Spondyloepimetaphyseal dysplasia with joint laxity, type 3

Summary

Spondyloepimetaphyseal dysplasia with joint laxity, type 3 (MONDO:0032724) is a disease caused by EXOC6B (GenCC Strong), with 1 cohort gene.

At a glance

• Prevalence: <1 / 1 000 000 (Worldwide) [Orphanet-validated]
• Causal gene: EXOC6B (GenCC Strong)
• Cohort genes: 1
• ClinVar variants: 10

Clinical features

Epidemiology

Prevalence records

2 prevalence record(s), Orphanet:

Type	Class	Value	Geography	Validation
Cases/families		6	Worldwide	Validated
Point prevalence	<1 / 1 000 000		Worldwide	Validated

Identifiers

Disease identifiers

Field	Value
Canonical name	spondyloepimetaphyseal dysplasia with joint laxity, type 3
Mondo ID	MONDO:0032724
OMIM	618395
Orphanet	642085
DOID	DOID:0112200
UMLS	C5193073
MedGen	1677378
GARD	0016348
Is cancer (heuristic)	no

Also known as: SEMDJL3 · spondyloepimetaphyseal dysplasia with joint laxity, EXOC6b type

Data availability: 10 ClinVar variants · 2 GenCC gene-disease records.

Disease family

Classification path: disease › human disease › disease by etiologic mechanism › disease of genetic or genomic mechanism › hereditary disease › autosomal genetic disease › autosomal recessive disease › spondyloepimetaphyseal dysplasia with joint laxity, type 3

