Hepatic Fibrinogen Storage Disease

Genetic MONDO:0018060 Pathograph 15 Show in embeddings browser Congenital Fibrinogen Disorder Coagulation Disorder Genetic Liver Disease

Hepatic fibrinogen storage disease (HFSD; also called hereditary hypofibrinogenemia with hepatic storage, HHHS) is an ultra-rare autosomal dominant endoplasmic-reticulum (ER) storage disease caused by heterozygous missense mutations in the C-terminal globular gamma module of the fibrinogen gamma-chain gene (FGG). Unlike simple (Type I) hypofibrinogenemia, which is a loss-of-function defect with a structurally normal liver, HFSD is a toxic gain-of-function disorder: the mutant fibrinogen is assembled but cannot be secreted, polymerizes, and aggregates within the hepatocyte ER as characteristic eosinophilic inclusions. The resulting proteotoxic ER stress drives hepatocyte injury, stellate-cell activation, and liver disease of highly variable severity (ranging from isolated transaminase elevation to cirrhosis), while the secondary hypofibrinogenemia is usually mild and rarely causes bleeding. Mechanistically it is closely analogous to the hepatic phenotype of alpha-1 antitrypsin deficiency.

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1
Inheritance
8
Pathophys.
6
Phenotypes
15
Pathograph
1
Genes
2
Medical Actions
3
References
1
Deep Research
👪

Inheritance

1
Autosomal dominant inheritance HP:0000006
HFSD is transmitted as an autosomal dominant trait; all reported FGG storage mutations occur in the heterozygous state. Penetrance is incomplete and expressivity is highly variable: carriers of the same FGG mutation within a single family may range from clinically unaffected (normal liver function and coagulation) to overt liver disease, implicating additional genetic (e.g., protein-degradation-pathway) or environmental modifiers.
Autosomal dominant inheritance Penetrance: INCOMPLETE Expressivity: VARIABLE
Show evidence (3 references)
PMID:33105716 SUPPORT Human Clinical
"In all cases, mutations have been reported in the heterozygous state, supporting the idea that HHHS is an autosomal dominant trait"
The review establishes the autosomal dominant, heterozygous mode of inheritance for HFSD.
PMID:31965886 SUPPORT Human Clinical
"sister and mother had normal findings in liver function and coagulation tests, although they harbored the same heterozygous mutation within the FGG gene"
Unaffected relatives carrying the same heterozygous FGG mutation as the proband demonstrate incomplete penetrance and variable expressivity.
PMID:33105716 SUPPORT Human Clinical
"patients display a tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis, with severe clinical pictures that can be present even in children"
The review documents the wide, variable range of liver-disease severity, supporting variable expressivity.
⚙

