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Classifications

Harrison's Part

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Inheritance

1

Autosomal recessive HP:0000007

Biallelic (usually homozygous) TRAPPC4 variants are required. Most reported families are consanguineous and homozygous for the recurrent c.454+3A>G splice variant; heterozygous carriers are clinically unaffected and the carrier frequency of that allele in healthy individuals is on the order of a few per 10,000.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:42543852 SUPPORT Human Clinical

"Neurodevelopmental disorder with spasticity, epilepsy and brain atrophy (NEDESBA) is a rare autosomal recessive condition, first described in 2020."

States the autosomal recessive mode of inheritance directly.

PMID:31794024 SUPPORT Human Clinical

"All seven affected subjects shared the same identical rare, homozygous, potentially pathogenic variant in a non-canonical, well-conserved splice site within TRAPPC4"

Homozygosity in all affected children of three unrelated families, with unaffected heterozygous parents, establishes recessive inheritance.

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Pathophysiology

11

Biallelic TRAPPC4 Loss of Function

Biallelic pathogenic variants in TRAPPC4 (11q23.3; historical protein name synbindin) reduce the amount or function of TRAPPC4, one of the small core subunits shared by the TRAPPII and TRAPPIII complexes. The overwhelmingly predominant allele worldwide is the recurrent non-canonical splice variant NM_016146.5:c.454+3A>G (hg19:chr11:g.118890966A>G), found homozygously in almost every reported family, mostly in the setting of consanguinity. Single nucleotide polymorphism array analysis found no shared haplotype between a Turkish and a Caucasian family, favouring a recurrent mutational hotspot over a single ancient founder allele. A small number of families carry other biallelic alleles: novel missense variants c.191T>C p.(Leu64Pro) and c.278C>T p.(Pro93Leu) in two Indian families, and a biallelic in-frame deletion causing stop-loss in one family with a milder phenotype. Because the recurrent splice allele is leaky, residual correctly spliced transcript persists; complete loss of this essential core subunit is thought to be incompatible with survival.

TRAPPC4 hgnc:19943

Downstream

Aberrant TRAPPC4 Pre-mRNA Splicing and Transcript Loss The recurrent c.454+3A>G allele acts at the RNA level, disrupting the splice donor of exon 3.

Show evidence (4 references)

PMID:31794024 SUPPORT Human Clinical

"All seven affected subjects shared the same identical rare, homozygous, potentially pathogenic variant in a non-canonical, well-conserved splice site within TRAPPC4 (hg19:chr11:g.118890966A>G; TRAPPC4: NM_016146.5; c.454+3A>G)."

Establishes the founding genotype and the exact recurrent allele.

PMID:31794024 SUPPORT Human Clinical

"Single nucleotide polymorphism array analysis revealed there was no haplotype shared between the tested Turkish and Caucasian families suggestive of a variant hotspot region rather than a founder effect."

Supports the description of the recurrent allele as a mutational hotspot rather than a proven founder variant.

PMID:34878169 SUPPORT Human Clinical

"We report three individuals from two Indian families harboring novel bi-allelic missense variants c.191T>C and c.278C>T (NM_016146.6) in TRAPPC4 with classic clinical presentation in one and milder and later onset in the other family."

Documents pathogenic TRAPPC4 alleles other than the recurrent splice variant, showing the mechanism is gene-level rather than allele-specific.

+ 1 more reference

Aberrant TRAPPC4 Pre-mRNA Splicing and Transcript Loss

The c.454+3A>G variant lies in the intron 3 splice donor region. RNA studies in patient cells show that it is an incompletely penetrant (leaky) splice defect: full-length TRAPPC4 transcript is reduced while a shorter transcript lacking exon 3 accumulates. RNA sequencing further resolved partial exon 3 skipping plus use of a downstream cryptic splice donor site, producing an aberrant transcript with a premature termination codon that is predicted to be degraded by nonsense-mediated decay. The net effect is a dosage reduction of normal TRAPPC4 protein rather than production of a dominant-negative product.

patient-derived dermal fibroblast CL:0000057

mRNA splicing, via spliceosome GO:0000398 ⚠ ABNORMAL nonsense-mediated mRNA decay of the aberrant TRAPPC4 transcript GO:0000184 ↑ INCREASED

Downstream

Reduced TRAPP Complex Assembly and Stability Less full-length TRAPPC4 protein is available to incorporate into the TRAPP complex.

Show evidence (2 references)

PMID:31794024 SUPPORT In Vitro

"experimental evidence showed both a reduction in full-length transcript levels and an increase in levels of a shorter transcript missing exon 3, suggestive of an incompletely penetrant splice defect"

Direct transcript-level demonstration of the leaky splice defect in patient cells.

PMID:32901138 SUPPORT In Vitro

"Based upon RNA sequencing, the variant resulted in partial exon 3 skipping and generation of an aberrant transcript owing to use of a downstream cryptic splice donor site, predicting a premature stop codon and nonsense mediated decay."

Resolves the precise mis-splicing event and the nonsense-mediated-decay route to transcript loss.

Reduced TRAPP Complex Assembly and Stability

TRAPPC4 is one of the small core subunits present in every TRAPP complex, and all four core subunits are essential for cell viability. Reduced TRAPPC4 protein selectively destabilizes the assembled machine: in patient fibroblasts TRAPPC4 protein levels fall while the levels of other TRAPP subunits are unchanged, yet native gel electrophoresis and size exclusion chromatography reveal a defect in assembly and/or stability of the intact complex. The lesion is therefore at the level of the holo-complex, not of an individual partner subunit.

patient-derived dermal fibroblast CL:0000057

TRAPP complex GO:0030008

Downstream

Impaired RAB1 Guanine Nucleotide Exchange Factor Activity The GEF active site is formed across several core subunits, so a destabilized complex has reduced exchange activity.

Show evidence (4 references)

PMID:31794024 SUPPORT In Vitro

"TRAPPC4 protein levels were significantly reduced whilst levels of other TRAPP complex subunits remained unaffected."

Shows the protein-level deficit is specific to TRAPPC4.

PMID:31794024 SUPPORT In Vitro

"Native polyacrylamide gel electrophoresis and size exclusion chromatography demonstrated a defect in TRAPP complex assembly and/or stability."

Direct biochemical demonstration of the complex-assembly defect.

PMID:32116085 SUPPORT In Vitro

"This variant results in lower levels of full-length TRAPPC4 protein and the TRAPP complex."

Independent restatement that both the subunit and the complex are reduced.

+ 1 more reference

Impaired RAB1 Guanine Nucleotide Exchange Factor Activity

The TRAPP complexes are Rab guanine-nucleotide-exchange factors: TRAPPIII activates RAB1 (the master regulator of the early secretory pathway and of the first step of macroautophagy) and TRAPPII activates RAB11. TRAPPC4 and its yeast orthologue Trs23 are among the essential subunits for the RAB1 GEF activity, and structural work localizes the exchange site to a conserved surface spanning several core subunits, so a destabilized core lowers exchange activity rather than abolishing a discrete catalytic site. Reduced RAB1 activation leaves less RAB1-GTP available on donor and acceptor membranes to recruit long coiled-coil tethers.

TRAPP complex GO:0030008

RAB1 guanyl-nucleotide exchange factor activity GO:0005085 ↓ DECREASED

Downstream

Impaired ER-to-Golgi Vesicular Tethering and Golgi Transit RAB1-GTP is required to tether COPII vesicles at the cis-Golgi.

Defective Autophagosome Formation and Autophagic Flux RAB1 is required for the first step of macroautophagy.

Show evidence (4 references)

PMID:31794024 SUPPORT Other

"TRAPPC4, like its yeast Trs23 orthologue, is a core component of the TRAPP complexes and one of the essential subunits for guanine nucleotide exchange factor activity for Rab1 GTPase."

Identifies TRAPPC4 as essential for the RAB1 GEF activity of TRAPP. Tagged OTHER rather than HUMAN_CLINICAL because this is a statement of established molecular cell biology in the paper's introduction, not an observation made on the patients.

PMID:39769094 SUPPORT Other

"TRAPP complexes comprise a core complex, TRAPPI, and the association of peripheral protein subunits to make two complexes, known as TRAPPII and TRAPPIII, which act as Guanine Nucleotide Exchange Factors (GEFs) of Rab11 and Rab1, respectively."

Review statement defining the division of GEF labour between TRAPPII/RAB11 and TRAPPIII/RAB1 that the core subunit is shared between.

PMID:34018214 SUPPORT In Vitro

"TRAPPII activates Rab11, and TRAPPIII activates Rab1, with the two complexes sharing a core of small subunits that affect nucleotide exchange but being distinguished by specific large subunits that are essential for activity in vivo."

Structural evidence that the shared small-subunit core (which includes TRAPPC4) is the part that governs nucleotide exchange.

+ 1 more reference

Impaired ER-to-Golgi Vesicular Tethering and Golgi Transit

The functional consequence in patient cells is a secretory-pathway defect. Using the temperature-sensitive Golgi cargo marker VSVG-GFP-ts045, patient fibroblasts show significantly delayed entry into and exit from the Golgi apparatus. The defect is a direct consequence of reduced TRAPPC4 dosage rather than of an unrelated cellular abnormality, because lentiviral expression of wild-type TRAPPC4 in the same fibroblasts restores normal trafficking. Relative to the autophagy arm below, the secretory defect is the milder of the two.

patient-derived dermal fibroblast CL:0000057

endoplasmic reticulum to Golgi vesicle-mediated transport GO:0006888 ↓ DECREASED vesicle-mediated transport GO:0016192 ⚠ ABNORMAL

Golgi apparatus GO:0005794 endoplasmic reticulum GO:0005783

Downstream

Neuronal Secretory and Autophagic Failure Chronic secretory-pathway impairment is presumed to be poorly tolerated by long-lived, highly polarized neurons.

Show evidence (3 references)

PMID:31794024 SUPPORT In Vitro

"Intracellular trafficking through the Golgi using the marker protein VSVG-GFP-ts045 demonstrated significantly delayed entry into and exit from the Golgi in fibroblasts derived from one of the affected subjects."

Direct cell-biological demonstration of the Golgi trafficking delay.

PMID:31794024 SUPPORT In Vitro

"Lentiviral expression of wild-type TRAPPC4 in these fibroblasts restored trafficking, suggesting that the trafficking defect was due to reduced TRAPPC4 levels."

Genetic rescue establishes causality between TRAPPC4 dosage and the defect.

PMID:32901138 SUPPORT Other

"Trafficking protein particle (TRAPP) complexes, which include the TRAPPC4 protein, regulate membrane trafficking between lipid organelles in a process termed vesicular tethering."

Identifies vesicular tethering as the process disrupted.

Defective Autophagosome Formation and Autophagic Flux

The second and, on current evidence, more severe cellular consequence is a macroautophagy defect. Patient fibroblasts have a basal autophagy defect and a delay in autophagic flux, attributed to autophagosomes that fail to seal. The same dissociation is reproduced in a yeast trs23 temperature-sensitive model, which shows constitutive and stress-induced autophagic defects at the permissive temperature while the secretory defect appears only at the restrictive temperature, i.e. autophagy is the more dosage-sensitive output of the core TRAPP complex.

patient-derived dermal fibroblast CL:0000057

autophagy GO:0006914 ↓ DECREASED autophagosome assembly GO:0000045 ⚠ ABNORMAL macroautophagy GO:0016236 ↓ DECREASED

Downstream

Neuronal Secretory and Autophagic Failure Post-mitotic neurons depend on autophagy for proteostasis and cannot dilute undegraded cargo by division.

Show evidence (4 references)

PMID:31794024 SUPPORT In Vitro

"we found that the fibroblasts had a basal autophagy defect and a delay in autophagic flux, possibly due to unsealed autophagosomes"

Direct demonstration of the autophagy defect in patient cells.

PMID:31794024 SUPPORT Model Organism

"These results were validated using a yeast trs23 temperature sensitive variant that exhibits constitutive and stress-induced autophagic defects at permissive temperature and a secretory defect at restrictive temperature."

Orthologous yeast model confirms the defect and shows autophagy is affected at a milder degree of subunit loss than secretion.

PMID:32116085 SUPPORT In Vitro

"Similarly, primary fibroblasts derived from human patients also exhibit minor and severe defects in secretion and autophagy, respectively."

Quantifies the relative severity of the two arms in human patient cells (secretion minor, autophagy severe).

+ 1 more reference

Neuronal Secretory and Autophagic Failure

The step from a fibroblast phenotype to a brain phenotype is the least directly evidenced link in the chain and is currently a well-motivated hypothesis rather than a demonstrated fact. The proposal, advanced by the discovery group, is that a chronic low-grade autophagy defect is especially harmful to neurons, which are post-mitotic, long-lived and unusually dependent on membrane trafficking and proteostasis. A second, neuron-specific route is suggested by TRAPPC4/synbindin biology: through its atypical PDZ-like domain synbindin binds the cytoplasmic tail of syndecan-2, and the synbindin/syndecan complex participates in synaptic membrane trafficking and dendritic spine morphogenesis, so reduced TRAPPC4 may also impair synapse formation and maturation directly. Neither route has been tested in patient-derived neurons.

neuron CL:0000540 cortical pyramidal neuron CL:0000598

regulation of dendritic spine development GO:0060998 ⚠ ABNORMAL intracellular protein transport GO:0006886 ↓ DECREASED

Downstream

Cortical Network Hyperexcitability and Epileptic Encephalopathy The intermediate steps linking trafficking failure to seizure generation in this disorder are not established.

Progressive Cerebral and Cerebellar Neurodegeneration Cumulative neuronal proteostatic failure is the presumed but untested driver of the atrophy.

Corticospinal Tract Dysfunction and Spasticity Upper-motor-neuron involvement follows cortical and white-matter loss.

Show evidence (4 references)

PMID:32116085 SUPPORT In Vitro

"Moreover, we hypothesize that low levels of the core TRAPP complex are more detrimental to autophagy than to secretion, and that the long-term autophagy defect is especially harmful to neuronal cells."

The explicit hypothesis linking the cellular defect to neuronal vulnerability; framed as a hypothesis by its authors, hence mechanism_confidence HYPOTHETICAL.

PMID:32116085 SUPPORT In Vitro

"We propose that the autophagy defect caused by the pathogenic-TRAPPC4 variant results in the severe neurological disorder."

States the causal proposal directly; the supporting data are from fibroblasts and yeast, not neurons, so support is partial.

PMID:34878169 SUPPORT Other

"This synbindin/syndecan complex plays a role in synaptic membrane trafficking, thereby regulating dendritic spine morphogenesis"

Supports the second, synapse-directed route by which reduced TRAPPC4 could affect neurons, and is the reason the reported missense variants in the atypical PDZ-like domain are considered plausible.

+ 1 more reference

Cortical Network Hyperexcitability and Epileptic Encephalopathy

Seizures are a defining feature and typically begin within the first six months of life, with onset in the first year in nearly all affected individuals. Semiology is varied: epileptic spasms, focal, tonic, atonic and generalized tonic-clonic seizures are all described. The electroencephalogram is not specific but shows epileptiform abnormalities, generalized disorganization and, in the more advanced cases, a strikingly low voltage background that tracks the cortical atrophy. Response to antiseizure medication is often only partial.

cortical pyramidal neuron CL:0000598

cerebral cortex UBERON:0000956

Downstream

Arrest of Psychomotor Development with Regression Early-onset, poorly controlled epileptic activity contributes to the developmental arrest characteristic of an epileptic encephalopathy.

Show evidence (2 references)

PMID:32901138 SUPPORT Human Clinical

"Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant showed profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly and progressive spastic tetraplegia."

Establishes early-onset epilepsy as a core feature of the largest cohort.

PMID:36211171 SUPPORT Human Clinical

"A variety of seizures, including spasms, occur early in NEDESBA. Epileptiform abnormalities, generalized disorganization and very low voltage background activity are reported."

Describes seizure semiology and the accompanying EEG signature.

Corticospinal Tract Dysfunction and Spasticity

Upper-motor-neuron signs dominate the motor examination. Spasticity affects all four limbs (spastic quadriparesis/tetraplegia) with brisk deep tendon reflexes, and it is progressive, ultimately contributing to complete loss of independent mobility. Spasticity is frequently refractory to baclofen and physical rehabilitation.

cerebral white matter UBERON:0002316

Downstream

Arrest of Psychomotor Development with Regression Spastic tetraplegia is a direct barrier to the acquisition of motor milestones such as sitting and walking.

Show evidence (2 references)

PMID:31794024 SUPPORT Human Clinical

"seven affected children that showed features of early-onset seizures, developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis and progressive cortical and cerebellar atrophy"

Spastic quadriparesis in all seven children of the founding cohort.

PMID:34878169 SUPPORT Human Clinical

"On re-evaluation at one year-two months, he had failure to thrive, dystonia, spasticity and brisk deep tendon reflexes."

Documents the upper-motor-neuron pattern (spasticity with hyperreflexia).

Progressive Cerebral and Cerebellar Neurodegeneration

Neuroimaging converts this from a static developmental disorder into a neurodegenerative one. Brain MRI shows a variable but progressive degree of cerebral cortical atrophy that is more severe in older children, commonly accompanied by cerebellar atrophy, enlarged subarachnoid spaces, white-matter volume loss with delayed myelination, ventriculomegaly and a thin corpus callosum. Serial imaging in individual patients documents the progression directly: repeat scans within months can show new severe cortical atrophy. The progressive brain volume loss is also the substrate for the progressive postnatal microcephaly.

neuron CL:0000540

neuron apoptotic process GO:0051402 ↑ INCREASED

brain UBERON:0000955 cerebral cortex UBERON:0000956 cerebellum UBERON:0002037 corpus callosum UBERON:0002336

Downstream

Arrest of Psychomotor Development with Regression Ongoing loss of brain volume underlies the loss of previously acquired milestones.

Show evidence (3 references)

PMID:36211171 SUPPORT Human Clinical

"Brain MRI findings show a variable degree of progressive cerebral atrophy with an increased severity in older age."

Establishes that the cerebral atrophy is progressive rather than static.

PMID:36211171 SUPPORT Human Clinical

"In the presented patient, spasms and very low voltage activity on EEG early in the course, led to a second MRI showing severe cortical atrophy, indicating the progressive course of the disease."

Serial imaging in a single patient directly documenting progression.

PMID:31794024 SUPPORT Human Clinical

"spastic quadriparesis and progressive cortical and cerebellar atrophy"

Progressive cortical and cerebellar atrophy in the founding cohort.

Arrest of Psychomotor Development with Regression

The organism-level outcome is a profound, essentially complete arrest of psychomotor development, with loss of the few milestones that were attained. Affected children do not walk or speak, cannot feed themselves and develop feeding difficulties and failure to thrive, and remain profoundly dependent. Because the substrate is a degenerative process superimposed on a developmental one, the trajectory is one of stagnation followed by decline rather than of slow ongoing gains. Death in the first decade, most often from intercurrent infection, is reported in a minority.

Show evidence (3 references)

PMID:32901138 SUPPORT Human Clinical

"Here, we report 23 patients from 17 independent families with an early-infantile-onset neurodegenerative presentation"

Frames the disorder as an early-infantile neurodegenerative presentation.

PMID:34878169 SUPPORT Human Clinical

"Regression of achieved milestones is seen in addition to delayed milestones in most individuals with this condition."

Documents regression on top of delay as the characteristic trajectory.

PMID:36211171 SUPPORT Human Clinical

"Some patients exhibit frequent infections, which can lead to death in the first decade, at a mean age of 8.8 years."

Documents the reported mortality and its usual proximate cause.

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Pathograph

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Phenotypes

33

Digestive 1

Feeding difficulties HP:0011968

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"P1 presented in the early infantile period with developmental delay, feeding difficulties and seizures as observed in most of the individuals with recurrent splicing TRAPPC4 variant"

Documents feeding difficulties as an early presenting feature seen in most individuals with the recurrent variant.

Ear 1

Sensorineural hearing impairment HP:0000407

Show evidence (2 references)

PMID:31794024 SUPPORT Human Clinical

"developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis"

Sensorineural deafness reported in the founding cohort.

PMID:34878169 SUPPORT Human Clinical

"Hearing evaluation was suggestive of non-recordable hearing response bilaterally."

Documents severe hearing impairment in an individually reported patient.

Eye 3

Visual impairment HP:0000505

Show evidence (2 references)

PMID:36211171 SUPPORT Human Clinical

"Eye problems occur in most of the TRAPPC4 patients with absence of pursuit and optic atrophy."

Establishes visual involvement in most patients.

PMID:34878169 SUPPORT Human Clinical

"Hearing and ophthalmological abnormalities (cortical visual defects, no tracking, roving eye movements, nystagmus and optic atrophy) as seen in P1 are also reported in 30 out of 31 previously affected individuals"

Enumerates the specific ophthalmological abnormalities reported.

Optic atrophy HP:0000648

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"Our patient also developed optic atrophy, which was not present at the first ophthalmological examination."

Documents the acquired, progressive nature of the optic atrophy.

Nystagmus HP:0000639

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"cortical visual defects, no tracking, roving eye movements, nystagmus and optic atrophy"

Nystagmus listed among the reported ophthalmological abnormalities.

Head and Neck 2

Long philtrum HP:0000343

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide mouth, thin and tinted upper lip, and pointed chin"

A long philtrum (spelled "long filtrum" in the source) is listed in the facial gestalt.

Pointed chin HP:0000307

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide mouth, thin and tinted upper lip, and pointed chin"

A pointed chin is listed in the facial gestalt.

Metabolism 1

Elevated creatine kinase Elevated circulating creatine kinase concentration HP:0003236

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"Elevated CPK were also observed in P1 and P3, thus reiterating the significance of assessing CPK levels for this condition."

Documents elevated creatine kinase in reported patients.

PMID:36211171 SUPPORT Human Clinical

"However, our patient had normal serum CK and lactate levels without any muscle involvement."

