| Domain | Key finding | Evidence type | Quantitative detail | Source / date / DOI / PMID | Knowledge-base ontology suggestions |
|---|---|---|---|---|---|
| Disease identity / gene | Lymphatic malformation 6 is linked to **PIEZO1**; disease-target association databases map LM6 to **MONDO:0014797** and PIEZO1 as the only strong associated target | Curated disease-resource + human genetics | OpenTargets evidence size: **5** literature-backed links for PIEZO1–LM6 association | OpenTargets disease-target association for “lymphatic malformation 6” (MONDO_0014797) (pqac-00000000) | MONDO:0014797; HGNC:13866 **PIEZO1**; NCIT: C129043 *Lymphatic Malformation* |
| Founding human cohort | **Autosomal recessive generalized lymphatic dysplasia (GLD)** due to homozygous/compound-heterozygous PIEZO1 variants; frequent **non-immune hydrops fetalis (NIHF)** and childhood facial/four-limb lymphedema | Human clinical / human genetics | **6 families**, **10 PIEZO1 variants** reported; high incidence of NIHF; onset of facial and four-limb lymphedema in childhood | Fotiou et al., **2015-09**, *Nature Communications*, DOI: https://doi.org/10.1038/ncomms9085 (PMID not available in context) (pqac-00000008) | HP:0001789 Lymphedema; HP:0001561 Hydrops fetalis; HP:0000978 Facial edema; HP:0002202 Pleural effusion; HP:0001744 Ascites; HP:0001733 Lymphangiectasia |
| Founding human cohort details | GLD phenotype includes widespread edema with systemic lymphatic involvement: intestinal/pulmonary lymphangiectasia, pleural/chylous/pericardial effusions; some prenatal demise, some postnatal hydrops resolution followed by later lymphedema | Human clinical | **5 patients across 4 families** highlighted; hydrops in at least **2 families**; one in utero demise at **34 weeks**; postnatal lymphedema onset reported around **6–9 years** in survivors | Fotiou et al., **2015-09**, DOI: https://doi.org/10.1038/ncomms9085 (pqac-00000010) | HP:0003573 Congenital onset; HP:0001789 Lymphedema; HP:0010318 Chylothorax; HP:0001698 Pericardial effusion; UBERON:0005409 lymphatic vessel |
| Variant classes / function | Disease-associated PIEZO1 variants include **nonsense, splice-site, and missense** alleles with segregation in affected families; evidence supports **loss of protein** and/or **loss of function** | Human genetics + in vitro / ex vivo functional | Examples in context include nonsense variants **p.E1630X, p.E755X, p.Q2228X** and splice variant **c.3796+1G>A**; reduced/absent protein on Western blot; subtle RBC abnormalities noted | Fotiou et al., **2015-09**, DOI: https://doi.org/10.1038/ncomms9085 (pqac-00000008, pqac-00000010) | SO:0001587 nonsense_variant; SO:0001629 splice_donor_variant; GO:0006816 calcium ion transport; GO:0008308 voltage-gated ion channel activity |
| Independent founding family | Biallelic PIEZO1 mutations identified in **2 siblings** with persistent congenital lymphedema; affected alleles showed markedly reduced channel activity | Human clinical + human genetics + heterologous functional assay | **2 affected siblings**; one splice/truncating allele plus one missense allele; channel function “greatly attenuated” | Lukacs et al., **2015-09**, *Nature Communications*, DOI: https://doi.org/10.1038/ncomms9329 (PMID not available in context) (pqac-00000007) | HP:0001789 Lymphedema; HP:0003577 Congenital onset; MONDO:0014797; GO:0005262 calcium channel activity |
| Recent human variant interpretation | Four novel GLD-associated missense variants can reach the cell surface as full-length protein but still show **reduced or abolished mechanical channel function**, supporting pathogenic LOF mechanisms beyond absent trafficking | Human genetics + in vitro | Variants in context: **E829V, G1978D, I2270T, R2335Q**; all rare/ultra-rare, with no homozygotes in gnomAD noted in context | Ludlow et al., **2023-08**, *medRxiv* preprint, DOI: https://doi.org/10.1101/2023.08.01.23292554 (pqac-00000012, pqac-00000013) | SO:0001583 missense_variant; GO:0005516 mechanosensitive ion channel activity; ECO:0001565 cell-based functional assay evidence |
