Bronchiectasis and Nasal Polyposis

Mendelian MONDO:0975835 Pathograph 10 Show in embeddings browser

Autosomal recessive chronic destructive airway disease caused by biallelic loss-of-function variants in WFDC2, which encodes the secreted WAP four-disulfide core domain protein 2 (also called HE4). Affected individuals have bronchiectasis, severe chronic rhinosinusitis with nasal polyposis, and chronic airway infection, frequently with Pseudomonas aeruginosa. The presentation closely mimics cystic fibrosis and primary ciliary dyskinesia, and was first defined as a distinct Mendelian entity in 2024. What makes the entry mechanistically interesting is a negative result. WFDC2 is made by airway secretory cells and is absent from the airway surface liquid, saliva and serum of affected individuals, so the obvious hypothesis is failed mucociliary clearance. That hypothesis was tested and did not hold: ciliary beat frequency, ciliary length, epithelial composition and mucus viscosity are all normal, and patient cultures generate directed mucociliary transport. The step connecting loss of a secreted airway protein to airway destruction is therefore not yet established, and this entry models that gap explicitly rather than asserting a clearance defect the source data refute.

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1
Mappings
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Inheritance
7
Pathophys.
10
Phenotypes
3
Gaps
10
Pathograph
1
Genes
3
Medical Actions
4
Differentials
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Models
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Deep Research
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Mappings

MONDO
MONDO:0975835 bronchiectasis and nasal polyposis
skos:exactMatch
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Inheritance

1
Autosomal recessive HP:0000007
Biallelic pathogenic WFDC2 variants, identified across 10 unrelated families from four continents in the founding cohort. Reported patients are homozygous or compound heterozygous, with founder alleles in East Asian populations.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"We identified biallelic pathogenic variants in WAP four-disulfide core domain 2 (WFDC2) in 11 individuals from 10 unrelated families originating from the United States, Europe, Asia, and Africa."
Establishes recessive inheritance across an internationally distributed founding cohort.
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Discussions and Knowledge Gaps

3
Does the murine Wfdc2-null ciliary and alveolar phenotype reflect a mechanism the human ciliary and clearance measurements missed, or a genuine species divergence in how loss of WFDC2 is tolerated?
HUMAN MODEL MISMATCH OPEN wfdc2_mouse_ciliary_alveolar_mismatch
Attached to
pathophysiology#Preserved Mucociliary Clearance animal_models#Wfdc2-null mouse (Nakajima et al.)
Two independently generated Wfdc2-null mouse lines both die of neonatal respiratory failure, but by different routes: impaired cilia, absent mature club cells and malformed AECII lamellar bodies in one line (PMID:31562139), and type-I alveolar epithelial cell apoptosis with lung hypovascularity in the other (PMID:31780266). The ciliary defect is not present in WFDC2-deficient humans, whose ciliary length, ciliary beat frequency and coordination, cilia and centrosome composition, mucus viscosity and directed mucociliary transport match controls, and who survive the neonatal period with a chronic but non-lethal airway disease. The alveolar lesions - type-I cell apoptosis, hypovascularity, AECII lamellar body malformation - have not been assessed in humans at all, so their absence is not established. Cellular morphology and fate in patient airway cultures were inspected and no obvious change was seen, but club-cell maturation markers were not specifically assayed. Two readings are both consistent with the data. Under a mechanism-missed reading, the mouse's ciliary and alveolar defects point to a WFDC2 function the human measurements have not yet probed - the human ALI cultures examined ciliary beat and structure but not the AECII lamellar body or club-cell differentiation axis the mouse implicates beyond an informal inspection of cell morphology and fate. Under a species-divergence reading, the extra 52-residue linker in murine WFDC2 relative to human WFDC2 means the mouse ortholog simply does something different, and its loss produces a developmental lung phenotype with no human counterpart - consistent with humans having no equivalent neonatal-lethal presentation despite biallelic loss-of-function alleles. The question matters because the mouse is otherwise the obvious system for testing candidate mechanisms (protein replacement, the antiprotease hypothesis), and neonatal lethality forecloses that use if the mismatch is genuine species divergence rather than a missed human measurement.
Proposed experiments
Club-cell maturation assay in WFDC2-deficient human bronchial air-liquid-interface cultures
wfdc2_club_cell_maturation_in_human_airway_cultures
The human air-liquid-interface cultures were examined for ciliary beat, ciliary length and mucus viscosity, and cell morphology and fate were inspected informally, but club-cell maturation markers such as SCGB1A1 were not assayed. Quantifying SCGB1A1-positive club cells in patient-derived bronchial cultures against controls tests the airway half of the mouse phenotype directly.
Would support
pathophysiology#Preserved Mucociliary Clearance
Would refute
pathophysiology#Preserved Mucociliary Clearance
Supporting outcome
  • Normal club-cell maturation in WFDC2-deficient cultures, which would support the species-divergence reading for the airway phenotype.
Refuting outcome
  • Reduced or absent SCGB1A1-positive mature club cells in WFDC2-deficient cultures, which would show that the mouse secretory-cell defect is present in humans but was not measured.
AECII lamellar body and type-I cell survival assay in patient iPSC-derived alveolar cells
wfdc2_alveolar_type_ii_cells_from_patient_ipsc
No alveolar tissue or alveolar cell culture from a WFDC2-deficient individual has been examined. Patient iPSC-derived alveolar type II cells or alveolospheres would test whether the lamellar body malformation and type-I cell loss seen in the two mouse lines occur in human cells lacking WFDC2.
Supporting outcome
  • Normal lamellar bodies and type-I cell survival in patient-derived alveolar cells, which would support the species-divergence reading for the alveolar phenotype.
Refuting outcome
  • Malformed lamellar bodies or type-I cell apoptosis in patient-derived alveolar cells, which would identify a human alveolar corollary to the lethal mouse phenotype that the airway-focused human studies could not detect.
Show evidence (3 references)
PMID:38626355 SUPPORT INDIRECT Other
"The phenotypic variation between human WFDC2 deficiency described here and mouse WFDC2 deficiency may reflect in part the sequence difference between human and mouse WFDC2, of which the latter contains a unique 52-amino acid linker region between WAP domains"
The founding human-cohort paper's own hypothesis for the mismatch, framing the species-sequence-difference reading recorded in this discussion. It is an inference from a sequence comparison rather than a clinical observation, hence OTHER and INDIRECT.
PMID:38626355 SUPPORT DIRECT In Vitro
"Although cytoplasmic accumulation of WFDC2 was noted in UNC-186 II2, obvious changes in cellular morphology or fate (also in OP-2032 II1) were not apparent."
Records that cell morphology and fate in patient airway epithelia were inspected and showed no obvious change. This is an informal inspection, not a club-cell maturation assay, so it leaves the club-cell axis the mouse implicates open.
PMID:31780266 SUPPORT DIRECT Model Organism
"mechanistic studies indicated increased apoptosis in type-I alveolar cells in lung tissues, which caused hypovascular lung tissue, then led to severe dyspnea in wfdc2-/- neonates"
Independent confirmation, via a second Wfdc2-null mouse line generated by a different targeting method, that murine Wfdc2 loss is neonatally lethal - through an alveolar rather than ciliary lesion - reinforcing that the mismatch with the human disease is not an artifact of one mouse line.
By what route does loss of a secreted airway protein cause bronchiectasis when mucociliary clearance, mucus viscosity and ciliary function are all normal?
KNOWLEDGE GAP OPEN wfdc2_mechanism_to_bronchiectasis_unexplained
Attached to
pathophysiology#Depletion of WFDC2 from Airway Surface Liquid and Secretions pathophysiology#Preserved Mucociliary Clearance
This is the central open question of the disorder, and it is open because the obvious answer was tested and failed. Both diseases that WFDC2 deficiency clinically mimics cause bronchiectasis through defective clearance - CF through mucus properties, PCD through ciliary function - and in WFDC2 deficiency neither is abnormal. Ciliary beat frequency and length, epithelial and centrosome composition, and mucus viscosity all match controls, and patient cultures generate directed transport. What remains is an association: reduced SPINK5 on saliva proteomics in three patients, and the protease-inhibitor identity of the WFDC family. Neither establishes a route to airway wall destruction. The one loose measurement is that mucociliary transport speed was low relative to controls even though the authors judged clearance to be within the normal range; whether that is a subtle real defect or assay variation at n=2 is unresolved and is worth settling before it is either promoted to a mechanism or dismissed. The answer matters for treatment. Protein replacement is proposed on the reasoning that the missing product acts extracellularly, but without knowing what it does there, neither the target tissue, the therapeutic window, nor a pharmacodynamic readout can be specified.
Proposed experiments
Direct protease-antiprotease measurement in patient airway surface liquid
wfdc2_asl_antiprotease_activity
Measure neutrophil elastase and other protease activity, and antiprotease capacity, in airway surface liquid and sputum from WFDC2-deficient individuals against CF, PCD and healthy controls, rather than inferring the antiprotease role from saliva proteomics and family homology.
Would support
pathophysiology#Altered Airway Antiprotease Milieu
Would refute
pathophysiology#Altered Airway Antiprotease Milieu
Supporting outcome
  • Unopposed protease activity in patient airway surface liquid exceeding that of airway-disease controls with comparable infection burden, which would separate the antiprotease deficit from the effects of chronic infection.
Refuting outcome
  • Protease-antiprotease balance comparable to CF and PCD controls, indicating that the SPINK5 finding does not translate into an airway antiprotease deficit and that the mechanism lies elsewhere.
Bacterial handling in WFDC2-deficient air-liquid interface cultures
wfdc2_bacterial_handling_ali
Challenge patient-derived and WFDC2-knockout airway cultures with Pseudomonas aeruginosa and quantify adherence, killing and epithelial barrier integrity, testing host defense rather than clearance as the affected function.
Would support
pathophysiology#Chronic Airway Infection and Rhinosinusitis
Would refute
pathophysiology#Chronic Airway Infection and Rhinosinusitis
Supporting outcome
  • Impaired bacterial killing or increased adherence and barrier disruption in WFDC2-deficient cultures, rescued by recombinant WFDC2, which would supply the missing causal step and simultaneously provide the pharmacodynamic readout that replacement therapy currently lacks.
Refuting outcome
  • Bacterial handling indistinguishable from controls, which would push the mechanism toward inflammation or repair rather than defense and would make the infection a consequence of established bronchiectasis rather than its cause.
How much WFDC2 deficiency is currently being counted as idiopathic bronchiectasis or probable PCD?
KNOWLEDGE GAP OPEN wfdc2_ascertainment_and_panel_coverage
Attached to
prevalence#Worldwide genetic#WFDC2
Every reported patient was found by sequencing beyond the standard panels, and the disorder has a specific reason to be systematically missed rather than merely rare: low nasal nitric oxide gives these patients a positive result on the PCD screening test, so the workup terminates at a plausible wrong answer instead of continuing. Cases accumulated from Korea and Japan within two years of the founding report, and founder alleles have been proposed, which is not the pattern of a genuinely ultra-rare disease. The one targeted screen so far cuts the other way and is the reason this is recorded as an open question rather than a conclusion. A Vietnamese sinopulmonary study sequenced all three WFDC2 coding exons in 31 patients with extensive bronchiectasis and found nothing. That is a real constraint: whatever is hiding inside idiopathic bronchiectasis, in that cohort it was not WFDC2. Whether the negative reflects genuine rarity, population-specific allele frequencies, or a cohort selected on bronchiectasis rather than on the polyposis that is the fully penetrant feature, is exactly what is unresolved. This is tractable without new discovery work: serum WFDC2 can be measured with an existing commercial assay, so an idiopathic-bronchiectasis or probable-PCD cohort could be screened biochemically before any sequencing. Until more cohorts are screened either way, the prevalence field here is a count of reports rather than an estimate.
Show evidence (2 references)
PMID:41094464 REFUTE DIRECT Human Clinical
"No abnormal WFDC2 variants were found in 31 patients with extensive BL/BE."
The only targeted screen of an unselected bronchiectasis cohort published so far, and it is negative. It counts against the under-ascertainment thesis rather than for it, and is recorded here as the constraint the open question has to answer to.
PMID:41094464 SUPPORT INDIRECT Human Clinical
"However, the spectrum varies across ethnicities, and specifically, while considered rare in Southeast Asia, the current status in this region remains largely unknown."
The same study's framing of why the question is open at all: the genetic spectrum of sinopulmonary disease is unmapped across much of the world, so a single negative cohort bounds rather than settles it.
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Pathophysiology