Counter-example establishing that CK elevation and muscle involvement are not universal features.

Nervous System 14

Profound global developmental delay HP:0012736

Show evidence (2 references)

PMID:32901138 SUPPORT Human Clinical

"Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant showed profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly and progressive spastic tetraplegia."

Profound psychomotor delay reported across the largest cohort.

PMID:31794024 SUPPORT Human Clinical

"seven affected children that showed features of early-onset seizures, developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis and progressive cortical and cerebellar atrophy"

Developmental delay in all seven children of the discovery cohort.

Developmental regression HP:0002376

Course: PROGRESSIVE

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"Regression of achieved milestones is seen in addition to delayed milestones in most individuals with this condition."

Direct statement that regression occurs in most affected individuals.

PMID:32901138 SUPPORT Human Clinical

"profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly and progressive spastic tetraplegia"

Regression listed as a core cohort feature.

Seizures FREQUENT HP:0001250

Temporal: RECURRENT

Frequency band derived from the count of 23 out of 31 individuals with the recurrent splicing variant reported to have early-onset seizures (74%), which falls in the FREQUENT (30-79%) band. Essentially all reported individuals develop seizures at some point, but the quotable count is for early onset.

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"Early-onset seizures (two months to six months) were noted in 23 out of 31 individuals with recurrent splicing variant along with P1 (one year)."

Provides both the age of onset and the quantitative denominator used for the frequency band.

PMID:32901138 SUPPORT Human Clinical

"profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly and progressive spastic tetraplegia"

Early-onset epilepsy as a core cohort feature.

Generalized tonic-clonic seizures Bilateral tonic-clonic seizure HP:0002069

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"They presented with generalized tonic-clonic seizures at seven years of age."

Documents generalized tonic-clonic seizures in reported patients.

EEG abnormality HP:0002353

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"Epileptiform abnormalities, generalized disorganization and very low voltage background activity are reported."

Describes the reported EEG abnormalities.

Hyperreflexia HP:0001347

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"On re-evaluation at one year-two months, he had failure to thrive, dystonia, spasticity and brisk deep tendon reflexes."

Documents brisk deep tendon reflexes in a reported patient.

Movement disorder (dystonia, ataxia, tremor) HP:0001332

The literature review reports involuntary movements in 12 of 33 individuals (36%). No `frequency` band is asserted here, because that count aggregates dystonia, ataxia and tremor and cannot be attributed to the bound term (HP:0001332 Dystonia) alone; per the frequency-evidence guidelines the band is omitted rather than over-attributed. The aggregate figure is retained in this note so the underlying data are not lost.

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"Involuntary movements in the form of ataxia, tremors and dystonia which were previously reported in 12 out of 33 individuals, were also noted in P1 and P2."

Documents ataxia, tremor and dystonia as the movement-disorder phenotypes of this condition. The aggregate 12-of-33 count covers all three together, so it is retained in notes rather than asserted as a frequency band on any single bound term.

Ataxia HP:0001251

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"Involuntary movements in the form of ataxia, tremors and dystonia which were previously reported in 12 out of 33 individuals"

Ataxia reported among the involuntary movements in this disorder.

Absent or severely limited speech Absent speech HP:0001344

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"Affected siblings attained age-appropriate motor milestones, however speech delay was noted in early childhood (three years). They could speak only small sentences at the age of five years."

Documents the language impairment, and in the mildest family shows the residual-speech end of the spectrum.

Cerebral cortical atrophy HP:0002120

Course: PROGRESSIVE

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"Marked cerebral atrophy is seen in those with recurrent splicing variant and was observed in P1 in the current study."

Cerebral atrophy in patients with the recurrent variant.

PMID:36211171 SUPPORT Human Clinical

"Brain MRI findings show a variable degree of progressive cerebral atrophy with an increased severity in older age."

Establishes progression of the cortical atrophy with age.

Cerebellar atrophy FREQUENT HP:0001272

Frequency band derived from the reported count of 21 out of 27 individuals (78%), which falls at the top of the FREQUENT (30-79%) band.

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"Cerebellar atrophy, another significant finding reported in 21 out of 27 individuals with TRAPPC4 variant, was not observed in individuals from our study."

Supplies the numerator/denominator for the frequency band and documents that the finding is not universal.

PMID:31794024 SUPPORT Human Clinical

"progressive cortical and cerebellar atrophy"

Cerebellar atrophy in the founding cohort.

Abnormal cerebral white matter Abnormal cerebral white matter morphology HP:0002500

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"Non-specific white matter abnormalities (delayed myelination, white matter volume loss, hyperintensities in periventricular region), thin corpus callosum and ventriculomegaly are also frequent imaging findings."

Describes the white-matter findings and their frequency.

Delayed myelination HP:0012448

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"MRI brain performed at four-months of age showed delayed myelination, dilated ventricles, hyperintensities in the periventricular white matter on T2-weighted (T2W) axial sections"

Documents delayed myelination on infant MRI in a reported patient.

Ventriculomegaly HP:0002119

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"thin corpus callosum and ventriculomegaly are also frequent imaging findings"

Ventriculomegaly listed among frequent imaging findings.

PMID:36211171 SUPPORT Human Clinical

"Enlarged subarachnoid spaces, loss of white matter, enlarged ventricles and cerebellar atrophy have also been reported frequently."

Independent confirmation of enlarged ventricles as a frequent finding.

Growth 1

Failure to thrive HP:0001508

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"On re-evaluation at one year-two months, he had failure to thrive, dystonia, spasticity and brisk deep tendon reflexes."

Failure to thrive documented in a reported patient.

Other 10

Severe to profound intellectual disability HP:0002187

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"Cognitive delay too has been consistently noted in all the reported individuals, including the individuals in our study, except for two individuals of a family reported by Saad et al."

Establishes that cognitive impairment is a consistent feature across every reported individual, with the mildest (stop-loss) family as the only exception.

PMID:42543852 SUPPORT Human Clinical

"Variants in these genes typically result in overlapping clinical features, including microcephaly, early-onset epilepsy, intellectual disability, neurodevelopmental regression, spasticity and abnormal brain MRI findings."

Intellectual disability listed among the core overlapping features.

Epileptic spasms Infantile spasms HP:0012469

Show evidence (2 references)

PMID:36211171 SUPPORT Human Clinical

"A variety of seizures, including spasms, occur early in NEDESBA."

Documents spasms among the early seizure types.

PMID:42543852 SUPPORT Human Clinical

"Here, we report a 13-month-old affected male born to consanguineous parents, presenting with epileptic spasms and progressive neurodevelopmental delay."

Epileptic spasms as the presenting seizure type in a reported infant.

Progressive microcephaly HP:0000253

Course: PROGRESSIVE

Show evidence (2 references)

PMID:34878169 SUPPORT Human Clinical

"TRAPPC4-related neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy (MIM# 618741) is a recently described TRAPPopathy with clinical findings of developmental delay, seizures, postnatal microcephaly, spasticity, facial dysmorphism, and cerebral and cerebellar atrophy."

Explicitly identifies the microcephaly as postnatal (i.e. acquired/progressive).

PMID:36211171 SUPPORT Human Clinical

"Patients all had progressive microcephaly due to severe brain atrophy, spastic quadriparesis, early-onset seizures, profound developmental delay"

States that the microcephaly is progressive and attributes it to the underlying brain atrophy.

Spastic tetraplegia HP:0002510

Course: PROGRESSIVE

Show evidence (2 references)

PMID:32901138 SUPPORT Human Clinical

"profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly and progressive spastic tetraplegia"

Progressive spastic tetraplegia as a core cohort feature.

PMID:31794024 SUPPORT Human Clinical

"microcephaly, sensorineural deafness, spastic quadriparesis and progressive cortical and cerebellar atrophy"

Spastic quadriparesis in the founding cohort.

Inability to walk HP:0002540

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"All individuals with NEDESBA, except for P2 and P3, either showed complete absence of motor development or had significant motor delay."

Documents the near-universal absence of motor development that precludes walking, with the mild family as the stated exception.

Thin corpus callosum HP:0033725

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"thin corpus callosum and ventriculomegaly are also frequent imaging findings"

Thin corpus callosum listed among frequent imaging findings.

Elevated circulating lactate Increased circulating lactate concentration HP:0002151

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"Additionally, P1 also had elevated serum lactate levels as observed in two individuals reported by Kaur et al. (2020) and Ghosh et al. (2020)."

Documents elevated lactate in a minority of reported patients.

Narrow forehead (bitemporal narrowing) HP:0000341

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"common facial dysmorphic features including bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide mouth, thin and tinted upper lip, and pointed chin"

Enumerates the facial gestalt, of which bitemporal narrowing (narrow forehead) is the anchoring HPO-codable element.

Thick eyebrow HP:0000574

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide mouth, thin and tinted upper lip, and pointed chin"

Thick eyebrows listed in the facial gestalt.

Full cheeks HP:0000293

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide mouth, thin and tinted upper lip, and pointed chin"

Full cheeks are listed in the facial gestalt.

🧬

Genetic Associations

1

TRAPPC4

Gene: TRAPPC4 hgnc:19943 relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal recessive

Show evidence (4 references)

PMID:31794024 SUPPORT Human Clinical

"This is the first report of a TRAPPC4 variant, and our findings add to the growing number of TRAPP-associated neurological disorders."

The founding gene-disease association.

PMID:32901138 SUPPORT Human Clinical

"These data confirm the pathogenicity of the TRAPPC4 c.454+3A>G variant, and refine the clinical presentation of TRAPPC4-related encephalopathy."

Independent multicentre confirmation of the gene-disease relationship.

PMID:34878169 SUPPORT Human Clinical

"of the 33 individuals from 22 families reported to date, 31 individuals from 21 families have been reported with a recurrent homozygous pathogenic variant"

Quantifies how strongly the allelic spectrum is dominated by one variant.

+ 1 more reference

💊

Medical Actions

5

Antiseizure pharmacotherapy

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: anticonvulsant agent NCIT:C264 levetiracetam CHEBI:6437 topiramate CHEBI:63631

Symptomatic treatment of the epilepsy. Levetiracetam, topiramate, clobazam and valproate have all been used; responses are frequently partial and seizures may persist or recur despite escalation, so drug substitution is common. No disease-modifying therapy exists.

Target Phenotypes: Seizure HP:0001250

Show evidence (2 references)

PMID:36211171 SUPPORT Human Clinical

"She was put on levetiracetam (LEV) treatment, although infrequent clonic seizures occurred despite LEV therapy of 40 mg/kg/day."

Documents levetiracetam use and the incomplete response that motivated a drug change; support is PARTIAL because efficacy was incomplete.

PMID:36211171 SUPPORT Human Clinical

"She had had no obvious seizure on topiramate treatment of 5 mg/kg/day."

Documents seizure control achieved after switching to topiramate.

Spasticity management

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: baclofen CHEBI:2972

Antispasticity pharmacotherapy, in reported practice baclofen, combined with a physical rehabilitation programme. Reported responses are poor: spasticity persisted despite baclofen and rehabilitation in a documented patient, so expectations should be set accordingly.

Target Phenotypes: Spastic tetraplegia HP:0002510

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"persistent spasticity in spite of baclofen treatment and a physical rehabilitation program were noted"

Documents baclofen plus rehabilitation as the treatment used, and its limited effect; hence PARTIAL rather than SUPPORT.

Rehabilitation and supportive therapy

Category: Therapeutic Action: Physical Therapy NCIT:C15302

Multidisciplinary physical, occupational and communication therapy for the profound motor and developmental impairment. Rehabilitation is supportive and does not alter the progressive course.

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"persistent spasticity in spite of baclofen treatment and a physical rehabilitation program were noted"

Documents that a physical rehabilitation programme forms part of management.

Nutritional and feeding support

Category: Therapeutic Action: Nutritional Support NCIT:C15433

Management of feeding difficulties, regurgitation and failure to thrive, with enteral or tube feeding when oral intake becomes unsafe or insufficient.

Target Phenotypes: Feeding difficulties HP:0011968

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"P1 presented in the early infantile period with developmental delay, feeding difficulties and seizures"

Establishes the feeding difficulty that this supportive measure addresses.

Genetic counseling and reproductive options

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

Autosomal recessive inheritance carries a 25% recurrence risk for each subsequent pregnancy. Because the recurrent c.454+3A>G allele has a measurable carrier frequency in the general population, on the order of a few per 10,000 and highest in Mediterranean and European ancestries, cascade carrier testing of relatives and, once the familial allele is known, prenatal or preimplantation testing are the practical preventive options.

Show evidence (2 references)

PMID:36211171 SUPPORT Human Clinical

"Carrier frequency of this neurodevelopmental and neurodegenerative disorder, NEDESBA, has been reported to be relatively high, varying from 2.4-5.4 per 10 000 individuals worldwide"

The carrier frequency that makes cascade testing and carrier screening a meaningful part of counseling.

PMID:40173375 SUPPORT Human Clinical

"Given a relatively high carrier frequency, it is crucial to recognize and consider this diagnosis."

Independent statement of the counseling/recognition imperative.

🔬

Diagnosis

5

Exome or Genome Sequencing (Diagnostic when biallelic pathogenic TRAPPC4 variants are identified)

Diagnosis is molecular. The clinical picture, an early-infantile epileptic encephalopathy with progressive microcephaly, spasticity and brain atrophy, overlaps a large number of neurometabolic and neurodegenerative disorders and has no specific biomarker, so unbiased broad sequencing is the practical first-line test. A thorough metabolic workup is commonly (and reasonably) performed first to exclude treatable mimics, but it is normal in this disorder.

whole exome sequencing NCIT:C101295

Results: Biallelic pathogenic TRAPPC4 variants. In practice this is nearly always homozygosity for the recurrent splice variant NM_016146.5:c.454+3A>G; biallelic missense and in-frame/stop-loss alleles account for the remainder.

Show evidence (2 references)

PMID:42543852 SUPPORT Human Clinical

"Whole exome sequencing revealed a homozygous splice-site variant (c.454+3A>G) in the TRAPPC4 gene, confirming the diagnosis of NEDESBA."

Documents exome sequencing as the diagnostic route actually used.

PMID:36211171 SUPPORT Human Clinical

"Before proceeding to next-generation sequencing, a thorough metabolic workup in order to exclude neurodegenerative diseases, which may present with a similar phenotype is advisable."

Supports the described sequencing-after-metabolic-screen diagnostic pathway.

Sanger Confirmation and Parental Segregation

Targeted Sanger sequencing confirms the candidate variant and demonstrates biallelic inheritance by showing both parents to be heterozygous carriers, which is particularly important for a non-canonical splice-region variant whose pathogenicity is not self-evident from the DNA sequence alone.

molecular genetic testing NCIT:C15709

Results: Proband homozygous, both parents heterozygous for the familial TRAPPC4 allele.

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"Segregation analysis by Sanger sequencing showed both healthy parents were heterozygous for the same variant."

Documents the Sanger segregation step in a reported diagnosis.

RNA Analysis of the Splice Variant

Transcript analysis (RT-PCR or RNA sequencing of patient fibroblasts) is the functional test that establishes pathogenicity of the recurrent splice-region allele. It is diagnostically valuable because a non-canonical +3 intronic variant can be filtered out or deprioritized by standard exome pipelines.

RNA sequencing NCIT:C124261

Results: Reduced full-length TRAPPC4 transcript with partial exon 3 skipping and use of a downstream cryptic splice donor, generating a premature termination codon subject to nonsense-mediated decay.

Show evidence (1 reference)

PMID:32901138 SUPPORT In Vitro

"Based upon RNA sequencing, the variant resulted in partial exon 3 skipping and generation of an aberrant transcript owing to use of a downstream cryptic splice donor site, predicting a premature stop codon and nonsense mediated decay."

The RNA-level finding that establishes pathogenicity of the splice allele.

Brain Magnetic Resonance Imaging

Cranial MRI is the principal phenotyping investigation. It is supportive rather than diagnostic, but the combination of progressive cortical (and usually cerebellar) atrophy with enlarged subarachnoid spaces in an infant with severe microcephaly and early seizures is what should prompt TRAPPC4 testing. Serial imaging is more informative than a single scan because it demonstrates progression.

brain magnetic resonance imaging NCIT:C16809

Results: Progressive cerebral cortical atrophy, cerebellar atrophy in most, enlarged subarachnoid spaces, white-matter volume loss and delayed myelination, thin corpus callosum, ventriculomegaly.

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"In patients presenting with severe microcephaly, typical dysmorphic facial features, early-onset seizures with very low voltage, abnormal EEG and progressive cortical atrophy, a TRAPPC4-related neurodevelopmental disorder should be considered in the differential diagnosis of neurodegenerative diseases."

States the imaging-plus-clinical trigger for considering the diagnosis.

Electroencephalography

EEG documents the epilepsy and, over serial recordings, the progressive background voltage suppression that parallels cortical atrophy. Findings are supportive and non-specific.

electroencephalography NCIT:C38054

Results: Epileptiform discharges with generalized disorganization; progressively very low voltage background in advanced disease.

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"Epileptiform abnormalities, generalized disorganization and very low voltage background activity are reported."

Describes the EEG findings that the investigation yields.

📈

Progression

4

Onset

Age: First months of life (early infancy)

Pregnancy and the neonatal period are usually unremarkable. Global developmental impairment becomes apparent within the first months, and seizures typically begin between two and six months of age (within the first year in nearly all patients).

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"Early-onset seizures (two months to six months) were noted in 23 out of 31 individuals with recurrent splicing variant along with P1 (one year)."

Establishes the typical age at seizure onset.

Developmental stagnation and regression

Age: Infancy to early childhood

Almost no psychomotor progress is made, and the few milestones that were attained are lost. Head growth decelerates and the child becomes spastic and tetraplegic. This is the phase in which the disorder declares itself as neurodegenerative rather than static.

Show evidence (1 reference)

PMID:32901138 SUPPORT Human Clinical

"Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant showed profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly and progressive spastic tetraplegia."

Describes the stagnation-plus-regression phase of the natural history.

Progressive brain atrophy

Age: Infancy through childhood

Serial MRI shows worsening cerebral (and usually cerebellar) atrophy, more severe in older children. Repeat imaging within a few months of presentation can already show new severe cortical atrophy. Optic atrophy may likewise appear during follow-up having been absent initially.

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"In the presented patient, spasms and very low voltage activity on EEG early in the course, led to a second MRI showing severe cortical atrophy, indicating the progressive course of the disease."

Serial imaging documenting the progressive phase.

Late complications and mortality

Age: First decade

Profound dependence, refractory spasticity and epilepsy, and susceptibility to intercurrent infection. Death in the first decade is reported in a minority, at a mean age of about 8.8 years. Mortality is deliberately recorded here rather than as a phenotype, because HP:0003819 ("Death in childhood") sits under Clinical modifier rather than Phenotypic abnormality and so is not a valid phenotype_term in this schema.

Show evidence (1 reference)

PMID:36211171 SUPPORT Human Clinical

"Some patients exhibit frequent infections, which can lead to death in the first decade, at a mean age of 8.8 years."

Documents the late phase and its mortality.

📊

Prevalence

2

Worldwide

Cases In Literature Ultra Rare

No population prevalence or incidence study exists. The founding report described seven children from three unrelated families (2020); a subsequent multicentre series added 23 patients from 17 independent families (2021), and by 2022 a review counted 33 individuals from 22 families. Later case reports have added a small number of further patients. Published counts overlap substantially between cohorts and must not be summed as independent cases.

Show evidence (1 reference)

PMID:34878169 SUPPORT Human Clinical

"of the 33 individuals from 22 families reported to date, 31 individuals from 21 families have been reported with a recurrent homozygous pathogenic variant"

Documents the small cumulative number of reported individuals and families.

Healthy individuals (GeneDx and 100,000 Genomes cohorts)

Carrier Frequency 39.0 per 100,000 (24.0–54.0) 1–9 per 10,000

Heterozygous carrier frequency of the recurrent NM_016146.5:c.454+3A>G allele, reported as 2.4-5.4 per 10,000 healthy individuals (i.e. 24-54 per 100,000). This is a carrier frequency for one allele, not a disease prevalence; the disorder itself remains ultra-rare.

Show evidence (2 references)

PMID:32901138 SUPPORT Human Clinical

"We found the carrier frequency of TRAPPC4 c.454+3A>G was 2.4-5.4 per 10,000 healthy individuals."

Direct quantitative statement of the carrier frequency.

PMID:36211171 SUPPORT Human Clinical

"varying from 2.4-5.4 per 10 000 individuals worldwide, and mostly frequent in Mediterranean and European ancestries"

Independent restatement of the carrier frequency with ancestry distribution.

🔀

Differential Diagnoses

6

Conditions with similar clinical presentations that must be differentiated from Neurodevelopmental Disorder with Epilepsy, Spasticity, and Brain Atrophy:

TRAPPC6B-related neurodevelopmental disorder (NEDMEBA) Not Yet Curated MONDO:0060640

Overlapping Features Biallelic TRAPPC6B variants cause a neurodevelopmental disorder with microcephaly, epilepsy and autistic features, with cortical atrophy, thin corpus callosum and, in some, cerebellar and brainstem atrophy. Like NEDESBA it is a core-subunit TRAPPopathy caused by a founder splice mutation in a consanguineous population.

Distinguishing Features

Causal gene: TRAPPC6B, not TRAPPC4.
The TRAPPC6B phenotype is substantially milder - affected individuals walk, have autistic features and ataxic gait, and survive into adulthood with only slow progression, whereas NEDESBA patients typically never walk or speak.
Zebrafish trappc6b morphants recapitulate the microcephaly and neuronal hyperexcitability; no comparable vertebrate model exists in the TRAPPC4 literature.

Show evidence (2 references)

PMID:28626029 SUPPORT Human Clinical

"We identified six individuals from three unrelated families with a founder homozygous splice mutation in TRAPPC6B, encoding a core subunit of the complex TRAPP I. Patients manifested a neurodevelopmental disorder characterised by microcephaly, epilepsy and autistic features, and showed splicing defect."

