Factor XIII A Subunit Deficiency: Comprehensive Research Report

Scope note on identifiers: The research brief names MONDO:0013187, but searches return MONDO:0018029 for "factor XIII deficiency" (general term) in cross-reference tables (MalaCards, Wikidata). I could not independently confirm MONDO:0013187 resolves to this disease in the sources retrieved. This is a lead requiring verification against the MONDO ontology browser directly before binding — do not treat either ID as confirmed without that check.

1. Disease Information

Overview: Congenital Factor XIII (FXIII) deficiency is a rare autosomal recessive bleeding disorder caused by biallelic loss-of-function variants in F13A1 (encoding the catalytic A subunit) or, less commonly, F13B (encoding the carrier B subunit). FXIII is the "last enzyme" of the coagulation cascade — a transglutaminase that cross-links fibrin after clot formation rather than participating in clot initiation. Deficiency therefore produces a paradoxical presentation: normal routine coagulation screening (PT, aPTT, thrombin time, fibrinogen, platelet count) with a clinically unstable, friable clot prone to premature dissolution and rebleeding (StatPearls NBK557467; Altahan et al., Clin Hematol Int, PMC12825037/PMID:41583548).

Key identifiers: | System | ID | |---|---| | OMIM gene | *134570 (F13A1) | | OMIM phenotype | #613225 (Factor XIII, A subunit, deficiency of) | | Orphanet | ORPHA331 (Congenital factor XIII deficiency) | | ICD-10-CM | D68.2 (Hereditary deficiency of other clotting factors) | | ICD-11 | 3B14.Z | | MeSH | D005177 | | HGNC (gene) | HGNC:3531 (F13A1) | | UniProt | P00488 (F13A1 protein) |

Synonyms: Fibrin-stabilizing factor (FSF) deficiency; congenital FXIII deficiency; FXIIIA deficiency; plasma transglutaminase deficiency.

Evidence base: Information is derived almost entirely from aggregated disease-level resources — case series, national/regional registries (notably the Iranian national FXIII deficiency registry), structured databases (OMIM, Orphanet, ClinVar), and individual case reports — rather than large EHR cohorts, reflecting the disorder's extreme rarity (<500 molecularly characterized families worldwide per recent reviews).

Sources: OMIM *134570 · OMIM #613225 · Orphanet ORPHA331 · StatPearls · Altahan et al. 2026, PMID:41583548

2. Etiology

Causal factors (congenital): Biallelic (homozygous or compound heterozygous) loss-of-function variants in F13A1 account for ~95% of congenital cases; F13B variants account for the remainder and produce a generally milder phenotype because the catalytic A subunit is intact. More than 200 causative F13A1 variants have been catalogued; missense variants predominate (>50%), with nonsense, splice-site, deep-intronic, and large structural deletions also described (Altahan et al., PMID:41583548; PMC6950900 — deep intronic splicing variant; PMC6657060 — large deletion via complex rearrangement).

Genetic risk factors: - Founder mutations create regional clustering: Trp187Arg (c.562T>C) is the dominant pathogenic allele in southeast Iran — in one series, 346 of 366 Iranian FXIIID patients resided in Sistan and Baluchestan Province and carried this single founder variant (How to Assess Founder Effect..., PMC7876424; Molecular Basis of Congenital FXIII Deficiency in Iran, PMC6714674). Arg77Cys is reported as a recurrent variant in the Swiss population (search result; not independently verified against a primary source in this pass — flag as lead). - Consanguinity is the dominant environmental/demographic risk amplifier for an autosomal recessive disorder of this rarity — Iran's ~12-fold elevated prevalence versus global estimates is attributed directly to consanguinity rates (StatPearls; Altahan et al.).

Protective factors: None specific to the deficiency state were identified — once activity falls below the disease threshold, no genetic or environmental factor mitigates bleeding risk other than replacement therapy. (Distinct from this disease entity: the common F13A1 Val34Leu polymorphism, present in normal-activity individuals at 0–44% allele frequency across populations, is associated with a different clinical question — reduced risk of myocardial infarction and venous thromboembolism, OR for VTE as low as 0.16 in Leu34 homozygotes — via accelerated FXIII activation kinetics and altered fibrin fiber architecture that is more fibrinolysis-susceptible. This is a separate phenotype of FXIII gain-of-function-type activation kinetics, not a modifier of the deficiency disease itself, and should not be conflated with it in curation. ([Role of factor XIII polymorphisms in clot formation, Blood, search result]; ClinVar RCV000017996 "protection against myocardial infarction").