Related subtypes (218): immunodeficiency-centromeric instability-facial anomalies syndrome, hypercalcemia, infantile, Ochoa syndrome, autosomal recessive Ehlers-Danlos syndrome, vascular type, hydrolethalus syndrome, 3-M syndrome, isolated hyperchlorhidrosis, dacryocystitis-osteopoikilosis syndrome, Hutchinson-Gilford progeria syndrome, achalasia microcephaly syndrome, acrorenal syndrome, autosomal recessive, beta-ketothiolase deficiency, autosomal recessive Alport syndrome, Alstrom syndrome, microphthalmia with limb anomalies, camptodactyly-arthropathy-coxa vara-pericarditis syndrome, Behr syndrome, bifid nose, autosomal recessive, Bloom syndrome, Bowen-Conradi syndrome, camptodactyly with fibrous tissue hyperplasia and skeletal dysplasia, heart defects-limb shortening syndrome, autosomal recessive palmoplantar keratoderma and congenital alopecia, COFS syndrome, craniometaphyseal dysplasia, autosomal recessive, Fraser syndrome, cystic fibrosis, polycystic lipomembranous osteodysplasia with sclerosing leukoencephaly, persistent hyperplastic primary vitreous, autosomal recessive, Donnai-Barrow syndrome, Schöpf-Schulz-Passarge syndrome, cleft lip/palate-ectodermal dysplasia syndrome, Ellis-van Creveld syndrome, Wolcott-Rallison syndrome, autosomal recessive faciodigitogenital syndrome, acromesomelic dysplasia 2B, brittle cornea syndrome, triple-A syndrome, autosomal recessive humeroradial synostosis, multinucleated neurons-anhydramnios-renal dysplasia-cerebellar hypoplasia-hydranencephaly syndrome, hydrocephalus, nonsyndromic, autosomal recessive 1, autosomal recessive hydrocephalus due to congenital stenosis of aqueduct of Sylvius, hypertelorism, microtia, facial clefting syndrome, hypoparathyroidism-retardation-dysmorphism syndrome, Vici syndrome, Johanson-Blizzard syndrome, autosomal recessive Kenny-Caffey syndrome, Papillon-Lefevre disease, Haim-Munk syndrome, Laurence-Moon syndrome, Donohue syndrome, lipase deficiency, combined, autosomal recessive familial Mediterranean fever, thiamine-responsive megaloblastic anemia syndrome, cartilage-hair hypoplasia, Nijmegen breakage syndrome, pseudo-TORCH syndrome, Galloway-Mowat syndrome, mulibrey nanism, myotonia congenita, autosomal recessive, Schwartz-Jampel syndrome, proteosome-associated autoinflammatory syndrome, Netherton syndrome, Niemann-Pick disease type A, oculodentodigital dysplasia, autosomal recessive, odonto-onycho-dermal dysplasia, autosomal recessive omodysplasia, osteoporosis-pseudoglioma syndrome, Shwachman-Diamond syndrome, phenylketonuria, Bjornstad syndrome, Laron syndrome, autosomal recessive polycystic kidney disease, autosomal recessive inherited pseudoxanthoma elasticum, autosomal recessive multiple pterygium syndrome, rapadilino syndrome, short-rib thoracic dysplasia 9 with or without polydactyly, autosomal recessive Robinow syndrome, Sjogren-Larsson syndrome, scapuloperoneal spinal muscular atrophy, autosomal recessive, spondyloepiphyseal dysplasia tarda, autosomal recessive, inherited threoninemia, Pendred syndrome, autosomal recessive spondylocostal dysostosis, Werner syndrome, ABCD syndrome, Naxos disease, autosomal recessive amelia, human HOXA1 syndromes, sickle cell disease, autosomal recessive proximal renal tubular acidosis, hyper-IgM syndrome type 2, temtamy preaxial brachydactyly syndrome, TH-deficient dopa-responsive dystonia, craniosynostosis syndrome, autosomal recessive, Niemann-Pick disease type B, skin fragility-woolly hair-palmoplantar keratoderma syndrome, CoQ-responsive OXPHOS deficiency, familial adenomatous polyposis 2, Pierson syndrome, palmoplantar keratoderma-XX sex reversal-predisposition to squamous cell carcinoma syndrome, cardiomyopathy-hypotonia-lactic acidosis syndrome, PHARC syndrome, Kahrizi syndrome, cutis laxa with severe pulmonary, gastrointestinal and urinary anomalies, congenital prothrombin deficiency, immunodeficiency 31B, dyskeratosis congenita, autosomal recessive 2, dyskeratosis congenita, autosomal recessive 3, Nestor-Guillermo progeria syndrome, leukoencephalopathy with calcifications and cysts, mitochondrial pyruvate carrier deficiency, branched-chain keto acid dehydrogenase kinase deficiency, dyskeratosis congenita, autosomal recessive 5, hypohidrosis-enamel hypoplasia-palmoplantar keratoderma-intellectual disability syndrome, alacrima, achalasia, and intellectual disability syndrome, hyperlipoproteinemia, type 1D, microcephaly and chorioretinopathy 2, congenital stationary night blindness 1G, combined oxidative phosphorylation