Establishes the distinct gene and the overlapping but milder microcephaly-plus-epilepsy phenotype.

PMID:28626029 SUPPORT Model Organism

"Zebrafish trappc6b morphants replicated the human phenotype, displaying decreased head size and neuronal hyperexcitability, leading to a lower seizure threshold."

Model-organism evidence specific to TRAPPC6B, which has no TRAPPC4 counterpart and helps keep the two entities distinct.

TRAPPC2L-related progressive encephalopathy with episodic rhabdomyolysis Not Yet Curated MONDO:0032681

Overlapping Features Biallelic TRAPPC2L variants cause neurodevelopmental delay with febrile-illness-induced encephalopathy and episodes of rhabdomyolysis, followed by developmental arrest, epilepsy and tetraplegia. The endpoint (developmental arrest, epilepsy, tetraplegia) closely resembles NEDESBA, and the muscle involvement reported in a subset of TRAPPC4 patients makes the overlap tighter still.

Distinguishing Features

Causal gene: TRAPPC2L, not TRAPPC4.
TRAPPC2L disease is defined by discrete febrile-illness-triggered encephalopathic and rhabdomyolysis crises, which are not the pattern in NEDESBA, where creatine kinase elevation, when present, is persistent and is not the presenting event.
Mechanistically TRAPPC2L acts through TRAPPII and RAB11, whereas the TRAPPC4 defect is felt principally through the RAB1/TRAPPIII arm.

Show evidence (2 references)

PMID:30120216 SUPPORT Human Clinical

"both of whom presented clinically with a similar phenotype that included neurodevelopmental delay, febrile illness-induced encephalopathy and episodes of rhabdomyolysis, followed by developmental arrest, epilepsy and tetraplegia"

Documents the overlapping endpoint and the distinguishing crisis pattern.

PMID:30120216 SUPPORT In Vitro

"Since TRAPP II activates the GTPase RAB11, we examined the activation state of this protein and found increased levels of the active RAB, correlating with changes in its cellular morphology."

Establishes the RAB11/TRAPPII mechanistic axis that distinguishes this TRAPPopathy from the RAB1/TRAPPIII-dominated TRAPPC4 disorder.

Early-infantile neurodegenerative and neurometabolic mimics

Overlapping Features Before molecular diagnosis, NEDESBA is routinely mistaken for a neurometabolic disease. The reported differential includes early-onset epileptic encephalopathies, lysosomal storage disorders such as neuronal ceroid lipofuscinosis, mitochondrial encephalopathies, and the leukodystrophies (metachromatic leukodystrophy, Krabbe disease). In one reported infant a low biotin level even suggested biotinidase deficiency before enzymatic testing excluded it.

Distinguishing Features

A thorough metabolic workup (plasma amino acids, acylcarnitines, urine organic acids, lysosomal enzymes, neuronal ceroid lipofuscinosis enzymes) is normal in NEDESBA.
Grey- versus white-matter predominance on MRI helps triage the mimics, but the definitive discriminator is biallelic TRAPPC4 variants on sequencing.

Show evidence (2 references)

PMID:36211171 SUPPORT Human Clinical

"Early-onset epileptic encephalopathies, lysosomal storage diseases, such as NCL, and mitochondrial encephalopathies present with prominent gray matter involvement, whereas white matter involvement occurs in disorders with demyelination, such as MLD and Krabbe disease."

Enumerates the neurodegenerative mimics and how imaging helps triage them.

PMID:42543852 SUPPORT Human Clinical

"However, confirmatory biochemical and enzymatic studies ruled out classic biotinidase deficiency."

A worked example of a metabolic mimic misleading the initial workup.