Gene-environment interactions: The clearest documented interaction is in acquired (non-congenital) FXIII deficiency, which is mechanistically distinct and more prevalent than the congenital form: - Autoimmune acquired FXIII deficiency: anti-FXIII autoantibodies, with HLA class I/II susceptibility alleles implicated — a whole-exome sequencing study found HLA-B, MICA, BTNL2, HLA-DQB1, and HLA-DPB1 variants correlating with elevated anti-FXIII autoantibody titers, invoking a breakdown of immune tolerance analogous to acquired hemophilia A (PMID:34506591, PLoS One 2021). Median age of onset ~75 years; ~50% idiopathic, remainder associated with autoimmune disease, diabetes, or malignancy. - Non-immune acquired deficiency (more common than autoimmune): hyperconsumption (DIC, sepsis, major surgery; ECMO carries an 80–90% reported incidence of acquired deficiency), decreased synthesis (liver disease), and drug-associated (valproic acid, isoniazid, penicillin, phenytoin; checkpoint-inhibitor immunotherapy reported in a case report) (StatPearls; A Rare Case of FXIII Deficiency in Cancer Immunotherapy, PMC8163106).

3. Phenotypes

Severity correlates with residual FXIII activity (EN-RBD classification): severe (undetectable–≤1%, spontaneous major bleeding), moderate (<30%, heterogeneous bleeding), mild (≥30%, typically asymptomatic) (Altahan et al., PMID:41583548).

A single case report also describes hydrocephalus in infancy as a rare sequela of intracranial hemorrhage (PMC12504050) — not a primary phenotype but a downstream structural consequence.

Quality-of-life impact: Not quantified with standardized instruments (EQ-5D/SF-36) in the literature surfaced here — this appears to be a genuine evidence gap rather than a retrieval failure; prophylactic therapy trial reports (Mentor™ series, below) emphasize bleeding-rate reduction rather than formal QoL metrics.

(Caveat, consistent with dismech practice: every HP term above is a candidate suggestion based on clinical description matching, not a verified OAK/HPO lookup — each must be independently confirmed against the HPO browser before binding, per the Ontology Term Contract.)

4. Genetic/Molecular Information

Causal gene: F13A1 — HGNC:3531, chromosome 6p24.3–p25.1 (sources vary slightly: 6p25.1 vs 6p24–p25; verify exact cytoband at curation time), 15 exons, encoding a 731-amino-acid catalytic subunit (UniProt P00488). The protein belongs to the transglutaminase superfamily, containing an N-terminal activation peptide (cleaved by thrombin), a β-sandwich domain, the catalytic core (containing the Cys-His-Asp catalytic triad), and two C-terminal β-barrel domains.

Secondary gene: F13B (chromosome 1q31–q32.1), encoding the non-catalytic B subunit (10 sushi/CCP domains), produced by hepatocytes; F13B deficiency accounts for ~5% of congenital cases and is generally milder.

Variant landscape: - >200 F13A1 pathogenic variants reported to date; missense variants >50% of cases, with nonsense, splice-site, deep-intronic, and gross deletion variants comprising the remainder. - ClinVar-documented examples include nonsense variants (R171X, Y441X) and missense variants (R681H) (search-derived; individual ClinVar accessions not independently verified here — treat as leads pending direct ClinVar lookup). - A novel Cys328 nonsense variant reported in a severe case (PMC7650518); eight novel F13A1 variants with structural modeling reported by PMC2878794. - Founder alleles: Trp187Arg (Iran/southeast Iran), Arg77Cys (Switzerland, per search lead).

Allele frequency / carrier frequency: No specific gnomAD allele-frequency table for individual pathogenic F13A1 variants was retrieved in this pass (a genuine gap — direct gnomAD query recommended at curation time). Aggregate carrier frequency for deficiency-causing alleles is estimated at ~1 in 1,000 globally (~7.5 million heterozygous carriers worldwide per epidemiological extrapolation cited in search results), consistent with the homozygote prevalence of 1 in 2–3 million.

Functional consequences: Predominantly loss of function — reduced/absent catalytic transglutaminase activity, either through reduced protein synthesis/stability (Type I: concordant reduction of antigen and activity) or a qualitative catalytic defect (Type II: normal/near-normal antigen, reduced activity).

Somatic vs. germline: Congenital FXIII-A deficiency is exclusively germline/inherited; acquired (autoimmune or consumptive) deficiency is a distinct, non-genetic disease process (see §2).

Epigenetics / chromosomal abnormalities: No epigenetic mechanism (DNA methylation, histone modification) specific to FXIII-A deficiency was found in the sources retrieved — this appears to be an absence of documented evidence rather than a negative finding, and should not be asserted either way without a dedicated search of ENCODE/Roadmap/DiseaseMeth. Chromosomal-scale abnormalities (aneuploidy, translocation) are not a recognized disease mechanism here; point mutations and small-to-large intragenic deletions dominate.

