| domain | evidence-backed fact | suggested ontology terms/IDs | evidence type/limitations |
|---|---|---|---|
| Disease identity | Hennekam lymphangiectasia-lymphedema syndrome 1 is the CCBE1-related subtype of Hennekam syndrome, a generalized lymphatic dysplasia with lymphedema, lymphangiectasia, characteristic facial features, and variable intellectual/developmental impairment (pqac-00000009, pqac-00000010) | Disease: Hennekam lymphangiectasia-lymphedema syndrome 1 (MONDO: verify); Hennekam syndrome (OMIM #235510 verify subtype mapping); MeSH: verify | Human clinical + mechanistic review/context; disease identifiers should be verified in OMIM/MONDO for subtype specificity |
| Causal gene | Biallelic pathogenic variants in **CCBE1** cause HKLLS1; CCBE1 encodes collagen and calcium-binding EGF domain-containing protein 1, a secreted extracellular matrix protein essential for lymphatic development (pqac-00000009, pqac-00000012, pqac-00000013) | Gene: **CCBE1** (HGNC: verify; NCBI Gene: verify); Protein: CCBE1 (UniProt: verify) | Human genetic + animal/mechanistic evidence; exact database IDs should be verified |
| Inheritance | The disorder is autosomal recessive; reported affected individuals carry homozygous or compound heterozygous CCBE1 variants (pqac-00000010, pqac-00000012, pqac-00000013) | Inheritance: HP:0000007 Autosomal recessive inheritance | Human clinical/genetic evidence; penetrance not well quantified |
| Variant spectrum | Published CCBE1 disease variants include missense, frameshift, and other loss-of-function or hypomorphic alleles; one reported prenatal HKLLS1 case had compound heterozygous **c.683_684insT p.Leu229fs** and **c.335C>T p.Thr112Ile** variants (pqac-00000009, pqac-00000013) | Sequence variant terms: SO:0001589 frameshift_variant; SO:0001583 missense_variant; ACMG class: pathogenic/likely pathogenic (verify per submission) | Human genetic evidence; allele frequencies and classification depend on current ClinVar/gnomAD review |
| Core edema phenotype | Edema is usually congenital and often progressive, commonly involving limbs, genitalia, and face (pqac-00000012) | HP:0001004 Lymphedema; HP:0009826 Facial edema; HP:0010318 Edema; onset: HP:0003577 Congenital onset | Human clinical evidence; frequency across CCBE1-only cases is not robustly quantified |
| Lymphangiectasia phenotype | Maldevelopment of the lymphatic system preferentially affects intestines and limbs, and can also affect pleura, pericardium, kidneys, lungs, and mesentery; case-level imaging documented pulmonary and mesenteric/small-bowel lymphangiectasia (pqac-00000012, pqac-00000011) | HP:0100769 Intestinal lymphangiectasia; HP:0005381 Pleural effusion; HP:0001698 Pericardial effusion; HP term for pulmonary lymphangiectasia: verify; UBERON small intestine UBERON:0002108; lung UBERON:0002048; pleura UBERON:0000977; pericardium UBERON:0002408; kidney UBERON:0002113 | Human clinical/imaging evidence; some involved-organ phenotypes are reported across Hennekam syndrome broadly rather than CCBE1-only cohorts |
| Neurodevelopment | Developmental delay/intellectual disability is variable; one pediatric case showed delays in gross motor, fine motor, personal-social, and functional activities (pqac-00000010, pqac-00000011) | HP:0001263 Global developmental delay; HP:0001249 Intellectual disability | Human clinical evidence; severity spectrum broad and incompletely quantified |
| Facial phenotype | Characteristic face may include flat/flattened midface, broad depressed nasal bridge, hypertelorism, epicanthal folds, small or narrow mouth, and other dysmorphic features, partly attributed to prenatal facial lymphedema (pqac-00000008, pqac-00000010, pqac-00000012) | HP:0012368 Flat face; HP:0000316 Hypertelorism; HP:0000280 Coarse face verify/not specific; HP:0000426 Depressed nasal bridge; HP:0000286 Epicanthus; HP:0000208 Small mouth | Human clinical evidence; exact HPO term mapping for each facial feature should be confirmed case-by-case |