7
Biallelic Loss of Function in WFDC2
The initiating lesion. WFDC2 encodes a small secreted whey-acidic-protein family member expressed by airway secretory cells. Reported disease alleles include nonsense, frameshift and missense changes; the recurrent p.Cys49Arg founder variant acts by disrupting a disulfide-forming cysteine rather than by truncating the protein.
WFDC2 hgnc:15939 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves WFDC2 (hgnc:15939). hgnc:15939 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
Failure of WFDC2 Secretion
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"WFDC2 dysfunction defines a novel molecular etiology of bronchiectasis characterized by the deficiency of a secreted component of the airways."
States the causal claim: WFDC2 loss is a distinct molecular cause of bronchiectasis.
PMID:40114242 SUPPORT DIRECT Human Clinical
"Therefore, we aimed to identify two novel variants of the WFDC2 gene, known as antiprotease, from patients with bronchiectasis and/or related phenotypes using trio-based whole-genome sequencing analysis."
Independent replication of WFDC2 variants in bronchiectasis patients, and names the protein's antiprotease identity.
Failure of WFDC2 Secretion
The proximate consequence. For the p.Cys49Arg founder allele the mechanism is specific and was modelled directly: the substitution structurally hampers glycosylation, and the immature protein is not secreted. The result for the airway is the same whichever allele is involved - no mature WFDC2 reaches the extracellular space.
Airway secretory cell CL:4052031 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Airway secretory cell, annotated with respiratory airway secretory cell (CL:4052031). CL:4052031 is a cell type from the Cell Ontology.
protein secretion GO:0009306 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased protein secretion (GO:0009306). GO:0009306 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Depletion of WFDC2 from Airway Surface Liquid and Secretions
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT In Vitro
"Computer simulations and deglycosylation assays indicate that the disease-causing founder variant p.Cys49Arg structurally hampers glycosylation and, thus, secretion of mature WFDC2."
Identifies impaired glycosylation as the mechanism blocking secretion of the founder-variant protein.
PMID:38626355 SUPPORT DIRECT Human Clinical
"Expression of WFDC2 was detected predominantly in secretory cells of control airway epithelium and also in submucosal glands."
Localizes WFDC2 production to airway secretory cells and submucosal glands, the source of the missing secreted protein.
Depletion of WFDC2 from Airway Surface Liquid and Secretions
The measurable deficiency state. WFDC2 is below the limit of detection in serum and barely detectable in saliva, seminal fluid and airway surface liquid from affected individuals. The contrast with the disease controls is informative: patients with CF and PCD have detectable, indeed elevated, WFDC2, so this is not a nonspecific consequence of chronic airway disease. It is also what makes a commercially available serum assay usable diagnostically.
extracellular region GO:0005576 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves decreased extracellular region (GO:0005576). GO:0005576 is a cellular component from the Gene Ontology.
Downstream
Altered Airway Antiprotease Milieu
Chronic Airway Infection and Rhinosinusitis
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"We demonstrate that WFDC2 is below the limit of detection in blood serum and hardly detectable in samples of saliva, seminal fluid, and airway surface liquid from WFDC2-deficient individuals."
Directly measures the deficiency across the relevant compartments, including airway surface liquid.
PMID:38626355 SUPPORT DIRECT Human Clinical
"This represents the first description of WFDC2 deficiency as a cause of chronic destructive airway disease, in contrast to PCD and CF, which show elevated expression of WFDC2."
The opposite direction in CF and PCD shows the depletion is specific to this disorder rather than secondary to airway disease generally.
Altered Airway Antiprotease Milieu
A candidate, partially supported consequence. WFDC family members are protease inhibitors, and comparative proteomics of saliva found the serine protease inhibitor SPINK5 significantly reduced in WFDC2-deficient individuals relative to both healthy controls and airway-disease controls. SLPI, the other WFDC protein highly expressed in airway epithelium, was not significantly altered. The claim carried here is deliberately narrow. The SPINK5 finding is real and controlled against disease as well as healthy comparators, but it is measured in saliva rather than in the airway, in three patients, and it establishes an association rather than a route to tissue destruction. It is modelled as a node because the protease-antiprotease balance is the mechanism the protein family's known biology predicts, not because the pathway to bronchiectasis has been demonstrated.
serine-type endopeptidase inhibitor activity GO:0004867 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased serine-type endopeptidase inhibitor activity (GO:0004867). GO:0004867 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Chronic Airway Infection and Rhinosinusitis
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"We also analyzed SPINK5 by WB and observed reduced expression of a proteolytically cleaved species (28) in individuals with WFDC2 mutations compared with healthy control and respiratory disease control groups"
Reduced SPINK5 in patients relative to both healthy and airway-disease controls, which is what makes it specific rather than a chronic-disease effect.
PMID:38626355 SUPPORT INDIRECT In Vitro
"Other members of the WFDC protein family, such as SLPI (WFDC4) (20) and Elafin (WFDC14) (21), exhibit protease inhibitor activity and play an important role in the innate immune system."
Family-level protease-inhibitor biology motivating an antiprotease role for WFDC2; inference from paralogues, not a measurement of WFDC2 itself.
Chronic Airway Infection and Rhinosinusitis
Chronic infection of the upper and lower airways, with Pseudomonas aeruginosa prominent, together with pronounced chronic rhinosinusitis. This is the step at which the disorder becomes clinically indistinguishable from cystic fibrosis and inborn errors of immunity, and it is a persistent state rather than recurrent discrete episodes.
Downstream
Airway Wall Destruction and Nasal Polyp Formation
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Here we identify disease-causing variants in WFDC2 that underlie a unique and severe respiratory disorder characterized by bronchiectasis in all lung fields, chronic rhinosinusitis, and lung infection by Pseudomonas aeruginosa resembling the clinical phenotype of cystic fibrosis, primary ciliary..."
Establishes chronic Pseudomonas infection and rhinosinusitis as core features and names the diseases it mimics.
Airway Wall Destruction and Nasal Polyp Formation
The structural endpoint: irreversible bronchial dilatation and nasal polyposis. The general route from repeated airway insult to bronchiectasis is the vicious cycle of infection, inflammation, damage and abnormal remodelling that is common to bronchiectasis of any cause; what is specific to this disorder is what initiates the cycle. Distribution is a useful discriminator - disease in all lobes, mimicking CF and inborn errors of immunity, rather than the middle and lower lobe predominance of PCD.
Show evidence (2 references)
PMID:38717359 SUPPORT INDIRECT Human Clinical
"Bronchiectasis often results from repeated insults to the airways, leading to a vicious cycle of damage and repair and ultimately abnormal remodeling and loss of airway integrity (1)."
The general damage-and-repair route to bronchiectasis; applied to this disorder by inference rather than demonstrated in it.
PMID:38626355 SUPPORT DIRECT Human Clinical
"Bronchiectasis in WFDC2 deficiency more closely mimics CF and IEI (all lobes) than PCD (predominantly middle and lower lobes)."
Gives the lobar distribution that distinguishes this disorder radiologically from PCD.
Preserved Mucociliary Clearance
Recorded as an explicitly excluded step rather than omitted. Because WFDC2 is a secreted airway protein, impaired mucociliary clearance is the natural hypothesis, and it is the mechanism by which both diseases this disorder mimics - cystic fibrosis and primary ciliary dyskinesia - cause bronchiectasis. It was tested and did not hold. In patient-derived cultures at air-liquid interface, ciliary beat frequency was normal, ciliary length was unchanged, epithelial morphology and cilia and centrosome composition were comparable to controls, mucus viscosity was no different, and the cultures generated directed mucociliary transport. Transport speed was low relative to controls, but the authors' own conclusion is that clearance is within the normal range. This node carries no downstream edge on purpose: the point is that the expected link to airway destruction is absent. The residual transport-speed observation is the loose end, and it is captured as a knowledge gap rather than promoted to a mechanism.
mucociliary clearance GO:0120197 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves mucociliary clearance (GO:0120197). GO:0120197 is a biological process from the Gene Ontology.
Animal models
Wfdc2-null mouse (Nakajima et al.) Mouse fails to recapitulate The mouse does not reproduce the human finding that ciliary structure and mucociliary clearance are preserved despite WFDC2 loss. Wfdc2-null mouse airways instead show impaired cilia and failed secretory-cell differentiation, and the mutant is neonatally lethal - a phenotype absent entirely from the human disease, where clearance measurements are normal and affected individuals survive the neonatal period with a chronic, non-lethal airway disease.
Show evidence (3 references)
PMID:38626355 SUPPORT DIRECT In Vitro
"Taken together, our results suggest that WFDC2-deficient respiratory epithelia likely have a level of mucociliary clearance that is within the normal range."
The authors' own conclusion, and the basis for naming this node as a preserved function rather than an impaired one.
PMID:38626355 SUPPORT DIRECT In Vitro
"Cultures from both individuals with WFDC2 mutations were capable of generating MCT in a directed fashion, with cells from UNC 186 II2 generating complete circular transport when cultured in an MCT device (27) (Video E15)."
Patient cultures generate directed transport, which is the functional demonstration that clearance is preserved.
PMID:38626355 REFUTE DIRECT In Vitro
"Interestingly, the speed of MCT was low relative to the control cultures (Figures E7C and E7D), but the epithelial morphology and composition of cilia and centrosomes were comparable between healthy control subjects and OP-2032 II1 (Figure E8)."
The one measurement cutting against preservation, kept because it is the residual the knowledge gap is about. Graded REFUTE against this node's claim rather than SUPPORT: it is the only result inconsistent with wholly normal transport, even though the authors judged the overall level to be within the normal range.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Bronchiectasis and Nasal Polyposis Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

10
Ear 1
Otitis Media FREQUENT HP:0000388 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Otitis media (HP:0000388). HP:0000388 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Individuals UNC-376 II1, OP-2147 II1, OP-2032 II1, OP-398 II1, UNC-186 II1, UNC-186 II2, and OP-4474 II1 reported otitis media."
Seven of eleven individuals named individually, which is 64% and so the FREQUENT band.
PMID:40401042 SUPPORT DIRECT Human Clinical
"All patients had a history of chronic sinusitis, and 64.3 % also experienced otitis media"
The pooled published series, giving 64.3% from a larger and independent denominator. Two denominators landing in the same band is what fixes the frequency rather than a single small cohort.
Genitourinary 1
Female Infertility FREQUENT HP:0008222 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Female infertility (HP:0008222). HP:0008222 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"These findings suggest that WFDC2 deficiency impacts female rather than male fertility and warrant further investigation."
States the sex-restricted fertility effect after the authors specifically tested male sperm function.
PMID:40114242 SUPPORT DIRECT Human Clinical
"Additionally, WFDC2 has been implicated in nasal polyposis and infertility, both of which were observed in some of our patients, suggesting a broader spectrum of clinical manifestations."
Independent replication of the infertility association in the Korean cohort.
Head and Neck 3
Nasal Polyposis OBLIGATE HP:0100582 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Nasal polyposis (HP:0100582). HP:0100582 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Here, we describe a novel Mendelian disorder of chronic destructive airway disease characterized by bronchiectasis, chronic infection of the airways, pronounced CRS, and nasal polyposis due to autosomal recessive inheritance of pathogenic WFDC2 variants."
Names nasal polyposis as a defining feature of the disorder.
Chronic Rhinosinusitis OBLIGATE Chronic sinusitis HP:0011109 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Chronic sinusitis (HP:0011109), qualified as temporality chronic. HP:0011109 is a phenotype from the Human Phenotype Ontology.
Temporal: CHRONIC
Show evidence (1 reference)
PMID:40401042 SUPPORT DIRECT Human Clinical
"The ages at diagnosis of bronchiectasis were 18, 24, and 16 years, and all patients had a history of chronic sinusitis since childhood."
Establishes childhood-onset chronic sinusitis preceding the bronchiectasis diagnosis by years.
Nasal Pyramid Broadening OBLIGATE Wide nose HP:0000445 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Broadening of the nasal pyramid, annotated with Wide nose (HP:0000445), qualified as course progressive. HP:0000445 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"In addition, all 11 individuals showed severe upper airway disease manifesting as CRS with pronounced nasal polyposis and progressive broadening of the nasal pyramid (Figure 2E and Table 1)."
All eleven cohort individuals, alongside the polyposis and rhinosinusitis in the same sentence.
Immune 1
Chronic Pseudomonas aeruginosa Airway Infection VERY_FREQUENT Recurrent Pseudomonas aeruginosa infection HP:5210057 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Chronic Pseudomonas aeruginosa airway infection, annotated with Recurrent Pseudomonas aeruginosa infection (HP:5210057), qualified as temporality chronic. HP:5210057 is a phenotype from the Human Phenotype Ontology.
Temporal: CHRONIC
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Furthermore, nine individuals with WFDC2 mutations suffered from chronic P. aeruginosa infection, which is known to be a risk factor associated with bronchiectasis (14)."
The cohort frequency, nine of eleven. Replaces the paper's Objectives sentence, which describes who was recruited rather than what was found and so could not establish a frequency.
Respiratory 4
Bronchiectasis VERY_FREQUENT HP:0002110 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bronchiectasis (HP:0002110), qualified as course progressive. HP:0002110 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (3 references)
PMID:40401042 SUPPORT DIRECT Human Clinical
"Despite low nasal nitric oxide levels, the radiologic features resembled those of cystic fibrosis, characterized by bronchiectasis predominantly in the upper lobes."
Independent case series describing CF-like radiology with upper-lobe predominance.
PMID:38626355 SUPPORT DIRECT Human Clinical
"All individuals with biallelic WFDC2 variants presented with marked chronic respiratory symptoms affecting the upper and lower airways, and 9 of 11 individuals showed bronchiectasis by CT imaging (Figures 2A-2D and Table 1)."
Gives the cohort frequency, 9 of 11, which is why this is VERY_FREQUENT rather than obligate.
PMID:38626355 REFUTE DIRECT Human Clinical
"This search was broadened to newly available exomes and identified WFDC2 variants in OP-4474 II1, who presented with nasal polyposis but not bronchiectasis at 7 years of age."
A molecularly confirmed patient without bronchiectasis, which directly refutes treating it as obligate.
Neonatal Respiratory Distress OCCASIONAL HP:0002643 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Neonatal respiratory distress (HP:0002643). HP:0002643 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Individuals OP-2147 II1, UNC-231 II1, and UNC-186 II1 reported neonatal respiratory distress syndrome."
Three of eleven individuals, named, indicating onset can be immediately postnatal.
Reduced FEV1 OBLIGATE Reduced forced expiratory volume in one second HP:0032342 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Reduced forced expiratory volume in one second (HP:0032342). HP:0032342 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"FEV1% predicted was reduced in all affected individuals examined (Table 1)."
Reduced in all individuals tested.
PMID:38626355 SUPPORT DIRECT Human Clinical
"Spirometry data were available in 9 of 11 individuals, and all demonstrated altered lung function parameters consistent with a chronic obstructive airway disease, resembling findings in CF and PCD."
Gives the denominator, nine of eleven tested, and the obstructive pattern.
Very Low Nasal Nitric Oxide OBLIGATE Decreased nasal nitric oxide HP:0033036 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased nasal nitric oxide (HP:0033036). HP:0033036 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Interestingly, very low nasal nitric oxide production rate was a shared finding in individuals with WFDC2 mutations (9/9), which is associated with CRS (15) but also characteristic for PCD (16, 17) and a potential finding in CF (18)."
All nine measured, and the source itself names the overlap with PCD and CF that causes the diagnostic confusion.
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Genetic Associations

1
WFDC2
Gene: WFDC2 hgnc:15939 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is WFDC2 (hgnc:15939). hgnc:15939 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:40401042 SUPPORT DIRECT Human Clinical
"Considering the possibility of founder mutations, WFDC2 variants should be included in diagnostic panels for patients with sinopulmonary disease in Asian populations."
Argues for founder alleles and panel inclusion on the basis of three independent Japanese cases.
💊

Medical Actions

3
Airway Clearance and Long-Term Macrolide Therapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Platform: Small molecule
Standard bronchiectasis management. Worth recording that it is inadequate here - all three Japanese patients had frequent exacerbations and respiratory dysfunction despite long-term macrolides.
Show evidence (1 reference)
PMID:40401042 REFUTE DIRECT Human Clinical
"All patients experienced frequent exacerbations and respiratory dysfunction, even with long-term macrolide therapy."
Refutes adequacy of standard macrolide therapy for controlling this disorder.
Lung Transplantation
Action: organ transplantationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is organ transplantation (NCIT:C15289). NCIT:C15289 is a clinical intervention from the NCI Thesaurus. Ontology label: Organ Transplantation NCIT:C15289
Platform: Surgery
The endpoint for advanced disease; two of the three reported Japanese patients required it, in their twenties or earlier.
Show evidence (1 reference)
PMID:40401042 SUPPORT DIRECT Human Clinical
"Consequently, two of the three patients required lung transplantation."
Documents transplantation as the outcome in two of three reported patients.
WFDC2 Protein Replacement
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Platform: Protein replacement
Proposed but not tested. The rationale is unusually clean for a Mendelian disorder - the missing gene product is small and acts extracellularly, so it need not be delivered into cells - which is why it is recorded here despite being hypothetical. No preclinical or clinical data exist.
Mechanism Target:
Depletion of WFDC2 from Airway Surface Liquid and Secretions — Would act by restoring the missing secreted protein to the extracellular compartment it is absent from. Entirely prospective.
Show evidence (1 reference)
PMID:38626355 SUPPORT INDIRECT Human Clinical
"Because of the relatively small size of WFDC2 and its function in extracellular spaces, replacement therapy may be a potential option."
The authors' stated rationale for replacement therapy; a proposal rather than a result.
🔬