| Recent families / phenotype expansion | Additional PIEZO1-GLD families show antenatal NIHF, polyhydramnios, congenital limb edema, chylothoraces and ascites; one family showed **adult-onset bilateral chylothoraces in the 30s** before later lymphedema | Human clinical | **3 families** in context (GLD07-09); GLD09 hydrothoraces detected at **19 weeks gestation**; pseudo-dominant appearance in one consanguineous family due to homozygous **I2270T** | Ludlow et al., **2023-08**, DOI: https://doi.org/10.1101/2023.08.01.23292554 (pqac-00000009, pqac-00000011) | HP:0001561 Hydrops fetalis; HP:0002023 Polyhydramnios; HP:0002202 Pleural effusion; HP:0010318 Chylothorax; HP:0001744 Ascites; HP:0001789 Lymphedema |
| Preclinical rescue | **Yoda1** and analogues rescued function of some GLD-associated PIEZO1 missense channels in vitro; this is **preclinical**, not an approved genotype-specific therapy | In vitro / preclinical | Missense variants showed **~65–90% reduction** in Ca2+ signaling vs WT in context; Yoda1 restored mechanically evoked responses in rescue assays | Ludlow et al., **2023-08**, DOI: https://doi.org/10.1101/2023.08.01.23292554 (preprint) (pqac-00000009, pqac-00000011) | CHEBI: not established here for Yoda1; NCIT suggestion: *Experimental Therapeutic Procedure*; GO:0051480 regulation of cytosolic calcium ion concentration |
| Valve-development mechanism | PIEZO1 is required for **lymphatic valve formation**; loss in endothelial/lymphatic endothelium reduces valve number and causes pleural effusion/postnatal lethality in mouse models | Mouse + cultured LECs | Endothelial-specific knockout mice showed **dramatic reduction** in lymphatic valves; pleural effusion and postnatal death reported | Nonomura et al., **2018-11**, *PNAS*, DOI: https://doi.org/10.1073/pnas.1817070115 (PMID not available in context) (pqac-00000007) | GO:0001946 lymphangiogenesis; GO:0035239 tube morphogenesis; CL:0000115 endothelial cell; CL lymphatic endothelial cell; UBERON:0005409 lymphatic vessel |
| Valve development and maintenance | PIEZO1 senses **oscillating shear stress** and drives the genetic program for **lymphatic valve development and maintenance**; adult deletion causes valve degeneration | Mouse + in vitro LECs | Newborn endothelial or lymphatic-specific deletion inhibited valve formation; adult deletion caused “substantial” valve degeneration | Choi et al., **2019-05**, *JCI Insight*, DOI: https://doi.org/10.1172/jci.insight.125068 (pqac-00000003, pqac-00000006) | GO:0034405 response to fluid shear stress; GO:0001946 lymphangiogenesis; HP:0002564 Lymphatic vessel abnormality |
| Sprouting / regression mechanism | PIEZO1 acts upstream of **ORAI1** in flow-activated lymphatic expansion; deletion causes sprouting defects and adult lymphatic regression; activation enhances regeneration | Mouse + in vitro LECs | Lymphatic-specific conditional KO phenocopied sprouting defects; postnatal deletion induced regression; **Yoda1** suppressed postsurgical lymphedema in mice | Choi et al., **2022-07**, *Circulation Research*, DOI: https://doi.org/10.1161/circresaha.121.320565 (pqac-00000004, pqac-00000005) | GO:0001946 lymphangiogenesis; GO:0035556 intracellular signal transduction; NCIT: Preclinical Study |
| 2024 pathway advance | PIEZO1 functions **upstream of ANGPT2/TIE/PI3K/AKT/FOXO1 signaling** in lymphatic endothelial cells, linking mechanosensation to transcriptional regulation relevant to lymphedema biology | Mouse + in vitro LECs | PIEZO1 activation triggered **rapid ANGPT2 exocytosis**, **TIE1 ectodomain shedding by ADAM17**, increased **TIE/PI3K/AKT**, and **FOXO1 nuclear export** | Du et al., **2024-05**, *J Clin Invest*, DOI: https://doi.org/10.1172/jci176577 (pqac-00000001) | GO:0034405 response to fluid shear stress; GO:0014068 positive regulation of phosphatidylinositol 3-kinase signaling; GO:0001525 angiogenesis/lymphatic vascular development; CL:0000115 endothelial cell |
| Current understanding of pathophysiology | Consensus model: biallelic PIEZO1 LOF impairs lymphatic endothelial mechanosensation, disrupting valve morphogenesis, sprouting, and maintenance, producing fetal effusions/hydrops and later systemic lymphedema | Synthesis of human + in vitro + mouse evidence | Supported across **2015–2024** human genetics and mechanistic studies | Supported by Fotiou 2015, Lukacs 2015, Nonomura 2018, Choi 2019/2022, Du 2024 (pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000007, pqac-00000008) | MONDO:0014797; GO:0001946 lymphangiogenesis; GO:0034405 response to fluid shear stress; CL: lymphatic endothelial cell |