Pathophysiology

8
Mutant Fibrinogen Gamma-Chain Production
Heterozygous missense mutations clustered in exons 8 and 9 of FGG, encoding the highly conserved C-terminal globular gamma module, produce a conformationally destabilized fibrinogen gamma chain. Recurrent named variants include Aguadilla, Brescia, Angers, Beograd, Ankara, and Pisa, with Aguadilla (FGG p.Arg401Trp) being the most common variant worldwide; mutations are dominant and have only been observed in the heterozygous state. In-silico protein-stability (delta-delta-G) analysis indicates the mutations destabilize the gamma module and cluster near the dimerization interface, favoring aberrant polymerization.
FGG hgnc:3694
Downstream
Hepatocellular ER Fibrinogen Aggregation The destabilized mutant gamma chain assembles into hexameric fibrinogen that cannot be secreted and instead polymerizes and aggregates within the hepatocyte endoplasmic reticulum.
Show evidence (6 references)
PMID:33105716 SUPPORT Human Clinical
"The genetic basis of HHHS are exclusively represented by mutations located in exons 8 and 9 of the FGG gene"
The review localizes the causative mutations to exons 8 and 9 of FGG.
PMID:33105716 SUPPORT Human Clinical
"In all cases, mutations have been reported in the heterozygous state, supporting the idea that HHHS is an autosomal dominant trait"
The review establishes the autosomal dominant, heterozygous nature of the FGG storage mutations.
PMID:33105716 SUPPORT Human Clinical
"According to the custom, fibrinogen defects have been named after the city where the proband was coming from."
The review explains the city-based naming convention for the recurrent FGG storage variants (e.g., Aguadilla, Brescia).
+ 3 more references
Hepatocellular ER Fibrinogen Aggregation
The mutant fibrinogen retains its ability to polymerize but is secretion- incompetent, so it accumulates as densely packed aggregates in the dilated cisternae of the rough ER, seen histologically as circular eosinophilic intracytoplasmic inclusion bodies that are immunoreactive for fibrinogen. Diagnostically, the inclusions do not stain with the periodic acid-Schiff (PAS) technique after diastase digestion and immunostain positively for fibrinogen but negatively for alpha-1-antitrypsin, distinguishing HFSD from alpha-1 antitrypsin deficiency. Spontaneous ER aggregation of variant fibrinogen is the central pathogenic event of HFSD, paralleling Z-AAT retention in alpha-1 antitrypsin deficiency.
hepatocyte CL:0000182
Downstream
ER Stress and Impaired Proteostasis The intracellular polymer burden imposes proteotoxic stress on the hepatocyte ER and overwhelms autophagic clearance.
Secondary Hypofibrinogenemia Retention of mutant fibrinogen impairs secretion, lowering circulating fibrinogen.
Show evidence (5 references)
PMID:33105716 SUPPORT Human Clinical
"it is usually determined by heterozygous mutations leading to an impaired secretion of the mutant fibrinogen, which however maintains its ability to polymerize and aggregates spontaneously within the ER of hepatocytes."
The review describes the secretion-incompetent, spontaneously polymerizing mutant fibrinogen aggregating in the hepatocyte ER.
PMID:33105716 SUPPORT Human Clinical
"Rare cases of hypofibrinogenemia are associated with liver disease, which is caused by the accumulation of mutant fibrinogens within hepatic cells."
The review attributes the liver disease of HFSD to intrahepatic accumulation of mutant fibrinogen.
PMID:31965886 SUPPORT Human Clinical
"Liver biopsy showed circular eosinophil inclusion bodies in the hepato-cytoplasm."
The case report documents the defining hepatocellular eosinophilic inclusion histopathology.
+ 2 more references
ER Stress and Impaired Proteostasis
Accumulated fibrinogen polymers trigger the endoplasmic-reticulum stress response and unfolded protein response. Autophagy is the principal pathway for intracellular clearance of the aggregated fibrinogen, and concomitant defects in protein-degradation pathways are thought to modify whether overt liver disease develops.
hepatocyte CL:0000182
response to endoplasmic reticulum stress GO:0034976 endoplasmic reticulum unfolded protein response GO:0030968 autophagy GO:0006914
Downstream
Hepatocyte Injury Sustained ER stress and polymer burden drive hepatocyte injury.
Show evidence (3 references)
PMID:33105716 SUPPORT Human Clinical
"point to autophagy as the main pathway responsible for intracellular fibrinogen clearance"
The review identifies autophagy as the principal route for clearing intracellular mutant fibrinogen.
PMID:33105716 SUPPORT In Vitro
"cleared by selective autophagy in human liver carcinoma cells (HepG2)"
In human HepG2 hepatoma cells, surplus fibrinogen assembly intermediates are cleared by selective autophagy, the in-vitro basis for autophagy as the clearance route for stored fibrinogen.
PMID:33105716 SUPPORT Model Organism
"mutant fibrinogen degradation was shown to be associated with both an ER-associated clearance and autophagy in yeast"
In a yeast model, mutant fibrinogen is degraded via both ER-associated clearance and autophagy, supporting the proteostatic-clearance mechanism and its candidate modifier genes.
Hepatocyte Injury
Chronic proteotoxic ER stress and the intracellular polymer burden injure hepatocytes, producing a clinically variable liver picture that ranges from no histologic injury through mild/moderate involvement to cirrhosis, with severe disease sometimes occurring even in children. The repeated cycle of hepatocyte death and regeneration provides the pro-fibrotic stimulus that activates resident hepatic mesenchyme.