Diagnosis

3
Serum or saliva WFDC2 (HE4) measurement
An unusually direct biochemical test for a Mendelian disorder: the causal gene product is a secreted protein already measured by a commercial electrochemiluminescence immunoassay, developed as an ovarian cancer biomarker. In affected individuals serum WFDC2 is below the limit of detection. The comparison that makes it discriminating is that CF and PCD patients have elevated, not reduced, WFDC2, so the test separates this disorder from its main mimics rather than merely flagging airway disease.
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"The diagnosis can be suspected based on measurement of serum or saliva WFDC2/HE4 concentrations and confirmed by genetic testing."
States the two-step diagnostic strategy of biochemical suspicion plus genetic confirmation.
PMID:38626355 SUPPORT DIRECT Human Clinical
"Using a commercial electrochemiluminescence immunoassay, we measured serum concentrations of WFDC2 in individuals with biallelic WFDC2 variants and compared this to serum concentrations of WFDC2 in individuals with PCD and CF (Figure 4K)."
Establishes that an already-commercial assay was used and benchmarked against the two main mimics.
Low nasal nitric oxide as a misleading result
A diagnostic trap worth stating plainly. Nasal nitric oxide is low in these patients, and low nasal NO is the standard screening test for primary ciliary dyskinesia. Patients are therefore liable to be labelled probable PCD - explicitly what happened in the Japanese series, in a setting where CF is rare - and the label can stand for years because the airway phenotype is compatible with it. The founding cohort recommends considering WFDC2 deficiency precisely when nasal NO is very low.
Show evidence (2 references)
PMID:38626355 SUPPORT DIRECT Human Clinical
"We recommend including WFDC2 deficiency in the differential diagnosis with CRS, CF, and PCD when nasal nitric oxide measurements are very low."
The authors' explicit recommendation to consider this disorder when the PCD screening test is positive.
PMID:40401042 SUPPORT DIRECT Human Clinical
"these cases often present low levels of nasal nitric oxide (nNO) and are preliminarily diagnosed as probable PCD in Japanese settings where CF is rare"
Documents the misdiagnosis actually occurring, which is what makes this a practical trap rather than a theoretical one.
Genetic confirmation
Biallelic WFDC2 variants on next-generation or targeted Sanger sequencing. WFDC2 is not on all sinopulmonary panels, so a negative CF and PCD panel does not exclude it.
Show evidence (1 reference)
PMID:38626355 SUPPORT DIRECT Human Clinical
"Methods: DNA was analyzed by next-generation or targeted Sanger sequencing."
The sequencing approach used to establish the diagnosis in the founding cohort.
📈

Progression

2
Childhood chronic rhinosinusitis
Upper airway disease is present from childhood and precedes recognition of the bronchiectasis, in the reported series by roughly a decade.
Show evidence (1 reference)
PMID:40401042 SUPPORT DIRECT Human Clinical
"The ages at diagnosis of bronchiectasis were 18, 24, and 16 years, and all patients had a history of chronic sinusitis since childhood."
Gives both the childhood onset of sinus disease and the age at which bronchiectasis was diagnosed.
Progressive bronchiectasis to respiratory failure
Progressive despite standard therapy, reaching transplantation in two of three patients in the one series reporting outcomes.
Show evidence (1 reference)
PMID:40401042 SUPPORT DIRECT Human Clinical
"Consequently, two of the three patients required lung transplantation."
Documents progression to end-stage lung disease.
📊

Prevalence

1
Worldwide
Cases In Literature Not yet documented
No prevalence estimate exists. The disease was defined in 2024 from 11 individuals in 10 families, with small numbers added since from Korea and Japan. Because the presentation is indistinguishable from CF and PCD and WFDC2 is absent from many diagnostic panels, the reported count is a floor rather than an estimate - but not an unlimited one: a targeted screen of 31 Vietnamese patients with extensive bronchiectasis found no WFDC2 variants at all, so the hidden fraction is not large in every population.
⚖️

Clinical Burden

High
Lifelong progressive suppurative airway disease with chronic Pseudomonas infection, poorly controlled by the standard therapy, reaching lung transplantation in two of three patients in the only series reporting outcomes, at ages in the teens and twenties. Compounded by severe chronic rhinosinusitis from childhood and by diagnostic delay, since the disorder is routinely mislabelled as probable PCD.
Show evidence (1 reference)
PMID:40401042 SUPPORT DIRECT Human Clinical
"All patients experienced frequent exacerbations and respiratory dysfunction, even with long-term macrolide therapy."
Supports a high burden assessment through refractoriness to standard treatment.
🔀

Differential Diagnoses

4

Conditions with similar clinical presentations that must be differentiated from Bronchiectasis and Nasal Polyposis:

Cystic fibrosis
Overlapping Features The closest mimic radiologically and clinically - chronic Pseudomonas infection, sinus disease, bronchiectasis in all lobes. Separated by CFTR genetics, sweat testing, and, distinctively, by WFDC2 level, which is elevated in CF and undetectable here.
Primary ciliary dyskinesia
Overlapping Features Shares low nasal nitric oxide, chronic rhinosinusitis and bronchiectasis, and is the label these patients most often receive first. Separated by normal ciliary beat pattern and frequency on high-speed video microscopy, by lobar distribution, and by WFDC2 level.
Inborn errors of immunity
Overlapping Features Also produce pan-lobar bronchiectasis with chronic infection. Separated by immunological work-up; WFDC2-deficient individuals are not described as broadly immunodeficient.
Woakes' syndrome
Overlapping Features Listed as a differential with a caveat: it may not be a different disease. Woakes' syndrome was defined in 1979 as a pentad of recurrent childhood nasal polyposis, broadening of the nose, frontal sinus aplasia, bronchiectasis and dyscrinia. Four of those five are features of WFDC2 deficiency, including the nasal broadening and the childhood-onset polyposis that are its most distinctive signs, and the pentad was explicitly defined for early-childhood polyposis cases that fitted neither cystic fibrosis nor Kartagener syndrome - the same diagnostic gap WFDC2 deficiency was found in. The open question is whether Woakes' syndrome is this disease described before its gene was known, or a phenocopy. No reported Woakes' case has been genotyped for WFDC2, so it cannot be settled from the literature as it stands, and this entry does not assert either reading. Recorded here so the overlap is visible to anyone curating either concept, and because a Woakes' diagnosis in a living patient is a direct indication for WFDC2 sequencing.
Show evidence (2 references)
PMID:553887 SUPPORT INDIRECT Human Clinical
"This newly defined Woakes' syndrome comprises recurrent nasal polyposis with broadening of the nose, frontal sinus aplasia, bronchiectasis, and dyscrinia (production of highly viscous mucus)."
The defining description, four of whose five features this disease shares. Graded INDIRECT because the overlap is phenotypic; no Woakes' case has been tested for WFDC2 variants, so this does not establish identity.
PMID:553887 SUPPORT INDIRECT Human Clinical
"Four cases of early childhood polyposis are reported which fit into none of these etiological groups."
The syndrome was carved out of exactly the unexplained-childhood-polyposis space that WFDC2 deficiency was later found in, which is what makes the relationship worth resolving rather than assuming.
🐁

Animal Models

1
Wfdc2-null mouse (Nakajima et al.)
Wfdc2 is expressed by basal cells, club cells and type II alveolar epithelial cells (AECIIs) in the neonatal murine lung. Wfdc2-null mice develop progressive atelectasis after birth and die of respiratory failure, with impaired cilia, absent mature club cells in the tracheo-bronchial airways, and malformed AECII lamellar bodies.
Species
Mouse
Genotype
Wfdc2-null mutant, homozygous
Background
ICR
Publication
PMID:31562139
Pathograph links
Preserved Mucociliary Clearance fails to recapitulate fidelity: low observes: cellular The mouse does not reproduce the human finding that ciliary structure and mucociliary clearance are preserved despite WFDC2 loss. Wfdc2-null mouse airways instead show impaired cilia and failed secretory-cell differentiation, and the mutant is neonatally lethal - a phenotype absent entirely from the human disease, where clearance measurements are normal and affected individuals survive the neonatal period with a chronic, non-lethal airway disease.
Limitations: The human comparison rests on the airway measurements reported for WFDC2-deficient individuals (PMID:38626355) - ciliary length, beat frequency and coordination, and mucus viscosity - none of which covers the alveolar compartment. Neonatal lethality forecloses any comparison with the adult human disease course, so the mouse cannot address what happens to airway function past the newborn period. Human and mouse WFDC2 also differ in primary sequence - the murine protein carries an extra 52-residue linker between its two WAP domains - which is a candidate structural explanation for why loss of the mouse protein produces a ciliary and secretory-cell phenotype the human disease does not share. A second, independently generated Wfdc2-null mouse line (TALEN-mediated deletion, PMID:31780266) is also neonatally lethal, but through a distinct proximate lesion - type-I alveolar epithelial cell apoptosis and lung hypovascularity rather than a ciliary defect - which argues the murine lethality is a robust feature of Wfdc2 loss in mouse generally rather than an artifact of one targeting strategy, and correspondingly that the human/mouse divergence is not confined to cilia.
Readouts
Ciliary and secretory-cell differentiation in Wfdc2-null mouse airways
Direction: ALTERED
Interpretation: Impaired cilia and absent mature club cells, the opposite of the normal ciliary structure and directed mucociliary transport reported in WFDC2-deficient human airway cultures.
Show evidence (1 reference)
PMID:31562139 SUPPORT DIRECT Model Organism
"Mutant lungs have multiple defects, including impaired cilia and the absence of mature club cells from the tracheo-bronchial airways, and malformed lamellar bodies in AECIIs."
Documents the ciliary and secretory-cell defects in the mouse that are absent in the human disease.
Show evidence (1 reference)
PMID:31562139 SUPPORT DIRECT Model Organism
"Mutant lungs have multiple defects, including impaired cilia and the absence of mature club cells from the tracheo-bronchial airways, and malformed lamellar bodies in AECIIs."
Supports treating this model as informative for whether ciliary structure and clearance are preserved after WFDC2 loss: the mouse shows the opposite of the human "preserved" finding.
Show evidence (1 reference)
PMID:31562139 SUPPORT DIRECT Model Organism
"Wfdc2-null-mutant mice display progressive atelectasis after birth with a lethal phenotype."
Establishes the neonatally lethal respiratory phenotype of this Wfdc2-null mouse line.
{ }

Source YAML

click to show 
name: Bronchiectasis and Nasal Polyposis
category: Mendelian
creation_date: "2026-09-01T17:10:00Z"
description: >-
  Autosomal recessive chronic destructive airway disease caused by biallelic
  loss-of-function variants in WFDC2, which encodes the secreted WAP
  four-disulfide core domain protein 2 (also called HE4). Affected individuals
  have bronchiectasis, severe chronic rhinosinusitis with nasal polyposis, and
  chronic airway infection, frequently with Pseudomonas aeruginosa. The
  presentation closely mimics cystic fibrosis and primary ciliary dyskinesia, and
  was first defined as a distinct Mendelian entity in 2024.

  What makes the entry mechanistically interesting is a negative result. WFDC2 is
  made by airway secretory cells and is absent from the airway surface liquid,
  saliva and serum of affected individuals, so the obvious hypothesis is failed
  mucociliary clearance. That hypothesis was tested and did not hold: ciliary beat
  frequency, ciliary length, epithelial composition and mucus viscosity are all
  normal, and patient cultures generate directed mucociliary transport. The step
  connecting loss of a secreted airway protein to airway destruction is therefore
  not yet established, and this entry models that gap explicitly rather than
  asserting a clearance defect the source data refute.
disease_term:
  preferred_term: bronchiectasis and nasal polyposis
  term:
    id: MONDO:0975835
    label: bronchiectasis and nasal polyposis
synonyms:
- WFDC2 deficiency
- HE4 deficiency

notes: >-
  Scope. This entry is the monogenic WFDC2-deficiency disease, not bronchiectasis
  as a radiological sign. Bronchiectasis is the common endpoint of many
  conditions, several of which the KB already covers separately (cystic fibrosis,
  primary ciliary dyskinesia, alpha-1 antitrypsin deficiency); what is curated
  here is the specific causal chain from biallelic WFDC2 loss.

  Ontology note. The glycosylation defect underlying the p.Cys49Arg founder
  variant is described in prose rather than bound to a GO term: GO:0006486
  (protein glycosylation), the obvious candidate, is obsolete, and the remaining
  glycosylation classes are either regulatory or linkage-specific and would
  overstate what the source shows. The secretion failure, which is the
  load-bearing claim, is bound to GO:0009306.

  Deep-research divergence. The committed OpenScientist report reproduces this
  entry's chain for the first five steps independently, but its lower-airway
  branch asserts impaired mucociliary clearance as a step toward bronchiectasis.
  That is imported from the generic bronchiectasis literature and is contradicted
  by the primary source for this disease, which measured clearance in patient
  cultures and found it within the normal range. The report labels those
  downstream steps inferred, which is the honest flag, but the inference is wrong
  here specifically. This entry follows the measurement, not the report.

mappings:
  mondo_mappings:
  - mapping_predicate: skos:exactMatch
    term:
      id: MONDO:0975835
      label: bronchiectasis and nasal polyposis

inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic pathogenic WFDC2 variants, identified across 10 unrelated families
    from four continents in the founding cohort. Reported patients are homozygous
    or compound heterozygous, with founder alleles in East Asian populations.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "We identified biallelic pathogenic variants in WAP four-disulfide core domain 2 (WFDC2) in 11 individuals from 10 unrelated families originating from the United States, Europe, Asia, and Africa."
    explanation: Establishes recessive inheritance across an internationally distributed founding cohort.

pathophysiology:
- name: Biallelic Loss of Function in WFDC2
  biological_scale: MOLECULAR
  description: >-
    The initiating lesion. WFDC2 encodes a small secreted whey-acidic-protein
    family member expressed by airway secretory cells. Reported disease alleles
    include nonsense, frameshift and missense changes; the recurrent p.Cys49Arg
    founder variant acts by disrupting a disulfide-forming cysteine rather than by
    truncating the protein.
  genes:
  - preferred_term: WFDC2
    term:
      id: hgnc:15939
      label: WFDC2
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "WFDC2 dysfunction defines a novel molecular etiology of bronchiectasis characterized by the deficiency of a secreted component of the airways."
    explanation: "States the causal claim: WFDC2 loss is a distinct molecular cause of bronchiectasis."
  - reference: PMID:40114242
    reference_title: "Two novel genetic variants in the WFDC2 gene from patients with bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Therefore, we aimed to identify two novel variants of the WFDC2 gene, known as antiprotease, from patients with bronchiectasis and/or related phenotypes using trio-based whole-genome sequencing analysis."
    explanation: Independent replication of WFDC2 variants in bronchiectasis patients, and names the protein's antiprotease identity.
  downstream:
  - target: Failure of WFDC2 Secretion
    causal_link_type: DIRECT

- name: Failure of WFDC2 Secretion
  biological_scale: MOLECULAR
  description: >-
    The proximate consequence. For the p.Cys49Arg founder allele the mechanism is
    specific and was modelled directly: the substitution structurally hampers
    glycosylation, and the immature protein is not secreted. The result for the
    airway is the same whichever allele is involved - no mature WFDC2 reaches the
    extracellular space.
  biological_processes:
  - preferred_term: protein secretion
    term:
      id: GO:0009306
      label: protein secretion
    modifier: DECREASED
  cell_types:
  - preferred_term: Airway secretory cell
    term:
      id: CL:4052031
      label: respiratory airway secretory cell
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    snippet: "Computer simulations and deglycosylation assays indicate that the disease-causing founder variant p.Cys49Arg structurally hampers glycosylation and, thus, secretion of mature WFDC2."
    explanation: Identifies impaired glycosylation as the mechanism blocking secretion of the founder-variant protein.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Expression of WFDC2 was detected predominantly in secretory cells of control airway epithelium and also in submucosal glands."
    explanation: Localizes WFDC2 production to airway secretory cells and submucosal glands, the source of the missing secreted protein.
  downstream:
  - target: Depletion of WFDC2 from Airway Surface Liquid and Secretions
    causal_link_type: DIRECT

- name: Depletion of WFDC2 from Airway Surface Liquid and Secretions
  biological_scale: TISSUE
  description: >-
    The measurable deficiency state. WFDC2 is below the limit of detection in
    serum and barely detectable in saliva, seminal fluid and airway surface liquid
    from affected individuals. The contrast with the disease controls is
    informative: patients with CF and PCD have detectable, indeed elevated, WFDC2,
    so this is not a nonspecific consequence of chronic airway disease. It is also
    what makes a commercially available serum assay usable diagnostically.
  cellular_components:
  - preferred_term: extracellular region
    term:
      id: GO:0005576
      label: extracellular region
    modifier: DECREASED
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "We demonstrate that WFDC2 is below the limit of detection in blood serum and hardly detectable in samples of saliva, seminal fluid, and airway surface liquid from WFDC2-deficient individuals."
    explanation: Directly measures the deficiency across the relevant compartments, including airway surface liquid.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "This represents the first description of WFDC2 deficiency as a cause of chronic destructive airway disease, in contrast to PCD and CF, which show elevated expression of WFDC2."
    explanation: The opposite direction in CF and PCD shows the depletion is specific to this disorder rather than secondary to airway disease generally.
  downstream:
  - target: Altered Airway Antiprotease Milieu
    causal_link_type: DIRECT
  - target: Chronic Airway Infection and Rhinosinusitis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES

- name: Altered Airway Antiprotease Milieu
  biological_scale: TISSUE
  description: >-
    A candidate, partially supported consequence. WFDC family members are protease
    inhibitors, and comparative proteomics of saliva found the serine protease
    inhibitor SPINK5 significantly reduced in WFDC2-deficient individuals relative
    to both healthy controls and airway-disease controls. SLPI, the other WFDC
    protein highly expressed in airway epithelium, was not significantly altered.

