish an international registry / natural-history study to capture prevalence, genotype–phenotype correlations (including the variable temporal cysts, hearing loss, dystonia), progression, and survival.
  6. Substrate-reduction and enzyme-replacement feasibility. Explore whether reducing lysosomal rRNA load (e.g., modulating ribophagy) or delivering functional RNase T2 to the CNS is achievable, addressing the upstream storage lesion rather than only the inflammatory consequence.
  7. Human tissue validation. Where autopsy/biopsy material is available, confirm microglial pyroptosis, ISG expression, and CD8+ T-cell infiltration in patient brain to close the model-to-human gap.

Report compiled from 14 confirmed findings across 5 iterations, drawing on 14 primary and review references. Evidence types are annotated per finding (human clinical/genetic, model organism, in vitro, review). Ontology suggestions: MONDO:0013058, HGNC:14015 (RNASET2), UniProt O00584, GO:0005764 (lysosome), GO:0060337 (type I IFN signaling), GO:0070269 (pyroptosis), UBERON:0000955/0002316/0001871/0002421, CL:0000129 (microglia)/0000540 (neuron)/0000128 (oligodendrocyte)/0000127 (astrocyte).

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 14
Resolved 14
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 14
On topic 7
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 25
Resolved 23
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 2
Terms whose name was checked 4
Terms named correctly 1
Terms named as a different term 0
Terms whose name is worth a second look 3

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:

  • CL:0000129 (2 mentions) - the report calls it "microglia"; CL calls it microglial cell, and lists "microglia" among its other names
  • GO:0060337 (2 mentions) - the report calls it "type I IFN signaling"; GO calls it type I interferon-mediated signaling pathway, and lists "type I interferon signaling pathway" among its other names
  • GO:0070269 (2 mentions) - the report calls it "pyroptosis"; GO calls it pyroptotic inflammatory response, and lists "pyroptosis" among its other names

Prefixes with no resolver

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

23 of 25 terms resolved to a current term; the rest could not be looked up either way.