hepatocyte CL:0000182
liver UBERON:0002107
Downstream
Hepatic Stellate Cell Activation The cycle of hepatocyte death and regeneration provides the pro-fibrotic stimulus that paracrine-activates hepatic stellate cells.
Elevated Hepatic Transaminases Hepatocyte injury releases hepatic transaminases into circulation.
Hepatomegaly Chronic hepatocellular storage and injury can enlarge the liver.
Show evidence (2 references)
PMID:33105716 SUPPORT Human Clinical
"The storage is exclusively related to the mutant protein, whose accumulation in the ER strongly predisposes to the development of chronic liver disease of variable severity, both in children and adults"
The review links ER accumulation of mutant fibrinogen to chronic liver disease of variable severity in children and adults.
PMID:33105716 SUPPORT Human Clinical
"patients display a tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis, with severe clinical pictures that can be present even in children"
The review documents the wide spectrum of liver involvement, up to cirrhosis, including in children.
Hepatic Stellate Cell Activation
Injury-derived pro-fibrotic signaling, including the conserved TGF-beta/Smad axis shared across organ fibrosis, activates hepatic stellate cells and drives their transdifferentiation into collagen-secreting myofibroblasts. This is the organ-specific instance of the conserved fibrotic_response mesenchymal-activation step, with hepatic stellate cells substituting for the generic fibroblast precursor.
hepatic stellate cell CL:0000632 myofibroblast cell CL:0000186
transforming growth factor beta receptor signaling pathway GO:0007179 ↑ INCREASED
liver UBERON:0002107
Downstream
Excessive Hepatic ECM Deposition Activated hepatic stellate cells and myofibroblasts drive excess extracellular matrix deposition.
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"patients display a tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis, with severe clinical pictures that can be present even in children"
The review documents that HFSD progresses through mild/moderate liver fibrosis to cirrhosis, the hepatic manifestation of stellate-cell-driven fibrogenesis; the conserved TGF-beta/Smad activation axis is inherited from the fibrotic_response module via conforms_to (the module carries the mechanistic evidence for that conserved signaling step).
Excessive Hepatic ECM Deposition
Collagen-secreting hepatic myofibroblasts deposit excessive collagen and other extracellular matrix while suppressing matrix degradation, progressively distorting hepatic architecture and producing the fibrosis and cirrhosis that define severe HFSD liver disease.
myofibroblast cell CL:0000186
extracellular matrix organization GO:0030198 ↑ INCREASED collagen biosynthetic process GO:0032964 ↑ INCREASED collagen fibril organization GO:0030199 ↑ INCREASED
liver UBERON:0002107
Downstream
Hepatic Fibrosis Progressive extracellular matrix accumulation manifests clinically as hepatic fibrosis.
Cirrhosis Sustained matrix deposition and architectural distortion progress to cirrhosis in the most severe cases.
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis"
The review documents progressive matrix accumulation manifesting as mild/moderate liver fibrosis up to cirrhosis, the structural endpoint of excessive hepatic ECM deposition.
Secondary Hypofibrinogenemia
Because mutant fibrinogen is retained intrahepatically rather than secreted, circulating fibrinogen is reduced. This hypofibrinogenemia is a downstream consequence of impaired secretion rather than the primary disease mechanism, distinguishing HFSD from simple quantitative fibrinogen deficiency.
hepatocyte CL:0000182
Downstream
Subclinical Coagulation Abnormality Reduced circulating fibrinogen mildly prolongs clot-based coagulation assays.
Hypofibrinogenemia Retention of mutant fibrinogen in hepatocytes lowers secreted circulating fibrinogen.
Hypo-apolipoprotein B Proteinemia Co-retention of apolipoprotein B with fibrinogen storage inclusions can lower circulating apolipoprotein B.
Show evidence (1 reference)
PMID:31965886 SUPPORT Human Clinical
"Hepatic fibrinogen storage disease is a rare autosomal dominant genetic disorder characterized by hypofibrinogenemia, as well as the retention of variant fibrinogen within the hepatocellular endoplasmic reticulum."
The case report defines HFSD by the combination of hypofibrinogenemia and hepatocellular ER retention of variant fibrinogen.
Subclinical Coagulation Abnormality
Despite reduced fibrinogen and prolonged coagulation parameters, HFSD patients characteristically do not have a clinically significant bleeding tendency; the liver is the principal target organ of the FGG mutation.
blood coagulation GO:0007596
Show evidence (2 references)
PMID:33105716 SUPPORT Human Clinical
"Concerning the coagulopathy, HHHS patients usually show prolonged coagulation parameters (Table 1) but no hemorrhagic manifestations nor abnormal wound healing."
The review reports prolonged coagulation parameters without hemorrhagic manifestations in HHHS.
PMID:31965886 SUPPORT Human Clinical
"the target organ affected by the mutation within the FGG gene may be the liver; coagulation or bleeding disorders may not occur in affected patients"
The case report concludes that the liver, rather than the hemostatic system, is the target organ of the FGG mutation, so overt coagulation or bleeding disorders typically do not occur.
⬡