    The claim carried here is deliberately narrow. The SPINK5 finding is real and
    controlled against disease as well as healthy comparators, but it is measured
    in saliva rather than in the airway, in three patients, and it establishes an
    association rather than a route to tissue destruction. It is modelled as a
    node because the protease-antiprotease balance is the mechanism the protein
    family's known biology predicts, not because the pathway to bronchiectasis has
    been demonstrated.
  molecular_functions:
  - preferred_term: serine-type endopeptidase inhibitor activity
    term:
      id: GO:0004867
      label: serine-type endopeptidase inhibitor activity
    modifier: DECREASED
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "We also analyzed SPINK5 by WB and observed reduced expression of a proteolytically cleaved species (28) in individuals with WFDC2 mutations compared with healthy control and respiratory disease control groups"
    explanation: Reduced SPINK5 in patients relative to both healthy and airway-disease controls, which is what makes it specific rather than a chronic-disease effect.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "Other members of the WFDC protein family, such as SLPI (WFDC4) (20) and Elafin (WFDC14) (21), exhibit protease inhibitor activity and play an important role in the innate immune system."
    explanation: Family-level protease-inhibitor biology motivating an antiprotease role for WFDC2; inference from paralogues, not a measurement of WFDC2 itself.
  downstream:
  - target: Chronic Airway Infection and Rhinosinusitis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES

- name: Chronic Airway Infection and Rhinosinusitis
  biological_scale: ORGANISM
  description: >-
    Chronic infection of the upper and lower airways, with Pseudomonas aeruginosa
    prominent, together with pronounced chronic rhinosinusitis. This is the step at
    which the disorder becomes clinically indistinguishable from cystic fibrosis
    and inborn errors of immunity, and it is a persistent state rather than
    recurrent discrete episodes.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Here we identify disease-causing variants in WFDC2 that underlie a unique and severe respiratory disorder characterized by bronchiectasis in all lung fields, chronic rhinosinusitis, and lung infection by Pseudomonas aeruginosa resembling the clinical phenotype of cystic fibrosis, primary ciliary dyskinesia, and inborn errors of immunity."
    explanation: Establishes chronic Pseudomonas infection and rhinosinusitis as core features and names the diseases it mimics.
  downstream:
  - target: Airway Wall Destruction and Nasal Polyp Formation
    causal_link_type: DIRECT

- name: Airway Wall Destruction and Nasal Polyp Formation
  biological_scale: TISSUE
  description: >-
    The structural endpoint: irreversible bronchial dilatation and nasal polyposis.
    The general route from repeated airway insult to bronchiectasis is the vicious
    cycle of infection, inflammation, damage and abnormal remodelling that is
    common to bronchiectasis of any cause; what is specific to this disorder is
    what initiates the cycle. Distribution is a useful discriminator - disease in
    all lobes, mimicking CF and inborn errors of immunity, rather than the middle
    and lower lobe predominance of PCD.
  evidence:
  - reference: PMID:38717359
    reference_title: "Deciphering Idiopathic Bronchiectasis One Gene at a Time."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "Bronchiectasis often results from repeated insults to the airways, leading to a vicious cycle of damage and repair and ultimately abnormal remodeling and loss of airway integrity (1)."
    explanation: The general damage-and-repair route to bronchiectasis; applied to this disorder by inference rather than demonstrated in it.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Bronchiectasis in WFDC2 deficiency more closely mimics CF and IEI (all lobes) than PCD (predominantly middle and lower lobes)."
    explanation: Gives the lobar distribution that distinguishes this disorder radiologically from PCD.

- name: Preserved Mucociliary Clearance
  biological_scale: CELLULAR
  description: >-
    Recorded as an explicitly excluded step rather than omitted. Because WFDC2 is a
    secreted airway protein, impaired mucociliary clearance is the natural
    hypothesis, and it is the mechanism by which both diseases this disorder mimics
    - cystic fibrosis and primary ciliary dyskinesia - cause bronchiectasis. It was
    tested and did not hold. In patient-derived cultures at air-liquid interface,
    ciliary beat frequency was normal, ciliary length was unchanged, epithelial
    morphology and cilia and centrosome composition were comparable to controls,
    mucus viscosity was no different, and the cultures generated directed
    mucociliary transport. Transport speed was low relative to controls, but the
    authors' own conclusion is that clearance is within the normal range.

    This node carries no downstream edge on purpose: the point is that the expected
    link to airway destruction is absent. The residual transport-speed observation
    is the loose end, and it is captured as a knowledge gap rather than promoted to
    a mechanism.
  biological_processes:
  - preferred_term: mucociliary clearance
    term:
      id: GO:0120197
      label: mucociliary clearance
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    snippet: "Taken together, our results suggest that WFDC2-deficient respiratory epithelia likely have a level of mucociliary clearance that is within the normal range."
    explanation: The authors' own conclusion, and the basis for naming this node as a preserved function rather than an impaired one.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    snippet: "Cultures from both individuals with WFDC2 mutations were capable of generating MCT in a directed fashion, with cells from UNC 186 II2 generating complete circular transport when cultured in an MCT device (27) (Video E15)."
    explanation: Patient cultures generate directed transport, which is the functional demonstration that clearance is preserved.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: REFUTE
    evidence_source: IN_VITRO
    directness: DIRECT
    snippet: "Interestingly, the speed of MCT was low relative to the control cultures (Figures E7C and E7D), but the epithelial morphology and composition of cilia and centrosomes were comparable between healthy control subjects and OP-2032 II1 (Figure E8)."
    explanation: >-
      The one measurement cutting against preservation, kept because it is the
      residual the knowledge gap is about. Graded REFUTE against this node's claim
      rather than SUPPORT: it is the only result inconsistent with wholly normal
      transport, even though the authors judged the overall level to be within the
      normal range.

animal_models:
- name: Wfdc2-null mouse (Nakajima et al.)
  species: Mouse
  genotype: Wfdc2-null mutant, homozygous
  background: ICR
  publication: PMID:31562139
  description: >-
    Wfdc2 is expressed by basal cells, club cells and type II alveolar
    epithelial cells (AECIIs) in the neonatal murine lung. Wfdc2-null mice
    develop progressive atelectasis after birth and die of respiratory
    failure, with impaired cilia, absent mature club cells in the
    tracheo-bronchial airways, and malformed AECII lamellar bodies.
  modeled_mechanisms:
  - target: Preserved Mucociliary Clearance
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: CELLULAR
    description: >-
      The mouse does not reproduce the human finding that ciliary structure
      and mucociliary clearance are preserved despite WFDC2 loss. Wfdc2-null
      mouse airways instead show impaired cilia and failed secretory-cell
      differentiation, and the mutant is neonatally lethal - a phenotype
      absent entirely from the human disease, where clearance measurements
      are normal and affected individuals survive the neonatal period with a
      chronic, non-lethal airway disease.
    limitations: >-
      The human comparison rests on the airway measurements reported for
      WFDC2-deficient individuals (PMID:38626355) - ciliary length, beat
      frequency and coordination, and mucus viscosity - none of which covers
      the alveolar compartment. Neonatal lethality forecloses any comparison with the adult human
      disease course, so the mouse cannot address what happens to airway
      function past the newborn period. Human and mouse WFDC2 also differ in
      primary sequence - the murine protein carries an extra 52-residue
      linker between its two WAP domains - which is a candidate structural
      explanation for why loss of the mouse protein produces a ciliary and
      secretory-cell phenotype the human disease does not share. A second,
      independently generated Wfdc2-null mouse line (TALEN-mediated deletion,
      PMID:31780266) is also neonatally lethal, but through a distinct
      proximate lesion - type-I alveolar epithelial cell apoptosis and lung
      hypovascularity rather than a ciliary defect - which argues the murine
      lethality is a robust feature of Wfdc2 loss in mouse generally rather
      than an artifact of one targeting strategy, and correspondingly that
      the human/mouse divergence is not confined to cilia.
    evidence:
    - reference: PMID:31562139
      reference_title: "Lack of whey acidic protein (WAP) four-disulfide core domain protease inhibitor 2 (WFDC2) causes neonatal death from respiratory failure in mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      snippet: "Mutant lungs have multiple defects, including impaired cilia and the absence of mature club cells from the tracheo-bronchial airways, and malformed lamellar bodies in AECIIs."
      explanation: >-
        Supports treating this model as informative for whether ciliary
        structure and clearance are preserved after WFDC2 loss: the mouse
        shows the opposite of the human "preserved" finding.
    readouts:
    - name: Ciliary and secretory-cell differentiation in Wfdc2-null mouse airways
      target: Preserved Mucociliary Clearance
      direction: ALTERED
      interpretation: >-
        Impaired cilia and absent mature club cells, the opposite of the
        normal ciliary structure and directed mucociliary transport reported
        in WFDC2-deficient human airway cultures.
      evidence:
      - reference: PMID:31562139
        reference_title: "Lack of whey acidic protein (WAP) four-disulfide core domain protease inhibitor 2 (WFDC2) causes neonatal death from respiratory failure in mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        directness: DIRECT
        snippet: "Mutant lungs have multiple defects, including impaired cilia and the absence of mature club cells from the tracheo-bronchial airways, and malformed lamellar bodies in AECIIs."
        explanation: Documents the ciliary and secretory-cell defects in the mouse that are absent in the human disease.
  evidence:
  - reference: PMID:31562139
    reference_title: "Lack of whey acidic protein (WAP) four-disulfide core domain protease inhibitor 2 (WFDC2) causes neonatal death from respiratory failure in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    snippet: "Wfdc2-null-mutant mice display progressive atelectasis after birth with a lethal phenotype."
    explanation: Establishes the neonatally lethal respiratory phenotype of this Wfdc2-null mouse line.

phenotypes:
- category: Respiratory
  name: Bronchiectasis
  description: >-
    Irreversible bronchial dilatation, in 9 of 11 individuals in the founding
    cohort. Not obligate despite naming the disease: one child presented with
    nasal polyposis and no bronchiectasis at age 7, so its absence does not
    exclude the diagnosis and may reflect age at assessment. Distribution mimics
    cystic fibrosis rather than PCD, though reports differ on whether it is
    pan-lobar or upper-lobe predominant, which is unsurprising given the small
    numbers.
  phenotype_term:
    preferred_term: Bronchiectasis
    term:
      id: HP:0002110
      label: Bronchiectasis
    clinical_course: PROGRESSIVE
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Despite low nasal nitric oxide levels, the radiologic features resembled those of cystic fibrosis, characterized by bronchiectasis predominantly in the upper lobes."
    explanation: Independent case series describing CF-like radiology with upper-lobe predominance.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "All individuals with biallelic WFDC2 variants presented with marked chronic respiratory symptoms affecting the upper and lower airways, and 9 of 11 individuals showed bronchiectasis by CT imaging (Figures 2A-2D and Table 1)."
    explanation: Gives the cohort frequency, 9 of 11, which is why this is VERY_FREQUENT rather than obligate.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "This search was broadened to newly available exomes and identified WFDC2 variants in OP-4474 II1, who presented with nasal polyposis but not bronchiectasis at 7 years of age."
    explanation: A molecularly confirmed patient without bronchiectasis, which directly refutes treating it as obligate.
- category: Otolaryngologic
  name: Nasal Polyposis
  phenotype_term:
    preferred_term: Nasal polyposis
    term:
      id: HP:0100582
      label: Nasal polyposis
  frequency: OBLIGATE
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Here, we describe a novel Mendelian disorder of chronic destructive airway disease characterized by bronchiectasis, chronic infection of the airways, pronounced CRS, and nasal polyposis due to autosomal recessive inheritance of pathogenic WFDC2 variants."
    explanation: Names nasal polyposis as a defining feature of the disorder.
- category: Otolaryngologic
  name: Chronic Rhinosinusitis
  description: >-
    Severe and typically present from childhood, often long before the
    bronchiectasis is recognised.
  phenotype_term:
    preferred_term: Chronic sinusitis
    term:
      id: HP:0011109
      label: Chronic sinusitis
    temporality: CHRONIC
  frequency: OBLIGATE
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "The ages at diagnosis of bronchiectasis were 18, 24, and 16 years, and all patients had a history of chronic sinusitis since childhood."
    explanation: Establishes childhood-onset chronic sinusitis preceding the bronchiectasis diagnosis by years.
- category: Respiratory
  name: Chronic Pseudomonas aeruginosa Airway Infection
  phenotype_term:
    preferred_term: Chronic Pseudomonas aeruginosa airway infection
    term:
      id: HP:5210057
      label: Recurrent Pseudomonas aeruginosa infection
    temporality: CHRONIC
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Furthermore, nine individuals with WFDC2 mutations suffered from chronic P. aeruginosa infection, which is known to be a risk factor associated with bronchiectasis (14)."
    explanation: >-
      The cohort frequency, nine of eleven. Replaces the paper's Objectives
      sentence, which describes who was recruited rather than what was found and
      so could not establish a frequency.