5. Environmental Information

Environmental/iatrogenic factors (relevant almost exclusively to acquired deficiency, not the congenital disease that is the primary curation target): - Extracorporeal membrane oxygenation (ECMO) — 80–90% reported incidence of acquired deficiency - Sepsis, disseminated intravascular coagulation, major surgery (consumptive) - Hepatic dysfunction (decreased synthesis) - Medications: valproic acid, isoniazid, penicillin, phenytoin; immune checkpoint inhibitor therapy (case report, PMC8163106) - Associated autoimmune conditions: systemic lupus erythematosus (~30% of immune-mediated acquired cases), IgA vasculitis, rheumatoid arthritis

Lifestyle factors: None identified as modifying congenital disease expression; trauma (including minor trauma and surgical trauma) is the principal precipitant of clinically apparent bleeding episodes in both congenital and acquired deficiency, rather than a "lifestyle" risk factor per se.

Infectious agents: Not a direct cause; sepsis is a recognized trigger of acquired consumptive deficiency but FXIII deficiency itself has no infectious etiology.

6. Mechanism / Pathophysiology

Ordered causal chain

1. Initiating lesion: Biallelic loss-of-function variant in F13A1 (or, less commonly, F13B) → absent or structurally/catalytically defective FXIII-A protein synthesized in megakaryocytes, platelets, and monocytes/macrophages. (Demonstrated — molecular/biochemical studies.)
2. This leads to markedly reduced circulating and intracellular FXIII-A2B2 tetramer and/or reduced transglutaminase catalytic capacity, while the upstream coagulation cascade (thrombin generation, fibrinogen cleavage to fibrin monomer) proceeds entirely normally — explaining the normal PT/aPTT/TT that is the disorder's central diagnostic trap. (Demonstrated.)
3. During clot formation, thrombin (in the presence of Ca²⁺) still cleaves the FXIII-A activation peptide when substrate is present, but with insufficient functional FXIII-A, this fails to generate adequate active FXIIIa transglutaminase → failure of γ-glutamyl-ε-lysyl isopeptide cross-linking between fibrin γ-chains (dimerization) and α-chains (multimerization), and failure to cross-link α2-antiplasmin and fibronectin onto the fibrin network. (Demonstrated biochemically — Reactome "Common Pathway of Fibrin Clot Formation"; [PMID search: Protransglutaminase-mediated crosslinking of fibrinogen and fibrin, PMID:11816711].)
4. This results in an uncross-linked, mechanically weak, and fibrinolysis-susceptible clot — lacking the tensile strength, viscoelastic stability, and protection from plasmin-mediated degradation that cross-linking normally confers (the α2-antiplasmin cross-link specifically retards premature fibrinolysis). (Demonstrated — Understanding blood clot mechanical stability, 2025.)
5. Branch A — hemostatic plug failure: The friable clot leads to delayed/recurrent hemorrhage at sites of vascular injury — classically the umbilical stump (minimal trauma, high vascular turnover site), soft tissue, and mucosa — and, most seriously, intracranial vasculature, where clot instability results in spontaneous or minor-trauma-triggered intracranial hemorrhage, the leading cause of death and neurological morbidity in untreated severe disease. (Demonstrated clinically.)
6. Branch B — wound healing failure: FXIIIa normally cross-links fibrin with fibronectin and collagen in the provisional wound matrix to support fibroblast migration and re-epithelialization; its absence leads to delayed re-epithelialization and wound dehiscence. (Demonstrated in F13a1-knockout mice — Inbal et al., Thromb Haemost 2005;94:432–437, DOI:10.1160/TH05-04-0291: wound closure reduced 15%/27%/27% at days 4/8/11 vs. controls; complete closure by day 11 in controls vs. 73.2% in FXIII-deficient mice.)
7. Branch C — reproductive/placental failure: Maternal FXIII-A normally localizes to the maternal-fetal interface and is required, around gestational weeks 6–8, for fibrin-fibronectin cross-linking that forms the cytotrophoblastic shell and Nitabuch's layer, anchoring the placenta to the decidua; its absence leads to poorly formed cytotrophoblastic shells, placental detachment, and spontaneous miscarriage. (Demonstrated histologically in human gestational tissue from FXIII-deficient pregnancies, and recapitulated in F13a1-knockout mice, which develop severe uterine bleeding and spontaneous miscarriage — Koseki-Kuno et al., Blood 2003;102(13):4410–4412, DOI:10.1182/blood-2003-05-1467; human tissue study: Maternal Blood Coagulation Factor XIII...Cytotrophoblastic Shell.)
8. Upstream vs. downstream summary: The genetic lesion (step 1) and loss of catalytic activity (steps 2–4) are strictly upstream, shared across all clinical branches; steps 5–7 are parallel downstream branches determined by the anatomical site of hemostatic/structural demand (vascular injury site, wound bed, maternal-fetal interface) rather than by distinct molecular mechanisms.