| Diagnostics | Most specific diagnostic evidence is **molecular**: exome sequencing/NGS identifying **biallelic PIEZO1 variants**, supported by segregation and functional testing when missense/VUS alleles are found | Human clinical / molecular diagnostics | WES identified causative variants in founding families and sibling pair; lymphoscintigraphy reported in Fotiou cohort; RBC film abnormalities can be supportive but nonspecific | Fotiou et al., **2015-09**; Lukacs et al., **2015-09** (pqac-00000010, pqac-00000007) | NCIT: Whole Exome Sequencing; HP:0001789; LOINC/NCIT suggestions for lymphoscintigraphy not disease-specific |
| Prognosis / natural history | Prenatal course can include NIHF and fetal demise; in survivors, edema may partially/fully resolve postnatally then recur as persistent or childhood-onset lymphedema with systemic complications | Human clinical | Context notes fetal demise, postnatal hydrops resolution, onset around **6–9 years** in some survivors, and adult presentations in later families | Fotiou 2015; Ludlow 2023 (pqac-00000010, pqac-00000009, pqac-00000014) | HP:0003573 Congenital onset; HP:0001789 Lymphedema; HP:0002202 Pleural effusion |
| Epidemiology | Disease-specific prevalence/incidence for LM6 is **not established** in retrieved sources; generalized lymphatic dysplasia is rare | Human clinical / review-level statement | No robust population rate found for LM6; one preprint excerpt mentioned GLD approx. **1 in 6000**, but this appears to refer broadly and should be treated cautiously | Ludlow et al., **2023-08** preprint (context summary only) (pqac-00000013) | MONDO:0014797; Orphan disease coding pending confirmation |
| Clinical treatment evidence | No approved **PIEZO1-genotype-specific** therapy was found in retrieved evidence; management in published human LM6 reports is largely supportive and complication-directed | Human clinical + evidence gap | No controlled LM6 treatment trial identified in retrieved sources | Evidence gap across retrieved LM6 literature (pqac-00000008, pqac-00000009, pqac-00000010) | NCIT: Supportive Care; NCIT: Lymphedema Therapy |
| Generic lymphatic-malformation trials | Active LM/vascular-anomaly trials exist for **sirolimus/rapamycin** and **alpelisib**, but these are **not PIEZO1-genotype-specific** and should not be interpreted as LM6-targeted evidence | Clinical trials, non-genotype-specific | Examples: **NCT06673290** recruiting, n=150; **NCT03243019** recruiting, n=28; **NCT06239480** active-not-recruiting, n=51; **NCT05948943** recruiting, n=232; **NCT00975819** completed, n=61 | ClinicalTrials.gov results retrieved in tool output (current statuses as returned) (pqac-00000000) | NCIT: Sirolimus; NCIT: Alpelisib; NCIT: Clinical Trial; note: not specific to MONDO:0014797 |
| Prevention / environment | No evidence supports environmental, infectious, lifestyle, or protective factors as causal for LM6; prevention is primarily **genetic counseling/reproductive risk management** in affected families | Human genetics / evidence gap | Autosomal recessive inheritance implies **25% recurrence risk** for carrier-couple pregnancies, though exact counseling numbers were not directly quoted in retrieved contexts | Inference from AR inheritance established by Fotiou/Lukacs (pqac-00000007, pqac-00000008) | NCIT: Genetic Counseling; HP/GO not applicable |
| Model systems | Best-supported disease models are **endothelial or lymphatic-specific Piezo1 knockout mice** and cultured lymphatic endothelial cells; these recapitulate valve/sprouting defects and enable pathway dissection | Mouse + in vitro | Multiple conditional models: Tie2Cre, Lyve1Cre, Prox1-CreERT2, Cdh5(PAC)-CreERT2 reported in context | Nonomura 2018; Choi 2019; Choi 2022; Du 2024 (pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000007) | CL: lymphatic endothelial cell; GO:0001946 lymphangiogenesis; NCIT: Disease Model |


*Table: This compact table organizes the key human, in vitro, mouse, and trial evidence for PIEZO1-related lymphatic malformation 6. It highlights the founding 2015 cohorts, recent mechanistic advances, and the important distinction between preclinical Yoda1 rescue and non-genotype-specific lymphatic-malformation trials.*