{ }

Source YAML

click to show

name: Neurodevelopmental Disorder with Epilepsy, Spasticity, and Brain Atrophy
creation_date: '2026-08-15T00:00:00Z'
category: Mendelian
synonyms:
- NEDESBA
- TRAPPC4-related neurodevelopmental disorder
- TRAPPC4-related encephalopathy
- TRAPPC4 trappopathy
- TRAPPC4-related early-infantile neurodegenerative syndrome
- severe syndromic intellectual disability due to TRAPPC4 deficiency
description: >-
  Neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy
  (NEDESBA; OMIM 618741) is an ultra-rare autosomal recessive TRAPPopathy caused
  by biallelic pathogenic variants in TRAPPC4, which encodes a core subunit
  (historically called synbindin) of the multisubunit TRAnsport Protein Particle
  (TRAPP) membrane-tethering complex. After a usually unremarkable pregnancy and
  neonatal period, affected infants develop profound global developmental
  impairment within the first months of life, seizures that typically begin in
  the first year, progressive postnatal microcephaly, and spastic tetraplegia.
  Psychomotor progress is minimal or absent, producing feeding difficulties and
  an inability to walk or speak, and early milestones that were attained are
  subsequently lost. Serial neuroimaging shows progressive cerebral cortical and
  (in most patients) cerebellar atrophy with white-matter volume loss,
  ventriculomegaly and a thin corpus callosum, so the disorder is best understood
  as a neurodegenerative process layered on a developmental one. Sensorineural
  hearing loss, cortical visual impairment and optic atrophy, a subtle
  recognizable facial gestalt, and, in a subset, elevated creatine kinase and
  lactate with muscle involvement complete the picture. Most reported individuals
  worldwide are homozygous for a single recurrent non-canonical splice variant,
  NM_016146.5:c.454+3A>G, which is leaky (hypomorphic): it reduces full-length
  TRAPPC4 transcript and protein rather than abolishing it, and complete loss is
  thought to be incompatible with life. Reduced TRAPPC4 destabilizes assembly of
  the TRAPP complex, impairing its guanine-nucleotide-exchange-factor activity
  towards RAB1 and hence endoplasmic-reticulum-to-Golgi vesicular tethering,
  Golgi transit, and autophagosome formation. Patient fibroblasts show delayed
  entry into and exit from the Golgi and a basal autophagy defect with delayed
  autophagic flux, both rescued by wild-type TRAPPC4, and a yeast trs23 model
  reproduces the secretory and autophagic defects. No disease-modifying therapy
  exists; management is molecular diagnosis, symptomatic antiseizure treatment,
  spasticity and feeding management, multidisciplinary rehabilitation, and
  genetic counseling.
disease_term:
  preferred_term: neurodevelopmental disorder with epilepsy, spasticity, and brain
    atrophy
  term:
    id: MONDO:0032894
    label: neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy
parents:
- Mendelian neurodevelopmental disorder
- Progressive encephalopathy
- Membrane trafficking disorder
- TRAPPopathy
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    evidence:
    - reference: PMID:42543852
      reference_title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: It has been associated with biallelic pathogenic variants in the Trafficking
        Protein Particle Complex Subunit 4 (TRAPPC4) gene.
      explanation: >-
        A monogenic autosomal recessive disorder defined by biallelic variants in
        a single gene belongs to the genetics chapter.
  - classification_value: NEUROLOGIC
    evidence:
    - reference: PMID:32901138
      reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
        with an early-infantile neurodegenerative syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant
        showed profound psychomotor delay, developmental regression, early-onset epilepsy,
        microcephaly and progressive spastic tetraplegia.
      explanation: >-
        The clinical picture is dominated by epileptic encephalopathy, spasticity
        and neurodegeneration, placing the entity in the neurology chapter.
inheritance:
- name: Autosomal recessive
  description: >-
    Biallelic (usually homozygous) TRAPPC4 variants are required. Most reported
    families are consanguineous and homozygous for the recurrent c.454+3A>G
    splice variant; heterozygous carriers are clinically unaffected and the
    carrier frequency of that allele in healthy individuals is on the order of a
    few per 10,000.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:42543852
    reference_title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neurodevelopmental disorder with spasticity, epilepsy and brain atrophy
      (NEDESBA) is a rare autosomal recessive condition, first described in 2020.
    explanation: States the autosomal recessive mode of inheritance directly.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All seven affected subjects shared the same identical rare, homozygous,
      potentially pathogenic variant in a non-canonical, well-conserved splice site
      within TRAPPC4
    explanation: >-
      Homozygosity in all affected children of three unrelated families, with
      unaffected heterozygous parents, establishes recessive inheritance.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No population prevalence or incidence study exists. The founding report
    described seven children from three unrelated families (2020); a subsequent
    multicentre series added 23 patients from 17 independent families (2021), and
    by 2022 a review counted 33 individuals from 22 families. Later case reports
    have added a small number of further patients. Published counts overlap
    substantially between cohorts and must not be summed as independent cases.
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: of the 33 individuals from 22 families reported to date, 31 individuals
      from 21 families have been reported with a recurrent homozygous pathogenic variant
    explanation: Documents the small cumulative number of reported individuals and families.
- population: Healthy individuals (GeneDx and 100,000 Genomes cohorts)
  measure_type: CARRIER_FREQUENCY
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 39.0
  rate_low: 24.0
  rate_high: 54.0
  notes: >-
    Heterozygous carrier frequency of the recurrent NM_016146.5:c.454+3A>G allele,
    reported as 2.4-5.4 per 10,000 healthy individuals (i.e. 24-54 per 100,000).
    This is a carrier frequency for one allele, not a disease prevalence; the
    disorder itself remains ultra-rare.
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We found the carrier frequency of TRAPPC4 c.454+3A>G was 2.4-5.4 per
      10,000 healthy individuals.
    explanation: Direct quantitative statement of the carrier frequency.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: varying from 2.4-5.4 per 10 000 individuals worldwide, and mostly frequent
      in Mediterranean and European ancestries
    explanation: Independent restatement of the carrier frequency with ancestry distribution.
pathophysiology:
- name: Biallelic TRAPPC4 Loss of Function
  description: >-
    Biallelic pathogenic variants in TRAPPC4 (11q23.3; historical protein name
    synbindin) reduce the amount or function of TRAPPC4, one of the small core
    subunits shared by the TRAPPII and TRAPPIII complexes. The overwhelmingly
    predominant allele worldwide is the recurrent non-canonical splice variant
    NM_016146.5:c.454+3A>G (hg19:chr11:g.118890966A>G), found homozygously in
    almost every reported family, mostly in the setting of consanguinity. Single
    nucleotide polymorphism array analysis found no shared haplotype between a
    Turkish and a Caucasian family, favouring a recurrent mutational hotspot over
    a single ancient founder allele. A small number of families carry other
    biallelic alleles: novel missense variants c.191T>C p.(Leu64Pro) and
    c.278C>T p.(Pro93Leu) in two Indian families, and a biallelic in-frame
    deletion causing stop-loss in one family with a milder phenotype. Because the
    recurrent splice allele is leaky, residual correctly spliced transcript
    persists; complete loss of this essential core subunit is thought to be
    incompatible with survival.
  role: root
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  gene:
    preferred_term: TRAPPC4
    term:
      id: hgnc:19943
      label: TRAPPC4
  downstream:
  - target: Aberrant TRAPPC4 Pre-mRNA Splicing and Transcript Loss
    causal_link_type: DIRECT
    description: >-
      The recurrent c.454+3A>G allele acts at the RNA level, disrupting the
      splice donor of exon 3.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'All seven affected subjects shared the same identical rare, homozygous,
      potentially pathogenic variant in a non-canonical, well-conserved splice site
      within TRAPPC4 (hg19:chr11:g.118890966A>G; TRAPPC4: NM_016146.5; c.454+3A>G).'
    explanation: Establishes the founding genotype and the exact recurrent allele.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Single nucleotide polymorphism array analysis revealed there was no haplotype
      shared between the tested Turkish and Caucasian families suggestive of a variant
      hotspot region rather than a founder effect.
    explanation: >-
      Supports the description of the recurrent allele as a mutational hotspot
      rather than a proven founder variant.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We report three individuals from two Indian families harboring novel
      bi-allelic missense variants c.191T>C and c.278C>T (NM_016146.6) in TRAPPC4
      with classic clinical presentation in one and milder and later onset in the
      other family.
    explanation: >-
      Documents pathogenic TRAPPC4 alleles other than the recurrent splice
      variant, showing the mechanism is gene-level rather than allele-specific.
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: No other clinically relevant TRAPPC4 variants were identified among any
      of over 10,000 patients with neurodevelopmental conditions.
    explanation: >-
      Shows how strongly the reported allelic spectrum is dominated by the single
      recurrent splice variant.
- name: Aberrant TRAPPC4 Pre-mRNA Splicing and Transcript Loss
  description: >-
    The c.454+3A>G variant lies in the intron 3 splice donor region. RNA studies
    in patient cells show that it is an incompletely penetrant (leaky) splice
    defect: full-length TRAPPC4 transcript is reduced while a shorter transcript
    lacking exon 3 accumulates. RNA sequencing further resolved partial exon 3
    skipping plus use of a downstream cryptic splice donor site, producing an
    aberrant transcript with a premature termination codon that is predicted to
    be degraded by nonsense-mediated decay. The net effect is a dosage reduction
    of normal TRAPPC4 protein rather than production of a dominant-negative
    product.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: mRNA splicing, via spliceosome
    term:
      id: GO:0000398
      label: mRNA splicing, via spliceosome
    modifier: ABNORMAL
  - preferred_term: nonsense-mediated mRNA decay of the aberrant TRAPPC4 transcript
    term:
      id: GO:0000184
      label: nuclear-transcribed mRNA catabolic process, nonsense-mediated decay
    modifier: INCREASED
  cell_types:
  - preferred_term: patient-derived dermal fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  downstream:
  - target: Reduced TRAPP Complex Assembly and Stability
    causal_link_type: DIRECT
    description: >-
      Less full-length TRAPPC4 protein is available to incorporate into the TRAPP
      complex.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: experimental evidence showed both a reduction in full-length transcript
      levels and an increase in levels of a shorter transcript missing exon 3, suggestive
      of an incompletely penetrant splice defect
    explanation: >-
      Direct transcript-level demonstration of the leaky splice defect in patient
      cells.
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Based upon RNA sequencing, the variant resulted in partial exon 3 skipping
      and generation of an aberrant transcript owing to use of a downstream cryptic
      splice donor site, predicting a premature stop codon and nonsense mediated decay.
    explanation: >-
      Resolves the precise mis-splicing event and the nonsense-mediated-decay
      route to transcript loss.
- name: Reduced TRAPP Complex Assembly and Stability
  description: >-
    TRAPPC4 is one of the small core subunits present in every TRAPP complex, and
    all four core subunits are essential for cell viability. Reduced TRAPPC4
    protein selectively destabilizes the assembled machine: in patient
    fibroblasts TRAPPC4 protein levels fall while the levels of other TRAPP
    subunits are unchanged, yet native gel electrophoresis and size exclusion
    chromatography reveal a defect in assembly and/or stability of the intact
    complex. The lesion is therefore at the level of the holo-complex, not of an
    individual partner subunit.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  protein_complexes:
  - preferred_term: TRAPP complex
    term:
      id: GO:0030008
      label: TRAPP complex
    modifier: DECREASED
  cell_types:
  - preferred_term: patient-derived dermal fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  downstream:
  - target: Impaired RAB1 Guanine Nucleotide Exchange Factor Activity
    causal_link_type: DIRECT
    description: >-
      The GEF active site is formed across several core subunits, so a
      destabilized complex has reduced exchange activity.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: TRAPPC4 protein levels were significantly reduced whilst levels of other
      TRAPP complex subunits remained unaffected.
    explanation: Shows the protein-level deficit is specific to TRAPPC4.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Native polyacrylamide gel electrophoresis and size exclusion chromatography
      demonstrated a defect in TRAPP complex assembly and/or stability.
    explanation: Direct biochemical demonstration of the complex-assembly defect.
  - reference: PMID:32116085
    reference_title: 'TRAPPing a neurological disorder: from yeast to humans.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: This variant results in lower levels of full-length TRAPPC4 protein and
      the TRAPP complex.
    explanation: Independent restatement that both the subunit and the complex are reduced.
  - reference: PMID:32116085
    reference_title: 'TRAPPing a neurological disorder: from yeast to humans.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: All TRAPP complexes contain four core subunits essential for cell viability,
      and until recently there were no human diseases associated with any core TRAPP
      subunit.
    explanation: >-
      Explains why complete loss of this core subunit is expected to be lethal and
      why only hypomorphic alleles are seen in patients.
- name: Impaired RAB1 Guanine Nucleotide Exchange Factor Activity
  description: >-
    The TRAPP complexes are Rab guanine-nucleotide-exchange factors: TRAPPIII
    activates RAB1 (the master regulator of the early secretory pathway and of
    the first step of macroautophagy) and TRAPPII activates RAB11. TRAPPC4 and
    its yeast orthologue Trs23 are among the essential subunits for the RAB1 GEF
    activity, and structural work localizes the exchange site to a conserved
    surface spanning several core subunits, so a destabilized core lowers
    exchange activity rather than abolishing a discrete catalytic site. Reduced
    RAB1 activation leaves less RAB1-GTP available on donor and acceptor
    membranes to recruit long coiled-coil tethers.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  molecular_functions:
  - preferred_term: RAB1 guanyl-nucleotide exchange factor activity
    term:
      id: GO:0005085
      label: guanyl-nucleotide exchange factor activity
    modifier: DECREASED
  protein_complexes:
  - preferred_term: TRAPP complex
    term:
      id: GO:0030008
      label: TRAPP complex
  downstream:
  - target: Impaired ER-to-Golgi Vesicular Tethering and Golgi Transit
    causal_link_type: DIRECT
    description: RAB1-GTP is required to tether COPII vesicles at the cis-Golgi.
  - target: Defective Autophagosome Formation and Autophagic Flux
    causal_link_type: DIRECT
    description: RAB1 is required for the first step of macroautophagy.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TRAPPC4, like its yeast Trs23 orthologue, is a core component of the
      TRAPP complexes and one of the essential subunits for guanine nucleotide exchange
      factor activity for Rab1 GTPase.
    explanation: >-
      Identifies TRAPPC4 as essential for the RAB1 GEF activity of TRAPP. Tagged
      OTHER rather than HUMAN_CLINICAL because this is a statement of established
      molecular cell biology in the paper's introduction, not an observation made
      on the patients.
  - reference: PMID:39769094
    reference_title: 'TRAPPopathies: Severe Multisystem Disorders Caused by Variants
      in Genes of the Transport Protein Particle (TRAPP) Complexes.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TRAPP complexes comprise a core complex, TRAPPI, and the association
      of peripheral protein subunits to make two complexes, known as TRAPPII and TRAPPIII,
      which act as Guanine Nucleotide Exchange Factors (GEFs) of Rab11 and Rab1, respectively.
    explanation: >-
      Review statement defining the division of GEF labour between TRAPPII/RAB11
      and TRAPPIII/RAB1 that the core subunit is shared between.
  - reference: PMID:34018214
    reference_title: Cryo-EM structure of metazoan TRAPPIII, the multi-subunit complex
      that activates the GTPase Rab1.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: TRAPPII activates Rab11, and TRAPPIII activates Rab1, with the two complexes
      sharing a core of small subunits that affect nucleotide exchange but being distinguished
      by specific large subunits that are essential for activity in vivo.
    explanation: >-
      Structural evidence that the shared small-subunit core (which includes
      TRAPPC4) is the part that governs nucleotide exchange.
  - reference: PMID:17110339
    reference_title: The architecture of the multisubunit TRAPP I complex suggests
      a model for vesicle tethering.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We have also localized the site of guanine nucleotide exchange activity
      to a highly conserved surface encompassing several subunits.
    explanation: >-
      Explains why a complex-assembly defect, rather than loss of a single
      catalytic residue, reduces GEF output.
- name: Impaired ER-to-Golgi Vesicular Tethering and Golgi Transit
  description: >-
    The functional consequence in patient cells is a secretory-pathway defect.
    Using the temperature-sensitive Golgi cargo marker VSVG-GFP-ts045, patient
    fibroblasts show significantly delayed entry into and exit from the Golgi
    apparatus. The defect is a direct consequence of reduced TRAPPC4 dosage
    rather than of an unrelated cellular abnormality, because lentiviral
    expression of wild-type TRAPPC4 in the same fibroblasts restores normal
    trafficking. Relative to the autophagy arm below, the secretory defect is the
    milder of the two.
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: endoplasmic reticulum to Golgi vesicle-mediated transport
    term:
      id: GO:0006888
      label: endoplasmic reticulum to Golgi vesicle-mediated transport
    modifier: DECREASED
  - preferred_term: vesicle-mediated transport
    term:
      id: GO:0016192
      label: vesicle-mediated transport
    modifier: ABNORMAL
  cellular_components:
  - preferred_term: Golgi apparatus
    term:
      id: GO:0005794
      label: Golgi apparatus
  - preferred_term: endoplasmic reticulum
    term:
      id: GO:0005783
      label: endoplasmic reticulum
  cell_types:
  - preferred_term: patient-derived dermal fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  downstream:
  - target: Neuronal Secretory and Autophagic Failure
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Chronic secretory-pathway impairment is presumed to be poorly tolerated by
      long-lived, highly polarized neurons.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Intracellular trafficking through the Golgi using the marker protein
      VSVG-GFP-ts045 demonstrated significantly delayed entry into and exit from the
      Golgi in fibroblasts derived from one of the affected subjects.
    explanation: Direct cell-biological demonstration of the Golgi trafficking delay.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Lentiviral expression of wild-type TRAPPC4 in these fibroblasts restored
      trafficking, suggesting that the trafficking defect was due to reduced TRAPPC4
      levels.
    explanation: Genetic rescue establishes causality between TRAPPC4 dosage and the defect.
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Trafficking protein particle (TRAPP) complexes, which include the TRAPPC4
      protein, regulate membrane trafficking between lipid organelles in a process
      termed vesicular tethering.
    explanation: Identifies vesicular tethering as the process disrupted.
- name: Defective Autophagosome Formation and Autophagic Flux
  description: >-
    The second and, on current evidence, more severe cellular consequence is a
    macroautophagy defect. Patient fibroblasts have a basal autophagy defect and
    a delay in autophagic flux, attributed to autophagosomes that fail to seal.
    The same dissociation is reproduced in a yeast trs23 temperature-sensitive
    model, which shows constitutive and stress-induced autophagic defects at the
    permissive temperature while the secretory defect appears only at the
    restrictive temperature, i.e. autophagy is the more dosage-sensitive output
    of the core TRAPP complex.
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: autophagy
    term:
      id: GO:0006914
      label: autophagy
    modifier: DECREASED
  - preferred_term: autophagosome assembly
    term:
      id: GO:0000045
      label: autophagosome assembly
    modifier: ABNORMAL
  - preferred_term: macroautophagy
    term:
      id: GO:0016236
      label: macroautophagy
    modifier: DECREASED
  cell_types:
  - preferred_term: patient-derived dermal fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  downstream:
  - target: Neuronal Secretory and Autophagic Failure
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Post-mitotic neurons depend on autophagy for proteostasis and cannot dilute
      undegraded cargo by division.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we found that the fibroblasts had a basal autophagy defect and a delay
      in autophagic flux, possibly due to unsealed autophagosomes
    explanation: Direct demonstration of the autophagy defect in patient cells.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: These results were validated using a yeast trs23 temperature sensitive
      variant that exhibits constitutive and stress-induced autophagic defects at permissive
      temperature and a secretory defect at restrictive temperature.
    explanation: >-
      Orthologous yeast model confirms the defect and shows autophagy is affected
      at a milder degree of subunit loss than secretion.
  - reference: PMID:32116085
    reference_title: 'TRAPPing a neurological disorder: from yeast to humans.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Similarly, primary fibroblasts derived from human patients also exhibit
      minor and severe defects in secretion and autophagy, respectively.
    explanation: >-
      Quantifies the relative severity of the two arms in human patient cells
      (secretion minor, autophagy severe).
  - reference: PMID:32116085
    reference_title: 'TRAPPing a neurological disorder: from yeast to humans.'
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Phenotypic analysis of the yeast mutant cells reveals a minor defect in
      secretion and a major defect in autophagy.
    explanation: The yeast counterpart of the same secretion-versus-autophagy dissociation.
- name: Neuronal Secretory and Autophagic Failure
  description: >-
    The step from a fibroblast phenotype to a brain phenotype is the least
    directly evidenced link in the chain and is currently a well-motivated
    hypothesis rather than a demonstrated fact. The proposal, advanced by the
    discovery group, is that a chronic low-grade autophagy defect is especially
    harmful to neurons, which are post-mitotic, long-lived and unusually
    dependent on membrane trafficking and proteostasis. A second,
    neuron-specific route is suggested by TRAPPC4/synbindin biology: through its
    atypical PDZ-like domain synbindin binds the cytoplasmic tail of syndecan-2,
    and the synbindin/syndecan complex participates in synaptic membrane
    trafficking and dendritic spine morphogenesis, so reduced TRAPPC4 may also
    impair synapse formation and maturation directly. Neither route has been
    tested in patient-derived neurons.
  biological_scale: CELLULAR
  mechanism_confidence: HYPOTHETICAL
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: cortical pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  biological_processes:
  - preferred_term: regulation of dendritic spine development
    term:
      id: GO:0060998
      label: regulation of dendritic spine development
    modifier: ABNORMAL
  - preferred_term: intracellular protein transport
    term:
      id: GO:0006886
      label: intracellular protein transport
    modifier: DECREASED
  downstream:
  - target: Cortical Network Hyperexcitability and Epileptic Encephalopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The intermediate steps linking trafficking failure to seizure generation in
      this disorder are not established.
  - target: Progressive Cerebral and Cerebellar Neurodegeneration
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Cumulative neuronal proteostatic failure is the presumed but untested driver
      of the atrophy.
  - target: Corticospinal Tract Dysfunction and Spasticity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Upper-motor-neuron involvement follows cortical and white-matter loss.
  evidence:
  - reference: PMID:32116085
    reference_title: 'TRAPPing a neurological disorder: from yeast to humans.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Moreover, we hypothesize that low levels of the core TRAPP complex are
      more detrimental to autophagy than to secretion, and that the long-term autophagy
      defect is especially harmful to neuronal cells.
    explanation: >-
      The explicit hypothesis linking the cellular defect to neuronal vulnerability;
      framed as a hypothesis by its authors, hence mechanism_confidence HYPOTHETICAL.
  - reference: PMID:32116085
    reference_title: 'TRAPPing a neurological disorder: from yeast to humans.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We propose that the autophagy defect caused by the pathogenic-TRAPPC4
      variant results in the severe neurological disorder.
    explanation: >-
      States the causal proposal directly; the supporting data are from fibroblasts
      and yeast, not neurons, so support is partial.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: This synbindin/syndecan complex plays a role in synaptic membrane trafficking,
      thereby regulating dendritic spine morphogenesis
    explanation: >-
      Supports the second, synapse-directed route by which reduced TRAPPC4 could
      affect neurons, and is the reason the reported missense variants in the
      atypical PDZ-like domain are considered plausible.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Trappopathies are a group of disorders related to the TRAnsport Protein
      Particle (TRAPP) associated proteins, which have critical roles in cellular trafficking
      events, autophagy and TRAPP proteins are essential for dendritic spine morphogenesis.
    explanation: Independent statement of the trafficking/autophagy/spine triad of TRAPP functions.
- name: Cortical Network Hyperexcitability and Epileptic Encephalopathy
  description: >-
    Seizures are a defining feature and typically begin within the first six
    months of life, with onset in the first year in nearly all affected
    individuals. Semiology is varied: epileptic spasms, focal, tonic, atonic and
    generalized tonic-clonic seizures are all described. The
    electroencephalogram is not specific but shows epileptiform abnormalities,
    generalized disorganization and, in the more advanced cases, a strikingly low
    voltage background that tracks the cortical atrophy. Response to antiseizure
    medication is often only partial.
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  locations:
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  cell_types:
  - preferred_term: cortical pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  downstream:
  - target: Arrest of Psychomotor Development with Regression
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Early-onset, poorly controlled epileptic activity contributes to the
      developmental arrest characteristic of an epileptic encephalopathy.
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant showed
      profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly
      and progressive spastic tetraplegia.
    explanation: Establishes early-onset epilepsy as a core feature of the largest cohort.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A variety of seizures, including spasms, occur early in NEDESBA. Epileptiform
      abnormalities, generalized disorganization and very low voltage background activity
      are reported.
    explanation: Describes seizure semiology and the accompanying EEG signature.
- name: Corticospinal Tract Dysfunction and Spasticity
  description: >-
    Upper-motor-neuron signs dominate the motor examination. Spasticity affects
    all four limbs (spastic quadriparesis/tetraplegia) with brisk deep tendon
    reflexes, and it is progressive, ultimately contributing to complete loss of
    independent mobility. Spasticity is frequently refractory to baclofen and
    physical rehabilitation.
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  locations:
  - preferred_term: cerebral white matter
    term:
      id: UBERON:0002316
      label: white matter
  downstream:
  - target: Arrest of Psychomotor Development with Regression
    causal_link_type: DIRECT
    description: >-
      Spastic tetraplegia is a direct barrier to the acquisition of motor
      milestones such as sitting and walking.
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: seven affected children that showed features of early-onset seizures,
      developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis
      and progressive cortical and cerebellar atrophy
    explanation: Spastic quadriparesis in all seven children of the founding cohort.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: On re-evaluation at one year-two months, he had failure to thrive, dystonia,
      spasticity and brisk deep tendon reflexes.
    explanation: Documents the upper-motor-neuron pattern (spasticity with hyperreflexia).
- name: Progressive Cerebral and Cerebellar Neurodegeneration
  description: >-
    Neuroimaging converts this from a static developmental disorder into a
    neurodegenerative one. Brain MRI shows a variable but progressive degree of
    cerebral cortical atrophy that is more severe in older children, commonly
    accompanied by cerebellar atrophy, enlarged subarachnoid spaces, white-matter
    volume loss with delayed myelination, ventriculomegaly and a thin corpus
    callosum. Serial imaging in individual patients documents the progression
    directly: repeat scans within months can show new severe cortical atrophy.
    The progressive brain volume loss is also the substrate for the progressive
    postnatal microcephaly.
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  - preferred_term: corpus callosum
    term:
      id: UBERON:0002336
      label: corpus callosum
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: neuron apoptotic process
    term:
      id: GO:0051402
      label: neuron apoptotic process
    modifier: INCREASED
  downstream:
  - target: Arrest of Psychomotor Development with Regression
    causal_link_type: DIRECT
    description: >-
      Ongoing loss of brain volume underlies the loss of previously acquired
      milestones.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Brain MRI findings show a variable degree of progressive cerebral atrophy
      with an increased severity in older age.
    explanation: Establishes that the cerebral atrophy is progressive rather than static.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In the presented patient, spasms and very low voltage activity on EEG
      early in the course, led to a second MRI showing severe cortical atrophy, indicating
      the progressive course of the disease.
    explanation: Serial imaging in a single patient directly documenting progression.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: spastic quadriparesis and progressive cortical and cerebellar atrophy
    explanation: Progressive cortical and cerebellar atrophy in the founding cohort.
- name: Arrest of Psychomotor Development with Regression
  description: >-
    The organism-level outcome is a profound, essentially complete arrest of
    psychomotor development, with loss of the few milestones that were attained.
    Affected children do not walk or speak, cannot feed themselves and develop
    feeding difficulties and failure to thrive, and remain profoundly dependent.
    Because the substrate is a degenerative process superimposed on a
    developmental one, the trajectory is one of stagnation followed by decline
    rather than of slow ongoing gains. Death in the first decade, most often from
    intercurrent infection, is reported in a minority.
  biological_scale: ORGANISM
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we report 23 patients from 17 independent families with an early-infantile-onset
      neurodegenerative presentation
    explanation: Frames the disorder as an early-infantile neurodegenerative presentation.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Regression of achieved milestones is seen in addition to delayed milestones
      in most individuals with this condition.
    explanation: Documents regression on top of delay as the characteristic trajectory.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Some patients exhibit frequent infections, which can lead to death in
      the first decade, at a mean age of 8.8 years.
    explanation: Documents the reported mortality and its usual proximate cause.
phenotypes:
- category: Neurologic
  name: Profound global developmental delay
  description: >-
    Global developmental impairment is apparent within the first months of life
    and is profound: affected children make almost no psychomotor progress. It
    was present in all seven children of the founding cohort and in the expanded
    multicentre series.
  phenotype_term:
    preferred_term: Profound global developmental delay
    term:
      id: HP:0012736
      label: Profound global developmental delay
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant showed
      profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly
      and progressive spastic tetraplegia.
    explanation: Profound psychomotor delay reported across the largest cohort.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: seven affected children that showed features of early-onset seizures,
      developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis
      and progressive cortical and cerebellar atrophy
    explanation: Developmental delay in all seven children of the discovery cohort.
- category: Neurologic
  name: Developmental regression
  description: >-
    Loss of previously acquired milestones is superimposed on the delay in most
    individuals, and is the feature that identifies the disorder as
    neurodegenerative rather than purely developmental. Regression is usually
    early; in the mildest reported family it began only after school age.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Regression of achieved milestones is seen in addition to delayed milestones
      in most individuals with this condition.
    explanation: Direct statement that regression occurs in most affected individuals.
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: profound psychomotor delay, developmental regression, early-onset epilepsy,
      microcephaly and progressive spastic tetraplegia
    explanation: Regression listed as a core cohort feature.
- category: Neurologic
  name: Severe to profound intellectual disability
  description: >-
    Cognitive impairment is severe to profound and has been noted consistently in
    all reported individuals other than the two siblings of the mildest reported
    family. The founding report characterised the phenotype as severe syndromic
    intellectual disability.
  phenotype_term:
    preferred_term: Profound intellectual disability
    term:
      id: HP:0002187
      label: Profound intellectual disability
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Cognitive delay too has been consistently noted in all the reported individuals,
      including the individuals in our study, except for two individuals of a family
      reported by Saad et al.
    explanation: >-
      Establishes that cognitive impairment is a consistent feature across every
      reported individual, with the mildest (stop-loss) family as the only exception.
  - reference: PMID:42543852
    reference_title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Variants in these genes typically result in overlapping clinical features,
      including microcephaly, early-onset epilepsy, intellectual disability, neurodevelopmental
      regression, spasticity and abnormal brain MRI findings.
    explanation: Intellectual disability listed among the core overlapping features.
- category: Neurologic
  name: Seizures
  description: >-
    Seizures are a defining feature and begin early, usually between two and six
    months of age and within the first year in nearly all patients. Seizure onset
    at seven years in the mildest reported family is the exception. Semiology
    includes epileptic spasms, focal, tonic, atonic and generalized tonic-clonic
    seizures, and control is often only partial.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
    temporality: RECURRENT
  frequency: FREQUENT
  notes: >-
    Frequency band derived from the count of 23 out of 31 individuals with the
    recurrent splicing variant reported to have early-onset seizures (74%), which
    falls in the FREQUENT (30-79%) band. Essentially all reported individuals
    develop seizures at some point, but the quotable count is for early onset.
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Early-onset seizures (two months to six months) were noted in 23 out of
      31 individuals with recurrent splicing variant along with P1 (one year).
    explanation: >-
      Provides both the age of onset and the quantitative denominator used for the
      frequency band.
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: profound psychomotor delay, developmental regression, early-onset epilepsy,
      microcephaly and progressive spastic tetraplegia
    explanation: Early-onset epilepsy as a core cohort feature.
- category: Neurologic
  name: Epileptic spasms
  description: >-
    Epileptic (infantile) spasms are one of the reported early seizure types and
    may be the presenting event, accompanied by a very low voltage EEG
    background.
  phenotype_term:
    preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A variety of seizures, including spasms, occur early in NEDESBA.
    explanation: Documents spasms among the early seizure types.
  - reference: PMID:42543852
    reference_title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we report a 13-month-old affected male born to consanguineous parents,
      presenting with epileptic spasms and progressive neurodevelopmental delay.
    explanation: Epileptic spasms as the presenting seizure type in a reported infant.
- category: Neurologic
  name: Generalized tonic-clonic seizures
  description: >-
    Generalized tonic-clonic seizures are among the reported semiologies and were
    the presenting seizure type in the individuals with novel missense TRAPPC4
    variants.
  phenotype_term:
    preferred_term: Bilateral tonic-clonic seizure
    term:
      id: HP:0002069
      label: Bilateral tonic-clonic seizure
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: They presented with generalized tonic-clonic seizures at seven years of
      age.
    explanation: Documents generalized tonic-clonic seizures in reported patients.
- category: Neurologic
  name: EEG abnormality
  description: >-
    The EEG is abnormal but not specific: epileptiform discharges, generalized
    disorganization, and progressive background voltage suppression that
    parallels the developing cortical atrophy.
  phenotype_term:
    preferred_term: EEG abnormality
    term:
      id: HP:0002353
      label: EEG abnormality
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Epileptiform abnormalities, generalized disorganization and very low voltage
      background activity are reported.
    explanation: Describes the reported EEG abnormalities.
- category: Neurologic
  name: Progressive microcephaly
  description: >-
    Head circumference is usually normal or near-normal at birth and falls
    steeply postnatally as brain volume is lost, reaching extreme values in older
    children. Microcephaly is one of the most consistent features of the
    disorder.
  phenotype_term:
    preferred_term: Progressive microcephaly
    term:
      id: HP:0000253
      label: Progressive microcephaly
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: TRAPPC4-related neurodevelopmental disorder with epilepsy, spasticity,
      and brain atrophy (MIM# 618741) is a recently described TRAPPopathy with clinical
      findings of developmental delay, seizures, postnatal microcephaly, spasticity,
      facial dysmorphism, and cerebral and cerebellar atrophy.
    explanation: Explicitly identifies the microcephaly as postnatal (i.e. acquired/progressive).
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients all had progressive microcephaly due to severe brain atrophy,
      spastic quadriparesis, early-onset seizures, profound developmental delay
    explanation: >-
      States that the microcephaly is progressive and attributes it to the
      underlying brain atrophy.
- category: Neurologic
  name: Spastic tetraplegia
  description: >-
    Spasticity involves all four limbs, is progressive, and is accompanied by
    brisk deep tendon reflexes. It is a cardinal feature and contributes directly
    to the inability to sit or walk; it is frequently refractory to baclofen.
  phenotype_term:
    preferred_term: Spastic tetraplegia
    term:
      id: HP:0002510
      label: Spastic tetraplegia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: profound psychomotor delay, developmental regression, early-onset epilepsy,
      microcephaly and progressive spastic tetraplegia
    explanation: Progressive spastic tetraplegia as a core cohort feature.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: microcephaly, sensorineural deafness, spastic quadriparesis and progressive
      cortical and cerebellar atrophy
    explanation: Spastic quadriparesis in the founding cohort.
- category: Neurologic
  name: Hyperreflexia
  description: >-
    Brisk deep tendon reflexes accompany the spasticity and confirm the
    upper-motor-neuron localization.
  phenotype_term:
    preferred_term: Hyperreflexia
    term:
      id: HP:0001347
      label: Hyperreflexia
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: On re-evaluation at one year-two months, he had failure to thrive, dystonia,
      spasticity and brisk deep tendon reflexes.
    explanation: Documents brisk deep tendon reflexes in a reported patient.
- category: Neurologic
  name: Movement disorder (dystonia, ataxia, tremor)
  description: >-
    A mixed movement disorder (dystonia, ataxia and tremor) is present in a
    substantial minority, reported in 12 of 33 individuals in the literature
    review and confirmed in subsequently reported patients.
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  notes: >-
    The literature review reports involuntary movements in 12 of 33 individuals
    (36%). No `frequency` band is asserted here, because that count aggregates
    dystonia, ataxia and tremor and cannot be attributed to the bound term
    (HP:0001332 Dystonia) alone; per the frequency-evidence guidelines the band is
    omitted rather than over-attributed. The aggregate figure is retained in this
    note so the underlying data are not lost.
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Involuntary movements in the form of ataxia, tremors and dystonia which
      were previously reported in 12 out of 33 individuals, were also noted in P1 and
      P2.
    explanation: >-
      Documents ataxia, tremor and dystonia as the movement-disorder phenotypes of
      this condition. The aggregate 12-of-33 count covers all three together, so it
      is retained in notes rather than asserted as a frequency band on any single
      bound term.
- category: Neurologic
  name: Ataxia
  description: >-
    Gait and limb ataxia occurs in the subset of patients with enough motor
    ability to demonstrate it, and is part of the same involuntary-movement
    spectrum as tremor and dystonia.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Involuntary movements in the form of ataxia, tremors and dystonia which
      were previously reported in 12 out of 33 individuals
    explanation: Ataxia reported among the involuntary movements in this disorder.
- category: Neurologic
  name: Inability to walk
  description: >-
    Almost all affected individuals show complete absence of motor development or
    such significant motor delay that independent ambulation is never achieved.
  phenotype_term:
    preferred_term: Inability to walk
    term:
      id: HP:0002540
      label: Inability to walk