Molecular pathways, processes, and profiling

• Pathway: Reactome "Common Pathway of Fibrin Clot Formation" (FXIII tetramer cleavage → FXIIIa → fibrin multimer cross-linking); candidate GO terms: GO:0003810 (protein-glutaminase gamma-glutamyltransferase activity — the core catalytic GO term for F13A1), GO:0007596 (blood coagulation), GO:0072378 (blood coagulation, fibrin clot formation), GO:0031639 (plasminogen activation) as a related/antagonized process.
• Cellular processes / cell types: FXIII-A is synthesized by megakaryocytes (CL:0000556) and stored in platelet (CL:0000233) α-granules/cytoplasm; also expressed in monocytes/macrophages (CL:0000576/CL:0000235). FXIII-B is synthesized by hepatocytes (CL:0000182). The placental mechanism implicates trophoblast (CL:0000351/CL:0000666 extravillous trophoblast) populations at the maternal-fetal interface.
• Protein structure/dysfunction: Predominantly simple loss of function via reduced protein stability/synthesis (Type I) or catalytic-site disruption (Type II); no prion-like aggregation or gain-of-function mechanism described.
• Subcellular localization: FXIII-A is a cytoplasmic transglutaminase lacking a classical secretory signal peptide; it reaches plasma via non-classical secretion from platelets/monocytes rather than conventional ER/Golgi trafficking — relevant GO Cellular Component candidate: GO:0005829 (cytosol).
• Non-hemostatic roles (beyond the classic pathograph): FXIII-A participates in macrophage function, innate immune regulation, angiogenesis, and broader extracellular-matrix cross-linking — reviewed in Factor XIII-A in Diseases: Role Beyond Blood Coagulation, PMC7867190.
• Omics/advanced technologies: No transcriptomic, proteomic, metabolomic, or single-cell/spatial datasets specific to FXIII-A deficiency were surfaced in this pass. This is flagged as an evidence gap rather than confirmed absence; GEO/Human Protein Atlas should be queried directly for F13A1 expression data if module-level curation requires it.

7. Anatomical Structures Affected

Organ level: - Primary: Skin/soft tissue (bruising, hematoma), umbilical cord stump (neonatal bleeding), central nervous system/brain (intracranial hemorrhage — most severe complication), female reproductive tract/placenta (pregnancy loss, postpartum hemorrhage), mucosal surfaces (nose, gingiva, GI tract). - Secondary: Joints (uncommon hemarthrosis, contrasting with hemophilia), muscle (intramuscular hematoma), surgical/wound sites generally (impaired healing, dehiscence). - Body systems: Hematologic (primary), integumentary, reproductive, nervous (via ICH), musculoskeletal (uncommon).

Tissue/cell level: Vascular endothelium and perivascular connective tissue at sites of hemorrhage; dermal/epidermal wound bed (impaired re-epithelialization); placental cytotrophoblast shell and decidual interface (Nitabuch's layer).

Subcellular level: Cytoplasmic localization of FXIII-A in platelets/monocytes (candidate GO:0005829 cytosol); no organelle-specific pathology (e.g., no mitochondrial or lysosomal component to this disease).

Anatomical term candidates (UBERON): umbilical cord (UBERON:0002331), brain (UBERON:0000955), placenta (UBERON:0001987), skin (UBERON:0002097), uterus (UBERON:0000995). (Candidates only — verify against OAK before binding.)

Lateralization: Not applicable — bleeding events are determined by site of trauma/vascular demand, not a lateralized anatomical predisposition.

8. Temporal Development

Onset: Severe congenital disease classically presents in the neonatal period with delayed umbilical stump bleeding occurring days to weeks after cord separation — described as potentially "the earliest manifestation," in up to 80% of affected neonates. Moderate/mild disease may remain asymptomatic until a hemostatic challenge (surgery, trauma, pregnancy) unmasks it.

Onset pattern: Typically insidious/chronic bleeding tendency punctuated by acute bleeding episodes, rather than a single acute presentation — though intracranial hemorrhage itself is an acute, life-threatening event.

Progression: Untreated severe disease follows a relapsing pattern of recurrent hemorrhagic events across the lifespan; intracranial hemorrhage specifically carries a ~30% recurrence rate, and ~50% of recurrences are fatal (StatPearls). With prophylactic replacement, the disease course is effectively stabilized.

Disease duration: Lifelong (congenital form); acquired immune-mediated disease may remit with immunosuppression and autoantibody clearance.

Critical periods: - Neonatal period — umbilical bleeding as sentinel event for diagnosis. - Gestational weeks 6–8 — cytotrophoblastic shell/Nitabuch's layer formation at the maternal-fetal interface is the specific developmental window in which FXIII-A deficiency precipitates early pregnancy loss. - Perioperative periods and late pregnancy/peripartum — periods of heightened hemostatic demand requiring dose escalation of replacement therapy.