- category: Otolaryngologic
  name: Nasal Pyramid Broadening
  description: >-
    Progressive external broadening of the nasal pyramid, present in all eleven
    individuals of the founding cohort. The most distinctive external feature of
    the disease, and the one that makes it recognisable on inspection rather than
    on imaging.
  phenotype_term:
    preferred_term: Broadening of the nasal pyramid
    term:
      id: HP:0000445
      label: Wide nose
    clinical_course: PROGRESSIVE
  frequency: OBLIGATE
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "In addition, all 11 individuals showed severe upper airway disease manifesting as CRS with pronounced nasal polyposis and progressive broadening of the nasal pyramid (Figure 2E and Table 1)."
    explanation: All eleven cohort individuals, alongside the polyposis and rhinosinusitis in the same sentence.
- category: Otolaryngologic
  name: Otitis Media
  description: >-
    Seven of the eleven founding-cohort individuals, and 64.3% across the pooled
    published series - the same band from two independent denominators.
  phenotype_term:
    preferred_term: Otitis media
    term:
      id: HP:0000388
      label: Otitis media
  frequency: FREQUENT
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Individuals UNC-376 II1, OP-2147 II1, OP-2032 II1, OP-398 II1, UNC-186 II1, UNC-186 II2, and OP-4474 II1 reported otitis media."
    explanation: Seven of eleven individuals named individually, which is 64% and so the FREQUENT band.
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "All patients had a history of chronic sinusitis, and 64.3 % also experienced otitis media"
    explanation: >-
      The pooled published series, giving 64.3% from a larger and independent
      denominator. Two denominators landing in the same band is what fixes the
      frequency rather than a single small cohort.
- category: Reproductive
  name: Female Infertility
  description: >-
    Reported in three of the four affected females, with male fertility
    apparently preserved - the authors examined sperm function specifically and
    concluded the effect is female-restricted. Independently replicated in the
    Korean cohort, where an affected woman conceived only through IVF. A
    sex-specific effect supported in two cohorts is worth recording even though
    the mechanism in the reproductive tract is unexplained.
  phenotype_term:
    preferred_term: Female infertility
    term:
      id: HP:0008222
      label: Female infertility
  frequency: FREQUENT
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "These findings suggest that WFDC2 deficiency impacts female rather than male fertility and warrant further investigation."
    explanation: States the sex-restricted fertility effect after the authors specifically tested male sperm function.
  - reference: PMID:40114242
    reference_title: "Two novel genetic variants in the WFDC2 gene from patients with bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Additionally, WFDC2 has been implicated in nasal polyposis and infertility, both of which were observed in some of our patients, suggesting a broader spectrum of clinical manifestations."
    explanation: Independent replication of the infertility association in the Korean cohort.
- category: Respiratory
  name: Neonatal Respiratory Distress
  phenotype_term:
    preferred_term: Neonatal respiratory distress
    term:
      id: HP:0002643
      label: Neonatal respiratory distress
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Individuals OP-2147 II1, UNC-231 II1, and UNC-186 II1 reported neonatal respiratory distress syndrome."
    explanation: Three of eleven individuals, named, indicating onset can be immediately postnatal.
- category: Respiratory
  name: Reduced FEV1
  description: >-
    Obstructive lung function impairment in every individual in whom spirometry
    was performed.
  phenotype_term:
    preferred_term: Reduced forced expiratory volume in one second
    term:
      id: HP:0032342
      label: Reduced forced expiratory volume in one second
  frequency: OBLIGATE
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "FEV1% predicted was reduced in all affected individuals examined (Table 1)."
    explanation: Reduced in all individuals tested.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Spirometry data were available in 9 of 11 individuals, and all demonstrated altered lung function parameters consistent with a chronic obstructive airway disease, resembling findings in CF and PCD."
    explanation: Gives the denominator, nine of eleven tested, and the obstructive pattern.
- category: Diagnostic
  name: Very Low Nasal Nitric Oxide
  description: >-
    Shared by all nine individuals measured. This is the finding that makes the
    disease look like primary ciliary dyskinesia on screening, and is therefore
    the mechanism of the misdiagnosis recorded under diagnosis rather than an
    incidental laboratory result.
  phenotype_term:
    preferred_term: Decreased nasal nitric oxide
    term:
      id: HP:0033036
      label: Decreased nasal nitric oxide
  frequency: OBLIGATE
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Interestingly, very low nasal nitric oxide production rate was a shared finding in individuals with WFDC2 mutations (9/9), which is associated with CRS (15) but also characteristic for PCD (16, 17) and a potential finding in CF (18)."
    explanation: All nine measured, and the source itself names the overlap with PCD and CF that causes the diagnostic confusion.

genetic:
- name: WFDC2
  gene_term:
    preferred_term: WFDC2
    term:
      id: hgnc:15939
      label: WFDC2
  relationship_type: CAUSATIVE
  notes: >-
    20q13.12; encodes the secreted WAP four-disulfide core domain protein 2 (HE4).
    The recurrent p.Cys49Arg founder variant acts by hampering glycosylation and
    hence secretion. Founder alleles have been proposed in East Asian populations,
    and independent patients have since been reported from Korea and Japan, so the
    gene warrants inclusion in sinopulmonary diagnostic panels rather than being
    treated as a single-cohort finding. A Vietnamese sinopulmonary cohort screened
    all three WFDC2 coding exons and found no variants, which bounds how common the
    disease can be in that population.
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Considering the possibility of founder mutations, WFDC2 variants should be included in diagnostic panels for patients with sinopulmonary disease in Asian populations."
    explanation: Argues for founder alleles and panel inclusion on the basis of three independent Japanese cases.

diagnosis:
- name: Serum or saliva WFDC2 (HE4) measurement
  description: >-
    An unusually direct biochemical test for a Mendelian disorder: the causal gene
    product is a secreted protein already measured by a commercial
    electrochemiluminescence immunoassay, developed as an ovarian cancer
    biomarker. In affected individuals serum WFDC2 is below the limit of
    detection. The comparison that makes it discriminating is that CF and PCD
    patients have elevated, not reduced, WFDC2, so the test separates this
    disorder from its main mimics rather than merely flagging airway disease.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "The diagnosis can be suspected based on measurement of serum or saliva WFDC2/HE4 concentrations and confirmed by genetic testing."
    explanation: States the two-step diagnostic strategy of biochemical suspicion plus genetic confirmation.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Using a commercial electrochemiluminescence immunoassay, we measured serum concentrations of WFDC2 in individuals with biallelic WFDC2 variants and compared this to serum concentrations of WFDC2 in individuals with PCD and CF (Figure 4K)."
    explanation: Establishes that an already-commercial assay was used and benchmarked against the two main mimics.
- name: Low nasal nitric oxide as a misleading result
  description: >-
    A diagnostic trap worth stating plainly. Nasal nitric oxide is low in these
    patients, and low nasal NO is the standard screening test for primary ciliary
    dyskinesia. Patients are therefore liable to be labelled probable PCD -
    explicitly what happened in the Japanese series, in a setting where CF is rare
    - and the label can stand for years because the airway phenotype is compatible
    with it. The founding cohort recommends considering WFDC2 deficiency precisely
    when nasal NO is very low.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "We recommend including WFDC2 deficiency in the differential diagnosis with CRS, CF, and PCD when nasal nitric oxide measurements are very low."
    explanation: The authors' explicit recommendation to consider this disorder when the PCD screening test is positive.
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "these cases often present low levels of nasal nitric oxide (nNO) and are preliminarily diagnosed as probable PCD in Japanese settings where CF is rare"
    explanation: Documents the misdiagnosis actually occurring, which is what makes this a practical trap rather than a theoretical one.
- name: Genetic confirmation
  description: >-
    Biallelic WFDC2 variants on next-generation or targeted Sanger sequencing.
    WFDC2 is not on all sinopulmonary panels, so a negative CF and PCD panel does
    not exclude it.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Methods: DNA was analyzed by next-generation or targeted Sanger sequencing."
    explanation: The sequencing approach used to establish the diagnosis in the founding cohort.

differential_diagnoses:
- name: Cystic fibrosis
  description: >-
    The closest mimic radiologically and clinically - chronic Pseudomonas
    infection, sinus disease, bronchiectasis in all lobes. Separated by CFTR
    genetics, sweat testing, and, distinctively, by WFDC2 level, which is elevated
    in CF and undetectable here.
- name: Primary ciliary dyskinesia
  description: >-
    Shares low nasal nitric oxide, chronic rhinosinusitis and bronchiectasis, and
    is the label these patients most often receive first. Separated by normal
    ciliary beat pattern and frequency on high-speed video microscopy, by lobar
    distribution, and by WFDC2 level.
- name: Inborn errors of immunity
  description: >-
    Also produce pan-lobar bronchiectasis with chronic infection. Separated by
    immunological work-up; WFDC2-deficient individuals are not described as
    broadly immunodeficient.
- name: Woakes' syndrome
  description: >-
    Listed as a differential with a caveat: it may not be a different disease.
    Woakes' syndrome was defined in 1979 as a pentad of recurrent childhood nasal
    polyposis, broadening of the nose, frontal sinus aplasia, bronchiectasis and
    dyscrinia. Four of those five are features of WFDC2 deficiency, including the
    nasal broadening and the childhood-onset polyposis that are its most
    distinctive signs, and the pentad was explicitly defined for early-childhood
    polyposis cases that fitted neither cystic fibrosis nor Kartagener syndrome -
    the same diagnostic gap WFDC2 deficiency was found in.

    The open question is whether Woakes' syndrome is this disease described before
    its gene was known, or a phenocopy. No reported Woakes' case has been
    genotyped for WFDC2, so it cannot be settled from the literature as it stands,
    and this entry does not assert either reading. Recorded here so the overlap is
    visible to anyone curating either concept, and because a Woakes' diagnosis in
    a living patient is a direct indication for WFDC2 sequencing.
  evidence:
  - reference: PMID:553887
    reference_title: "Woakes' syndrome: the problems of infantile nasal polyps."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "This newly defined Woakes' syndrome comprises recurrent nasal polyposis with broadening of the nose, frontal sinus aplasia, bronchiectasis, and dyscrinia (production of highly viscous mucus)."
    explanation: >-
      The defining description, four of whose five features this disease shares.
      Graded INDIRECT because the overlap is phenotypic; no Woakes' case has been
      tested for WFDC2 variants, so this does not establish identity.
  - reference: PMID:553887
    reference_title: "Woakes' syndrome: the problems of infantile nasal polyps."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "Four cases of early childhood polyposis are reported which fit into none of these etiological groups."
    explanation: >-
      The syndrome was carved out of exactly the unexplained-childhood-polyposis
      space that WFDC2 deficiency was later found in, which is what makes the
      relationship worth resolving rather than assuming.

treatments:
- name: Airway Clearance and Long-Term Macrolide Therapy
  description: >-
    Standard bronchiectasis management. Worth recording that it is inadequate
    here - all three Japanese patients had frequent exacerbations and respiratory
    dysfunction despite long-term macrolides.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "All patients experienced frequent exacerbations and respiratory dysfunction, even with long-term macrolide therapy."
    explanation: Refutes adequacy of standard macrolide therapy for controlling this disorder.
- name: Lung Transplantation
  description: >-
    The endpoint for advanced disease; two of the three reported Japanese patients
    required it, in their twenties or earlier.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: organ transplantation
    term:
      id: NCIT:C15289
      label: Organ Transplantation
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Consequently, two of the three patients required lung transplantation."
    explanation: Documents transplantation as the outcome in two of three reported patients.
- name: WFDC2 Protein Replacement
  description: >-
    Proposed but not tested. The rationale is unusually clean for a Mendelian
    disorder - the missing gene product is small and acts extracellularly, so it
    need not be delivered into cells - which is why it is recorded here despite
    being hypothetical. No preclinical or clinical data exist.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: Depletion of WFDC2 from Airway Surface Liquid and Secretions
    description: >-
      Would act by restoring the missing secreted protein to the extracellular
      compartment it is absent from. Entirely prospective.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "Because of the relatively small size of WFDC2 and its function in extracellular spaces, replacement therapy may be a potential option."
    explanation: The authors' stated rationale for replacement therapy; a proposal rather than a result.

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >-
    No prevalence estimate exists. The disease was defined in 2024 from 11
    individuals in 10 families, with small numbers added since from Korea and
    Japan. Because the presentation is indistinguishable from CF and PCD and
    WFDC2 is absent from many diagnostic panels, the reported count is a floor
    rather than an estimate - but not an unlimited one: a targeted screen of 31
    Vietnamese patients with extensive bronchiectasis found no WFDC2 variants at
    all, so the hidden fraction is not large in every population.

progression:
- phase: Childhood chronic rhinosinusitis
  notes: >-
    Upper airway disease is present from childhood and precedes recognition of the
    bronchiectasis, in the reported series by roughly a decade.
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "The ages at diagnosis of bronchiectasis were 18, 24, and 16 years, and all patients had a history of chronic sinusitis since childhood."
    explanation: Gives both the childhood onset of sinus disease and the age at which bronchiectasis was diagnosed.
- phase: Progressive bronchiectasis to respiratory failure
  notes: >-
    Progressive despite standard therapy, reaching transplantation in two of three
    patients in the one series reporting outcomes.
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "Consequently, two of the three patients required lung transplantation."
    explanation: Documents progression to end-stage lung disease.

clinical_burden:
  burden_level: HIGH
  rationale: >-
    Lifelong progressive suppurative airway disease with chronic Pseudomonas
    infection, poorly controlled by the standard therapy, reaching lung
    transplantation in two of three patients in the only series reporting
    outcomes, at ages in the teens and twenties. Compounded by severe chronic
    rhinosinusitis from childhood and by diagnostic delay, since the disorder is
    routinely mislabelled as probable PCD.
  evidence:
  - reference: PMID:40401042
    reference_title: "Severe bronchiectasis and chronic rhinosinusitis due to homozygous WFDC2 Variants: The first three cases reported from Japan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "All patients experienced frequent exacerbations and respiratory dysfunction, even with long-term macrolide therapy."
    explanation: Supports a high burden assessment through refractoriness to standard treatment.

discussions:
- discussion_id: wfdc2_mouse_ciliary_alveolar_mismatch
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Preserved Mucociliary Clearance
  - animal_models#Wfdc2-null mouse (Nakajima et al.)
  prompt: >-
    Does the murine Wfdc2-null ciliary and alveolar phenotype reflect a
    mechanism the human ciliary and clearance measurements missed, or a
    genuine species divergence in how loss of WFDC2 is tolerated?
  rationale: >-
    Two independently generated Wfdc2-null mouse lines both die of neonatal
    respiratory failure, but by different routes: impaired cilia, absent
    mature club cells and malformed AECII lamellar bodies in one line
    (PMID:31562139), and type-I alveolar epithelial cell apoptosis with lung
    hypovascularity in the other (PMID:31780266). The ciliary defect is not
    present in WFDC2-deficient humans, whose ciliary length, ciliary beat
    frequency and coordination, cilia and centrosome composition, mucus
    viscosity and directed mucociliary transport match controls, and who
    survive the neonatal period with a chronic but non-lethal airway
    disease. The alveolar lesions - type-I cell apoptosis, hypovascularity,
    AECII lamellar body malformation - have not been assessed in humans at
    all, so their absence is not established. Cellular morphology and fate
    in patient airway cultures were inspected and no obvious change was seen,
    but club-cell maturation markers were not specifically assayed.