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All individuals with NEDESBA, except for P2 and P3, either showed complete
      absence of motor development or had significant motor delay.
    explanation: >-
      Documents the near-universal absence of motor development that precludes
      walking, with the mild family as the stated exception.
- category: Neurologic
  name: Absent or severely limited speech
  description: >-
    Expressive language does not develop in the classic severe presentation. In
    the mildest reported family speech was delayed and limited to short sentences
    by age five, before regression.
  phenotype_term:
    preferred_term: Absent speech
    term:
      id: HP:0001344
      label: Absent speech
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Affected siblings attained age-appropriate motor milestones, however speech
      delay was noted in early childhood (three years). They could speak only small
      sentences at the age of five years.
    explanation: >-
      Documents the language impairment, and in the mildest family shows the
      residual-speech end of the spectrum.
- category: Neuroimaging
  name: Cerebral cortical atrophy
  description: >-
    Progressive cerebral cortical atrophy, most marked in frontotemporal regions,
    is the imaging hallmark. It is present in essentially all imaged patients
    with the recurrent splice variant and worsens with age, with enlarged
    subarachnoid spaces and secondary ventricular enlargement.
  phenotype_term:
    preferred_term: Cerebral cortical atrophy
    term:
      id: HP:0002120
      label: Cerebral cortical atrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Marked cerebral atrophy is seen in those with recurrent splicing variant
      and was observed in P1 in the current study.
    explanation: Cerebral atrophy in patients with the recurrent variant.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Brain MRI findings show a variable degree of progressive cerebral atrophy
      with an increased severity in older age.
    explanation: Establishes progression of the cortical atrophy with age.
- category: Neuroimaging
  name: Cerebellar atrophy
  description: >-
    Cerebellar atrophy accompanies the cerebral atrophy in most, but not all,
    imaged patients; it was reported in 21 of 27 individuals in a literature
    review and was absent in the two Indian families with novel missense
    variants.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  frequency: FREQUENT
  notes: >-
    Frequency band derived from the reported count of 21 out of 27 individuals
    (78%), which falls at the top of the FREQUENT (30-79%) band.
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Cerebellar atrophy, another significant finding reported in 21 out of
      27 individuals with TRAPPC4 variant, was not observed in individuals from our
      study.
    explanation: >-
      Supplies the numerator/denominator for the frequency band and documents that
      the finding is not universal.
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: progressive cortical and cerebellar atrophy
    explanation: Cerebellar atrophy in the founding cohort.
- category: Neuroimaging
  name: Abnormal cerebral white matter
  description: >-
    White-matter involvement is non-specific but frequent: delayed myelination,
    white-matter volume loss, and periventricular T2/FLAIR hyperintensities.
  phenotype_term:
    preferred_term: Abnormal cerebral white matter morphology
    term:
      id: HP:0002500
      label: Abnormal cerebral white matter morphology
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Non-specific white matter abnormalities (delayed myelination, white matter
      volume loss, hyperintensities in periventricular region), thin corpus callosum
      and ventriculomegaly are also frequent imaging findings.
    explanation: Describes the white-matter findings and their frequency.
- category: Neuroimaging
  name: Delayed myelination
  description: >-
    Delayed myelination is reported on early infant MRI and forms part of the
    non-specific white-matter picture.
  phenotype_term:
    preferred_term: Delayed myelination
    term:
      id: HP:0012448
      label: Delayed myelination
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: MRI brain performed at four-months of age showed delayed myelination,
      dilated ventricles, hyperintensities in the periventricular white matter on T2-weighted
      (T2W) axial sections
    explanation: Documents delayed myelination on infant MRI in a reported patient.
- category: Neuroimaging
  name: Thin corpus callosum
  description: >-
    A thin corpus callosum is a frequent, though non-specific, accompanying
    imaging finding.
  phenotype_term:
    preferred_term: Thin corpus callosum
    term:
      id: HP:0033725
      label: Thin corpus callosum
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: thin corpus callosum and ventriculomegaly are also frequent imaging findings
    explanation: Thin corpus callosum listed among frequent imaging findings.
- category: Neuroimaging
  name: Ventriculomegaly
  description: >-
    Ventricular enlargement is common and is largely secondary (ex vacuo) to the
    progressive loss of brain parenchyma.
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: thin corpus callosum and ventriculomegaly are also frequent imaging findings
    explanation: Ventriculomegaly listed among frequent imaging findings.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Enlarged subarachnoid spaces, loss of white matter, enlarged ventricles
      and cerebellar atrophy have also been reported frequently.
    explanation: Independent confirmation of enlarged ventricles as a frequent finding.
- category: Ophthalmologic
  name: Visual impairment
  description: >-
    Visual dysfunction is near-universal and largely cortical: absent visual
    pursuit and tracking, roving eye movements, and cortical visual defects.
    Bilateral cataracts have been reported in a small number of patients.
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Eye problems occur in most of the TRAPPC4 patients with absence of pursuit
      and optic atrophy.
    explanation: Establishes visual involvement in most patients.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hearing and ophthalmological abnormalities (cortical visual defects, no
      tracking, roving eye movements, nystagmus and optic atrophy) as seen in P1 are
      also reported in 30 out of 31 previously affected individuals
    explanation: Enumerates the specific ophthalmological abnormalities reported.
- category: Ophthalmologic
  name: Optic atrophy
  description: >-
    Optic atrophy develops during the course of the illness rather than being
    present at first assessment, mirroring the progressive nature of the
    disorder.
  phenotype_term:
    preferred_term: Optic atrophy
    term:
      id: HP:0000648
      label: Optic atrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Our patient also developed optic atrophy, which was not present at the
      first ophthalmological examination.
    explanation: Documents the acquired, progressive nature of the optic atrophy.
- category: Ophthalmologic
  name: Nystagmus
  description: Roving eye movements and nystagmus are part of the ophthalmological
    picture.
  phenotype_term:
    preferred_term: Nystagmus
    term:
      id: HP:0000639
      label: Nystagmus
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: cortical visual defects, no tracking, roving eye movements, nystagmus
      and optic atrophy
    explanation: Nystagmus listed among the reported ophthalmological abnormalities.
- category: Otologic
  name: Sensorineural hearing impairment
  description: >-
    Sensorineural deafness was present in the founding cohort and has been
    reported subsequently, including a patient with a bilaterally non-recordable
    hearing response. It is not universal: the newborn hearing screen was normal
    in at least one reported patient.
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis
    explanation: Sensorineural deafness reported in the founding cohort.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hearing evaluation was suggestive of non-recordable hearing response bilaterally.
    explanation: Documents severe hearing impairment in an individually reported patient.
- category: Gastrointestinal
  name: Feeding difficulties
  description: >-
    Feeding difficulties, including regurgitation of feeds from the newborn
    period, are an early consequence of the profound neurological impairment and
    are a common reason for enteral feeding support.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: P1 presented in the early infantile period with developmental delay, feeding
      difficulties and seizures as observed in most of the individuals with recurrent
      splicing TRAPPC4 variant
    explanation: >-
      Documents feeding difficulties as an early presenting feature seen in most
      individuals with the recurrent variant.
- category: Growth
  name: Failure to thrive
  description: >-
    Poor weight gain and failure to thrive follow from the feeding difficulties
    and the overall severity of the encephalopathy.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: On re-evaluation at one year-two months, he had failure to thrive, dystonia,
      spasticity and brisk deep tendon reflexes.
    explanation: Failure to thrive documented in a reported patient.
- category: Musculoskeletal
  name: Elevated creatine kinase
  description: >-
    A subset of patients has laboratory evidence of muscle involvement, with
    persistently or episodically elevated serum creatine kinase, in one instance
    amounting to probable episodic rhabdomyolysis. Muscle involvement is a
    recurring theme across the TRAPPopathies and its presence should prompt CK
    measurement, but it is not universal: CK was normal in other reported
    patients.
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase concentration
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase concentration
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Elevated CPK were also observed in P1 and P3, thus reiterating the significance
      of assessing CPK levels for this condition.
    explanation: Documents elevated creatine kinase in reported patients.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: However, our patient had normal serum CK and lactate levels without any
      muscle involvement.
    explanation: >-
      Counter-example establishing that CK elevation and muscle involvement are not
      universal features.
- category: Metabolic
  name: Elevated circulating lactate
  description: >-
    Elevated serum lactate has been reported in a minority of patients, and can
    prompt an (ultimately negative) mitochondrial or metabolic workup before the
    genetic diagnosis is made.
  phenotype_term:
    preferred_term: Increased circulating lactate concentration
    term:
      id: HP:0002151
      label: Increased circulating lactate concentration
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Additionally, P1 also had elevated serum lactate levels as observed in
      two individuals reported by Kaur et al. (2020) and Ghosh et al. (2020).
    explanation: Documents elevated lactate in a minority of reported patients.
- category: Craniofacial
  name: Narrow forehead (bitemporal narrowing)
  description: >-
    A subtle but recognizable facial appearance is described in many patients
    with the recurrent splice variant: bitemporal narrowing, thick eyebrows, full
    cheeks, a long philtrum, a wide mouth with a thin, tented upper lip, and a
    pointed chin. It is not present in every patient; no obvious dysmorphism was
    noted in the families with novel missense variants.
  phenotype_term:
    preferred_term: Narrow forehead
    term:
      id: HP:0000341
      label: Narrow forehead
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: common facial dysmorphic features including bitemporal narrowing, thick
      eyebrows, full cheeks, long filtrum, wide mouth, thin and tinted upper lip, and
      pointed chin
    explanation: >-
      Enumerates the facial gestalt, of which bitemporal narrowing (narrow forehead)
      is the anchoring HPO-codable element.
- category: Craniofacial
  name: Thick eyebrow
  description: Thick eyebrows form part of the recognizable facial gestalt.
  phenotype_term:
    preferred_term: Thick eyebrow
    term:
      id: HP:0000574
      label: Thick eyebrow
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide
      mouth, thin and tinted upper lip, and pointed chin
    explanation: Thick eyebrows listed in the facial gestalt.
- category: Craniofacial
  name: Long philtrum
  description: A long philtrum forms part of the recognizable facial gestalt.
  phenotype_term:
    preferred_term: Long philtrum
    term:
      id: HP:0000343
      label: Long philtrum
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide
      mouth, thin and tinted upper lip, and pointed chin
    explanation: A long philtrum (spelled "long filtrum" in the source) is listed in
      the facial gestalt.
- category: Craniofacial
  name: Pointed chin
  description: A pointed chin forms part of the recognizable facial gestalt.
  phenotype_term:
    preferred_term: Pointed chin
    term:
      id: HP:0000307
      label: Pointed chin
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide
      mouth, thin and tinted upper lip, and pointed chin
    explanation: A pointed chin is listed in the facial gestalt.
- category: Craniofacial
  name: Full cheeks
  description: Full cheeks form part of the recognizable facial gestalt.
  phenotype_term:
    preferred_term: Full cheeks
    term:
      id: HP:0000293
      label: Full cheeks
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: bitemporal narrowing, thick eyebrows, full cheeks, long filtrum, wide
      mouth, thin and tinted upper lip, and pointed chin
    explanation: Full cheeks are listed in the facial gestalt.
progression:
- phase: Onset
  age_range: First months of life (early infancy)
  notes: >-
    Pregnancy and the neonatal period are usually unremarkable. Global
    developmental impairment becomes apparent within the first months, and
    seizures typically begin between two and six months of age (within the first
    year in nearly all patients).
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Early-onset seizures (two months to six months) were noted in 23 out of
      31 individuals with recurrent splicing variant along with P1 (one year).
    explanation: Establishes the typical age at seizure onset.
- phase: Developmental stagnation and regression
  age_range: Infancy to early childhood
  notes: >-
    Almost no psychomotor progress is made, and the few milestones that were
    attained are lost. Head growth decelerates and the child becomes spastic and
    tetraplegic. This is the phase in which the disorder declares itself as
    neurodegenerative rather than static.
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Affected individuals with the homozygous TRAPPC4 c.454+3A>G variant showed
      profound psychomotor delay, developmental regression, early-onset epilepsy, microcephaly
      and progressive spastic tetraplegia.
    explanation: Describes the stagnation-plus-regression phase of the natural history.
- phase: Progressive brain atrophy
  age_range: Infancy through childhood
  notes: >-
    Serial MRI shows worsening cerebral (and usually cerebellar) atrophy, more
    severe in older children. Repeat imaging within a few months of presentation
    can already show new severe cortical atrophy. Optic atrophy may likewise
    appear during follow-up having been absent initially.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In the presented patient, spasms and very low voltage activity on EEG
      early in the course, led to a second MRI showing severe cortical atrophy, indicating
      the progressive course of the disease.
    explanation: Serial imaging documenting the progressive phase.
- phase: Late complications and mortality
  age_range: First decade
  notes: >-
    Profound dependence, refractory spasticity and epilepsy, and susceptibility to
    intercurrent infection. Death in the first decade is reported in a minority,
    at a mean age of about 8.8 years. Mortality is
    deliberately recorded here rather than as a phenotype, because HP:0003819
    ("Death in childhood") sits under Clinical modifier rather than Phenotypic
    abnormality and so is not a valid phenotype_term in this schema.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Some patients exhibit frequent infections, which can lead to death in
      the first decade, at a mean age of 8.8 years.
    explanation: Documents the late phase and its mortality.
diagnosis:
- name: Exome or Genome Sequencing
  description: >-
    Diagnosis is molecular. The clinical picture, an early-infantile epileptic
    encephalopathy with progressive microcephaly, spasticity and brain atrophy,
    overlaps a large number of neurometabolic and neurodegenerative disorders and
    has no specific biomarker, so unbiased broad sequencing is the practical
    first-line test. A thorough metabolic workup is commonly (and reasonably)
    performed first to exclude treatable mimics, but it is normal in this
    disorder.
  diagnosis_term:
    preferred_term: whole exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  results: >-
    Biallelic pathogenic TRAPPC4 variants. In practice this is nearly always
    homozygosity for the recurrent splice variant NM_016146.5:c.454+3A>G;
    biallelic missense and in-frame/stop-loss alleles account for the remainder.
  presence: Diagnostic when biallelic pathogenic TRAPPC4 variants are identified
  evidence:
  - reference: PMID:42543852
    reference_title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Whole exome sequencing revealed a homozygous splice-site variant (c.454+3A>G)
      in the TRAPPC4 gene, confirming the diagnosis of NEDESBA.
    explanation: Documents exome sequencing as the diagnostic route actually used.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Before proceeding to next-generation sequencing, a thorough metabolic
      workup in order to exclude neurodegenerative diseases, which may present with
      a similar phenotype is advisable.
    explanation: Supports the described sequencing-after-metabolic-screen diagnostic pathway.
- name: Sanger Confirmation and Parental Segregation
  description: >-
    Targeted Sanger sequencing confirms the candidate variant and demonstrates
    biallelic inheritance by showing both parents to be heterozygous carriers,
    which is particularly important for a non-canonical splice-region variant
    whose pathogenicity is not self-evident from the DNA sequence alone.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  results: Proband homozygous, both parents heterozygous for the familial TRAPPC4 allele.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Segregation analysis by Sanger sequencing showed both healthy parents
      were heterozygous for the same variant.
    explanation: Documents the Sanger segregation step in a reported diagnosis.
- name: RNA Analysis of the Splice Variant
  description: >-
    Transcript analysis (RT-PCR or RNA sequencing of patient fibroblasts) is the
    functional test that establishes pathogenicity of the recurrent
    splice-region allele. It is diagnostically valuable because a non-canonical
    +3 intronic variant can be filtered out or deprioritized by standard exome
    pipelines.
  diagnosis_term:
    preferred_term: RNA sequencing
    term:
      id: NCIT:C124261
      label: Whole Transcriptome Sequencing
  results: >-
    Reduced full-length TRAPPC4 transcript with partial exon 3 skipping and use
    of a downstream cryptic splice donor, generating a premature termination
    codon subject to nonsense-mediated decay.
  evidence:
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Based upon RNA sequencing, the variant resulted in partial exon 3 skipping
      and generation of an aberrant transcript owing to use of a downstream cryptic
      splice donor site, predicting a premature stop codon and nonsense mediated decay.
    explanation: The RNA-level finding that establishes pathogenicity of the splice allele.
- name: Brain Magnetic Resonance Imaging
  description: >-
    Cranial MRI is the principal phenotyping investigation. It is supportive
    rather than diagnostic, but the combination of progressive cortical (and
    usually cerebellar) atrophy with enlarged subarachnoid spaces in an infant
    with severe microcephaly and early seizures is what should prompt TRAPPC4
    testing. Serial imaging is more informative than a single scan because it
    demonstrates progression.
  diagnosis_term:
    preferred_term: brain magnetic resonance imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  results: >-
    Progressive cerebral cortical atrophy, cerebellar atrophy in most, enlarged
    subarachnoid spaces, white-matter volume loss and delayed myelination, thin
    corpus callosum, ventriculomegaly.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In patients presenting with severe microcephaly, typical dysmorphic facial
      features, early-onset seizures with very low voltage, abnormal EEG and progressive
      cortical atrophy, a TRAPPC4-related neurodevelopmental disorder should be considered
      in the differential diagnosis of neurodegenerative diseases.
    explanation: States the imaging-plus-clinical trigger for considering the diagnosis.
- name: Electroencephalography
  description: >-
    EEG documents the epilepsy and, over serial recordings, the progressive
    background voltage suppression that parallels cortical atrophy. Findings are
    supportive and non-specific.
  diagnosis_term:
    preferred_term: electroencephalography
    term:
      id: NCIT:C38054
      label: Electroencephalography
  results: >-
    Epileptiform discharges with generalized disorganization; progressively very
    low voltage background in advanced disease.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Epileptiform abnormalities, generalized disorganization and very low voltage
      background activity are reported.
    explanation: Describes the EEG findings that the investigation yields.
differential_diagnoses:
- name: TRAPPC12-related encephalopathy (PEBAS)
  description: >-
    The closest phenotypic mimic within the TRAPPopathies. Biallelic TRAPPC12
    variants cause progressive childhood encephalopathy with severe disability,
    microcephaly, hearing loss, spasticity and progressive brain atrophy, an
    almost superimposable clinical description.
  disease_term:
    preferred_term: TRAPPC12-related encephalopathy
    term:
      id: MONDO:0044696
      label: early-onset progressive encephalopathy-hearing loss-pons hypoplasia-brain
        atrophy syndrome
  distinguishing_features:
  - 'Causal gene: TRAPPC12, a TRAPPIII-specific large subunit, not TRAPPC4, a small
    subunit of the shared core.'
  - Imaging in TRAPPC12 disease characteristically includes pontine hypoplasia, which
    is not a described feature of NEDESBA.
  - There is no single recurrent TRAPPC12 allele analogous to TRAPPC4 c.454+3A>G, so
    separation is by sequencing rather than by clinical examination.
  evidence:
  - reference: PMID:28777934
    reference_title: Mutations in TRAPPC12 Manifest in Progressive Childhood Encephalopathy
      and Golgi Dysfunction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'The clinical phenotypes of the three individuals are strikingly similar:
      severe disability, microcephaly, hearing loss, spasticity, and characteristic
      brain imaging findings.'
    explanation: Documents the closely overlapping phenotype of the TRAPPC12 disorder.
  - reference: PMID:28777934
    reference_title: Mutations in TRAPPC12 Manifest in Progressive Childhood Encephalopathy
      and Golgi Dysfunction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we report that variants in TRAPPC12 result in progressive childhood
      encephalopathy.
    explanation: Establishes the distinct causal gene for this differential.
- name: TRAPPC6B-related neurodevelopmental disorder (NEDMEBA)
  description: >-
    Biallelic TRAPPC6B variants cause a neurodevelopmental disorder with
    microcephaly, epilepsy and autistic features, with cortical atrophy, thin
    corpus callosum and, in some, cerebellar and brainstem atrophy. Like NEDESBA
    it is a core-subunit TRAPPopathy caused by a founder splice mutation in a
    consanguineous population.
  disease_term:
    preferred_term: neurodevelopmental disorder with microcephaly, epilepsy, and brain
      atrophy
    term:
      id: MONDO:0060640
      label: neurodevelopmental disorder with microcephaly, epilepsy, and brain atrophy
  distinguishing_features:
  - 'Causal gene: TRAPPC6B, not TRAPPC4.'
  - The TRAPPC6B phenotype is substantially milder - affected individuals walk, have
    autistic features and ataxic gait, and survive into adulthood with only slow progression,
    whereas NEDESBA patients typically never walk or speak.
  - Zebrafish trappc6b morphants recapitulate the microcephaly and neuronal hyperexcitability;
    no comparable vertebrate model exists in the TRAPPC4 literature.
  evidence:
  - reference: PMID:28626029
    reference_title: A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental
      disorder characterised by microcephaly, epilepsy and autistic features.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified six individuals from three unrelated families with a founder
      homozygous splice mutation in TRAPPC6B, encoding a core subunit of the complex
      TRAPP I. Patients manifested a neurodevelopmental disorder characterised by microcephaly,
      epilepsy and autistic features, and showed splicing defect.
    explanation: >-
      Establishes the distinct gene and the overlapping but milder
      microcephaly-plus-epilepsy phenotype.
  - reference: PMID:28626029
    reference_title: A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental
      disorder characterised by microcephaly, epilepsy and autistic features.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Zebrafish trappc6b morphants replicated the human phenotype, displaying
      decreased head size and neuronal hyperexcitability, leading to a lower seizure
      threshold.
    explanation: >-
      Model-organism evidence specific to TRAPPC6B, which has no TRAPPC4
      counterpart and helps keep the two entities distinct.
- name: TRAPPC2L-related progressive encephalopathy with episodic rhabdomyolysis
  description: >-
    Biallelic TRAPPC2L variants cause neurodevelopmental delay with
    febrile-illness-induced encephalopathy and episodes of rhabdomyolysis,
    followed by developmental arrest, epilepsy and tetraplegia. The endpoint
    (developmental arrest, epilepsy, tetraplegia) closely resembles NEDESBA, and
    the muscle involvement reported in a subset of TRAPPC4 patients makes the
    overlap tighter still.
  disease_term:
    preferred_term: encephalopathy, progressive, early-onset, with episodic rhabdomyolysis
    term:
      id: MONDO:0032681
      label: encephalopathy, progressive, early-onset, with episodic rhabdomyolysis
  distinguishing_features:
  - 'Causal gene: TRAPPC2L, not TRAPPC4.'
  - TRAPPC2L disease is defined by discrete febrile-illness-triggered encephalopathic
    and rhabdomyolysis crises, which are not the pattern in NEDESBA, where creatine
    kinase elevation, when present, is persistent and is not the presenting event.
  - Mechanistically TRAPPC2L acts through TRAPPII and RAB11, whereas the TRAPPC4 defect
    is felt principally through the RAB1/TRAPPIII arm.
  evidence:
  - reference: PMID:30120216
    reference_title: Bi-allelic mutations in TRAPPC2L result in a neurodevelopmental
      disorder and have an impact on RAB11 in fibroblasts.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: both of whom presented clinically with a similar phenotype that included
      neurodevelopmental delay, febrile illness-induced encephalopathy and episodes
      of rhabdomyolysis, followed by developmental arrest, epilepsy and tetraplegia
    explanation: Documents the overlapping endpoint and the distinguishing crisis pattern.
  - reference: PMID:30120216
    reference_title: Bi-allelic mutations in TRAPPC2L result in a neurodevelopmental
      disorder and have an impact on RAB11 in fibroblasts.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Since TRAPP II activates the GTPase RAB11, we examined the activation
      state of this protein and found increased levels of the active RAB, correlating
      with changes in its cellular morphology.
    explanation: >-
      Establishes the RAB11/TRAPPII mechanistic axis that distinguishes this
      TRAPPopathy from the RAB1/TRAPPIII-dominated TRAPPC4 disorder.
- name: TRAPPC11-related limb-girdle muscular dystrophy R18 and syndromic myopathy
  description: >-
    Biallelic TRAPPC11 variants cause a spectrum from pure limb-girdle muscular
    dystrophy to a syndromic myopathy with infantile hyperkinetic movements,
    ataxia and intellectual disability. It is the TRAPPopathy to consider when a
    child with a neurodevelopmental disorder has prominent muscle involvement and
    a high creatine kinase, exactly the situation created by the CK elevations
    reported in a subset of TRAPPC4 patients.
  disease_term:
    preferred_term: autosomal recessive limb-girdle muscular dystrophy type R18
    term:
      id: MONDO:0014144
      label: autosomal recessive limb-girdle muscular dystrophy type R18
  distinguishing_features:
  - 'Causal gene: TRAPPC11, a TRAPPIII-specific large subunit, not TRAPPC4.'
  - Muscle disease is the primary and defining feature in TRAPPC11 disorders, whereas
    in NEDESBA the muscle findings are a secondary, inconsistent laboratory observation
    on a background of profound epileptic encephalopathy and brain atrophy.
  - TRAPPC11 patients do not show the progressive severe microcephaly with cortical
    and cerebellar atrophy that defines NEDESBA.
  evidence:
  - reference: PMID:23830518
    reference_title: Recessive TRAPPC11 mutations cause a disease spectrum of limb
      girdle muscular dystrophy and myopathy with movement disorder and intellectual
      disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: we report the identification of mutations in transport protein particle
      complex 11 (TRAPPC11) in three individuals of a consanguineous Syrian family
      presenting with LGMD and in five individuals of Hutterite descent presenting with
      myopathy, infantile hyperkinetic movements, ataxia, and intellectual disability
    explanation: >-
      Establishes the muscle-dominant phenotype and distinct gene for this
      differential.
- name: TRAPPC9-related autosomal recessive intellectual disability 13
  description: >-
    Biallelic TRAPPC9 variants cause autosomal recessive intellectual disability
    with postnatal microcephaly and a thin corpus callosum. It shares the
    microcephaly-plus-intellectual-disability core with NEDESBA and is a
    frequently cited member of the TRAPPopathy differential.
  disease_term:
    preferred_term: intellectual disability, autosomal recessive 13
    term:
      id: MONDO:0013173
      label: intellectual disability, autosomal recessive 13
  distinguishing_features:
  - 'Causal gene: TRAPPC9, a TRAPPII-specific subunit, not TRAPPC4.'
  - The TRAPPC9 phenotype is a comparatively static intellectual disability with microcephaly
    and thin corpus callosum.
  - It lacks the early-onset epileptic encephalopathy, spastic tetraplegia, and relentlessly
    progressive cerebral and cerebellar atrophy that define NEDESBA.
  evidence:
  - reference: PMID:28626029
    reference_title: A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental
      disorder characterised by microcephaly, epilepsy and autistic features.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: intellectual disability with microcephaly (TrappC9 (MIM 611966); TRAPP
      II)
    explanation: >-
      Places TRAPPC9 in the TRAPPopathy differential with an
      intellectual-disability-with-microcephaly phenotype and identifies it as a
      TRAPPII subunit.
- name: Early-infantile neurodegenerative and neurometabolic mimics
  description: >-
    Before molecular diagnosis, NEDESBA is routinely mistaken for a
    neurometabolic disease. The reported differential includes early-onset
    epileptic encephalopathies, lysosomal storage disorders such as neuronal
    ceroid lipofuscinosis, mitochondrial encephalopathies, and the
    leukodystrophies (metachromatic leukodystrophy, Krabbe disease). In one
    reported infant a low biotin level even suggested biotinidase deficiency
    before enzymatic testing excluded it.
  distinguishing_features:
  - A thorough metabolic workup (plasma amino acids, acylcarnitines, urine organic
    acids, lysosomal enzymes, neuronal ceroid lipofuscinosis enzymes) is normal in
    NEDESBA.
  - Grey- versus white-matter predominance on MRI helps triage the mimics, but the
    definitive discriminator is biallelic TRAPPC4 variants on sequencing.
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Early-onset epileptic encephalopathies, lysosomal storage diseases, such
      as NCL, and mitochondrial encephalopathies present with prominent gray matter
      involvement, whereas white matter involvement occurs in disorders with demyelination,
      such as MLD and Krabbe disease.
    explanation: Enumerates the neurodegenerative mimics and how imaging helps triage them.
  - reference: PMID:42543852
    reference_title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: However, confirmatory biochemical and enzymatic studies ruled out classic
      biotinidase deficiency.
    explanation: A worked example of a metabolic mimic misleading the initial workup.
treatments:
- name: Antiseizure pharmacotherapy
  description: >-
    Symptomatic treatment of the epilepsy. Levetiracetam, topiramate, clobazam
    and valproate have all been used; responses are frequently partial and
    seizures may persist or recur despite escalation, so drug substitution is
    common. No disease-modifying therapy exists.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: anticonvulsant agent
      term:
        id: NCIT:C264
        label: Anticonvulsant Agent
    - preferred_term: levetiracetam
      term:
        id: CHEBI:6437
        label: levetiracetam
    - preferred_term: topiramate
      term:
        id: CHEBI:63631
        label: topiramate
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She was put on levetiracetam (LEV) treatment, although infrequent clonic
      seizures occurred despite LEV therapy of 40 mg/kg/day.
    explanation: >-
      Documents levetiracetam use and the incomplete response that motivated a drug
      change; support is PARTIAL because efficacy was incomplete.
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She had had no obvious seizure on topiramate treatment of 5 mg/kg/day.
    explanation: Documents seizure control achieved after switching to topiramate.
- name: Spasticity management
  description: >-
    Antispasticity pharmacotherapy, in reported practice baclofen, combined with
    a physical rehabilitation programme. Reported responses are poor: spasticity
    persisted despite baclofen and rehabilitation in a documented patient, so
    expectations should be set accordingly.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: baclofen
      term:
        id: CHEBI:2972
        label: baclofen
  target_phenotypes:
  - preferred_term: Spastic tetraplegia
    term:
      id: HP:0002510
      label: Spastic tetraplegia
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: persistent spasticity in spite of baclofen treatment and a physical rehabilitation
      program were noted
    explanation: >-
      Documents baclofen plus rehabilitation as the treatment used, and its limited
      effect; hence PARTIAL rather than SUPPORT.
- name: Rehabilitation and supportive therapy
  description: >-
    Multidisciplinary physical, occupational and communication therapy for the
    profound motor and developmental impairment. Rehabilitation is supportive and
    does not alter the progressive course.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Physical Therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: persistent spasticity in spite of baclofen treatment and a physical rehabilitation
      program were noted
    explanation: Documents that a physical rehabilitation programme forms part of management.
- name: Nutritional and feeding support
  description: >-
    Management of feeding difficulties, regurgitation and failure to thrive, with
    enteral or tube feeding when oral intake becomes unsafe or insufficient.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Nutritional Support
    term:
      id: NCIT:C15433
      label: Nutritional Support
  target_phenotypes:
  - preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: P1 presented in the early infantile period with developmental delay, feeding
      difficulties and seizures
    explanation: Establishes the feeding difficulty that this supportive measure addresses.
- name: Genetic counseling and reproductive options
  description: >-
    Autosomal recessive inheritance carries a 25% recurrence risk for each
    subsequent pregnancy. Because the recurrent c.454+3A>G allele has a
    measurable carrier frequency in the general population, on the order of a few
    per 10,000 and highest in Mediterranean and European ancestries, cascade
    carrier testing of relatives and, once the familial allele is known, prenatal
    or preimplantation testing are the practical preventive options.
  action_category: COUNSELING_INFORMATIONAL
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:36211171
    reference_title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy
      in Early Infancy: Consider TRAPPC4 Trappopathy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Carrier frequency of this neurodevelopmental and neurodegenerative disorder,
      NEDESBA, has been reported to be relatively high, varying from 2.4-5.4 per 10
      000 individuals worldwide
    explanation: >-
      The carrier frequency that makes cascade testing and carrier screening a
      meaningful part of counseling.
  - reference: PMID:40173375
    reference_title: 'Child Neurology: TRAPPC4-Related Neurodevelopmental Disorder.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Given a relatively high carrier frequency, it is crucial to recognize
      and consider this diagnosis.
    explanation: Independent statement of the counseling/recognition imperative.
genetic:
- name: TRAPPC4
  gene_term:
    preferred_term: TRAPPC4
    term:
      id: hgnc:19943
      label: TRAPPC4
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  presence: Biallelic pathogenic or likely pathogenic variants
  notes: >-
    TRAPPC4 (aliases SBDN, synbindin, TRS23) lies at 11q23.3 and encodes one of
    the small core subunits shared by the TRAPPII and TRAPPIII complexes. The
    allelic spectrum is unusually narrow. The recurrent non-canonical splice
    variant NM_016146.5:c.454+3A>G (hg19:chr11:g.118890966A>G;
    hg38:11:119020256 A>G; ClinVar VCV000812649.1) accounts for 31 of 33
    reported individuals from 21 of 22 families, almost always homozygous and
    usually in a consanguineous setting; a screen of over 10,000 patients with
    neurodevelopmental conditions found no other clinically relevant TRAPPC4
    variant. The remaining reported alleles are two novel homozygous missense
    variants in Indian families, c.191T>C p.(Leu64Pro) and c.278C>T p.(Pro93Leu)
    (both predicted to destabilize the protein), and a biallelic in-frame
    deletion causing stop-loss in one family with a milder, later-onset
    phenotype and normal head circumference. All are hypomorphic: complete loss
    of this essential core subunit is thought to be incompatible with survival.
    Penetrance: every reported homozygote for c.454+3A>G has been clinically
    affected, so penetrance appears complete for that genotype; heterozygous
    carriers are unaffected. Penetrance across the wider (very small) allelic
    spectrum is not established, and no unaffected homozygote has been described.
    The residual level of correctly spliced transcript is the presumed determinant
    of both viability and severity, but this has not been measured against
    clinical severity in a patient series.
  inheritance:
  - name: Autosomal recessive
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:31794024
    reference_title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated
      with severe syndromic intellectual disability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This is the first report of a TRAPPC4 variant, and our findings add to
      the growing number of TRAPP-associated neurological disorders.
    explanation: The founding gene-disease association.
  - reference: PMID:32901138
    reference_title: A relatively common homozygous TRAPPC4 splicing variant is associated
      with an early-infantile neurodegenerative syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These data confirm the pathogenicity of the TRAPPC4 c.454+3A>G variant,
      and refine the clinical presentation of TRAPPC4-related encephalopathy.
    explanation: Independent multicentre confirmation of the gene-disease relationship.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: of the 33 individuals from 22 families reported to date, 31 individuals
      from 21 families have been reported with a recurrent homozygous pathogenic variant
    explanation: Quantifies how strongly the allelic spectrum is dominated by one variant.
  - reference: PMID:34878169
    reference_title: Further evidence of muscle involvement in neurodevelopmental disorder
      with epilepsy, spasticity, and brain atrophy.
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: Further, I-Mutant also predicts the decreased stability of the mutant
      protein
    explanation: >-
      In silico stability prediction supporting the destabilizing effect of the
      p.(Leu64Pro) missense allele; classified COMPUTATIONAL because it is a
      prediction, not a measurement.
datasets: []
notes: >-
  GeneReviews baseline: a PubMed search for a GeneReviews chapter on TRAPPC4,
  NEDESBA, or the TRAPPopathies returned no results, so no GeneReviews phenotype
  baseline was available for this entry. Phenotype coverage was instead
  cross-referenced against the two largest primary cohorts (PMID:31794024,
  PMID:32901138) and the literature review tabulated in PMID:34878169.
  Named-entity-confusion preflight: MONDO:0032894 was confirmed by OAK to carry
  OMIM:618741 and the RO:0004003 relationship to HGNC:19943 (TRAPPC4), and
  `just preflight-dr` on the falcon deep-research report returned PASS with 56
  TRAPPC4 mentions and no competing TRAPPC-family gene dominating the report.
  Every citation in this entry was individually checked to be TRAPPC4-specific,
  except the deliberately cross-family citations used in
  `differential_diagnoses`, where the sibling gene is named explicitly in the
  distinguishing_features text. Two cited papers (PMID:32125366, PMID:33011761)
  are Brain correspondence letters whose full text is not retrievable through
  the reference cache; they are listed under `references` for completeness but
  are deliberately not used as evidence snippets anywhere in the entry.
  Deliberate phenotype omissions: muscle wasting (HP:0003202) and joint
  contracture (HP:0001371) are plausible and are mentioned in secondary review
  syntheses, but no exact-quote snippet supporting either could be found in any
  cached reference for this entry, so neither is asserted as a phenotype. They
  are recorded here as candidates for a future pass if a citable primary source
  becomes available. The muscle axis that IS citable is captured as the elevated
  creatine kinase and elevated lactate phenotypes.
references:
- reference: PMID:31794024
  title: Deficiencies in vesicular transport mediated by TRAPPC4 are associated with
    severe syndromic intellectual disability.
- reference: PMID:32901138
  title: A relatively common homozygous TRAPPC4 splicing variant is associated with
    an early-infantile neurodegenerative syndrome.
- reference: PMID:32125366
  title: Recurrent bi-allelic splicing variant c.454+3A>G in TRAPPC4 is associated
    with progressive encephalopathy and muscle involvement.
- reference: PMID:33011761
  title: Biallelic in-frame deletion in TRAPPC4 in a family with developmental delay
    and cerebellar atrophy.
- reference: PMID:34878169
  title: Further evidence of muscle involvement in neurodevelopmental disorder with
    epilepsy, spasticity, and brain atrophy.
- reference: PMID:36211171
  title: 'Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy in Early
    Infancy: Consider TRAPPC4 Trappopathy.'
- reference: PMID:40173375
  title: 'Child Neurology: TRAPPC4-Related Neurodevelopmental Disorder.'
- reference: PMID:42543852
  title: A Case Report and a Review of TRAPPC4-Related TRAPPopathy.
- reference: PMID:32116085
  title: 'TRAPPing a neurological disorder: from yeast to humans.'
- reference: PMID:39769094
  title: 'TRAPPopathies: Severe Multisystem Disorders Caused by Variants in Genes of
    the Transport Protein Particle (TRAPP) Complexes.'
- reference: PMID:30152084
  title: 'TRAPPopathies: An emerging set of disorders linked to variations in the genes
    encoding transport protein particle (TRAPP)-associated proteins.'
- reference: PMID:34018214
  title: Cryo-EM structure of metazoan TRAPPIII, the multi-subunit complex that activates
    the GTPase Rab1.
- reference: PMID:17110339
  title: The architecture of the multisubunit TRAPP I complex suggests a model for
    vesicle tethering.
- reference: PMID:28777934
  title: Mutations in TRAPPC12 Manifest in Progressive Childhood Encephalopathy and
    Golgi Dysfunction.
- reference: PMID:28626029
  title: A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental
    disorder characterised by microcephaly, epilepsy and autistic features.
- reference: PMID:30120216
  title: Bi-allelic mutations in TRAPPC2L result in a neurodevelopmental disorder and
    have an impact on RAB11 in fibroblasts.
- reference: PMID:23830518
  title: Recessive TRAPPC11 mutations cause a disease spectrum of limb girdle muscular
    dystrophy and myopathy with movement disorder and intellectual disability.