Pathograph

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

Phenotypes

6
Digestive 3
Hepatic Fibrosis Hepatic fibrosis HP:0001395
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis"
The review documents hepatic fibrosis within the disease's variable liver-injury spectrum.
Cirrhosis OCCASIONAL Cirrhosis HP:0001394
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"up to cirrhosis, with severe clinical pictures that can be present even in children"
The review documents progression to cirrhosis, sometimes in childhood, within the HHHS liver-disease spectrum.
Hepatomegaly Hepatomegaly HP:0002240
Severity: MILD
Show evidence (1 reference)
PMID:31965886 SUPPORT Human Clinical
"Abdominal ultrasonography showed mild hepatomegaly."
The case report documents mild hepatomegaly on abdominal ultrasonography in an asymptomatic child with HFSD.
Metabolism 1
Elevated Hepatic Transaminases Elevated circulating hepatic transaminase concentration HP:0002910
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"It is associated with mild and intermittent hypertransaminasemia"
The review identifies mild, intermittent transaminase elevation as the characteristic biochemical feature.
Other 2
Hypofibrinogenemia Hypofibrinogenemia HP:0011900
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"a disorder characterized by protein aggregation in the endoplasmic reticulum, hypofibrinogenemia, and liver disease of variable severity"
The review lists hypofibrinogenemia as one of the defining features of the disorder.
Hypo-apolipoprotein B Proteinemia Decreased circulating apolipoprotein B concentration HP:0034075
Show evidence (2 references)
PMID:33105716 SUPPORT Human Clinical
"HHHS has been associated with hypo-apo-β (APOB) proteinemia in several cases"
The review reports an association between HHHS and hypo-apo-β (APOB) proteinemia in several cases.
PMID:33105716 SUPPORT Human Clinical
"who were demonstrated to simultaneously accumulate fibrinogen and APOB in the same ER liver inclusions"
The review documents that fibrinogen and APOB co-accumulate within the same hepatocellular ER inclusions, the mechanistic basis for the secondary hypo-APOB proteinemia; the absence of APOB/MTTP mutations in these patients indicates it is secondary to the FGG defect.
🧬

Genetic Associations

1
FGG (Causative)
Gene: FGG hgnc:3694
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"The genetic basis of HHHS are exclusively represented by mutations located in exons 8 and 9 of the FGG gene"
The review establishes FGG as the exclusive causative gene for HFSD.
💊

Medical Actions

2
Carbamazepine and Ursodeoxycholic Acid
Action: Pharmacotherapy NCIT:C15986
Agent: carbamazepine CHEBI:3387 ursodeoxycholic acid CHEBI:9907
Carbamazepine, an autophagy enhancer, combined with ursodeoxycholic acid has been reported to reduce aggregate-related hepatotoxicity and normalize transaminases in HFSD; supporting evidence is limited to case-level experience.
Show evidence (2 references)
PMID:33105716 SUPPORT Human Clinical
"Data on medical management of HHHS are sparse; carbamazepine (CBZ) and ursodeoxycholic acid (UDCA) have been demonstrated to be beneficial in some cases"
The review identifies carbamazepine and ursodeoxycholic acid as the reported, sparsely evidenced disease-directed management.
PMID:33105716 SUPPORT Human Clinical
"This drug is a well-tolerated anticonvulsive treatment, known to enhance autophagy, and its efficacy seems to be related to the normalization of ALT levels"
The review explains the mechanistic rationale for carbamazepine (autophagy enhancement) and its observed normalization of transaminases.
Supportive Care and Monitoring
Action: supportive care MAXO:0000950
Most patients require monitoring of liver function and fibrinogen rather than active intervention; fibrinogen supplementation is reserved for the rare bleeding or perioperative situations.
Show evidence (1 reference)
PMID:36055263 SUPPORT Human Clinical
"Fibrinogen supplementation is the cornerstone of bleeding management in fibrinogen disorders."
The review identifies fibrinogen supplementation as the mainstay only of bleeding management, which is rarely needed in HFSD.
{ }