deficiency 29, hypermanganesemia with dystonia 2, growth retardation, intellectual developmental disorder, hypotonia, and hepatopathy, gnb5-related intellectual disability-cardiac arrhythmia syndrome, autosomal recessive spastic paraplegia type 78, autosomal recessive limb-girdle muscular dystrophy, Bardet-Biedl syndrome, autosomal recessive cerebellar ataxia, neuronopathy, distal hereditary motor, autosomal recessive, UV-sensitive syndrome, Ehlers-Danlos syndrome, kyphoscoliotic type 1, Cockayne syndrome, hyperphenylalaninemia due to tetrahydrobiopterin deficiency, leukoencephalopathy-palmoplantar keratoderma syndrome, autosomal recessive hypohidrotic ectodermal dysplasia, Warburg micro syndrome, autosomal recessive primary microcephaly, autosomal recessive progressive external ophthalmoplegia, Meier-Gorlin syndrome, autosomal recessive sideroblastic anemia, autosomal recessive intermediate Charcot-Marie-Tooth disease, Perrault syndrome, autosomal recessive hypophosphatemic rickets, de Barsy syndrome, leukocyte adhesion deficiency, Senior-Loken syndrome, autosomal recessive spastic ataxia, childhood-onset autosomal recessive myopathy with external ophthalmoplegia, autosomal recessive cerebral atrophy, GM3 synthase deficiency, autosomal recessive distal renal tubular acidosis, pigmentation defects-palmoplantar keratoderma-skin carcinoma syndrome, autosomal recessive brachyolmia, Aicardi-Goutieres syndrome, homocystinuria without methylmalonic aciduria, Niemann-Pick disease type C, nephronophthisis, autosomal recessive osteopetrosis, peroxisome biogenesis disorder, congenital non-bullous ichthyosiform erythroderma, Seckel syndrome, Usher syndrome, autosomal recessive cutis laxa type 1, autosomal recessive cutis laxa type 2, hearing loss, autosomal recessive, microcephaly, growth restriction, and increased sister chromatid exchange 2, encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy, 1, congenital vertebral-cardiac-renal anomalies syndrome, hair defect with photosensitivity and intellectual disability syndrome, autosomal recessive severe congenital neutropenia, severe combined immunodeficiency due to CARMIL2 deficiency, extraoral halitosis due to methanethiol oxidase deficiency, neurodevelopmental disorder with microcephaly, impaired language, epilepsy, and gait abnormalities, mitochondrial complex 2 deficiency, nuclear type 3, mitochondrial complex 2 deficiency, nuclear type 4, mismatch repair cancer syndrome, Kilquist syndrome, Duane anomaly-myopathy-scoliosis syndrome, autosomal recessive axonal charcot-marie-tooth disease due to copper metabolism defect, immune dysregulation-inflammatory bowel disease-arthritis-recurrent infections-lymphopenia syndrome, optic atrophy-ataxia-peripheral neuropathy-global developmental delay syndrome, congenital myopathy with reduced type 2 muscle fibers, NAD(P)HX dehydratase deficiency, autosomal recessive ocular albinism, ichthyosis linearis circumflexa, eosinophil peroxidase deficiency, hyperphenylalaninemia due to DNAJC12 deficiency, autosomal recessive epidermolytic ichthyosis, Ehlers-Danlos syndrome, classic-like, 2, joint laxity, short stature, and myopia, HELIX syndrome, auditory neuropathy-optic atrophy syndrome, glycosylphosphatidylinositol biosynthesis defect 15, neurodegeneration, childhood-onset, stress-induced, with variable ataxia and seizures, SCN4A-related myopathy, autosomal recessive, Uner Tan Syndrome, nephropathic cystinosis, Imerslund-Grasbeck syndrome type 1, Imerslund-Grasbeck syndrome type 2, permanent neonatal diabetes mellitus 1, growth hormone insensitivity with immune dysregulation 1, autosomal recessive, Rajab interstitial lung disease with brain calcifications 1, Roberts-SC phocomelia syndrome, neurodevelopmental disorder with microcephaly, impaired language, and gait abnormalities, RPE65-related recessive retinopathy, GUCY2D-related recessive retinopathy, autosomal recessive titinopathy, intellectual disability, autosomal recessive, ALPL-related autosomal recessive hypophosphatasia, spastic paraplegia 18b, autosomal recessive, CEP164-related ciliopathy, RP1-related recessive retinopathy, pseudohypoaldosteronism, type IB2, autosomal recessive, pseudohypoaldosteronism, type IB3, autosomal recessive, spastic paraplegia 30B, autosomal recessive, cerebral arteriopathy, autosomal recessive, with subcortical infarcts and leukoencephalopathy 1, brain small vessel disease 2B, autosomal recessive, IMPG1-related recessive retinopathy, PROM1-related recessive retinopathy