📚

References & Deep Research

References

17

PMID:31794024

Deficiencies in vesicular transport mediated by TRAPPC4 are associated with severe syndromic intellectual disability.

No top-level findings curated for this source.

PMID:32901138

A relatively common homozygous TRAPPC4 splicing variant is associated with an early-infantile neurodegenerative syndrome.

No top-level findings curated for this source.

PMID:32125366

Recurrent bi-allelic splicing variant c.454+3A>G in TRAPPC4 is associated with progressive encephalopathy and muscle involvement.

No top-level findings curated for this source.

PMID:33011761

Biallelic in-frame deletion in TRAPPC4 in a family with developmental delay and cerebellar atrophy.

No top-level findings curated for this source.

PMID:34878169

Further evidence of muscle involvement in neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy.

No top-level findings curated for this source.

PMID:36211171

Severe Microcephaly and Rapid Deterioration Due to Cortical Atrophy in Early Infancy: Consider TRAPPC4 Trappopathy.

No top-level findings curated for this source.

PMID:40173375

Child Neurology: TRAPPC4-Related Neurodevelopmental Disorder.

No top-level findings curated for this source.

PMID:42543852

A Case Report and a Review of TRAPPC4-Related TRAPPopathy.

No top-level findings curated for this source.

PMID:32116085

TRAPPing a neurological disorder: from yeast to humans.

No top-level findings curated for this source.

PMID:39769094

TRAPPopathies: Severe Multisystem Disorders Caused by Variants in Genes of the Transport Protein Particle (TRAPP) Complexes.

No top-level findings curated for this source.

PMID:30152084

TRAPPopathies: An emerging set of disorders linked to variations in the genes encoding transport protein particle (TRAPP)-associated proteins.

No top-level findings curated for this source.

PMID:34018214

Cryo-EM structure of metazoan TRAPPIII, the multi-subunit complex that activates the GTPase Rab1.

No top-level findings curated for this source.

PMID:17110339

The architecture of the multisubunit TRAPP I complex suggests a model for vesicle tethering.

No top-level findings curated for this source.

PMID:28777934

Mutations in TRAPPC12 Manifest in Progressive Childhood Encephalopathy and Golgi Dysfunction.

No top-level findings curated for this source.

PMID:28626029

A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental disorder characterised by microcephaly, epilepsy and autistic features.

No top-level findings curated for this source.

PMID:30120216

Bi-allelic mutations in TRAPPC2L result in a neurodevelopmental disorder and have an impact on RAB11 in fibroblasts.

No top-level findings curated for this source.

PMID:23830518

Recessive TRAPPC11 mutations cause a disease spectrum of limb girdle muscular dystrophy and myopathy with movement disorder and intellectual disability.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 17 citations 2026-08-15T08:43:07.981619

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Neurodevelopmental Disorder with Epilepsy, Spasticity, and Brain Atrophy
MONDO ID: (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Neurodevelopmental Disorder with Epilepsy, Spasticity, and Brain Atrophy covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Neurodevelopmental Disorder With Epilepsy, Spasticity, and Brain Atrophy (NEDESBA)

Executive summary

NEDESBA is an ultra-rare, autosomal-recessive, progressive neurodevelopmental/neurodegenerative TRAPPopathy caused by biallelic pathogenic variants in TRAPPC4. The usual presentation is an initially unremarkable neonatal period followed during early infancy by profound developmental impairment or regression, progressive microcephaly, epilepsy, spastic tetraplegia, impaired vision, and progressive cerebral—often also cerebellar—atrophy. The recurrent hypomorphic splice variant NM_016146.5:c.454+3A>G accounts for most published cases. Patient-fibroblast and yeast experiments directly demonstrate impaired TRAPP-complex assembly, delayed Golgi trafficking, and defective autophagic flux. No disease-modifying treatment or disease-specific clinical trial has been established; current practice is molecular diagnosis, symptomatic epilepsy management, multidisciplinary supportive care, and genetic counseling. (bergen2020deficienciesinvesicular pages 1-2, ghosh2021arelativelycommon pages 1-2, hall2024trappopathiesseveremultisystem pages 7-9)