| Prenatal presentation | HKLLS1 can present prenatally as recurrent nonimmune hydrops fetalis with cystic hygroma, pleural/pericardial effusions, scalp edema, ascites, hepatomegaly, and hypoplastic lungs (pqac-00000012, pqac-00000013) | HP:0001789 Hydrops fetalis; HP:0000476 Scalp edema; HP:0000473 Cystic hygroma; HP:0001541 Ascites; HP:0002240 Hepatomegaly; HP:0002089 Pulmonary hypoplasia | Human prenatal case evidence; based on case report, so not all patients present this way |
| Pathophysiology | CCBE1 is a crucial regulator of **VEGF-C/VEGFR3** signaling; it enhances proteolytic processing/activation of VEGF-C via **ADAMTS3**, enabling lymphatic endothelial sprouting and lymphangiogenesis (pqac-00000009, pqac-00000008) | Pathway: VEGF-C/VEGFR3 signaling pathway (Reactome/KEGG: verify); GO:0001946 lymphangiogenesis; GO:0001525 angiogenesis; GO term for VEGF-C activation/proteolytic processing: verify | Strong mechanistic support from mouse, zebrafish, and in vitro systems; human inference is biologically well supported but indirect |
| Cellular context | The key affected cell population is the **lymphatic endothelial cell (LEC)**; CCBE1-dependent VEGF-C signaling is required for LEC migration/sprouting from embryonic veins and lymphatic vessel morphogenesis (pqac-00000009, pqac-00000008) | Cell Ontology: lymphatic endothelial cell (CL ID: verify); GO:0035855 megakaryocyte? not relevant; GO:0043542 endothelial cell migration verify; UBERON cardinal vein: verify | Animal/mechanistic evidence; cell ontology ID should be verified before KB ingestion |
| Protein/domain mechanism | CCBE1 contains EGF/calcium-binding EGF domains and collagen repeat domains; functional studies indicate collagen domains are crucial for VEGF-C activation, while EGF domains are required for full in vivo lymphangiogenic activity (pqac-00000009) | Protein domains: EGF-like domain (InterPro/Pfam: verify); collagen repeat domain (InterPro/Pfam: verify) | Mouse, zebrafish, in vitro domain-dissection evidence; not a routine clinical biomarker |
| Anatomy affected | Primary involvement is the lymphatic vasculature across limb soft tissues and viscera; secondary involvement may include intestine, lung, pleura, pericardium, mesentery, face, and possibly kidney (pqac-00000010, pqac-00000011, pqac-00000012) | UBERON lymph vessel: UBERON:0002019 verify; small intestine UBERON:0002108; mesentery UBERON:0002385; lung UBERON:0002048; face UBERON:0001684; limb UBERON:0002101/0002102 verify | Human imaging/clinical evidence; organ distribution heterogeneous |
| Diagnostic workup | Diagnosis is clinical plus imaging and molecular confirmation. Reported tests include lymphatic scan showing absent visible lymphatic flow, CT angiography for lymphedema, chest CT and abdominal ultrasound for lymphangiectasia, MRI for CNS findings, and prenatal WES after nondiagnostic karyotype/microarray/workup (pqac-00000011, pqac-00000012, pqac-00000013) | NCIT: Whole Exome Sequencing (verify); LOINC/NCIT for lymphoscintigraphy, CT angiography, MRI, ultrasound: verify; HP:0000478 Abnormality of the eye? not relevant | Human clinical evidence; no universally standardized disease-specific diagnostic criteria were identified |
| Genetic testing strategy | WES is useful when phenotype is nonspecific, especially in prenatal hydrops; trio exome identified causal CCBE1 variants after normal karyotype, microarray, infectious, hematologic, and metabolic testing (pqac-00000012, pqac-00000013) | Test strategy terms: trio exome sequencing (NCIT: verify); prenatal diagnosis (NCIT: verify) | Human prenatal case evidence; WGS/panel utility for HKLLS1 specifically not systematically studied |
| Differential diagnosis | Differential diagnosis includes other monogenic primary lymphedema/generalized lymphatic dysplasia disorders involving genes such as FAT4, ADAMTS3, FLT4/VEGFR3, VEGFC, PIEZO1, EPHB4, FOXC2, GATA2 and related syndromic/non-syndromic hydrops etiologies (pqac-00000008, pqac-00000012) | Differential disease terms: primary lymphedema (MONDO/Orphanet verify); generalized lymphatic dysplasia (verify) | Mostly broader disease-context evidence; not an exhaustive formal differential list |