9. Inheritance and Population

Epidemiology: - Prevalence of severe congenital FXIII deficiency: ~1 in 2–3 million live births globally (multiple concordant sources). - Iran: ~12-fold higher prevalence than the global estimate, attributed to consanguinity, with strong founder-effect clustering (Trp187Arg) in Sistan and Baluchestan Province. - Carrier frequency: ~1 in 1,000 individuals globally (heterozygotes), translating to an estimated ~7.5 million carriers worldwide. - No specific incidence (new-case) rate was identified distinct from birth prevalence — appropriate, since this is a congenital condition present from birth rather than one with a variable incident onset.

Inheritance pattern: Autosomal recessive.

Penetrance/expressivity: Phenotype severity correlates closely with residual FXIII activity level (severe <1%, moderate <30%, mild ≥30%), implying substantial genotype-phenotype correlation for biallelic null alleles, though no formal penetrance estimate (e.g., proportion of homozygotes who never bleed) was found in the sources retrieved.

Anticipation / germline mosaicism: No evidence of genetic anticipation (expected, as this is not a repeat-expansion disorder) or germline mosaicism specific to this condition was found.

Founder effects: Well documented — Trp187Arg (Iran/southeast Iran) is the clearest example, with a dedicated methodological paper on assessing founder effects in this disease (PMC7876424). Arg77Cys in the Swiss population is a secondary lead requiring independent verification.

Population demographics: - Sex ratio: Equal (autosomal recessive; no sex-linked modifier identified for the bleeding phenotype itself, though pregnancy-related morbidity is obviously female-specific). - Geographic distribution: Elevated prevalence wherever consanguinity rates are high — Iran most prominently; also historically documented clustering in other Middle Eastern and South Asian populations per the broader rare-bleeding-disorder literature (not independently itemized with PMIDs in this pass). - Age distribution: Severe cases are predominantly diagnosed in infancy/early childhood (umbilical bleeding, early ICH); moderate/mild cases may be diagnosed incidentally in adulthood (surgical bleeding, recurrent miscarriage workup) or remain undiagnosed.

10. Diagnostics

The central diagnostic principle: PT, aPTT, thrombin time, fibrinogen, and platelet count are all normal in FXIII deficiency, because FXIII acts after fibrin polymer formation. High clinical suspicion — especially with a history of delayed umbilical bleeding, consanguinity, family history, or unexplained recurrent miscarriage — is required to trigger specific testing.

Laboratory tests: 1. Clot solubility test (5 mol/L urea or 1% monochloroacetic acid) — the traditional screening test; simple and cheap but poor sensitivity/specificity, missing mild-to-moderate deficiency; increasingly regarded as obsolete/"deprecated" in current reviews (Altahan et al.; PMID:42682775 review). 2. Quantitative functional activity assays (preferred first-line): - Ammonia-release assay (e.g., Berichrom®, Technochrom®) — most widely used; FXIII activated by thrombin/Ca²⁺, liberated ammonia measured via glutamate dehydrogenase-coupled NADH oxidation at 340 nm; lower limit of quantification ~3–5%. - Isopeptidase/fluorogenic assay (Technofluor® FXIII Activity) — direct fluorescence from isopeptide bond cleavage. - Amine incorporation assay — high sensitivity but more time-consuming, and notably confounded by the Val34Leu polymorphism, which accelerates activation and can cause overestimation of activity in this assay type (ammonia-release assays are unaffected by Val34Leu). 3. Antigen assays (ELISA, latex agglutination, chemiluminescence) — distinguish Type I (concordant reduction in antigen and activity) from Type II (isolated activity reduction with preserved antigen), and differentiate FXIII-A–specific from FXIII-B–specific deficiency — directly relevant to treatment selection (see §12). 4. Inhibitor/mixing studies — 1:1 mixing of patient plasma with pooled normal plasma, activity measured immediately and after 1–2 h incubation at 37 °C, to distinguish deficiency from acquired autoantibody inhibition; ELISA detects non-neutralizing antibodies. 5. Preanalytical requirement: Platelet-poor plasma is essential, since platelet-associated FXIII-A can spuriously elevate apparent plasma activity. 6. Viscoelastic testing (TEG/ROTEM): Standard tracings reflect thrombin-driven fibrin formation and cannot reliably exclude clinically significant FXIII deficiency — an important limitation given the increasing point-of-care use of these assays.

Genetic testing: Targeted NGS panels covering F13A1 and F13B, with deletion/duplication analysis to capture structural variants and deep-intronic mutations, confirm a causative variant in the large majority (~95%) of congenital cases. Molecular confirmation has direct therapeutic implications (recombinant FXIII-A₂ is ineffective for F13B-driven disease — see §12).