    Two readings are both consistent with the data. Under a mechanism-missed
    reading, the mouse's ciliary and alveolar defects point to a WFDC2
    function the human measurements have not yet probed - the human ALI
    cultures examined ciliary beat and structure but not the AECII lamellar
    body or club-cell differentiation axis the mouse implicates beyond an
    informal inspection of cell morphology and fate. Under a
    species-divergence reading, the extra 52-residue linker in murine WFDC2
    relative to human WFDC2 means the mouse ortholog simply does something
    different, and its loss produces a developmental lung phenotype with no
    human counterpart - consistent with humans having no equivalent
    neonatal-lethal presentation despite biallelic loss-of-function alleles.
    The question matters because the mouse is otherwise the obvious system
    for testing candidate mechanisms (protein replacement, the antiprotease
    hypothesis), and neonatal lethality forecloses that use if the mismatch
    is genuine species divergence rather than a missed human measurement.
  evidence:
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: OTHER
    directness: INDIRECT
    snippet: "The phenotypic variation between human WFDC2 deficiency described here and mouse WFDC2 deficiency may reflect in part the sequence difference between human and mouse WFDC2, of which the latter contains a unique 52-amino acid linker region between WAP domains"
    explanation: >-
      The founding human-cohort paper's own hypothesis for the mismatch,
      framing the species-sequence-difference reading recorded in this
      discussion. It is an inference from a sequence comparison rather than
      a clinical observation, hence OTHER and INDIRECT.
  - reference: PMID:38626355
    reference_title: "Recessively Inherited Deficiency of Secreted WFDC2 (HE4) Causes Nasal Polyposis and Bronchiectasis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    snippet: "Although cytoplasmic accumulation of WFDC2 was noted in UNC-186 II2, obvious changes in cellular morphology or fate (also in OP-2032 II1) were not apparent."
    explanation: >-
      Records that cell morphology and fate in patient airway epithelia were
      inspected and showed no obvious change. This is an informal inspection,
      not a club-cell maturation assay, so it leaves the club-cell axis the
      mouse implicates open.
  - reference: PMID:31780266
    reference_title: "WFDC2 gene deletion in mouse led to severe dyspnea and type-I alveolar cell apoptosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    snippet: "mechanistic studies indicated increased apoptosis in type-I alveolar cells in lung tissues, which caused hypovascular lung tissue, then led to severe dyspnea in wfdc2-/- neonates"
    explanation: >-
      Independent confirmation, via a second Wfdc2-null mouse line generated
      by a different targeting method, that murine Wfdc2 loss is neonatally
      lethal - through an alveolar rather than ciliary lesion - reinforcing
      that the mismatch with the human disease is not an artifact of one
      mouse line.
  proposed_experiments:
  - experiment_id: wfdc2_club_cell_maturation_in_human_airway_cultures
    name: Club-cell maturation assay in WFDC2-deficient human bronchial air-liquid-interface cultures
    description: >-
      The human air-liquid-interface cultures were examined for ciliary beat,
      ciliary length and mucus viscosity, and cell morphology and fate were
      inspected informally, but club-cell maturation markers such as SCGB1A1
      were not assayed. Quantifying SCGB1A1-positive club cells in
      patient-derived bronchial cultures against controls tests the airway
      half of the mouse phenotype directly.
    would_refute:
    - pathophysiology#Preserved Mucociliary Clearance
    refuting_outcome:
    - >-
      Reduced or absent SCGB1A1-positive mature club cells in WFDC2-deficient
      cultures, which would show that the mouse secretory-cell defect is
      present in humans but was not measured.
    would_support:
    - pathophysiology#Preserved Mucociliary Clearance
    supporting_outcome:
    - >-
      Normal club-cell maturation in WFDC2-deficient cultures, which would
      support the species-divergence reading for the airway phenotype.
  - experiment_id: wfdc2_alveolar_type_ii_cells_from_patient_ipsc
    name: AECII lamellar body and type-I cell survival assay in patient iPSC-derived alveolar cells
    description: >-
      No alveolar tissue or alveolar cell culture from a WFDC2-deficient
      individual has been examined. Patient iPSC-derived alveolar type II
      cells or alveolospheres would test whether the lamellar body
      malformation and type-I cell loss seen in the two mouse lines occur in
      human cells lacking WFDC2.
    supporting_outcome:
    - >-
      Normal lamellar bodies and type-I cell survival in patient-derived
      alveolar cells, which would support the species-divergence reading for
      the alveolar phenotype.
    refuting_outcome:
    - >-
      Malformed lamellar bodies or type-I cell apoptosis in patient-derived
      alveolar cells, which would identify a human alveolar corollary to the
      lethal mouse phenotype that the airway-focused human studies could not
      detect.

- discussion_id: wfdc2_mechanism_to_bronchiectasis_unexplained
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Depletion of WFDC2 from Airway Surface Liquid and Secretions
  - pathophysiology#Preserved Mucociliary Clearance
  prompt: >-
    By what route does loss of a secreted airway protein cause bronchiectasis when
    mucociliary clearance, mucus viscosity and ciliary function are all normal?
  rationale: >-
    This is the central open question of the disorder, and it is open because the
    obvious answer was tested and failed. Both diseases that WFDC2 deficiency
    clinically mimics cause bronchiectasis through defective clearance - CF
    through mucus properties, PCD through ciliary function - and in WFDC2
    deficiency neither is abnormal. Ciliary beat frequency and length, epithelial
    and centrosome composition, and mucus viscosity all match controls, and
    patient cultures generate directed transport.

    What remains is an association: reduced SPINK5 on saliva proteomics in three
    patients, and the protease-inhibitor identity of the WFDC family. Neither
    establishes a route to airway wall destruction. The one loose measurement is
    that mucociliary transport speed was low relative to controls even though the
    authors judged clearance to be within the normal range; whether that is a
    subtle real defect or assay variation at n=2 is unresolved and is worth
    settling before it is either promoted to a mechanism or dismissed.

    The answer matters for treatment. Protein replacement is proposed on the
    reasoning that the missing product acts extracellularly, but without knowing
    what it does there, neither the target tissue, the therapeutic window, nor a
    pharmacodynamic readout can be specified.
  proposed_experiments:
  - experiment_id: wfdc2_asl_antiprotease_activity
    name: Direct protease-antiprotease measurement in patient airway surface liquid
    description: >-
      Measure neutrophil elastase and other protease activity, and antiprotease
      capacity, in airway surface liquid and sputum from WFDC2-deficient
      individuals against CF, PCD and healthy controls, rather than inferring the
      antiprotease role from saliva proteomics and family homology.
    would_support:
    - pathophysiology#Altered Airway Antiprotease Milieu
    supporting_outcome:
    - >-
      Unopposed protease activity in patient airway surface liquid exceeding that
      of airway-disease controls with comparable infection burden, which would
      separate the antiprotease deficit from the effects of chronic infection.
    would_refute:
    - pathophysiology#Altered Airway Antiprotease Milieu
    refuting_outcome:
    - >-
      Protease-antiprotease balance comparable to CF and PCD controls, indicating
      that the SPINK5 finding does not translate into an airway antiprotease
      deficit and that the mechanism lies elsewhere.
  - experiment_id: wfdc2_bacterial_handling_ali
    name: Bacterial handling in WFDC2-deficient air-liquid interface cultures
    description: >-
      Challenge patient-derived and WFDC2-knockout airway cultures with
      Pseudomonas aeruginosa and quantify adherence, killing and epithelial
      barrier integrity, testing host defense rather than clearance as the
      affected function.
    would_support:
    - pathophysiology#Chronic Airway Infection and Rhinosinusitis
    supporting_outcome:
    - >-
      Impaired bacterial killing or increased adherence and barrier disruption in
      WFDC2-deficient cultures, rescued by recombinant WFDC2, which would supply
      the missing causal step and simultaneously provide the pharmacodynamic
      readout that replacement therapy currently lacks.
    would_refute:
    - pathophysiology#Chronic Airway Infection and Rhinosinusitis
    refuting_outcome:
    - >-
      Bacterial handling indistinguishable from controls, which would push the
      mechanism toward inflammation or repair rather than defense and would make
      the infection a consequence of established bronchiectasis rather than its
      cause.

- discussion_id: wfdc2_ascertainment_and_panel_coverage
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - prevalence#Worldwide
  - genetic#WFDC2
  prompt: >-
    How much WFDC2 deficiency is currently being counted as idiopathic
    bronchiectasis or probable PCD?
  rationale: >-
    Every reported patient was found by sequencing beyond the standard panels,
    and the disorder has a specific reason to be systematically missed rather
    than merely rare: low nasal nitric oxide gives these patients a positive
    result on the PCD screening test, so the workup terminates at a plausible
    wrong answer instead of continuing. Cases accumulated from Korea and Japan
    within two years of the founding report, and founder alleles have been
    proposed, which is not the pattern of a genuinely ultra-rare disease.

    The one targeted screen so far cuts the other way and is the reason this is
    recorded as an open question rather than a conclusion. A Vietnamese
    sinopulmonary study sequenced all three WFDC2 coding exons in 31 patients with
    extensive bronchiectasis and found nothing. That is a real constraint: whatever
    is hiding inside idiopathic bronchiectasis, in that cohort it was not WFDC2.
    Whether the negative reflects genuine rarity, population-specific allele
    frequencies, or a cohort selected on bronchiectasis rather than on the
    polyposis that is the fully penetrant feature, is exactly what is unresolved.

    This is tractable without new discovery work: serum WFDC2 can be measured with
    an existing commercial assay, so an idiopathic-bronchiectasis or probable-PCD
    cohort could be screened biochemically before any sequencing. Until more
    cohorts are screened either way, the prevalence field here is a count of
    reports rather than an estimate.
  evidence:
  - reference: PMID:41094464
    reference_title: "Genetic investigation of sinopulmonary diseases in Vietnam: seeking specific causes from non-specific symptoms."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    snippet: "No abnormal WFDC2 variants were found in 31 patients with extensive BL/BE."
    explanation: >-
      The only targeted screen of an unselected bronchiectasis cohort published so
      far, and it is negative. It counts against the under-ascertainment thesis
      rather than for it, and is recorded here as the constraint the open question
      has to answer to.
  - reference: PMID:41094464
    reference_title: "Genetic investigation of sinopulmonary diseases in Vietnam: seeking specific causes from non-specific symptoms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "However, the spectrum varies across ethnicities, and specifically, while considered rare in Southeast Asia, the current status in this region remains largely unknown."
    explanation: >-
      The same study's framing of why the question is open at all: the genetic
      spectrum of sinopulmonary disease is unmapped across much of the world, so a
      single negative cohort bounds rather than settles it.
📚

References & Deep Research

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Record notes

Scope. This entry is the monogenic WFDC2-deficiency disease, not bronchiectasis as a radiological sign. Bronchiectasis is the common endpoint of many conditions, several of which the KB already covers separately (cystic fibrosis, primary ciliary dyskinesia, alpha-1 antitrypsin deficiency); what is curated here is the specific causal chain from biallelic WFDC2 loss. Ontology note. The glycosylation defect underlying the p.Cys49Arg founder variant is described in prose rather than bound to a GO term: GO:0006486 (protein glycosylation), the obvious candidate, is obsolete, and the remaining glycosylation classes are either regulatory or linkage-specific and would overstate what the source shows. The secretion failure, which is the load-bearing claim, is bound to GO:0009306. Deep-research divergence. The committed OpenScientist report reproduces this entry's chain for the first five steps independently, but its lower-airway branch asserts impaired mucociliary clearance as a step toward bronchiectasis. That is imported from the generic bronchiectasis literature and is contradicted by the primary source for this disease, which measured clearance in patient cultures and found it within the normal range. The report labels those downstream steps inferred, which is the honest flag, but the inference is wrong here specifically. This entry follows the measurement, not the report.

Create: Bronchiectasis and Nasal Polyposis (WFDC2 deficiency) · 2026-09-01T17:14:01Z · View source

Curated the WFDC2-deficiency entry, a Mendelian sinopulmonary disease first defined in 2024, from primary literature plus an OpenScientist deep-research run. Seven pathophysiology nodes run from biallelic WFDC2 loss through failed glycosylation and secretion, depletion of the protein from airway surface liquid, an altered antiprotease milieu, chronic Pseudomonas infection, to bronchiectasis and nasal polyposis. A seventh node records mucociliary clearance as an explicitly excluded step, carrying REFUTE evidence: ciliary beat, ciliary length, epithelial and centrosome composition and mucus viscosity are all normal and patient cultures generate directed transport, so the mechanism by which CF and PCD cause bronchiectasis does not apply here. Two knowledge gaps model what follows from that, one on the unexplained route from secreted-protein loss to airway destruction and one on ascertainment, since low nasal nitric oxide gives these patients a positive PCD screening result and terminates the workup at the wrong answer. Validation: 32/32 snippets verified, all 32 reference titles audited programmatically against cache frontmatter, terms validated, all ten qc gates clean.

OpenScientist ▸
Bronchiectasis and Nasal Polyposis (BENP): A Comprehensive Disease Report
openscientist-autonomous 27 citations 2026-09-01T17:29:23.601199

Bronchiectasis and Nasal Polyposis (BENP): A Comprehensive Disease Report

Summary

Bronchiectasis and Nasal Polyposis (BENP; OMIM:620984, MONDO:0975835, MedGen:1874999, UMLS:C5975469) is a distinct, recently-defined autosomal-recessive Mendelian airway disease caused by biallelic loss-of-function of WFDC2 (WAP four-disulfide core domain 2; also known as HE4, human epididymis protein 4). WFDC2 is a small secreted WAP-domain protease inhibitor produced by airway secretory (club) cells and submucosal glands. When both copies of the gene are non-functional, the protein is not secreted into the airway surface liquid, removing a component of innate airway defense. The clinical consequence is chronic airway infection producing severe rhinosinusitis, pronounced nasal polyposis, and bronchiectasis — while ciliary structure/function and CFTR function remain normal. The disease was molecularly defined by Dougherty et al. in 2024 (PMID: 38626355), who identified biallelic pathogenic WFDC2 variants in 11 individuals from 10 unrelated families across the United States, Europe, Asia, and Africa. A recurrent founder missense variant, p.Cys49Arg, disrupts glycosylation and blocks secretion of mature WFDC2.

This report distinguishes the molecularly-defined Mendelian entity BENP (WFDC2 deficiency) from the historically-described, clinically-overlapping Woakes' syndrome — a rare hereditary chronic rhinosinusitis with nasal polyposis (CRSwNP) variant defined by a clinical pentad (recurrent nasal polyposis, nasal broadening, frontal sinus aplasia, bronchiectasis, and dyscrinia). Woakes' syndrome, first delineated in 1979 (PMID: 553887), has never been assigned a molecular cause and has no OMIM/MONDO/Orphanet ID; it likely represents a clinically-recognized subset of the broader phenotypic spectrum that BENP now molecularly explains for a proportion of cases. Both entities share the core "unified airway" pathology linking upper-airway polyposis to lower-airway bronchiectasis via impaired mucociliary clearance and chronic infection.

Because WFDC2 (HE4) is undetectable in the serum of affected individuals, a blood HE4 test combined with WFDC2 genetic testing enables diagnosis — a rare instance of a simple, accessible biomarker for a genetic airway disease. Management combines endoscopic sinus surgery (universal in reported Woakes' cases), type-2-targeted biologics for the polyp component (dupilumab is the leading agent), and standard bronchiectasis care (airway clearance, anti-inflammatory DPP-1 inhibition, and infection control).

Disease Information

Overview

BENP is an autosomal recessive airway disease characterized by chronic infection of the airways resulting in rhinosinusitis and pronounced nasal polyposis (MedGen definition, after Dougherty et al., 2024). The disease spans the entire respiratory tract: upper airway (chronic rhinosinusitis, nasal polyposis, frequently with nasal broadening and frontal sinus abnormalities) and lower airway (bronchiectasis with chronic productive cough, recurrent infections, and progressive bronchial dilatation).

Key Identifiers

Resource Identifier
OMIM 620984
MONDO MONDO:0975835
MedGen 1874999
UMLS C5975469
Causal gene (NCBI Gene) WFDC2, Gene ID 10406
Cytogenetic locus 20q13.12
HGNC HGNC:15466
Gene alias HE4; the WFDC2 alias list literally includes "BENP"
Related historical entity Woakes' syndrome (no OMIM/MONDO/Orphanet ID; closest MedGen concept "Polypoid sinus degeneration", UMLS C0155822)

Synonyms and Alternative Names

  • Bronchiectasis and nasal polyposis (BENP)
  • Recessively inherited WFDC2 (HE4) deficiency
  • (Clinically overlapping) Woakes' syndrome — synonyms: necrotic ethmoiditis with nasal polyposis; Woakes' ethmoiditis

Source of Information

Information is derived from aggregated disease-level resources (OMIM, MONDO, MedGen) and from primary clinical genetics literature (a multi-family international case series, Dougherty et al., 2024). Epidemiologic descriptors of the overlapping Woakes' phenotype come from a PRISMA systematic review of published individual cases (PMID: 41416018).

Etiology

Disease Causal Factors

BENP is a monogenic (Mendelian) disease. The primary and sufficient cause is biallelic (homozygous or compound heterozygous) loss-of-function of WFDC2. As stated by Dougherty et al.: "We identified biallelic pathogenic variants in WAP four-disulfide core domain 2 (WFDC2) in 11 individuals from 10 unrelated families originating from the United States, Europe, Asia, and Africa" and "WFDC2 dysfunction defines a novel molecular etiology of bronchiectasis characterized by the deficiency of a secreted component of the airways" (PMID: 38626355).

A secondary infectious/mechanistic contribution is inherent: loss of the WFDC2 airway-defense protein permits chronic bacterial colonization and infection, which drives the inflammatory and structural airway damage.

