| Field | Evidence-backed value | Suggested ontology/identifier |
|---|---|---|
| Disease name | Neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy (NEDESBA); TRAPPC4-related neurodevelopmental disorder (pqac-00000003, pqac-00000013) | 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 (pqac-00000000, pqac-00000002, pqac-00000019) | Disease category: Mendelian disorder |
| Causal gene | **TRAPPC4** (trafficking protein particle complex subunit 4; synbindin), core TRAPP subunit (pqac-00000004, pqac-00000013, pqac-00000019) | 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) (pqac-00000000, pqac-00000011, pqac-00000019) | GO: vesicle-mediated transport; GO: autophagy; Rab1 GEF-related TRAPP function |
| Inheritance | Autosomal recessive; all confirmed affected individuals reported with biallelic/homozygous pathogenic variants (pqac-00000002, pqac-00000003, pqac-00000017) | HP:0000007 |
| MONDO/target association | Open Targets shows disease-target association between MONDO_0032894 and **TRAPPC4** (pqac-00000010) | 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 (pqac-00000000, pqac-00000002, pqac-00000005, pqac-00000019) | 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) (pqac-00000000, pqac-00000019) | 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 (pqac-00000011, pqac-00000017) | 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 (pqac-00000005, pqac-00000008, pqac-00000013, pqac-00000016) | 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 (pqac-00000006, pqac-00000008) | 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** (pqac-00000014, pqac-00000019) | HPO onset: infantile onset |
| Disease course | Severe **progressive encephalopathy/neurodegeneration** with developmental stagnation, regression, microcephaly progression, and worsening brain atrophy (pqac-00000006, pqac-00000008, pqac-00000016) | HP:0002344; progressive course |
| Developmental phenotype | Profound psychomotor delay / severe developmental delay is a core feature; developmental stagnation and loss of acquired milestones common (pqac-00000005, pqac-00000008, pqac-00000013, pqac-00000014) | HP:0011344; HP:0001263; HP:0002376 |
| Regression frequency | Psychomotor regression reported in **all phenotyped individuals** in expanded cohort text (pqac-00000008, pqac-00000016) | 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 (pqac-00000007, pqac-00000014, pqac-00000018) | HP:0001250 |
| Seizure types | Variable: infantile spasms, focal, tonic-clonic, atonic, tonic; occasional gelastic seizures reported in earlier cases (pqac-00000014, pqac-00000016) | HP:0012469; HP:0002123; HP:0002069 |
| EEG | Non-specific; generalized disorganization and epileptiform discharges reported (pqac-00000014) | 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** (pqac-00000007, pqac-00000014, pqac-00000019) | 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 (pqac-00000007, pqac-00000008, pqac-00000014) | HP:0000252 |
| Intellectual disability | Severe/profound intellectual disability/developmental impairment; initial cohort **7/7** (pqac-00000007, pqac-00000019) | 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 (pqac-00000001, pqac-00000007, pqac-00000014) | HP:0000505; HP:0000657; HP:0001133 |
| Cataracts / optic findings | Bilateral cataracts reported in some patients; optic nerve pallor in 2025 case report/reviewed siblings (pqac-00000014, pqac-00000003) | HP:0000518; HP:0000648 |
| Hearing involvement | Sensorineural hearing loss reported; initial cohort hearing loss **2/6**; later review-level estimate ~14% (pqac-00000001, pqac-00000007, pqac-00000019) | HP:0000407 |
| Movement disorders | Dystonia/ataxia/dyskinesia present in a subset; review-level estimate ~44% movement disorder, but direct cohort counts are smaller (pqac-00000001, pqac-00000014) | 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 (pqac-00000016, pqac-00000017) | 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 (pqac-00000014) | 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 (pqac-00000006, pqac-00000014, pqac-00000016, pqac-00000019) | HP:0002059; HP:0001272; HP:0001273; HP:0002120; HP:0002079 |
| MRI progression | Older children often show more severe cerebral/cerebellar atrophy, suggesting progression (pqac-00000016) | 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) (pqac-00000004, pqac-00000017) | 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) (pqac-00000000, pqac-00000018, pqac-00000019) | 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 (pqac-00000000, pqac-00000012, pqac-00000019) | 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) (pqac-00000011, pqac-00000017) | 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 (pqac-00000009, pqac-00000016) | 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 (pqac-00000014, pqac-00000015, pqac-00000016, pqac-00000019) | 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 (pqac-00000013, pqac-00000016) | 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** (pqac-00000013, pqac-00000018) | 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 (pqac-00000016, pqac-00000017) | 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 (pqac-00000003, pqac-00000014, pqac-00000017) | NCIT: Anticonvulsant Therapy; Supportive Care |
| Clinical trials | **No disease-specific interventional clinical trials identified** in search results available here (clinical-trials search negative) (pqac-00000010) | 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 (pqac-00000016) | 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 (pqac-00000009, pqac-00000016) | 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 (pqac-00000001) | 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 (pqac-00000015, pqac-00000019) | Geographic distribution: multicontinental case reports |
| Sex ratio | **Not established** from available summarized evidence (pqac-00000008) | Unknown/not established |
| Natural disease in other species | **Not established**; no naturally occurring veterinary disease linked to TRAPPC4 identified in available evidence (pqac-00000017) | 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 (pqac-00000011, pqac-00000012, pqac-00000019) | 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 (pqac-00000011, pqac-00000017) | 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.*