Differential diagnosis: Afibrinogenemia/dysfibrinogenemia, hemophilia A/B, von Willebrand disease, platelet function disorders (Glanzmann thrombasthenia, Bernard-Soulier syndrome), and other rare factor deficiencies (FII, FV, FVII, FX, FXI) — all of which, unlike FXIII deficiency, typically show an abnormal screening coagulation profile.

Screening: FXIII deficiency is not part of standard newborn screening panels; diagnosis is case-finding, triggered by the clinical sentinel of delayed umbilical bleeding or a positive family history/consanguinity.

11. Outcome/Prognosis

Untreated severe congenital disease: - 66.7% experience a serious hemorrhagic event over their lifetime (StatPearls). - Intracranial hemorrhage is the primary cause of death; recurrence risk ~30%, with ~50% mortality per recurrence, and ~50% of survivors developing neurological sequelae.

With replacement prophylaxis: Patients receiving regular replacement therapy can expect life expectancy comparable to the general population (StatPearls), and prophylaxis is reported to essentially eliminate spontaneous and intracranial bleeding.

Quantified bleeding-rate outcomes (recombinant FXIII-A₂, Mentor™ trial series): - Monthly 35 IU/kg prophylaxis achieved an annualized bleeding rate (ABR) of 0.138, versus 2.91 with historical on-demand treatment (Mentor™1). - Mentor™2 long-term extension: ABR declined further to 0.043 (mean spontaneous ABR 0.011) over 186.5 patient-years.

Acquired immune-mediated deficiency: Carries a substantially worse near-term prognosis — ~25% mortality within the first year of diagnosis, reflecting both the typically older, comorbid patient population (median age ~75) and diagnostic delay.

Morbidity: Recurrent miscarriage (reproductive morbidity) and impaired wound healing (surgical/procedural morbidity) are the dominant non-fatal outcomes; both are reported to be "dramatically improved" with prophylactic treatment, though formal quality-of-life instrument data were not found in this search pass.

12. Treatment

Plasma-derived FXIII concentrate — Corifact (US) / Fibrogammin P (EU/other regions): contains both A and B subunits, making it effective regardless of whether the causative gene is F13A1 or F13B. Available in Europe since 1993; FDA-approved in the US as Corifact. Dosing: ~40 IU/kg initial/loading dose, maintenance dosing approximately every 28 days, titrated to a trough activity target of 5–20%. Half-life ~7–9 days.

Recombinant FXIII-A₂ (catridecacog) — Tretten (US) / NovoThirteen (EU), Novo Nordisk: FDA-approved December 2013 for routine prophylaxis in congenital FXIII A-subunit deficiency specifically; a homodimer of recombinant A subunits that binds endogenous B subunits in circulation; not effective for F13B-driven (B-subunit) deficiency. Monthly dosing 35 IU/kg; half-life ~11 days. Pediatric dosing validated down to age ≤6 years without age-based adjustment (Mentor™4 trial).

On-demand/perioperative therapy: 20–40 IU/kg targeting 20–30% activity for minor-to-moderate procedures, with proportionally higher targets for major surgery.

Bridge therapies (when concentrate unavailable): Fresh frozen plasma (~288 ± 77 IU/unit) and cryoprecipitate (~60 ± 30 IU/unit) — both have highly variable FXIII content between units/products and are regarded as second-line.

Pregnancy management: Early initiation (by 5 weeks' gestation in one described regimen); fortnightly or weekly dosing to maintain trough activity ≥10–20% through early/mid gestation, escalating to ≥30% in late pregnancy and peripartum; neuraxial anesthesia considered safe at ≥30% activity; tranexamic acid is emphasized for postpartum hemorrhage prevention; planned cesarean delivery is recommended in affected/potentially affected severe-deficiency pregnancies; multidisciplinary (obstetrics/hematology/anesthesia) management is recommended throughout.

Acquired immune-mediated deficiency: First-line immunosuppression with corticosteroids ± rituximab (response typically 4–8 weeks); cyclophosphamide or mycophenolate mofetil for non-responders; plasma exchange for short-term autoantibody removal in acute severe bleeding; FXIII replacement alongside immunosuppression; identification and treatment of the underlying trigger is emphasized as essential.

Anticoagulation co-management: No established guideline exists; a single case-report-level source (Bounaix et al., cited secondhand) suggests rivaroxaban may be used safely with adjusted FXIII replacement intensity (50% activity during anticoagulant loading, 30% maintenance, 20% prophylactic) — this is case-report-level evidence only and should be labeled as such, not as a guideline-supported approach.