Field	Evidence-backed value	Suggested ontology/identifier
Disease name	Neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy (NEDESBA); TRAPPC4-related neurodevelopmental disorder (forno2025childneurologytrappc4related pages 1-2, ghosh2021arelativelycommon pages 1-2)	MONDO:0032894; OMIM phenotype: 618741
Disease type / evidence granularity	Mendelian, aggregated disease-level knowledge derived primarily from published case series/cohorts plus functional cellular/yeast studies, not EHR-derived population studies (bergen2020deficienciesinvesicular pages 1-2, ghosh2021arelativelycommon pages 2-3)	Disease category: Mendelian disorder
Causal gene	TRAPPC4 (trafficking protein particle complex subunit 4; synbindin), core TRAPP subunit (bergen2020deficienciesinvesicular pages 2-3, ghosh2021arelativelycommon pages 1-2, bergen2020deficienciesinvesicular pages 1-2)	HGNC: TRAPPC4; Ensembl: ENSG00000196655; OMIM gene: 610971
Primary disease mechanism class	Autosomal recessive TRAPPopathy with defective vesicular trafficking and autophagy due to reduced/altered TRAPPC4 function (direct evidence) (bergen2020deficienciesinvesicular pages 1-2, hall2024trappopathiesseveremultisystem pages 7-9)	GO: vesicle-mediated transport; GO: autophagy; Rab1 GEF-related TRAPP function
Inheritance	Autosomal recessive; all confirmed affected individuals reported with biallelic/homozygous pathogenic variants (ghosh2021arelativelycommon pages 2-3, forno2025childneurologytrappc4related pages 1-2, hall2024trappopathiesseveremultisystem pages 7-9)	HP:0000007
MONDO/target association	Open Targets shows disease-target association between MONDO_0032894 and TRAPPC4 (OpenTargets Search: neurodevelopmental disorder with epilepsy spasticity and brain atrophy-TRAPPC4)	MONDO_0032894 ↔ ENSG00000196655
Recurrent pathogenic variant	Homozygous splice-site variant NM_016146.5:c.454+3A>G; rs375776811; recurrent across unrelated families; causes aberrant/leaky splicing with reduced full-length transcript and protein (bergen2020deficienciesinvesicular pages 1-2, ghosh2021arelativelycommon pages 2-3, ghosh2021arelativelycommon pages 1-2)	ClinVar: VCV000812649.1; variant type: splice-region/intronic
Founder vs hotspot	Not established as a founder allele; SNP array/haplotype data favored hotspot or recurrent variant rather than shared founder effect in at least some families (direct evidence) (bergen2020deficienciesinvesicular pages 1-2)	Population-genetic note: founder effect not established
Additional reported TRAPPC4 variants	2024 review summarizes missense p.Leu64Pro and p.Pro93Leu in Indian families; also ClinVar-listed p.Leu125Pro and p.Gly213Ter220delinsXaa reported as pathogenic/likely pathogenic in AR NEDESBA spectrum. These statements are review-level synthesis and should be independently verified in variant databases/primary case reports before KB hard-coding (hall2024trappopathiesseveremultisystem pages 7-9)	HGVS protein variants; ACMG class: verify in ClinVar/lab submission
Allele frequency	Carrier frequency for c.454+3A>G estimated at 2.4–5.4 per 10,000 healthy individuals; heterozygous MAF reported about 0.033–0.054% in unaffected cohorts/public datasets (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7)	Population databases: gnomAD/100K Genomes/GeneDx cohorts (study-reported)
Penetrance	Reported homozygous individuals were clinically affected, suggesting full penetrance in known cases for homozygous c.454+3A>G; broader penetrance across all TRAPPC4 variants remains not established (ghosh2021arelativelycommon pages 4-6)	Penetrance: appears high/complete for known homozygotes
Typical onset	Usually normal pregnancy/neonatal course followed by onset in first months of life; seizures often begin in the first 6 months (ghosh2021arelativelycommon pages 4-6, bergen2020deficienciesinvesicular pages 1-2)	HPO onset: infantile onset
Disease course	Severe progressive encephalopathy/neurodegeneration with developmental stagnation, regression, microcephaly progression, and worsening brain atrophy (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7)	HP:0002344; progressive course
Developmental phenotype	Profound psychomotor delay / severe developmental delay is a core feature; developmental stagnation and loss of acquired milestones common (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 4-6)	HP:0011344; HP:0001263; HP:0002376
Regression frequency	Psychomotor regression reported in all phenotyped individuals in expanded cohort text (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7)	HP:0002376
Epilepsy frequency	Early-onset epilepsy is a core feature; in initial Brain cohort seizures in 7/7; larger cohort states all patients had seizure onset in first 6 months where described (bergen2020deficienciesinvesicular pages 15-16, ghosh2021arelativelycommon pages 4-6)	HP:0001250
Seizure types	Variable: infantile spasms, focal, tonic-clonic, atonic, tonic; occasional gelastic seizures reported in earlier cases (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7)	HP:0012469; HP:0002123; HP:0002069
EEG	Non-specific; generalized disorganization and epileptiform discharges reported (ghosh2021arelativelycommon pages 4-6)	EEG abnormality; HPO term suggestion: HP:0002353
Spasticity / motor syndrome	Spastic tetraplegia/spastic quadriparesis and hyperreflexia are major hallmarks; initial cohort had impaired mobility 7/7 (bergen2020deficienciesinvesicular pages 15-16, ghosh2021arelativelycommon pages 4-6, bergen2020deficienciesinvesicular pages 1-2)	HP:0002510; HP:0001270; HP:0001347
Microcephaly	Common and often progressive/severe; initial cohort 7/7; expanded cohort mean OFC approximately -5.77 SD at ~5 years (bergen2020deficienciesinvesicular pages 15-16, ghosh2021arelativelycommon pages 4-6)	HP:0000252
Intellectual disability	Severe/profound intellectual disability/developmental impairment; initial cohort 7/7 (bergen2020deficienciesinvesicular pages 15-16, bergen2020deficienciesinvesicular pages 1-2)	HP:0001249
Visual involvement	Visual impairment/poor pursuits common; initial cohort vision issues 3/6; later review estimated visual impairment around 83% but this is secondary synthesis and may reflect ascertainment differences (forno2025childneurologytrappc4related pages 2-4, bergen2020deficienciesinvesicular pages 15-16, ghosh2021arelativelycommon pages 4-6)	HP:0000505; HP:0000657; HP:0001133
Cataracts / optic findings	Bilateral cataracts reported in some patients; optic nerve pallor in 2025 case report/reviewed siblings (ghosh2021arelativelycommon pages 4-6, forno2025childneurologytrappc4related pages 1-2)	HP:0000518; HP:0000648
Hearing involvement	Sensorineural hearing loss reported; initial cohort hearing loss 2/6; later review-level estimate ~14% (forno2025childneurologytrappc4related pages 2-4, bergen2020deficienciesinvesicular pages 15-16, bergen2020deficienciesinvesicular pages 1-2)	HP:0000407
Movement disorders	Dystonia/ataxia/dyskinesia present in a subset; review-level estimate ~44% movement disorder, but direct cohort counts are smaller (forno2025childneurologytrappc4related pages 2-4, ghosh2021arelativelycommon pages 4-6)	HP:0001332; HP:0001251; HP:0100022
Muscle involvement	Reduced muscle mass/wasting common clinically; primary muscle disease not established. Rare cases with elevated lactate/CK and episodic rhabdomyolysis-like features reported (ghosh2021arelativelycommon pages 6-7, hall2024trappopathiesseveremultisystem pages 7-9)	HP:0003202; HP:0003391; possible HP:0003201
Dysmorphism	Subtle, non-specific facial dysmorphism frequent: bitemporal narrowing, thick eyebrows, full cheeks, long philtrum, wide mouth, tented upper lip, pointed chin (ghosh2021arelativelycommon pages 4-6)	HPO suggestions: HP:0000341, HP:0000316, HP:0000179
Brain MRI	Consistent global cerebral atrophy, often cortical + cerebellar atrophy, ventriculomegaly/ventricular enlargement, white matter loss/abnormalities, enlarged subarachnoid spaces, thin corpus callosum/hypoplasia; sometimes brainstem or basal ganglia involvement (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7, bergen2020deficienciesinvesicular pages 1-2)	HP:0002059; HP:0001272; HP:0001273; HP:0002120; HP:0002079
MRI progression	Older children often show more severe cerebral/cerebellar atrophy, suggesting progression (ghosh2021arelativelycommon pages 6-7)	Progressive neuroimaging abnormality
Affected anatomy	Primary: CNS/brain—cerebral cortex, cerebellum, corpus callosum, white matter; likely vulnerable neuronal populations include pyramidal neurons, Purkinje cells, and motor neurons based on expression/biology (direct + inference) (bergen2020deficienciesinvesicular pages 2-3, hall2024trappopathiesseveremultisystem pages 7-9)	UBERON: brain, cerebellum, cerebral cortex, corpus callosum; CL: pyramidal neuron, Purkinje cell, motor neuron
Upstream molecular defect	TRAPPC4 is a core component of TRAPP complexes and essential for Rab1 GEF activity; pathogenic variants reduce TRAPPC4 transcript/protein and destabilize/impair TRAPP complex assembly (direct evidence) (bergen2020deficienciesinvesicular pages 1-2, bergen2020deficienciesinvesicular pages 15-16)	GO:0034058? Rab GEF complex-related; Rab1 pathway
Cellular mechanism	Direct evidence: delayed trafficking into and out of the Golgi in patient fibroblasts; basal autophagy defect and delayed autophagic flux, possibly due to unsealed autophagosomes; rescue by lentiviral WT TRAPPC4 (bergen2020deficienciesinvesicular pages 1-2, bergen2020deficienciesinvesicular pages 16-17)	GO:0006888 ER-to-Golgi vesicle-mediated transport; GO:0006914 autophagy; GO:0048193 Golgi vesicle transport
Neuronal mechanism beyond fibroblasts	Inference/expert synthesis: neurodegeneration likely reflects high neuronal dependence on membrane trafficking/autophagy; TRAPPC4 may contribute to dendrite maturation via syndecan-2-associated vesicle recruitment (review of prior basic science, not direct NEDESBA patient evidence) (hall2024trappopathiesseveremultisystem pages 7-9)	GO: dendrite development; CL: pyramidal neuron
Environmental/lifestyle risks	Not established. No disease-specific environmental, toxin, lifestyle, sex, or infectious causal risk factors identified. Infections are reported as causes of death/clinical stressors, not established etiologic triggers (ghosh2021arelativelycommon pages 6-7)	Unknown/not established
Diagnostics: core approach	Molecular diagnosis by WES/WGS with segregation analysis; RNA studies useful because splice variant may be missed/deprioritized by exome filtering. Ancillary evaluation includes MRI and EEG (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 2-3, ghosh2021arelativelycommon pages 6-7, bergen2020deficienciesinvesicular pages 1-2)	WES/WGS; RNA-seq; Sanger confirmation
RNA-based diagnosis	RNA-seq from fibroblasts demonstrated partial exon 3 skipping and aberrant cryptic splice donor usage, supporting pathogenicity and utility of transcript analysis (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 6-7)	Transcriptomics / RNA-seq
Differential diagnostic neighborhood	Other TRAPPopathies and early infantile neurodegenerative/developmental epileptic encephalopathies with microcephaly, spasticity, and brain atrophy; disease-specific formal criteria not established (ghosh2021arelativelycommon pages 1-2, bergen2020deficienciesinvesicular pages 15-16)	TRAPPopathy spectrum
Biomarkers	No validated disease-specific circulating biomarker established. Occasional elevated lactate/CK/transaminases reported in some individuals with muscle involvement, but not specific or consistently present (ghosh2021arelativelycommon pages 6-7, hall2024trappopathiesseveremultisystem pages 7-9)	Biomarker status: not established
Treatment	No disease-modifying therapy established. Symptomatic treatment includes anti-seizure medications with often partial response (levetiracetam, clobazam; in a 2025 case levetiracetam/valproate initially responsive) plus multidisciplinary supportive care (forno2025childneurologytrappc4related pages 1-2, ghosh2021arelativelycommon pages 4-6, hall2024trappopathiesseveremultisystem pages 7-9)	NCIT: Anticonvulsant Therapy; Supportive Care
Clinical trials	No disease-specific interventional clinical trials identified in search results available here (clinical-trials search negative) (OpenTargets Search: neurodevelopmental disorder with epilepsy spasticity and brain atrophy-TRAPPC4)	ClinicalTrials.gov: none found
Prevention / family planning	Primary prevention not established. Practical prevention is genetic counseling, cascade family testing, carrier detection, and reproductive options (prenatal/preimplantation testing) once familial variant is known; screening utility specifically suggested because recurrent allele has measurable carrier frequency in some populations (ghosh2021arelativelycommon pages 6-7)	Genetic counseling; carrier screening
Prognosis	Severe lifelong neurodevelopmental disability with progressive neurologic decline. Early death reported in 5/23 individuals in one series, mean 8.8 years, mainly from infections; full survival distribution remains unknown (ghosh2021arelativelycommon pages 6-7)	Prognosis: poor, progressive
Epidemiology	Ultra-rare; no population prevalence/incidence studies. By 2025, review/case literature suggested approximately 32 reported cases, but this likely includes overlapping published cohorts and should be treated cautiously (forno2025childneurologytrappc4related pages 2-4)	Prevalence/incidence: unknown
Population distribution	Families reported from multiple ancestries including Iranian, Egyptian, Portuguese, English, mixed European-American, Turkish, Caucasian, French-Canadian; no single founder proven (ghosh2021arelativelycommon pages 2-3, bergen2020deficienciesinvesicular pages 1-2)	Geographic distribution: multicontinental case reports
Sex ratio	Not established from available summarized evidence (ghosh2021arelativelycommon pages 4-6)	Unknown/not established
Natural disease in other species	Not established; no naturally occurring veterinary disease linked to TRAPPC4 identified in available evidence (hall2024trappopathiesseveremultisystem pages 7-9)	OMIA: no evidence found
Experimental models	Direct models: patient fibroblasts and yeast trs23 temperature-sensitive model validated trafficking/autophagy defects. Mouse: complete knockout is embryonic lethal (review-level statement). Disease-specific advanced neuronal/iPSC/organoid models are limited/not yet established in published direct evidence summarized here (hall2024trappopathiesseveremultisystem pages 7-9, bergen2020deficienciesinvesicular pages 16-17, bergen2020deficienciesinvesicular pages 1-2)	Model systems: fibroblast; Saccharomyces cerevisiae trs23; mouse KO (embryonic lethal)
Key knowledge gaps	Variant spectrum beyond c.454+3A>G, natural history, standardized outcome measures, prognostic biomarkers, tissue-specific mechanisms in neurons, and therapeutic strategies all remain incompletely defined (hall2024trappopathiesseveremultisystem pages 7-9)	Research gap annotation

Table: This table condenses the main evidence-backed knowledge-base fields for TRAPPC4-related NEDESBA, including identifiers, recurrent and additional variants, phenotype frequencies, mechanism, diagnostics, prognosis, and model systems. It also flags where evidence is direct versus inferred and where items remain unknown or not established.

1. Disease information

Definition. NEDESBA is a severe Mendelian encephalopathy in which deficient TRAPPC4 function disrupts intracellular membrane trafficking and autophagy. It was first molecularly delineated by Van Bergen et al.; the report was accepted October 7, 2019 and published in Brain in 2020. Open Targets links the disease to one target, TRAPPC4, supported by five evidence records. (OpenTargets Search: neurodevelopmental disorder with epilepsy spasticity and brain atrophy-TRAPPC4, bergen2020deficienciesinvesicular pages 1-2)

Identifiers and names

MONDO: MONDO:0032894.
OMIM phenotype: 618741.
OMIM gene: TRAPPC4, 610971.
Gene: TRAPPC4, trafficking protein particle complex subunit 4; Ensembl ENSG00000196655; historical protein name synbindin.
Synonyms: NEDESBA; TRAPPC4-related neurodevelopmental disorder; TRAPPC4-related encephalopathy; TRAPPC4-related early-infantile neurodegenerative syndrome; severe syndromic intellectual disability due to TRAPPC4 deficiency.
Orphanet: no confidently verified disease-specific ORPHA identifier was found in the retrieved evidence.
ICD-10/ICD-11 and MeSH: no specific code or descriptor is established; coding ordinarily uses broader categories for developmental/epileptic encephalopathy, intellectual disability, epilepsy, microcephaly, and spastic quadriplegia.

The knowledge base is aggregated from published families, case series, diagnostic cohorts, patient-derived fibroblasts, and experimental models—not from population-level EHR surveillance. The foundational article studied seven children from three families; the subsequent expansion described 23 patients from 17 families and brought the authors’ combined reported total to 27. Counts in later reviews overlap these publications and must not be summed as independent cases. (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 2-3, bergen2020deficienciesinvesicular pages 1-2)

Exact primary-literature quotation: “Here, we report 23 patients from 17 independent families with an early-infantile-onset neurodegenerative presentation” carrying homozygous c.454+3A>G. (ghosh2021arelativelycommon pages 1-2)

2. Etiology, risk, protective factors, and gene–environment interaction

Causal factor

The primary cause is germline biallelic TRAPPC4 dysfunction. The predominant allele, c.454+3A>G, is a leaky noncanonical splice-site variant: RNA sequencing showed partial exon 3 skipping and use of a downstream cryptic donor, producing frameshifted transcripts predicted to undergo nonsense-mediated decay. Residual correctly spliced transcript explains viability and supports a hypomorphic loss-of-function mechanism. Complete Trappc4 knockout is reportedly embryonic lethal in mice. (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 4-6, hall2024trappopathiesseveremultisystem pages 7-9)

Genetic risk

Homozygosity or compound heterozygosity for pathogenic TRAPPC4 alleles is the established risk.
Heterozygous c.454+3A>G carriers appear clinically unaffected.
Study-reported carrier frequency was 2.4–5.4 per 10,000 healthy individuals; heterozygous allele frequencies were approximately 0.033–0.054% in GeneDx and 100,000 Genomes datasets. (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 4-6)
No shared haplotype was demonstrated across Turkish and Caucasian families, favoring a recurrent hotspot over a proven founder effect. A remote common ancestor cannot be excluded. (ghosh2021arelativelycommon pages 6-7, bergen2020deficienciesinvesicular pages 1-2)

Environmental, infectious, lifestyle, and protective factors

No toxin, diet, lifestyle, occupational exposure, pathogen, sex, parental age, or environmental exposure is known to cause NEDESBA. Infections caused several reported deaths but are not established etiologic triggers. No genetic protective variants, modifier genes, dietary protection, or validated gene–environment interaction has been identified. Residual wild-type TRAPPC4 expression is likely a determinant of viability and may modify severity, but this is a mechanistic inference rather than a validated protective allele. (ghosh2021arelativelycommon pages 6-7, hall2024trappopathiesseveremultisystem pages 7-9)

3. Phenotypes

The best quantified initial cohort had seizures, intellectual disability, developmental delay/regression, microcephaly, and impaired mobility in 7/7; MRI abnormalities in 4/4, hearing loss in 2/6, and visual problems in 3/6 evaluable individuals. Later series broadened the spectrum, but missing data and cohort overlap limit precise percentages. (bergen2020deficienciesinvesicular pages 15-16)

Phenotype and type	Characteristics and frequency	Suggested HPO term
Developmental delay/intellectual disability	Severe-to-profound; motor, language, and social stagnation begins in the first months	Global developmental delay HP:0001263; intellectual disability HP:0001249
Developmental regression	Progressive loss of early milestones; reported in all phenotyped individuals in the expanded series	Developmental regression HP:0002376
Epilepsy	Usually begins before 6 months; spasms, focal, tonic, atonic, and tonic-clonic seizures; occasional gelastic seizures	Seizure HP:0001250; infantile spasms HP:0012469
EEG abnormality	Nonspecific generalized disorganization and epileptiform discharges	Abnormal EEG HP:0002353
Progressive microcephaly	Severe; mean OFC approximately −5.77 SD at about age 5 years in the expanded cohort	Microcephaly HP:0000252; progressive microcephaly HP:0000253
Spastic tetraplegia/hyperreflexia	Core progressive motor manifestation; contractures and severe mobility impairment follow	Spastic tetraplegia HP:0002510; hyperreflexia HP:0001347; joint contracture HP:0001371
Movement disorder	Dystonia, dyskinesia, or ataxia in a subset; a later synthesis estimated 44%	Dystonia HP:0001332; ataxia HP:0001251
Visual dysfunction	Poor/absent visual pursuit, cortical visual dysfunction, optic pallor/atrophy; later synthesis estimated 83%, but ascertainment differs	Visual impairment HP:0000505; optic atrophy HP:0000648
Cataract	Bilateral cataracts in three expanded-cohort patients	Cataract HP:0000518
Sensorineural hearing loss	2/6 in the initial cohort; later synthesis estimated 14%	Sensorineural hearing impairment HP:0000407
Brain atrophy	Universal or near-universal in imaged cohorts; progressive cerebral ± cerebellar involvement	Cerebral atrophy HP:0002059; cerebellar atrophy HP:0001272
White-matter/callosal abnormalities	White-matter loss, ventriculomegaly, enlarged subarachnoid spaces, thin/hypoplastic corpus callosum	Abnormal cerebral white matter HP:0002500; ventriculomegaly HP:0002119; thin corpus callosum HP:0002079
Muscle wasting	Common, probably often secondary to immobility; occasional CK/lactate elevation or rhabdomyolysis-like episodes	Muscle wasting HP:0003202; elevated CK HP:0003236
Facial appearance	Subtle bitemporal narrowing, thick eyebrows, full cheeks, long philtrum, wide mouth, tented upper lip, pointed chin	Long philtrum HP:0000343; thick eyebrow HP:0000574; pointed chin HP:0000307

Seizures showed partial responses to levetiracetam or clobazam in many patients, although refractory epilepsy occurred. The profound cognitive, motor, visual, communication, and feeding/mobility burden implies major lifelong impairment in activities of daily living. No NEDESBA-specific EQ-5D, SF-36, PROMIS, caregiver-burden, or quality-of-life study is available. (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7)

4. Genetic and molecular information

Gene and variant spectrum

TRAPPC4 encodes a core component shared by mammalian TRAPPII and TRAPPIII complexes. The major allele is:

NM_016146.5:c.454+3A>G, hg38 chr11:119020256A>G, rs375776811; ClinVar aggregate accession reported as VCV000812649.1. It is an intronic splice-altering, hypomorphic loss-of-function allele. (ghosh2021arelativelycommon pages 2-3, ghosh2021arelativelycommon pages 6-7)

The December 2024 expert review also summarized homozygous missense variants p.Leu64Pro and p.Pro93Leu in three individuals from two Indian families, plus ClinVar-listed p.Leu125Pro and p.Gly213Ter220delinsXaa. The missense changes were predicted to reduce stability or alter intramolecular interactions, but these claims require variant-level confirmation in the original case reports and current ClinVar submissions before assigning definitive ACMG classes in a production database. (hall2024trappopathiesseveremultisystem pages 7-9)

All reported disease variants are germline. Somatic TRAPPC4 mutation is not part of NEDESBA. No recurrent disease-causing chromosomal deletion, translocation, inversion, repeat expansion, mitochondrial variant, modifier gene, or disease-specific epigenetic signature has been established. The absence of additional clinically relevant TRAPPC4 variants among more than 10,000 screened neurodevelopmental cases in the 2021 study emphasized the unusual dominance of c.454+3A>G in early reports. (ghosh2021arelativelycommon pages 1-2, ghosh2021arelativelycommon pages 2-3)

Penetrance and expressivity

All known c.454+3A>G homozygotes in the expanded study were affected, suggesting high or complete penetrance in identified homozygotes. Expressivity is variable for seizure type/control, cataract, hearing loss, dystonia/ataxia, muscle biochemical abnormalities, and hypothalamic findings. Anticipation has not been reported. Germline mosaicism is theoretically possible for any recessive variant but has not been documented. (ghosh2021arelativelycommon pages 4-6)

5. Environmental information

No environmental toxicant, radiation, pollution, smoking, alcohol, diet, exercise pattern, occupation, or infectious agent is implicated in causation. Infection is clinically relevant as a complication: five deaths in one series were attributed to infections. Unlike some other TRAPPopathies, infection-triggered regression or metabolic crises have not been established systematically for TRAPPC4 disease. (ghosh2021arelativelycommon pages 6-7)

6. Mechanism and pathophysiology

Evidence-supported causal chain

Upstream genetic lesion: biallelic hypomorphic TRAPPC4 variants reduce correctly spliced transcript and TRAPPC4 protein.
Complex dysfunction: reduced TRAPPC4 impairs assembly or stability of core TRAPP complexes. TRAPPC4 is required for Rab1 guanine-nucleotide exchange activity.
Trafficking defect: patient fibroblasts show delayed entry into and exit from the Golgi using VSVG-GFP-ts045.
Autophagy defect: fibroblasts show impaired basal autophagy and delayed autophagic flux, possibly involving unsealed autophagosomes.
Cellular vulnerability: long-lived neurons depend heavily on membrane/protein homeostasis, axodendritic transport, and autophagy; pyramidal neurons, Purkinje cells, and motor neurons express TRAPPC4 and are plausible vulnerable populations.
Tissue phenotype: neuronal dysfunction and loss produce developmental regression, epilepsy, cortical/cerebellar atrophy, microcephaly, and corticospinal spasticity. Steps 1–4 are directly demonstrated; the detailed neuron-to-phenotype bridge remains biologically compelling but incompletely tested in disease-specific neuronal models. (bergen2020deficienciesinvesicular pages 2-3, bergen2020deficienciesinvesicular pages 16-17, hall2024trappopathiesseveremultisystem pages 7-9, bergen2020deficienciesinvesicular pages 1-2)

Exact primary-literature quotation: “Lentiviral expression of wild-type TRAPPC4 in these fibroblasts restored trafficking, suggesting that the trafficking defect was due to reduced TRAPPC4 levels.” (bergen2020deficienciesinvesicular pages 1-2)

Exact primary-literature quotation: “the fibroblasts had a basal autophagy defect and a delay in autophagic flux, possibly due to unsealed autophagosomes.” (bergen2020deficienciesinvesicular pages 1-2)

Suggested annotations include GO:0006888 ER-to-Golgi vesicle-mediated transport, GO:0048193 Golgi vesicle transport, GO:0006914 autophagy, GO:0016192 vesicle-mediated transport, and Rab-protein signal transduction. Candidate cell terms include pyramidal neuron, Purkinje cell, upper motor neuron, lower motor neuron, oligodendrocyte, and astrocyte; only neuronal expression/vulnerability is reasonably supported, whereas glial involvement remains inferential.