| Laboratory findings | Intestinal lymphangiectasia can cause hypoproteinemia, hypoalbuminemia, hypogammaglobulinemia, lymphopenia, and growth problems, although these were absent in one pediatric case with mesenteric lymphangiectasia (pqac-00000011) | HP:0003073 Hypoproteinemia; HP:0003075 Hypoalbuminemia; HP:0004313 Hypogammaglobulinemia; HP:0001888 Lymphopenia; HP:0001510 Growth delay | Evidence mainly from syndrome-level literature/case discussion rather than CCBE1-only cohort statistics |
| Treatment/supportive care | No curative therapy is established. Supportive lymphedema care includes complete decongestive therapy: manual lymph drainage, compression bandaging/garments, exercise, skin care/rehabilitation; one Hennekam case improved arm circumference after 7 sessions (pqac-00000010, pqac-00000011, pqac-00000005) | NCIT: Manual Lymphatic Drainage (verify); Compression Bandage (verify); Exercise Therapy (NCIT: verify); Physical Therapy (NCIT: C15329 verify) | Disease-specific evidence is limited to single-case rehabilitation report; larger lymphedema trial data are not HKLLS1-specific |
| Enteropathy management | For protein-losing enteropathy due to intestinal lymphangiectasia, recommended supportive management includes high-protein, low-fat diet with medium-chain triglyceride supplementation (pqac-00000011) | NCIT/CHEBI: Medium-Chain Triglyceride (verify); dietary management term (verify) | Syndrome-level supportive recommendation; efficacy in HKLLS1 not tested in controlled trials |
| Surgical/interventional care | Surgery is considered a last resort for severe lymphedema that does not respond to conservative treatment (pqac-00000011) | NCIT surgical procedure for lymphedema: verify | Supportive statement from case discussion/referenced literature; no HKLLS1 surgical outcomes series identified |
| Prognosis | Prognosis is variable and depends on extent of visceral lymphatic involvement; prenatal hydrops and pulmonary involvement are poor prognostic features, whereas surviving children may have chronic morbidity dominated by edema and developmental issues (pqac-00000011, pqac-00000012) | Prognostic features: HP:0001789 Hydrops fetalis; HP:0002089 Pulmonary hypoplasia; HP:0001004 Lymphedema | Evidence from case reports and syndrome-level observations; no survival curves or life-expectancy estimates specific to HKLLS1 |
| Prevention/genetic counseling | Primary prevention is not available for the Mendelian disease itself; secondary prevention/reproductive options include carrier testing of parents, recurrence-risk counseling for autosomal recessive inheritance, and prenatal molecular diagnosis if familial variants are known (pqac-00000012, pqac-00000013) | HP:0000007 Autosomal recessive inheritance; prenatal diagnosis term (NCIT: verify); carrier testing term (NCIT: verify) | Logic follows established Mendelian counseling practice; disease-specific counseling guidelines not identified |
| Recent developments (2023-2024 relevance) | Recent literature continues to frame CCBE1 disease within dysregulated lymphatic **VEGFR3 signaling** and developmental lymphatic biology, but no 2023-2024 HKLLS1-specific therapeutic breakthrough or interventional trial was identified (pqac-00000008, pqac-00000007) | Pathway annotations above; clinical trial terms: primary lymphedema exercise trial NCT06327412 | Recent sources are mostly mechanistic or broader lymphedema-focused, not subtype-specific |
| Major data gaps | Major gaps include subtype-specific prevalence/incidence, natural history, penetrance/expressivity estimates, standardized diagnostic criteria, validated biomarkers, genotype-phenotype correlations across CCBE1 alleles, long-term QoL data, and controlled treatment studies specific to HKLLS1 (pqac-00000010, pqac-00000012) | Evidence gap annotation; ontology IDs not applicable | Explicitly based on absence of robust cohort-level evidence in retrieved sources |


*Table: This table summarizes ontology-ready, evidence-backed facts for CCBE1-related Hennekam lymphangiectasia-lymphedema syndrome 1 only. It is designed to support knowledge-base curation while clearly flagging where identifiers or conclusions require verification or where evidence remains sparse.*