Adverse effects: Both replacement products are generally well tolerated; reported adverse events (≥1%) include headache, leucopenia, joint inflammation, and skin reactions; rare serious events include hypersensitivity, thromboembolic complications, and (extremely rarely) neutralizing inhibitor development.

NCIT mapping candidates: NCIT:C15986 (Pharmacotherapy) as the generic treatment_term, with therapeutic_agent bound to the specific product — a dedicated NCIT code for catridecacog/Corifact was not confirmed in this search pass and should be looked up directly in the NCIT browser at curation time (candidate search term: "Factor XIII Concentrate" / "Catridecacog").

No gene therapy, cell therapy, or RNA-based therapeutics for this disorder were identified — protein replacement remains the entire therapeutic armamentarium; this is consistent with the disease being a straightforward enzyme-replacement-amenable deficiency rather than one requiring correction at the genomic/transcript level.

13. Prevention

Primary prevention: Genetic counseling for known carrier couples, particularly in consanguineous unions or communities with known founder mutations (e.g., Iranian populations with Trp187Arg); carrier testing is the principal actionable primary-prevention lever given the condition's Mendelian, fully recessive architecture.

Secondary prevention / early detection: No population-based newborn screening program exists for this condition; early detection instead relies on clinical vigilance for the sentinel sign of delayed umbilical stump bleeding, prompting targeted FXIII activity testing. Cascade testing of siblings/relatives of an index case is a reasonable extrapolation from general AR-disorder practice, though a specific citation for FXIII deficiency cascade-screening programs was not retrieved in this pass (flagged as a gap, not a negative finding).

Tertiary prevention: Regular prophylactic replacement therapy is the dominant tertiary-prevention strategy, directly preventing recurrent and spontaneous bleeding (including the life-threatening ICH complication) and improving obstetric outcomes in affected women.

Genetic counseling / prenatal options: Once a familial pathogenic variant is known, prenatal diagnosis (chorionic villus sampling or amniocentesis) is mechanistically feasible by standard molecular genetics practice for AR disorders — this specific application to FXIII deficiency was not independently documented by a retrieved source in this pass and should be treated as a reasonable inference pending direct literature confirmation rather than an established citation.

Immunization / public health / prophylactic medication beyond replacement therapy: Not applicable — this is not a disease with a vaccine-preventable or public-health-intervention-amenable etiology.

14. Other Species / Natural Disease

Naturally occurring disease in other species: - Japanese Black cattle — naturally occurring FXIII deficiency reported (cited in a 2026 comparative veterinary paper; primary citation not independently retrieved in this pass). - Domestic dog — a 2026 case report describes a 4-month-old male Black and Tan Coonhound presenting with spontaneous hemoperitoneum, thrombocytopenia, and persistent post-surgical bleeding, found to carry an F13A1 frameshift (deletion-insertion) variant producing a premature stop codon; viscoelastic testing showed reduced clot firmness and enhanced fibrinolysis in high-urea conditions suggestive of FXIII deficiency (PMID:42184124 / PMC13200534). Search results explicitly note this is the first well-characterized canine case and did not identify a Dachshund-specific founder condition, despite that breed association appearing plausible a priori — do not assume a Dachshund-specific form without further verification.

Comparative biology: The transglutaminase cross-linking mechanism and thrombin-dependent activation are conserved across mammalian species studied (human, mouse, cattle, dog), consistent with FXIII's role as a terminal, highly conserved step of the coagulation cascade.

Orthologous genes: Mouse F13a1 (MGI:1921395); rat F13a1 (RGD:621495 / RGD:732286 per search results — two RGD entries appeared, requiring disambiguation at curation time).

Zoonotic potential: Not applicable — this is a non-infectious, genetically determined disorder with no cross-species transmission mechanism.

15. Model Organisms

Primary model: F13a1-knockout mouse - Original line: Targeted inactivation of the mouse F13a1 locus (deletion of exon 7), establishing hemostatic abnormalities and characterizing the coagulation deficit — Lauer et al., PMID:12529747. - Reproductive phenotype: F13a1-deficient female mice develop severe uterine bleeding events and subsequent spontaneous miscarriages, directly recapitulating the human reproductive phenotype and supporting the cytotrophoblastic-shell mechanism described in §6 — Koseki-Kuno et al., Blood 2003;102(13):4410–4412, DOI:10.1182/blood-2003-05-1467. - Wound-healing phenotype: Knockout mice show delayed wound closure (15%, 27%, 27% reductions at days 4, 8, 11 vs. controls; 73.2% vs. 100% closure by day 11) with histologic evidence of delayed re-epithelialization and necrotized fissures, rescued by exogenous FXIII treatment (90.1% closure by day 11 in treated knockouts) — Inbal et al., Thromb Haemost 2005;94:432–437, DOI:10.1160/TH05-04-0291. - Other reported phenotypes in this model: impaired clot retraction (Impaired clot retraction in FXIII A subunit–deficient mice, Blood 115(6):1277); aggravated cardiac rupture and impaired post-infarct wound healing/remodeling in a myocardial infarction model (Circulation 2006, PMC4066325) — relevant to FXIII's broader tissue-repair role (§6) rather than to the bleeding-disorder phenotype per se; metabolic phenotype (signs of "metabolically healthy obesity" on high-fat diet) has also been reported, indicating pleiotropic non-hemostatic roles (Sci Rep 2016, srep35574). - Phenotype recapitulation assessment: The mouse model recapitulates the two best-characterized human mechanistic branches (reproductive loss, impaired wound healing) with good fidelity, including a histological and functional correlate of the human cytotrophoblastic-shell defect. Limitation: the model's relevance to the intracranial hemorrhage phenotype — arguably the most clinically important human complication — was not specifically described in the sources retrieved in this pass; this should be checked directly against the primary mouse-model literature before treating ICH as "recapitulated" in any computational-model link.