Risk Factors

Genetic risk factors - Causal variants: biallelic pathogenic WFDC2 variants. The recurrent founder missense variant p.Cys49Arg is the best-characterized; computer simulations and deglycosylation assays indicate it "structurally" disrupts glycosylation and blocks secretion of the mature protein (PMID: 38626355). - Susceptibility for the broader (non-Mendelian) nasal-polyp phenotype: CRSwNP has a strong heritable component. A Utah genealogical study (1,638 CRSwNP probands) found first-degree relatives had a 4.1-fold increased risk (p < 10⁻³) and second-degree relatives a 3.3-fold risk of the same diagnosis, with no increased risk in spouses: "First-degree relatives (1stDRs) of CRSwNP patients demonstrated a 4.1-fold increased risk (p < 10(-3)) of carrying the same diagnosis, whereas second-degree relatives (2ndDRs) demonstrated a 3.3-fold increased risk" and "No increased risk was observed in spouses of CRSwNP patients" (PMID: 25677865).

Environmental risk factors - For BENP specifically, environment is not a primary driver, but chronic airway infection (opportunistic bacterial colonization) perpetuates disease. In the reported Woakes' aggregate, disease was male-predominant (65%) with childhood-through-adult onset (PMID: 41416018). - Consanguinity increases the likelihood of recessive disease (relevant to a recessive disorder like BENP); in pediatric non-CF bronchiectasis cohorts consanguinity was positive in 59.4% (PMID: 29605210).

Protective Factors

No specific genetic or dietary protective factors are established for BENP. Heterozygous carriers of a single pathogenic WFDC2 allele are unaffected (recessive inheritance), implying one functional allele is protective/sufficient.

Gene–Environment Interactions

The core interaction is genotype (WFDC2 loss) × airway microbial exposure: absent WFDC2-mediated innate defense, ordinary airway microbial exposure produces chronic infection and the self-sustaining "vicious vortex" of bronchiectasis. This is inferred from the protein's antibacterial function and the infection-dominated phenotype rather than directly demonstrated with GxE modeling.

Phenotypes

Phenotype Type HPO suggestion Onset Severity/Course Frequency
Nasal polyposis (recurrent, severe) Clinical sign / physical manifestation HP:0100582 (Nasal polyposis) Childhood (classically early) to adult Severe, recurrent/relapsing Defining feature; universal
Bronchiectasis Clinical sign / imaging HP:0002110 (Bronchiectasis) Childhood–adult Progressive, chronic Defining feature
Chronic rhinosinusitis Symptom/sign HP:0000246 (Sinusitis) Childhood–adult Chronic, relapsing Very frequent
Chronic productive cough / sputum Symptom HP:0031245 (Productive cough) With bronchiectasis onset Chronic Frequent
Recurrent respiratory infections Symptom HP:0002205 (Recurrent respiratory infections) Childhood Recurrent Frequent
Nasal broadening Physical manifestation HP:0000414 (Broad nasal tip) Childhood Progressive with polyp mass Woakes' feature
Frontal sinus aplasia Physical/imaging HP:0002688 (Aplasia of the frontal sinus) Congenital/developmental Stable Woakes' feature
Dyscrinia (highly viscous mucus) Laboratory/physical HP:0011950 Early Chronic Woakes' feature
Anosmia/hyposmia Symptom HP:0000458 (Anosmia) With polyp burden Fluctuating Frequent in CRSwNP

Clinical characteristics. The Woakes' pentad — "recurrent nasal polyposis with broadening of the nose, frontal sinus aplasia, bronchiectasis, and dyscrinia (production of highly viscous mucus)" (PMID: 553887) — captures the phenotype. A modern series reiterates "severe recurrent nasal polyps in early childhood with broadening of the nose, nasal dyscrinia, frontal sinus aplasia and bronchiectasis" (PMID: 27143164). Age of onset is variable — the systematic review of Woakes' cases found mean age 39.5 years (range 5–81), with both paediatric- and adult-onset cases (PMID: 41416018).

Quality-of-life impact. Substantial. The nasal-polyp component causes nasal obstruction, anosmia, and rhinorrhea (measured by SNOT-22); the bronchiectasis component causes chronic cough, sputum, dyspnea, and recurrent exacerbations. Endoscopic sinus surgery improves symptoms and QoL, but "recurrences are common and multiple surgeries are often required" (PMID: 41261359).

Genetic / Molecular Information

Causal Gene

WFDC2 (WAP four-disulfide core domain 2 / HE4 / human epididymis protein 4); NCBI Gene 10406; HGNC:15466; UniProt Q14508; chromosome 20q13.12. OMIM phenotype 620984.

Pathogenic Variants

  • Variant type/class: predominantly missense (recurrent founder p.Cys49Arg), consistent with disruption of a disulfide-bonded WAP-domain cysteine. Other biallelic pathogenic/likely-pathogenic variants were identified across the 10 families.
  • Classification (ACMG/AMP): pathogenic/likely-pathogenic biallelic variants in affected individuals.
  • Functional consequence: loss of function via loss of secretion. "Computer simulations and deglycosylation assays indicate that the disease-causing founder variant p.Cys49Arg structurall[y]" alters the protein such that mature, glycosylated WFDC2 is not secreted (PMID: 38626355). The net effect is deficiency of a secreted airway component.
  • Origin: germline, biallelic (recessive).
  • Allele frequency: pathogenic alleles are rare; the founder p.Cys49Arg suggests population-specific recurrence. (Exact gnomAD frequencies not extracted in this investigation.)

Modifier Genes

Not established for BENP. For the shared CRSwNP/AERD phenotype, arachidonic-acid-pathway and type-2 immune loci modulate severity (see Mechanism).

Epigenetic Information

Not established for BENP. Of note, in cystic fibrosis airway epithelium, WFDC2/HE4 mRNA is upregulated with decreased miR-140-5p, indicating HE4 expression is under microRNA regulation (PMID: 27105680) — relevant to WFDC2 biology though not to BENP pathogenesis per se.

Chromosomal Abnormalities

None reported; BENP is a single-gene disorder, not a structural/aneuploidy syndrome.

Environmental Information

  • Environmental factors: Not primary. Chronic airway microbial exposure is the permissive environmental substrate on which the genetic defect acts.
  • Lifestyle factors: No established BENP-specific lifestyle drivers. General bronchiectasis worsens with smoking and environmental exposures (extrapolated).
  • Infectious agents: Chronic bacterial airway infection is central to the downstream pathology. In bronchiectasis broadly, microbiome dysbiosis with increased pathogenic bacteria correlates with severity (PMID: 42051198); older/advanced bronchiectasis shows a shift toward Pseudomonas aeruginosa and Enterobacteriaceae (PMID: 42474633). Staphylococcus aureus enterotoxins can amplify type-2 airway inflammation along the nasobronchial axis (PMID: 42646747).

Mechanism / Pathophysiology

Ordered Causal Chain

1. Biallelic loss-of-function WFDC2 variant (e.g., p.Cys49Arg)          [demonstrated]
│  leads to
2. Misglycosylation and blocked secretion of mature WFDC2 protein        [demonstrated]
│  results in
3. Deficiency of secreted WFDC2 in airway surface liquid                 [demonstrated]
   (undetectable in serum)
│  removes
4. A protease-inhibitor / antibacterial innate-defense component          [demonstrated/known]
   of the airway
│  permits
5. Chronic bacterial airway infection and microbiome dysbiosis            [inferred/known]
│  triggers
6. Persistent airway inflammation (neutrophilic ± type-2/eosinophilic)    [inferred/known]
│  branches:
├──(UPPER AIRWAY)── epithelial injury + type-2 inflammation → mucus
│    hypersecretion (dyscrinia) + tissue remodeling → recurrent NASAL
│    POLYPOSIS, rhinosinusitis, nasal broadening                   [observed]
│
└──(LOWER AIRWAY)── impaired mucociliary clearance + neutrophil
     elastase / DPP-1-driven inflammation → "vicious vortex" →
     irreversible bronchial wall damage → BRONCHIECTASIS           [observed]

Steps 1–4 are demonstrated by the primary genetic/biochemical study (PMID: 38626355). Steps 5–7 integrate established airway-disease mechanisms and are partly inferred for BENP specifically from the known biology of nasal polyposis and bronchiectasis.

Molecular Pathways and Cellular Processes

  • Upstream — loss of airway defense. WFDC2/HE4 is a secreted serine-protease inhibitor. Curated GO annotations for WFDC2 (Gene 10406) include serine-type endopeptidase inhibitor activity (GO:0004867), peptidase inhibitor activity (GO:0030414), negative regulation of endopeptidase activity (GO:0010951), antibacterial humoral response (GO:0019731), innate immune response (GO:0045087), club cell differentiation (GO:0060486), and positive regulation of lung ciliated cell differentiation (GO:1901248). Localization: extracellular region (GO:0005576) and extracellular exosome (GO:0070062) — consistent with a secreted protein. Loss of this protease-inhibitory/antibacterial shield underlies the "loss-of-airway-defense" mechanism.
  • Downstream (upper airway) — type-2 inflammation and remodeling. Epithelial alarmins (IL-25, IL-33, TSLP) activate ILC2/Th2 cells → IL-4/IL-5/IL-13 → eosinophilia, local IgE, mast-cell activation: "initial allergen exposure disrupts epithelial integrity, triggering local inflammation via alarmins including IL-25, IL-33, and TSLP, which activate type 2 innate lymphoid cells as well as other immune cells to secrete type 2 cytokines IL-4, IL-5 and IL-13, promoting Th2 cell development and eosinophil recruitment" (PMID: 39158477). Eosinophil–epithelial interactions drive mucin and profibrotic cytokine secretion: "Eosinophil-epithelial interactions significantly stimulated the secretion of MUC5AC, PDGF-AB, VEGF, TGF-beta1, and IL-8 in culture supernatants" (PMID: 24717945) — the molecular basis of mucus hypersecretion (dyscrinia) and polyp remodeling.
  • Downstream (lower airway) — vicious vortex. "Bronchiectasis is a chronic respiratory disease characterised by irreversible bronchial dilatation, persistent airway inflammation and recurrent infections" (PMID: 42342265). Neutrophil-driven inflammation via DPP-1/neutrophil elastase perpetuates airway damage; targeting DPP-1 (brensocatib) reduces exacerbations (PMID: 42048140).

Immune System Involvement

Combined innate immunodeficiency (loss of secreted WFDC2 antibacterial defense; GO:0045087) plus chronic mixed inflammation — type-2/eosinophilic in the polyp compartment and neutrophilic in the bronchiectatic compartment. A subset overlaps with AERD/Samter's triad, driven by dysregulated arachidonic-acid metabolism: "Alterations in arachidonic acid metabolism may induce an imbalance between pro-inflammatory and anti-inflammatory substances, expressed as an overproduction of cysteinyl leukotrienes and an underproduction of prostaglandin E2" (PMID: 29414455). Samter's triad was the most common comorbidity in reported Woakes' cases (7/39) (PMID: 41416018).

Cell Types and Tissues

  • Airway secretory/club cells (CL:0000158) and submucosal gland cells — normal source of WFDC2.
  • Respiratory epithelial cells (CL:0002633) and ciliated cells (CL:0005012) — mucociliary interface.
  • Eosinophils (CL:0000771), mast cells (CL:0000097), type-2 innate lymphoid cells / Th2 cells (CL:0000899) — polyp inflammation.
  • Neutrophils (CL:0000775) — bronchiectasis inflammation.

GO biological processes: GO:0019731 (antibacterial humoral response), GO:0045087 (innate immune response), GO:0002376 (immune system process), GO:0060486 (club cell differentiation), GO:1901248 (positive regulation of lung ciliated cell differentiation).

Molecular Profiling

WFDC2/HE4 is measurable in serum and airway. In BENP it is undetectable in serum, enabling diagnosis. By contrast, in cystic fibrosis, serum HE4 is elevated and correlates with disease severity — median 99.5 pmol/L in children with CF vs 36.3 pmol/L in controls (P < .0001) (PMID: 27105680) — illustrating that HE4 is dynamically regulated in airway disease and that its absence is the specific BENP signature.

Anatomical Structures Affected

Organ Level

  • Primary organs: paranasal sinuses and nasal cavity (UBERON:0001707 nasal cavity; UBERON:0001825 paranasal sinus; frontal sinus UBERON:0002264) and the lungs/bronchi (UBERON:0002185 bronchus; UBERON:0002048 lung).
  • Secondary involvement: middle ear (eosinophilic otitis media reported with Woakes', PMID: 27143164); nasal external framework (nasal broadening).
  • Body system: respiratory system (UBERON:0001004), upper and lower airways ("unified airway").

Tissue and Cell Level

  • Airway epithelium (respiratory epithelium), submucosal glands, and inflammatory infiltrate.
  • Cell populations: club/secretory cells, ciliated cells, eosinophils, neutrophils, mast cells (CL terms above).

Subcellular Level

  • Extracellular region / airway surface liquid (GO:0005576) — site of WFDC2 deficiency.
  • Secretory pathway / ER–Golgi glycosylation machinery — where the p.Cys49Arg defect blocks maturation and secretion.

Localization / Lateralization

  • Sinonasal disease is typically bilateral. Bronchiectasis in comparable pediatric cohorts preferentially involves lower lobes (left-lower 53.9–71%, right-lower 47–59%) (PMID: 30961955, PMID: 29605210).

Temporal Development

  • Onset: variable — classically early childhood for the nasal-polyp component (Woakes'), but the systematic review documents onset from age 5 to adulthood (mean age at report 39.5 years) (PMID: 41416018). Onset pattern is chronic/insidious.
  • Progression: chronic and progressive for bronchiectasis (irreversible bronchial dilatation) and relapsing/recurrent for nasal polyposis. Bronchiectasis follows a self-perpetuating "vicious vortex" (PMID: 42474633).
  • Duration: chronic, lifelong.
  • Remission patterns: treatment-induced partial remission (surgery, biologics) is common but polyps frequently recur; spontaneous remission is not characteristic.
  • Critical periods: childhood diagnosis offers a window to institute airway-clearance and infection-control measures before irreversible bronchiectatic damage accrues.

Inheritance and Population

  • Inheritance pattern: autosomal recessive (biallelic WFDC2 loss-of-function).
  • Penetrance: presumed high/complete for biallelic loss-of-function, though variable expressivity of individual phenotype components is expected.
  • Founder effects: the recurrent p.Cys49Arg variant indicates a founder allele; affected families span the US, Europe, Asia, and Africa (PMID: 38626355).
  • Consanguinity: relevant for a recessive disorder; high consanguinity rates characterize pediatric non-CF bronchiectasis cohorts generally (59.4%, PMID: 29605210).
  • Carrier frequency: not precisely established; expected rare.

Epidemiology

BENP is ultra-rare: the defining series comprised 11 individuals from 10 families. The clinically overlapping Woakes' phenotype is similarly rare — a PRISMA systematic review identified only 39 unique patients across 23 studies ("Twenty-three studies met the inclusion criteria, comprising 39 unique patients (mean age 39.5 years; range 5-81; 65% male)", PMID: 41416018). Precise prevalence/incidence figures are not available.

Population Demographics

  • Sex ratio: male-predominant in the Woakes' aggregate (65% male).
  • Geographic distribution: multi-ancestry (worldwide) with a founder allele. In a Vietnamese sinopulmonary cohort, WFDC2 abnormalities were specifically screened but not identified, underscoring rarity and possible population variation (PMID: 41094464).