Source YAML

click to show 
name: Hepatic Fibrinogen Storage Disease
creation_date: '2026-05-16T00:00:00Z'
updated_date: '2026-05-16T00:00:00Z'
category: Genetic
parents:
- Congenital Fibrinogen Disorder
- Coagulation Disorder
- Genetic Liver Disease
disease_term:
  preferred_term: hepatic fibrinogen storage disease
  term:
    id: MONDO:0018060
    label: congenital fibrinogen deficiency
description: >-
  Hepatic fibrinogen storage disease (HFSD; also called hereditary
  hypofibrinogenemia with hepatic storage, HHHS) is an ultra-rare autosomal
  dominant endoplasmic-reticulum (ER) storage disease caused by heterozygous
  missense mutations in the C-terminal globular gamma module of the fibrinogen
  gamma-chain gene (FGG). Unlike simple (Type I) hypofibrinogenemia, which is a
  loss-of-function defect with a structurally normal liver, HFSD is a toxic
  gain-of-function disorder: the mutant fibrinogen is assembled but cannot be
  secreted, polymerizes, and aggregates within the hepatocyte ER as
  characteristic eosinophilic inclusions. The resulting proteotoxic ER stress
  drives hepatocyte injury, stellate-cell activation, and liver disease of
  highly variable severity (ranging from isolated transaminase elevation to
  cirrhosis), while the secondary hypofibrinogenemia is usually mild and rarely
  causes bleeding. Mechanistically it is closely analogous to the hepatic
  phenotype of alpha-1 antitrypsin deficiency.
prevalence:
- population: General population
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    HFSD is ultra-rare. Only a small number of molecularly characterized
    families have been reported worldwide, and analyses of large public genomic
    databases have failed to detect the known FGG storage mutations,
    consistent with an ultra-rare (in the EU, <2:100,000) disorder that is
    probably also underdiagnosed.
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "strongly suggests that HHHS is an ultra-rare disease"
    explanation: >-
      The review's interrogation of public genomic databases concludes that
      HHHS is an ultra-rare disorder.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "To date, only 21 index cases characterized at the molecular level"
    explanation: >-
      The review quantifies the very small number of molecularly characterized
      HHHS index cases, underscoring its rarity.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "only 27 affected individuals from 17 families have been reported worldwide"
    explanation: >-
      A 2020 case report independently tallies the total reported world
      literature at 27 affected individuals from 17 families, corroborating the
      disorder's rarity.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "HFSD is presumably an underdiagnosed condition and its prevalence may be underestimated."
    explanation: >-
      The case report notes that HFSD is probably underdiagnosed, so reported
      prevalence likely underestimates the true frequency.
pathophysiology:
- name: Mutant Fibrinogen Gamma-Chain Production
  description: >-
    Heterozygous missense mutations clustered in exons 8 and 9 of FGG, encoding
    the highly conserved C-terminal globular gamma module, produce a
    conformationally destabilized fibrinogen gamma chain. Recurrent named
    variants include Aguadilla, Brescia, Angers, Beograd, Ankara, and Pisa,
    with Aguadilla (FGG p.Arg401Trp) being the most common variant worldwide;
    mutations are dominant and have only been observed in the heterozygous
    state. In-silico protein-stability (delta-delta-G) analysis indicates the
    mutations destabilize the gamma module and cluster near the dimerization
    interface, favoring aberrant polymerization.
  genes:
  - preferred_term: FGG
    term:
      id: hgnc:3694
      label: FGG
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The genetic basis of HHHS are exclusively represented by mutations located in exons 8 and 9 of the FGG gene"
    explanation: >-
      The review localizes the causative mutations to exons 8 and 9 of FGG.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In all cases, mutations have been reported in the heterozygous state, supporting the idea that HHHS is an autosomal dominant trait"
    explanation: >-
      The review establishes the autosomal dominant, heterozygous nature of the
      FGG storage mutations.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "According to the custom, fibrinogen defects have been named after the city where the proband was coming from."
    explanation: >-
      The review explains the city-based naming convention for the recurrent
      FGG storage variants (e.g., Aguadilla, Brescia).
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Aguadilla appears to be the most common mutation worldwide (with a total of 12 described index cases)"
    explanation: >-
      The review identifies Aguadilla as the most common HHHS-causing FGG
      variant worldwide.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a heterozygous missense mutation c.1201C > T (p. Arg401Trp)"
    explanation: >-
      The case report defines the Aguadilla variant at the molecular level as
      the heterozygous FGG missense mutation c.1201C>T (p.Arg401Trp).
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "all mutations cluster near the interface of dimerization, thus reinforcing the notion that they can play a fundamental role in the polymerization process"
    explanation: >-
      In-silico modeling shows the FGG storage mutations cluster near the
      dimerization interface, supporting a role in aberrant polymerization.
  downstream:
  - target: Hepatocellular ER Fibrinogen Aggregation
    description: >-
      The destabilized mutant gamma chain assembles into hexameric fibrinogen
      that cannot be secreted and instead polymerizes and aggregates within the
      hepatocyte endoplasmic reticulum.
- name: Hepatocellular ER Fibrinogen Aggregation
  description: >-
    The mutant fibrinogen retains its ability to polymerize but is secretion-