Resource: IMPC/MGI phenotype data for F13a1 (MGI:1921395) is available via mousephenotype.org for further systematic phenotype mining.

Other model systems (zebrafish, Drosophila, C. elegans, iPSC/organoid): None were identified in this search pass. Given that FXIII-mediated fibrin cross-linking is a vertebrate-coagulation-specific mechanism, invertebrate models are mechanistically implausible; no evidence of a zebrafish or iPSC-derived model was found, and this is reported as an absence of retrieved evidence, not a confirmed non-existence.

Summary of Evidence Gaps (flagged explicitly per attribution discipline)

1. MONDO ID discrepancy between the brief (MONDO:0013187) and what search results return (MONDO:0018029) — resolve against the ontology directly.
2. No gnomAD-level allele-frequency table for specific pathogenic F13A1 variants was retrieved.
3. No epigenetic (DNA methylation/histone) data specific to this disease were found.
4. No formal QoL-instrument (EQ-5D/SF-36) data specific to FXIII deficiency were found.
5. No transcriptomic/proteomic/single-cell dataset specific to this disease was retrieved.
6. Prenatal diagnosis practice (CVS/amniocentesis) for FXIII deficiency specifically is inferred from general AR-disorder practice, not directly documented in a retrieved source.
7. The Swiss Arg77Cys founder-variant claim and several individual ClinVar accession numbers are search-engine-summarized leads, not independently verified against primary ClinVar/literature records.
8. Mouse-model fidelity for the intracranial hemorrhage phenotype specifically was not addressed in the sources reviewed.

Sources (primary links retrieved in this research pass)

• OMIM *134570 — F13A1
• OMIM #613225 — Factor XIII, A Subunit, Deficiency Of
• Orphanet ORPHA331 — Congenital factor XIII deficiency
• StatPearls — Factor XIII Deficiency, NBK557467
• StatPearls — Physiology, Factor XIII, NBK538271
• Altahan et al., "Factor XIII Deficiency: A Review of Biology, Testing, and Treatment," PMID:41583548 (PMC12825037)
• PMID:42682775, Frontiers in Medicine 2026 — diagnosis and management update (PMC13530902)
• PMID:11826242 — Delayed umbilical bleeding as presenting feature
• Lauer et al., PMID:12529747 — Targeted inactivation of mouse F13a1
• Koseki-Kuno et al., Blood 2003;102(13):4410 — uterine bleeding/miscarriage in F13a1-deficient mice
• Inbal et al., Thromb Haemost 2005;94:432 — impaired wound healing in FXIII-deficient mice
• PMID:34506591 — HLA associations in autoimmune FXIII deficiency (PMC8432773)
• PMID:42184124 — F13A1 frameshift variant in a Coonhound dog (PMC13200534)
• How to Assess Founder Effect in Congenital FXIII Deficiency, PMC7876424
• Molecular Basis of Congenital FXIII Deficiency in Iran, PMC6714674
• Factor XIII-A in Diseases: Role Beyond Blood Coagulation, PMC7867190
• GeneCards — F13A1
• MGI — F13a1, MGI:1921395
• MalaCards — Factor XIII Deficiency

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

• PMID:11816711 (abstract only): "Common Pathway of Fibrin Clot Formation"
• closest text in source: "Thus, factor XIII displays constitutive enzymatic activity with respect to fibrinogen and fibrin"

Term Validation

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

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:0013187 (3 mentions) - the report calls it "MONDO ID discrepancy between the brief"; MONDO calls it factor XIII, A subunit, deficiency of**

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:

• GO:0003810 (1 mention) - the report calls it "protein-glutaminase gamma-glutamyltransferase activity — the core catalytic GO term for F13A1"; GO calls it protein-glutamine gamma-glutamyltransferase activity

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: MGI, RGD.