Diagnostics

Clinical Tests

  • Serum HE4 (WFDC2) assay: the key BENP-specific test — WFDC2 is undetectable in serum of affected individuals (contrast: elevated in CF). Combined with genetic testing, this enables diagnosis (PMID: 38626355, PMID: 27105680).
  • Imaging: chest HRCT documents bronchiectasis (broncho-arterial ratio >1, lack of tapering, bronchial wall thickening, mucus plugging, tree-in-bud) (PMID: 31508157); sinus CT scored by Lund-Mackay; nasal endoscopy scored by Lund-Kennedy.
  • Biopsy/pathology: nasal polyp histology shows eosinophilic mucosa with MUC5AC-rich mucus hypersecretion and remodeling.

Genetic Testing

  • Recommended approach: targeted single-gene WFDC2 sequencing, or a sinopulmonary/bronchiectasis gene panel (should include CFTR, PCD genes DNAI1/DNAH5/DNAH11, and WFDC2), or WES/WGS for undiagnosed sinopulmonary disease. Vietnamese sinopulmonary genetic screening explicitly incorporated WFDC2 alongside CF and PCD genes (PMID: 41094464).

Clinical Criteria and Differential Diagnosis

BENP/Woakes' diagnosis is partly exclusionary: childhood nasal polyposis is classically caused by CF or Kartagener/PCD — "Usually, nasal polyposis in early childhood (children aged less than 5 years) is caused by cystic fibrosis of Kartagener's syndrome" (PMID: 553887) — which must be excluded.

Differential Gene(s) Inheritance Distinguishing tests
Cystic fibrosis CFTR AR Sweat chloride ≥60 mmol/L; two pathogenic CFTR variants; elevated serum HE4 (PMID: 41919747, PMID: 27105680)
PCD / Kartagener DNAI1, DNAH5, DNAH11 AR Low nasal nitric oxide; ciliary EM; ± situs inversus (PMID: 16203616, PMID: 34391405)
AERD / Samter's triad polygenic — NSAID hypersensitivity; aspirin challenge (PMID: 29414455)
BENP WFDC2 AR Undetectable serum HE4; biallelic WFDC2 variants; normal cilia and CFTR

For PCD exclusion: "As a screening test nasal nitric oxide (NO) measurement is widely used. Establishment of diagnosis currently relies on electron microscopy, direct evaluation of ciliary beat by light microscopy" (PMID: 16203616). The absence of serum HE4 (vs its elevation in CF) plus normal cilia distinguishes BENP.

Screening

Cascade genetic testing of at-risk relatives once a proband's biallelic WFDC2 variants are identified; carrier testing for reproductive partners.

Outcome / Prognosis

  • Survival/mortality: BENP is not directly lethal, but the bronchiectasis component drives long-term morbidity and mortality. In the European Bronchiectasis Registry (EMBARC, n=13,484), "Sputum colour is a simple marker of disease severity and future risk of exacerbations, severe exacerbations and mortality in patients with bronchiectasis" (PMID: 38609095).
  • Morbidity/QoL: substantial — chronic nasal obstruction, anosmia, rhinorrhea (SNOT-22) plus chronic cough, sputum, dyspnea, and recurrent exacerbations.
  • Disease course: chronic-relapsing. Sinus surgery relieves symptoms but "endoscopic sinus surgery offers relief of symptoms and improvement of quality of life, recurrences are common and multiple surgeries are often required" (PMID: 41261359).
  • Complications: recurrent respiratory infections, progressive airflow obstruction, and (in overlap syndromes) eosinophilic otitis media.
  • Prognostic factors: sputum purulence, Pseudomonas colonization, exacerbation frequency, and lung-function decline predict worse bronchiectasis outcomes (PMID: 38609095, PMID: 42474633).

Treatment

Surgical / Interventional

Functional endoscopic sinus surgery (FESS) is universal in reported cases — "All patients underwent surgical treatment, most commonly functional endoscopic sinus surgery, with adjunctive procedures including digital nasal bone compression (six cases) and formal rhinoplasty or septorhinoplasty (seven cases)" (PMID: 41416018). NCIT: Endoscopic Sinus Surgery.

Pharmacotherapy — Type-2-Targeted Biologics (for the polyp component)

Network meta-analyses of RCTs establish biologics as effective for the CRSwNP component:

Biologic Target Effect on Nasal Polyp Score (WMD vs placebo) Source
Dupilumab IL-4Rα (IL-4/IL-13) −2.16 (95% CI −2.44 to −1.89) PMID: 41178615
Tezepelumab TSLP −1.50 PMID: 41178615
Mepolizumab IL-5 ~ −0.9 to −1.25 PMID: 41178615
Omalizumab IgE ~ −0.9 PMID: 41178615

"NPS was significantly improved by dupilumab (WMD: -2.16, 95% CI [-2.44, -1.89])" (PMID: 41178615). Larger NMAs (3,642 patients, 7 biologics) rank dupilumab, stapokibart, and tezepelumab in the top efficacy tier (PMID: 42398863). A real-world cohort (n=360) achieved good-to-excellent response in 51% (PMID: 41989130). NCIT: Dupilumab, Mepolizumab, Omalizumab.

Pharmacotherapy — Bronchiectasis Component

  • Airway clearance / mucoactive agents (hypertonic saline, mannitol, carbocisteine); evidence is mixed — a meta-analysis did not show a significant reduction in exacerbations (PMID: 42342264).
  • Anti-inflammatory DPP-1 inhibition: brensocatib (recently approved) reduces neutrophil-driven inflammation and exacerbations — "the inhibition of dipeptidyl peptidase-1 (DPP-1) which can reduce neutrophil-driven airway inflammation and, consequently, exacerbations" (PMID: 42048140). NCIT: Brensocatib.
  • Macrolides (azithromycin) and targeted antibiotics for infection control.

Advanced / Experimental (Rational, Not Yet Available)

Because BENP is a deficiency of a secreted protein, it is conceptually amenable to protein-replacement or gene-directed therapy (inhaled/topical recombinant WFDC2, or WFDC2 gene therapy) — analogous in spirit to CFTR modulation for CF. This is a proposed, not established, strategy.

Personalized Medicine

Genotype-guided care: confirmed WFDC2 biallelic loss identifies patients for whom future WFDC2-directed therapy would apply and rationalizes aggressive combined upper/lower-airway management.

Prevention

  • Primary prevention: not possible for a germline recessive disorder; genetic counseling and carrier/cascade screening in affected families are the key preventive tools.
  • Secondary prevention: early diagnosis (serum HE4 + genetics) to institute airway-clearance and infection control before irreversible bronchiectasis develops (critical-period concept).
  • Tertiary prevention: minimize exacerbations and structural progression via airway clearance, prompt antibiotics, DPP-1 inhibition, and polyp control (biologics/surgery).
  • Immunization: routine respiratory immunizations (influenza, pneumococcal) are advisable to reduce infective exacerbations (standard bronchiectasis practice).
  • Counseling: genetic counseling for autosomal-recessive recurrence risk (25% per pregnancy for carrier couples); prenatal/preimplantation options where variants are known.

Other Species / Natural Disease

  • Taxonomy / orthologs: WFDC2 is highly conserved with 1:1 mammalian orthologs — mouse Wfdc2 (Gene 67701), rat (286888), dog (403919), cow (618044), macaque (710469), chimpanzee (458283). NCBI Taxon: Homo sapiens (9606); Mus musculus (10090); Rattus norvegicus (10116).
  • Natural disease: no naturally-occurring animal BENP homolog has been reported (OMIA search not positive in this investigation).
  • Evolutionary conservation: strong ortholog conservation supports the feasibility of murine models and cross-species mechanistic study.

Model Organisms

  • Recommended primary model: mouse Wfdc2 knockout (Gene 67701) — the conserved 1:1 ortholog makes a targeted knockout the logical model to test whether WFDC2 loss recapitulates rhinosinusitis/nasal polyposis and bronchiectasis-like airway pathology with chronic infection.
  • Complementary in-vitro models: air–liquid interface (ALI) cultures of human nasal/bronchial epithelium (used widely in CRS and CF research, e.g., PMID: 40683569, PMID: 27105680) with WFDC2 knockdown/knockout to assay secretion, antibacterial activity, and mucin production; patient-derived iPSC airway organoids.
  • Model types available/needed: knockout, conditional (airway-secretory-cell-specific), knock-in of p.Cys49Arg (to model the founder secretion defect), and humanized lines.
  • Phenotype recapitulation / limitations: to be established — a key uncertainty is whether mice reproduce the human nasal-polyp phenotype (rodents rarely form true nasal polyps), which may limit face validity for the upper-airway component.
  • Resources: MGI, IMPC/KOMP (for Wfdc2 alleles), Cellosaurus/ATCC (epithelial lines).

Mechanistic Model / Interpretation

BENP is best understood as a "loss-of-airway-defense" Mendelian disease. A single secreted protein, WFDC2/HE4 — a WAP-domain protease inhibitor with antibacterial and protease-regulatory functions made by airway club cells and submucosal glands — is a non-redundant component of airway surface liquid. Biallelic loss (often via the p.Cys49Arg secretion-blocking founder variant) removes this defense, licensing chronic airway infection. The infection/inflammation then plays out along the unified airway: in the sinonasal compartment it drives type-2/eosinophilic inflammation, MUC5AC hypersecretion (dyscrinia), and remodeling → recurrent polyposis; in the bronchial compartment it drives the neutrophilic "vicious vortex" → irreversible bronchiectasis.

This model elegantly explains why BENP mimics CF and PCD (all three cause combined upper+lower airway suppurative disease) yet is molecularly distinct: cilia are structurally normal (unlike PCD) and CFTR/chloride transport is normal (unlike CF). The serum HE4 test provides an unusually clean diagnostic discriminator — absent in BENP, elevated in CF — turning a rare genetic diagnosis into a two-step (blood biomarker → confirmatory sequencing) workflow.

UPSTREAM (genetic/molecular)          DOWNSTREAM (clinical)
   WFDC2 biallelic LoF ──► no secreted    ──► chronic infection ──► ┬─► NASAL POLYPOSIS
   (p.Cys49Arg etc.)      WFDC2 in ASL         + inflammation        └─► BRONCHIECTASIS
   [demonstrated]         [demonstrated]       [inferred/known]          [observed]

Evidence Base

PMID Contribution Weight
38626355 Defining paper — biallelic WFDC2 LoF causes BENP; founder p.Cys49Arg blocks secretion; serum HE4 undetectable Landmark (human clinical + in vitro/computational)
27105680 HE4 biology in airway disease; elevated in CF (contrast with BENP); miR-140-5p regulation Supporting
553887 Original Woakes' pentad; CF/PCD as differentials; hereditary basis Historical/clinical
41416018 Systematic review — epidemiology (39 patients, 65% male), universal surgery, comorbidities Aggregate clinical
25677865 Strong heritability of CRSwNP (4.1× first-degree relative risk; no spousal risk) Supporting genetic basis
24717945 Eosinophil–epithelial MUC5AC/profibrotic mechanism (dyscrinia + remodeling) Mechanism
39158477 Type-2 alarmin–cytokine cascade (upstream polyp inflammation) Mechanism
42342265, 42048140, 42474633 Bronchiectasis "vicious vortex"; DPP-1 inhibition (brensocatib) Mechanism/treatment
41178615, 42398863, 41989130 Biologic efficacy for CRSwNP (dupilumab leading) Treatment
29414455 AERD/Samter's triad leukotriene mechanism (overlap endotype) Mechanism
16203616, 34391405, 41919747 PCD and CF differential diagnosis Diagnostics
38609095 Bronchiectasis prognosis (EMBARC registry) Prognosis
29605210, 30961955, 40832796 Pediatric bronchiectasis etiology/lobar distribution Context
41094464 WFDC2 screening in a sinopulmonary cohort (not identified — rarity) Epidemiology

Limitations and Knowledge Gaps

  1. Small defining cohort. BENP is molecularly established from only 11 individuals in 10 families (PMID: 38626355); penetrance, expressivity, full variant spectrum, and natural history remain to be characterized in larger cohorts.
  2. Prevalence/carrier frequency undefined. Precise gnomAD allele frequencies for pathogenic WFDC2 variants and population carrier rates were not extracted here.
  3. Woakes'–BENP relationship not fully resolved. How many historical Woakes' cases carry WFDC2 variants is unknown; some Woakes'/CRSwNP-bronchiectasis cases are likely genetically heterogeneous (AERD, other loci). A Vietnamese cohort screened for WFDC2 and found none (PMID: 41094464).
  4. Mechanistic steps 5–7 are partly inferred. The infection→inflammation→structural-damage chain in BENP specifically is extrapolated from general airway-disease biology, not yet demonstrated in a BENP-specific model.
  5. No validated animal model of BENP is yet reported; rodent nasal-polyp face-validity is a concern.
  6. Citation-integrity note. Some citation snippets for the defining paper (PMID 38626355) were flagged as "mismatch" during automated validation; the quoted content is consistent with the paper's established conclusions but exact abstract wording should be re-verified before database ingestion.

Proposed Follow-up Experiments / Actions

  1. Confirm/curate ontology mappings (OMIM:620984 ≡ MONDO:0975835 ≡ MedGen:1874999) and re-verify the exact abstract quotes from PMID: 38626355 to resolve the "mismatch"-flagged snippets before knowledge-base entry.
  2. Assemble a larger BENP case series via GeneMatcher/international collaboration to define penetrance, expressivity, age-of-onset distribution, and the full WFDC2 variant spectrum with gnomAD frequencies.
  3. Validate the two-step diagnostic algorithm (serum HE4 → WFDC2 sequencing) prospectively in unexplained combined rhinosinusitis-plus-bronchiectasis cohorts, quantifying sensitivity/specificity against CF and PCD.
  4. Generate a Wfdc2-knockout (and p.Cys49Arg knock-in) mouse and WFDC2-null human ALI/organoid cultures; assay airway antibacterial activity, secretion, mucin production, and infection susceptibility to test causal steps 4–7.
  5. Assess WFDC2 protein-replacement or gene therapy conceptually (recombinant WFDC2 in ALI/organoid rescue experiments) as a rational disease-modifying strategy.
  6. Retrospectively genotype archived Woakes'-syndrome cases for WFDC2 to quantify the molecular overlap between the historical clinical entity and the new Mendelian disease.

Report compiled from 12 confirmed findings across 5 investigation iterations and 60 reviewed papers. Evidence types are noted throughout as human clinical, in vitro, computational, or inferred/extrapolated.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 29
Resolved 29
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 29
On topic 9
Off topic 0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome Count
Terms checked 37
Resolved 34
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 3
Terms whose name was checked 21
Terms named correctly 13
Terms named as a different term 2
Terms whose name is worth a second look 6

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

  • MONDO:0975835 (3 mentions) - the report calls it "MONDO"; MONDO calls it bronchiectasis and nasal polyposis
  • HP:0011950 (1 mention) - the report calls it "Laboratory/physical"; HP calls it Unusual bronchiolitis

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

  • HP:0000414 (1 mention) - the report calls it "Broad nasal tip"; HP calls it Bulbous nose, and lists "Bulbous nasal tip" among its other names
  • HP:0002688 (1 mention) - the report calls it "Aplasia of the frontal sinus"; HP calls it Absent frontal sinuses, and lists "Aplasia of frontal sinus" among its other names
  • GO:0005576 (2 mentions) - the report calls it "Extracellular region / airway surface liquid"; GO calls it extracellular region
  • CL:0000158 (1 mention) - the report calls it "Airway secretory/club cells"; CL calls it club cell
  • CL:0002633 (1 mention) - the report calls it "Respiratory epithelial cells"; CL calls it respiratory basal cell
  • UBERON:0001004 (1 mention) - the report calls it "respiratory system", "Body system: respiratory system"; UBERON calls it respiratory system

Terms named inconsistently

The report gives these identifiers more than one name of its own:

  • UBERON:0001004 - called "respiratory system", "Body system: respiratory system"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: OMIM, UMLS.