    incompetent, so it accumulates as densely packed aggregates in the dilated
    cisternae of the rough ER, seen histologically as circular eosinophilic
    intracytoplasmic inclusion bodies that are immunoreactive for fibrinogen.
    Diagnostically, the inclusions do not stain with the periodic acid-Schiff
    (PAS) technique after diastase digestion and immunostain positively for
    fibrinogen but negatively for alpha-1-antitrypsin, distinguishing HFSD from
    alpha-1 antitrypsin deficiency. Spontaneous ER aggregation of variant
    fibrinogen is the central pathogenic event of HFSD, paralleling Z-AAT
    retention in alpha-1 antitrypsin deficiency.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "it is usually determined by heterozygous mutations leading to an impaired secretion of the mutant fibrinogen, which however maintains its ability to polymerize and aggregates spontaneously within the ER of hepatocytes."
    explanation: >-
      The review describes the secretion-incompetent, spontaneously
      polymerizing mutant fibrinogen aggregating in the hepatocyte ER.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rare cases of hypofibrinogenemia are associated with liver disease, which is caused by the accumulation of mutant fibrinogens within hepatic cells."
    explanation: >-
      The review attributes the liver disease of HFSD to intrahepatic
      accumulation of mutant fibrinogen.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Liver biopsy showed circular eosinophil inclusion bodies in the hepato-cytoplasm."
    explanation: >-
      The case report documents the defining hepatocellular eosinophilic
      inclusion histopathology.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Following pretreatment with diastase, the inclusion bodies failed to stain with the periodic acid-Schiff technique; moreover, immunostaining results were positive for fibrinogen, but negative for alpha-1-antitrypsin"
    explanation: >-
      The case report establishes the diagnostic staining profile of the
      inclusions: diastase-resistant, PAS-negative, fibrinogen-positive, and
      alpha-1-antitrypsin-negative, distinguishing HFSD from alpha-1 antitrypsin
      deficiency.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ERSDs comprise alpha-1-antitrypsin, fibrinogen, and alpha-1-antichymotrypsin deficiencies"
    explanation: >-
      The review groups HFSD with alpha-1-antitrypsin deficiency among the ER
      storage diseases, supporting the mechanistic analogy.
  downstream:
  - target: ER Stress and Impaired Proteostasis
    description: >-
      The intracellular polymer burden imposes proteotoxic stress on the
      hepatocyte ER and overwhelms autophagic clearance.
  - target: Secondary Hypofibrinogenemia
    description: >-
      Retention of mutant fibrinogen impairs secretion, lowering circulating
      fibrinogen.
- name: ER Stress and Impaired Proteostasis
  description: >-
    Accumulated fibrinogen polymers trigger the endoplasmic-reticulum stress
    response and unfolded protein response. Autophagy is the principal pathway
    for intracellular clearance of the aggregated fibrinogen, and concomitant
    defects in protein-degradation pathways are thought to modify whether overt
    liver disease develops.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  biological_processes:
  - preferred_term: response to endoplasmic reticulum stress
    term:
      id: GO:0034976
      label: response to endoplasmic reticulum stress
  - preferred_term: endoplasmic reticulum unfolded protein response
    term:
      id: GO:0030968
      label: endoplasmic reticulum unfolded protein response
  - preferred_term: autophagy
    term:
      id: GO:0006914
      label: autophagy
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "point to autophagy as the main pathway responsible for intracellular fibrinogen clearance"
    explanation: >-
      The review identifies autophagy as the principal route for clearing
      intracellular mutant fibrinogen.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "cleared by selective autophagy in human liver carcinoma cells (HepG2)"
    explanation: >-
      In human HepG2 hepatoma cells, surplus fibrinogen assembly intermediates
      are cleared by selective autophagy, the in-vitro basis for autophagy as
      the clearance route for stored fibrinogen.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "mutant fibrinogen degradation was shown to be associated with both an ER-associated clearance and autophagy in yeast"
    explanation: >-
      In a yeast model, mutant fibrinogen is degraded via both ER-associated
      clearance and autophagy, supporting the proteostatic-clearance mechanism
      and its candidate modifier genes.
  downstream:
  - target: Hepatocyte Injury
    description: >-
      Sustained ER stress and polymer burden drive hepatocyte injury.
- name: Hepatocyte Injury
  description: >-
    Chronic proteotoxic ER stress and the intracellular polymer burden injure
    hepatocytes, producing a clinically variable liver picture that ranges from
    no histologic injury through mild/moderate involvement to cirrhosis, with
    severe disease sometimes occurring even in children. The repeated cycle of
    hepatocyte death and regeneration provides the pro-fibrotic stimulus that
    activates resident hepatic mesenchyme.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The storage is exclusively related to the mutant protein, whose accumulation in the ER strongly predisposes to the development of chronic liver disease of variable severity, both in children and adults"
    explanation: >-
      The review links ER accumulation of mutant fibrinogen to chronic liver
      disease of variable severity in children and adults.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients display a tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis, with severe clinical pictures that can be present even in children"
    explanation: >-
      The review documents the wide spectrum of liver involvement, up to