No validated NEDESBA transcriptomic signature beyond aberrant TRAPPC4 splicing, nor disease-specific proteomic, metabolomic, lipidomic, single-cell, spatial-transcriptomic, or integrated multi-omics atlas, is available. Occasional lactate/CK elevations do not establish a primary metabolic pathway defect. Immune dysregulation is not established. (ghosh2021arelativelycommon pages 6-7, hall2024trappopathiesseveremultisystem pages 7-9)

7. Anatomical structures affected

The primary organ is the central nervous system. MRI implicates bilateral cerebral cortex and subcortical white matter, corpus callosum, cerebellum, ventricles/subarachnoid spaces, and variably brainstem and basal ganglia. Suggested anatomy terms include UBERON:0000955 brain, UBERON:0001954 Ammon’s horn/hippocampal formation where relevant to basic expression studies, UBERON:0002037 cerebellum, UBERON:0001851 cortex, UBERON:0002336 corpus callosum, and UBERON:0002437 cerebral white matter. Disease is generally diffuse and bilateral rather than lateralized. Skeletal muscle wasting is often secondary, though primary muscle involvement may occur in a minority. (ghosh2021arelativelycommon pages 6-7, hall2024trappopathiesseveremultisystem pages 7-9)

At the subcellular level, implicated compartments are the endoplasmic reticulum–Golgi trafficking axis, Golgi apparatus, transport vesicles, recycling endosomes, autophagosomes, and lysosomal degradation pathway. Suggested GO Cellular Component annotations are Golgi apparatus, ER–Golgi intermediate compartment, transport vesicle, TRAPP complex, autophagosome, and lysosome. (hall2024trappopathiesseveremultisystem pages 7-9, bergen2020deficienciesinvesicular pages 1-2)

8. Temporal development

Pregnancy, delivery, and the neonatal period are often unremarkable. Developmental stagnation and encephalopathy emerge within the first months; seizures usually begin by six months. Some children acquire limited early milestones before losing them. Microcephaly, spasticity, contractures, disability, and MRI atrophy progress through childhood. Cerebellar and cerebral atrophy appeared more severe in older children. The disease is chronic, lifelong, and progressive rather than relapsing-remitting; spontaneous remission is not reported. (ghosh2021arelativelycommon pages 4-6, ghosh2021arelativelycommon pages 6-7)

The infancy period is probably the key diagnostic and therapeutic window because injury begins early, but no trial has established that presymptomatic intervention changes outcome. Later-onset regression and seizures are possible with some missense alleles, suggesting genotype-dependent timing. (forno2025childneurologytrappc4related pages 1-2, hall2024trappopathiesseveremultisystem pages 7-9)

9. Inheritance and population

Inheritance is autosomal recessive (HPO HP:0000007). For two carrier parents, standard Mendelian counseling predicts a 25% affected, 50% carrier, and 25% non-carrier probability per pregnancy, assuming both parental variants are pathogenic and penetrance is high.

No population prevalence or incidence has been measured. The disease is therefore best classified as ultra-rare. A 2025 report estimated approximately 32 published cases, but this includes overlapping cohorts and should not be treated as a prevalence numerator. Families have Iranian, Egyptian, Portuguese, English, mixed European-American, Caucasian, Turkish, French-Canadian, and Indian backgrounds; there is no demonstrated ethnic restriction. Sex ratio and age-specific population distribution are unknown. (forno2025childneurologytrappc4related pages 2-4, ghosh2021arelativelycommon pages 2-3, bergen2020deficienciesinvesicular pages 1-2)

Consanguinity may facilitate homozygosity but is not required; several families were nonconsanguineous. No confirmed founder population, genetic anticipation, or population-specific disease prevalence is known. (ghosh2021arelativelycommon pages 6-7)

10. Diagnostics

Recommended clinical and molecular approach

Recognize the combination of infantile developmental stagnation/regression, progressive microcephaly, epilepsy, spastic quadriparesis, and diffuse brain atrophy.
Obtain brain MRI, EEG, audiology, ophthalmology assessment, feeding/swallowing assessment, and neurologic/rehabilitation evaluation.
Use a developmental-and-epileptic-encephalopathy or spasticity/brain-atrophy multigene panel containing TRAPPC4, or preferably trio WES/WGS where the phenotype is nonspecific.
Confirm candidate variants and segregation with Sanger sequencing.
If c.454+3A>G or another potential splice variant is found—or WES is negative despite a compelling phenotype—perform RNA studies from fibroblasts or another informative tissue. RNA-seq directly demonstrated exon 3 skipping and cryptic donor use. (ghosh2021arelativelycommon pages 2-3, ghosh2021arelativelycommon pages 6-7)

Exact abstract quotation: “No other clinically relevant TRAPPC4 variants were identified among any of over 10,000 patients with neurodevelopmental conditions.” (ghosh2021arelativelycommon pages 1-2)

CMA can detect alternative copy-number diagnoses but is not the primary test for the recurrent single-nucleotide allele. Karyotyping, FISH, mitochondrial DNA, and repeat-expansion testing have no disease-specific indication unless suggested by the differential diagnosis. There are no formal clinical diagnostic criteria and no validated biochemical biomarker. CK, lactate, and transaminases may be checked when weakness, rhabdomyolysis, or acute deterioration occurs, but abnormalities are inconsistent and nonspecific. (ghosh2021arelativelycommon pages 6-7)

Important differentials include other TRAPPopathies—particularly TRAPPC2L, TRAPPC6B, TRAPPC9, TRAPPC11, and TRAPPC12 disorders—and other developmental/epileptic encephalopathies, hereditary spastic paraplegias, pontocerebellar degenerations, mitochondrial disorders, congenital disorders of glycosylation, and neurodegenerative conditions causing microcephaly and atrophy. (ghosh2021arelativelycommon pages 1-2, bergen2020deficienciesinvesicular pages 15-16)

11. Outcome and prognosis

The expected outcome is severe lifelong disability, typically with profound cognitive and communication impairment, nonambulatory spastic tetraplegia, epilepsy, visual dysfunction, and complete dependence for daily care. Recovery of lost skills has not been documented. Complications likely include aspiration/feeding difficulty, respiratory infections, contractures, scoliosis, pain, low bone density, immobility, and antiseizure-drug adverse effects, although not all have been systematically quantified.

In the expanded cohort, 5/23 (21.7%) died from infections at a mean age of 8.8 years. This is not a population mortality estimate: the cohort was small, follow-up heterogeneous, and survival curves were not reported. Five- and ten-year survival, overall life expectancy, validated prognostic biomarkers, and standardized quality-of-life outcomes remain unknown. (ghosh2021arelativelycommon pages 6-7)

12. Treatment and current applications

There is no approved disease-modifying, gene, cell, RNA, or targeted therapy for NEDESBA. No disease-specific interventional trial was identified in the ClinicalTrials.gov searches performed for this report.

Current implementation is supportive and individualized:

Epilepsy: standard antiseizure medications selected by seizure type; levetiracetam, clobazam, and valproate have been used. Partial response is common, but drug resistance occurs. Suggested NCIT concept: Anticonvulsant Therapy.
Motor management: physical and occupational therapy, positioning, stretching, orthoses, mobility/seating equipment, surveillance for hip displacement/scoliosis, and management of spasticity/contractures. Suggested NCIT concepts: Physical Therapy, Occupational Therapy, Rehabilitation Therapy, Supportive Care.
Communication and feeding: speech/augmentative-communication therapy; swallow and nutritional assessment; enteral feeding when clinically indicated.
Vision/hearing: ophthalmologic and audiologic surveillance; treat cataract or hearing impairment where feasible.
Respiratory and infection prevention: airway-clearance plans, aspiration mitigation, routine vaccination, and prompt treatment of infections.
Bone health and pain: assess vitamin D/calcium status, immobility-related osteopenia, fractures, and discomfort.

The most compelling experimental direction is restoration of adequate TRAPPC4 expression because wild-type transduction rescued trafficking in patient fibroblasts. This is proof of mechanism, not evidence that gene replacement is safe or effective in patients. Autophagy or Rab-pathway modulation is likewise hypothetical and may have broad off-target effects. The 2024 review concluded that therapeutic development remains largely unexplored. (bergen2020deficienciesinvesicular pages 16-17, hall2024trappopathiesseveremultisystem pages 7-9)

No disease-specific pharmacogenomic guidance, treatment-response rate, surgical algorithm, immunotherapy, or combination-therapy evidence exists.

13. Prevention

The genetic defect cannot currently be prevented through lifestyle modification, vaccination, environmental control, or prophylactic medication. Relevant prevention is genetic and tertiary:

Primary/reproductive: counseling, parental confirmation, cascade testing, partner testing where appropriate, prenatal diagnosis, or preimplantation genetic testing after familial variants are established.
Secondary: no population or newborn biochemical screening exists. Targeted carrier testing may be reasonable in an affected family; broader carrier screening requires validation despite the measurable c.454+3A>G carrier frequency.
Tertiary: early seizure management, rehabilitation, aspiration precautions, vaccination, infection control, contracture prevention, nutritional support, and bone-health surveillance may reduce complications but do not prevent neurodegeneration. The 2021 investigators specifically suggested that the recurrent allele’s frequency could support screening-based early carrier detection in some populations. (ghosh2021arelativelycommon pages 6-7)

14. Other species and natural disease

TRAPPC4 is evolutionarily conserved; its yeast ortholog is Trs23. No naturally occurring companion-animal, livestock, or wildlife disorder definitively homologous to human NEDESBA was identified, and there is no zoonotic or cross-species transmission. Relevant taxa for experimental work include Homo sapiens (NCBI Taxon 9606), Mus musculus (10090), and Saccharomyces cerevisiae (4932). Breed-specific VBO annotation is not applicable. (hall2024trappopathiesseveremultisystem pages 7-9, bergen2020deficienciesinvesicular pages 1-2)

15. Model organisms and experimental systems

Direct disease models

Patient fibroblasts: reproduce reduced TRAPPC4, impaired TRAPP assembly/stability, delayed Golgi trafficking, and defective autophagic flux. Wild-type TRAPPC4 rescue establishes causal specificity.
Yeast trs23 temperature-sensitive model: shows constitutive/stress-induced autophagy defects and temperature-dependent secretory defects, validating conserved function.
Mouse knockout: complete loss is embryonic lethal, demonstrating essentiality but limiting its utility as a postnatal disease model. A hypomorphic or conditional neural model would be more appropriate. (hall2024trappopathiesseveremultisystem pages 7-9, bergen2020deficienciesinvesicular pages 1-2)

The 2024 review emphasized that disease-specific neurological modeling remained limited to fibroblasts and yeast. Neuronal iPSC lines, brain organoids, conditional/hypomorphic mice, and zebrafish would enable study of cell-type vulnerability, developmental timing, electrophysiology, and therapeutic rescue, but published NEDESBA-specific validation was not available through 2024. Data from other TRAPP-gene models may illuminate shared biology but cannot be assumed to reproduce TRAPPC4 disease. (hall2024trappopathiesseveremultisystem pages 7-9)

Recent developments and expert assessment

The principal 2023–2024 developments were continued recognition of TRAPPC4 within the broader TRAPPopathy spectrum, clinical reports expanding muscle and radiologic findings, and the December 2024 review’s synthesis of additional missense variants and major research gaps. The expert consensus remains that TRAPP complexes regulate ER–Golgi/plasma-membrane traffic and autophagy, but the reasons particular subunits produce distinct neurological, muscular, or skeletal phenotypes are unresolved. For TRAPPC4 specifically, neuronal models, prospective natural-history cohorts, standardized outcomes, biomarkers, and preclinical treatment studies are priorities. (hall2024trappopathiesseveremultisystem pages 7-9)

Key publications

Van Bergen NJ et al. “Deficiencies in vesicular transport mediated by TRAPPC4 are associated with severe syndromic intellectual disability.” Brain. Published 2020; accepted October 7, 2019. PMID: 31794024. DOI: https://doi.org/10.1093/brain/awz374. Foundational human cohort and direct trafficking/autophagy experiments. (bergen2020deficienciesinvesicular pages 1-2)
Kaur P et al. “Recurrent bi-allelic splicing variant c.454+3A>G in TRAPPC4 is associated with progressive encephalopathy and muscle involvement.” Brain. 2020. PMID: 32125366. DOI: https://doi.org/10.1093/brain/awaa046. Clinical expansion emphasizing muscle involvement. (OpenTargets Search: neurodevelopmental disorder with epilepsy spasticity and brain atrophy-TRAPPC4)
Ghosh SG et al. “A relatively common homozygous TRAPPC4 splicing variant is associated with an early-infantile neurodegenerative syndrome.” European Journal of Human Genetics. Online 2020; volume publication 2021. PMID: 33011761. DOI: https://doi.org/10.1038/s41431-020-00717-5. Expanded cohort, carrier frequency, natural history, and RNA-seq. (OpenTargets Search: neurodevelopmental disorder with epilepsy spasticity and brain atrophy-TRAPPC4, ghosh2021arelativelycommon pages 1-2)
Hall R et al. “TRAPPopathies: Severe Multisystem Disorders Caused by Variants in Genes of the Transport Protein Particle (TRAPP) Complexes.” International Journal of Molecular Sciences. December 2024;25:13329. DOI: https://doi.org/10.3390/ijms252413329. Current expert review and research agenda. (hall2024trappopathiesseveremultisystem pages 7-9)

Evidence limitations

NEDESBA evidence remains dominated by one recurrent allele, small retrospective cohorts, overlapping cases, inconsistent follow-up, and functional studies in non-neuronal fibroblasts and yeast. Frequencies should therefore be interpreted as reported-cohort frequencies, not population estimates. No prospective natural-history registry, formal diagnostic guideline, validated biomarker, controlled treatment study, disease-specific quality-of-life instrument, or robust neuronal/animal therapeutic model was identified. Claims concerning newer rare variants should be checked against their primary reports and current ClinVar records before clinical classification.

References

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(ghosh2021arelativelycommon pages 4-6): Shereen G. Ghosh, Marcello Scala, Christian Beetz, Guy Helman, Valentina Stanley, Xiaoxu Yang, Martin W. Breuss, Neda Mazaheri, Laila Selim, Fatemeh Hadipour, Lynn Pais, Chloe A. Stutterd, Vasiliki Karageorgou, Amber Begtrup, Amy Crunk, Jane Juusola, Rebecca Willaert, Leigh A. Flore, Kelly Kennelly, Christopher Spencer, Martha Brown, Pamela Trapane, Anna C. E. Hurst, S. Lane Rutledge, Dana H. Goodloe, Marie T. McDonald, Vandana Shashi, Kelly Schoch, Hoda Tomoum, Raghda Zaitoun, Zahra Hadipour, Hamid Galehdari, Alistair T. Pagnamenta, Majid Mojarrad, Alireza Sedaghat, Patrícia Dias, Sofia Quintas, Atiyeh Eslahi, Gholamreza Shariati, Peter Bauer, Cas Simons, Henry Houlden, Mahmoud Y. Issa, Maha S. Zaki, Reza Maroofian, and Joseph G. Gleeson. A relatively common homozygous trappc4 splicing variant is associated with an early-infantile neurodegenerative syndrome. European Journal of Human Genetics, 29:271-279, Sep 2021. URL: https://doi.org/10.1038/s41431-020-00717-5, doi:10.1038/s41431-020-00717-5. This article has 24 citations and is from a domain leading peer-reviewed journal.
(ghosh2021arelativelycommon pages 6-7): Shereen G. Ghosh, Marcello Scala, Christian Beetz, Guy Helman, Valentina Stanley, Xiaoxu Yang, Martin W. Breuss, Neda Mazaheri, Laila Selim, Fatemeh Hadipour, Lynn Pais, Chloe A. Stutterd, Vasiliki Karageorgou, Amber Begtrup, Amy Crunk, Jane Juusola, Rebecca Willaert, Leigh A. Flore, Kelly Kennelly, Christopher Spencer, Martha Brown, Pamela Trapane, Anna C. E. Hurst, S. Lane Rutledge, Dana H. Goodloe, Marie T. McDonald, Vandana Shashi, Kelly Schoch, Hoda Tomoum, Raghda Zaitoun, Zahra Hadipour, Hamid Galehdari, Alistair T. Pagnamenta, Majid Mojarrad, Alireza Sedaghat, Patrícia Dias, Sofia Quintas, Atiyeh Eslahi, Gholamreza Shariati, Peter Bauer, Cas Simons, Henry Houlden, Mahmoud Y. Issa, Maha S. Zaki, Reza Maroofian, and Joseph G. Gleeson. A relatively common homozygous trappc4 splicing variant is associated with an early-infantile neurodegenerative syndrome. European Journal of Human Genetics, 29:271-279, Sep 2021. URL: https://doi.org/10.1038/s41431-020-00717-5, doi:10.1038/s41431-020-00717-5. This article has 24 citations and is from a domain leading peer-reviewed journal.
(bergen2020deficienciesinvesicular pages 15-16): Nicole J Van Bergen, Yiran Guo, Noraldin Al-Deri, Zhanna Lipatova, Daniela Stanga, Sarah Zhao, Rakhilya Murtazina, Valeriya Gyurkovska, Davut Pehlivan, Tadahiro Mitani, Alper Gezdirici, Jayne Antony, Felicity Collins, Mary J H Willis, Zeynep H Coban Akdemir, Pengfei Liu, Jaya Punetha, Jill V Hunter, Shalini N Jhangiani, Jawid M Fatih, Jill A Rosenfeld, Jennifer E Posey, Richard A Gibbs, Ender Karaca, Sean Massey, Thisara G Ranasinghe, Patrick Sleiman, Chris Troedson, James R Lupski, Michael Sacher, Nava Segev, Hakon Hakonarson, and John Christodoulou. Deficiencies in vesicular transport mediated by trappc4 are associated with severe syndromic intellectual disability. Brain : a journal of neurology, 143:112-130, Dec 2020. URL: https://doi.org/10.1093/brain/awz374, doi:10.1093/brain/awz374. This article has 58 citations.
(forno2025childneurologytrappc4related pages 2-4): Andreia Forno, Joana Oliveira, Marta Zegre Amorim, Carla Conceição, and Paulo Rego Sousa. Child neurology: trappc4-related neurodevelopmental disorder. May 2025. URL: https://doi.org/10.1212/wnl.0000000000213538, doi:10.1212/wnl.0000000000213538. This article has 1 citations and is from a highest quality peer-reviewed journal.
(bergen2020deficienciesinvesicular pages 16-17): Nicole J Van Bergen, Yiran Guo, Noraldin Al-Deri, Zhanna Lipatova, Daniela Stanga, Sarah Zhao, Rakhilya Murtazina, Valeriya Gyurkovska, Davut Pehlivan, Tadahiro Mitani, Alper Gezdirici, Jayne Antony, Felicity Collins, Mary J H Willis, Zeynep H Coban Akdemir, Pengfei Liu, Jaya Punetha, Jill V Hunter, Shalini N Jhangiani, Jawid M Fatih, Jill A Rosenfeld, Jennifer E Posey, Richard A Gibbs, Ender Karaca, Sean Massey, Thisara G Ranasinghe, Patrick Sleiman, Chris Troedson, James R Lupski, Michael Sacher, Nava Segev, Hakon Hakonarson, and John Christodoulou. Deficiencies in vesicular transport mediated by trappc4 are associated with severe syndromic intellectual disability. Brain : a journal of neurology, 143:112-130, Dec 2020. URL: https://doi.org/10.1093/brain/awz374, doi:10.1093/brain/awz374. This article has 58 citations.

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Inheritance

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Progression

Prevalence

Differential Diagnoses

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References & Deep Research

References

Deep Research

Disease Characteristics Research Template

Target Disease

Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

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Neurodevelopmental Disorder With Epilepsy, Spasticity, and Brain Atrophy (NEDESBA)

Executive summary

1. Disease information

2. Etiology, risk, protective factors, and gene–environment interaction

Causal factor

Genetic risk

Environmental, infectious, lifestyle, and protective factors

3. Phenotypes

4. Genetic and molecular information

Gene and variant spectrum

Penetrance and expressivity

5. Environmental information

6. Mechanism and pathophysiology

Evidence-supported causal chain

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

Recommended clinical and molecular approach

11. Outcome and prognosis

12. Treatment and current applications

13. Prevention

14. Other species and natural disease

15. Model organisms and experimental systems

Direct disease models

Recent developments and expert assessment

Key publications

Evidence limitations

Artifacts

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