Genetics & variants

GWAS landscape

No GWAS associations recorded — common-variant (GWAS) studies don’t cover this disease (typical for Mendelian / rare diseases). See the curated gene cohort and Mendelian overlap below.

Variant details and genetic-evidence tiers

ClinVar germline variants

10 retrieved; paginated sample, class counts are floors:

5 pathogenic, 3 likely pathogenic, 2 uncertain significance

ClinVar	Variant (HGVS)	Gene	Classification	Review
1335877	NM_015189.3(EXOC6B):c.401T>G (p.Leu134Ter)	EXOC6B	Pathogenic	no assertion criteria provided
1704251	NM_015189.1:c.2122+15447_2197-59588del	EXOC6B	Pathogenic	criteria provided, single submitter
3775346	NM_015189.3(EXOC6B):c.2127del (p.Phe709fs)	EXOC6B	Pathogenic	criteria provided, single submitter
625845	NM_015189.3(EXOC6B):c.906T>A (p.Tyr302Ter)	EXOC6B	Pathogenic	no assertion criteria provided
625846	NG_050967.1:g.291668_510915del	EXOC6B	Pathogenic	no assertion criteria provided
3250437	NM_015189.3(EXOC6B):c.933del (p.Phe311fs)	EXOC6B	Likely pathogenic	criteria provided, single submitter
3335928	NM_015189.3(EXOC6B):c.2122+1G>A	EXOC6B	Likely pathogenic	criteria provided, single submitter
4849342	NM_015189.3(EXOC6B):c.2122C>T (p.Gln708Ter)	EXOC6B	Likely pathogenic	criteria provided, single submitter
2441307	NM_015189.3(EXOC6B):c.925G>T (p.Glu309Ter)	EXOC6B	Uncertain significance	criteria provided, single submitter
2900558	NM_015189.3(EXOC6B):c.1483C>T (p.Pro495Ser)	EXOC6B	Uncertain significance	criteria provided, multiple submitters, no conflicts

Genes & proteins

Mendelian disease overlap and somatic drivers

GenCC: 4 · Orphanet: 1 · OMIM-shared: 0 · Dual-evidence (GWAS+Mendelian): 0

GenCC gene–disease validity (cohort genes)

the Disease column is the GenCC-asserted condition — a cohort gene’s strongest validity may be for a related predisposition syndrome.

Gene	Classification	Inheritance	Disease	Records
EXOC6B	Strong	Autosomal recessive	spondyloepimetaphyseal dysplasia with joint laxity, type 3	4

Orphanet rare-disease linkage (cohort genes)

Gene	Orphanet ID	Rare disease
EXOC6B	Orphanet:642085	EXOC6B-related spondyloepimetaphyseal dysplasia with joint laxity

Cohort genes → proteins

1 cohort genes, 1 distinct canonical proteins.

Evidence partition

Subset	Genes
multi_evidence	1

Cohort genes (full)

Symbol	HGNC	Ensembl	UniProt	Name	Evidence
EXOC6B	HGNC:17085	ENSG00000144036	Q9Y2D4	Exocyst complex component 6B	gencc,clinvar

Cohort function summary

Lead sentence per gene, UniProt-curated.

Symbol	Protein name	Function (lead sentence)
EXOC6B	Exocyst complex component 6B	Component of the exocyst complex involved in the docking of exocytic vesicles with fusion sites on the plasma membrane.

Protein-family classification

Druggable: 0 · Difficult: 0 · Unknown: 1 · Druggable fraction: 0.0

Family distribution

Cohort families vs a genome-wide background (hypergeometric, BH-FDR; fold = observed/expected). Counts kept; sorted by enrichment, so the catch-all Other/Unknown bucket no longer leads.

Family	Genes	Fold	FDR
Other/Unknown	1	1.8×	0.558

Per-gene assignment

Symbol	Family	Druggable?	EC	InterPro (top 3)
EXOC6B	Other/Unknown	no		EXOC6/Sec15, EXOC6PINT-1/Sec15/Tip20_C_dom2, EXOC6/Sec15_C_dom1

Expression context

Cohort genes with no expression data: 0.