      cirrhosis, including in children.
  downstream:
  - target: Hepatic Stellate Cell Activation
    description: >-
      The cycle of hepatocyte death and regeneration provides the pro-fibrotic
      stimulus that paracrine-activates hepatic stellate cells.
  - target: Elevated Hepatic Transaminases
    description: >-
      Hepatocyte injury releases hepatic transaminases into circulation.
  - target: Hepatomegaly
    description: >-
      Chronic hepatocellular storage and injury can enlarge the liver.
- name: Hepatic Stellate Cell Activation
  conforms_to: fibrotic_response#Mesenchymal Cell Activation
  description: >-
    Injury-derived pro-fibrotic signaling, including the conserved
    TGF-beta/Smad axis shared across organ fibrosis, activates hepatic stellate
    cells and drives their transdifferentiation into collagen-secreting
    myofibroblasts. This is the organ-specific instance of the conserved
    fibrotic_response mesenchymal-activation step, with hepatic stellate cells
    substituting for the generic fibroblast precursor.
  cell_types:
  - preferred_term: hepatic stellate cell
    term:
      id: CL:0000632
      label: hepatic stellate cell
  - preferred_term: myofibroblast cell
    term:
      id: CL:0000186
      label: myofibroblast cell
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  biological_processes:
  - preferred_term: transforming growth factor beta receptor signaling pathway
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
    modifier: INCREASED
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients display a tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis, with severe clinical pictures that can be present even in children"
    explanation: >-
      The review documents that HFSD progresses through mild/moderate liver
      fibrosis to cirrhosis, the hepatic manifestation of stellate-cell-driven
      fibrogenesis; the conserved TGF-beta/Smad activation axis is inherited
      from the fibrotic_response module via conforms_to (the module carries
      the mechanistic evidence for that conserved signaling step).
  downstream:
  - target: Excessive Hepatic ECM Deposition
    description: >-
      Activated hepatic stellate cells and myofibroblasts drive excess
      extracellular matrix deposition.
- name: Excessive Hepatic ECM Deposition
  conforms_to: fibrotic_response#Excessive ECM Deposition
  description: >-
    Collagen-secreting hepatic myofibroblasts deposit excessive collagen and
    other extracellular matrix while suppressing matrix degradation,
    progressively distorting hepatic architecture and producing the fibrosis
    and cirrhosis that define severe HFSD liver disease.
  cell_types:
  - preferred_term: myofibroblast cell
    term:
      id: CL:0000186
      label: myofibroblast cell
  locations:
  - preferred_term: liver
    term:
      id: UBERON:0002107
      label: liver
  biological_processes:
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: INCREASED
  - preferred_term: collagen biosynthetic process
    term:
      id: GO:0032964
      label: collagen biosynthetic process
    modifier: INCREASED
  - preferred_term: collagen fibril organization
    term:
      id: GO:0030199
      label: collagen fibril organization
    modifier: INCREASED
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis"
    explanation: >-
      The review documents progressive matrix accumulation manifesting as
      mild/moderate liver fibrosis up to cirrhosis, the structural endpoint of
      excessive hepatic ECM deposition.
  downstream:
  - target: Hepatic Fibrosis
    description: >-
      Progressive extracellular matrix accumulation manifests clinically as
      hepatic fibrosis.
  - target: Cirrhosis
    description: >-
      Sustained matrix deposition and architectural distortion progress to
      cirrhosis in the most severe cases.
- name: Secondary Hypofibrinogenemia
  description: >-
    Because mutant fibrinogen is retained intrahepatically rather than
    secreted, circulating fibrinogen is reduced. This hypofibrinogenemia is a
    downstream consequence of impaired secretion rather than the primary
    disease mechanism, distinguishing HFSD from simple quantitative
    fibrinogen deficiency.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  evidence:
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hepatic fibrinogen storage disease is a rare autosomal dominant genetic disorder characterized by hypofibrinogenemia, as well as the retention of variant fibrinogen within the hepatocellular endoplasmic reticulum."
    explanation: >-
      The case report defines HFSD by the combination of hypofibrinogenemia
      and hepatocellular ER retention of variant fibrinogen.
  downstream:
  - target: Subclinical Coagulation Abnormality
    description: >-
      Reduced circulating fibrinogen mildly prolongs clot-based coagulation
      assays.
  - target: Hypofibrinogenemia
    description: >-
      Retention of mutant fibrinogen in hepatocytes lowers secreted circulating
      fibrinogen.
  - target: Hypo-apolipoprotein B Proteinemia
    description: >-
      Co-retention of apolipoprotein B with fibrinogen storage inclusions can
      lower circulating apolipoprotein B.
- name: Subclinical Coagulation Abnormality
  description: >-
    Despite reduced fibrinogen and prolonged coagulation parameters, HFSD
    patients characteristically do not have a clinically significant bleeding
    tendency; the liver is the principal target organ of the FGG mutation.
  biological_processes:
  - preferred_term: blood coagulation
    term:
      id: GO:0007596
      label: blood coagulation
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Concerning the coagulopathy, HHHS patients usually show prolonged coagulation parameters (Table 1) but no hemorrhagic manifestations nor abnormal wound healing."
    explanation: >-
      The review reports prolonged coagulation parameters without hemorrhagic