1 cohort gene are a single-cell marker in ≥1 SCXA experiment.

Breadth distribution (Bgee present_calls)

Bucket	Genes
narrow (1-5 tissues)	0
moderate (6-20)	0
broad (>20)	1
unknown	0

Top tissues across cohort

Tissue	Cohort genes
calcaneal tendon	1
globus pallidus	1
medial globus pallidus	1

Per-gene tissue summary (top 30)

Symbol	Bgee breadth	FANTOM5 breadth	SCXA	Top tissues
EXOC6B	259	ubiquitous	marker	calcaneal tendon, medial globus pallidus, globus pallidus

Protein interactions among cohort

Intra-cohort edges: 0.

Hub genes (top 10 by interactor count)

Symbol	Interactor count
EXOC6B	1,353

Structural data

PDB: 0 · AlphaFold-only: 1 · No structure: 0

AlphaFold-only cohort genes (top 30 by pLDDT)

Symbol	UniProt	pLDDT
EXOC6B	Q9Y2D4	80.08

Function

Pathway analysis

Distinct Reactome pathways touched by cohort: 0. Enrichment computed across 1 evidence-associated genes (0 with Reactome annotation).

GO biological processes by enrichment

Over-representation of cohort genes vs the genome-wide background (hypergeometric test, Benjamini-Hochberg FDR; fold = observed/expected over 1 annotated cohort genes). Counts and members are kept as ground-truth; sorted by enrichment.

GO term	Cohort genes	Fold	FDR	Sample cohort genes
obsolete vesicle tethering involved in exocytosis	1	1872.4×	0.004	EXOC6B
obsolete vesicle docking involved in exocytosis	1	674.1×	0.004	EXOC6B
Golgi to plasma membrane transport	1	561.7×	0.004	EXOC6B
membrane fission	1	411.0×	0.004	EXOC6B
mitotic cytokinesis	1	259.3×	0.005	EXOC6B
exocytosis	1	151.8×	0.008	EXOC6B
intracellular protein transport	1	64.8×	0.015	EXOC6B

Therapeutics

Drug target analysis

Approved (phase 4): 0 · Phase ≥3: 0 · Phased (≥1): 0 · Undrugged: 1

Druggability breadth: 0 of 1 evidence-associated genes (0%) have a ChEMBL target (buckets above are over the deeply-mined display cohort).

Top cohort targets by molecule count

Symbol	Molecules	Max phase
EXOC6B	0	0

Bioactivity and enzyme data

Enzyme cohort genes (≥1 EC): 0.

Pharmacogenomics

Cohort genes with a PharmGKB record: 1; with CPIC/DPWG dosing guidelines: 0.

No cohort gene has a CPIC/DPWG genotype-guided dosing guideline (PharmGKB).

Chemical tractability of cohort targets

0 approved/phased compounds have measured bioactivity against a cohort gene (and aren’t yet in disease-level trials). This is a research / tractability signal, NOT a therapeutic recommendation — a bioactivity row often reflects off-target or screening binding (e.g. promiscuous kinase inhibitors against a cohort kinase), implying no disease mechanism.

Druggability pyramid

Cohort genes binned by druggability tier (high → low):

Tier	Definition	Genes	Symbols
A	Approved (phase 4 drug)	0
B	Phased (≥1) drug, not yet approved	0
C	Druggable family + PDB, no drug	0
D	Druggable family + AlphaFold only, no drug	0
E	Difficult family or no structure, no drug	1	EXOC6B

Undrugged target profiles

1 cohort genes are undrugged. Ranked by ‘starting-point quality’ (assay depth + drugged-partner adjacency).

Symbol	ChEMBL assays	Drugged partners (top 3)
EXOC6B	0	—

Clinical trials & evidence

Clinical trials

Clinical trials: 0.