      manifestations in HHHS.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the target organ affected by the mutation within the FGG gene may be the liver; coagulation or bleeding disorders may not occur in affected patients"
    explanation: >-
      The case report concludes that the liver, rather than the hemostatic
      system, is the target organ of the FGG mutation, so overt coagulation or
      bleeding disorders typically do not occur.
phenotypes:
- name: Elevated Hepatic Transaminases
  category: Hepatic
  description: >-
    Mild, often intermittent elevation of serum transaminases is the usual
    presenting laboratory abnormality, frequently detected incidentally.
  phenotype_term:
    preferred_term: Elevated circulating hepatic transaminase concentration
    term:
      id: HP:0002910
      label: Elevated circulating hepatic transaminase concentration
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is associated with mild and intermittent hypertransaminasemia"
    explanation: >-
      The review identifies mild, intermittent transaminase elevation as the
      characteristic biochemical feature.
- name: Hypofibrinogenemia
  category: Hematologic
  description: >-
    Reduced circulating fibrinogen secondary to impaired hepatic secretion;
    may be absent in some carriers with isolated hepatic storage.
  phenotype_term:
    preferred_term: Hypofibrinogenemia
    term:
      id: HP:0011900
      label: Hypofibrinogenemia
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a disorder characterized by protein aggregation in the endoplasmic reticulum, hypofibrinogenemia, and liver disease of variable severity"
    explanation: >-
      The review lists hypofibrinogenemia as one of the defining features of
      the disorder.
- name: Hepatic Fibrosis
  category: Hepatic
  description: >-
    Progressive hepatic fibrosis can develop from sustained hepatocyte injury
    and stellate-cell activation.
  phenotype_term:
    preferred_term: Hepatic fibrosis
    term:
      id: HP:0001395
      label: Hepatic fibrosis
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis"
    explanation: >-
      The review documents hepatic fibrosis within the disease's variable
      liver-injury spectrum.
- name: Cirrhosis
  category: Hepatic
  frequency: OCCASIONAL
  description: >-
    A subset of patients progress to cirrhosis, sometimes in childhood.
  phenotype_term:
    preferred_term: Cirrhosis
    term:
      id: HP:0001394
      label: Cirrhosis
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "up to cirrhosis, with severe clinical pictures that can be present even in children"
    explanation: >-
      The review documents progression to cirrhosis, sometimes in childhood,
      within the HHHS liver-disease spectrum.
- name: Hepatomegaly
  category: Hepatic
  description: >-
    Mild hepatomegaly can be present and may be the incidental finding that
    prompts evaluation in otherwise asymptomatic patients.
  phenotype_term:
    preferred_term: Hepatomegaly
    term:
      id: HP:0002240
      label: Hepatomegaly
    severity: MILD
  evidence:
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Abdominal ultrasonography showed mild hepatomegaly."
    explanation: >-
      The case report documents mild hepatomegaly on abdominal ultrasonography
      in an asymptomatic child with HFSD.
- name: Hypo-apolipoprotein B Proteinemia
  category: Hematologic
  description: >-
    Reduced circulating apolipoprotein B has been observed in several HFSD
    cases as a secondary phenomenon, with fibrinogen and APOB co-accumulating
    within the same hepatocellular ER inclusions.
  phenotype_term:
    preferred_term: Hypo-apolipoprotein B proteinemia
    term:
      id: HP:0034075
      label: Decreased circulating apolipoprotein B concentration
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "HHHS has been associated with hypo-apo-β (APOB) proteinemia in several cases"
    explanation: >-
      The review reports an association between HHHS and hypo-apo-β (APOB)
      proteinemia in several cases.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "who were demonstrated to simultaneously accumulate fibrinogen and APOB in the same ER liver inclusions"
    explanation: >-
      The review documents that fibrinogen and APOB co-accumulate within the
      same hepatocellular ER inclusions, the mechanistic basis for the secondary
      hypo-APOB proteinemia; the absence of APOB/MTTP mutations in these patients
      indicates it is secondary to the FGG defect.
genetic:
- name: FGG
  gene_term:
    preferred_term: FGG
    term:
      id: hgnc:3694
      label: FGG
  association: Causative
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The genetic basis of HHHS are exclusively represented by mutations located in exons 8 and 9 of the FGG gene"
    explanation: >-
      The review establishes FGG as the exclusive causative gene for HFSD.
inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  expressivity: VARIABLE
  description: >-
    HFSD is transmitted as an autosomal dominant trait; all reported FGG storage
    mutations occur in the heterozygous state. Penetrance is incomplete and
    expressivity is highly variable: carriers of the same FGG mutation within a
    single family may range from clinically unaffected (normal liver function
    and coagulation) to overt liver disease, implicating additional genetic
    (e.g., protein-degradation-pathway) or environmental modifiers.
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In all cases, mutations have been reported in the heterozygous state, supporting the idea that HHHS is an autosomal dominant trait"
    explanation: >-
      The review establishes the autosomal dominant, heterozygous mode of
      inheritance for HFSD.
  - reference: PMID:31965886
    reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "sister and mother had normal findings in liver function and coagulation tests, although they harbored the same heterozygous mutation within the FGG gene"
    explanation: >-
      Unaffected relatives carrying the same heterozygous FGG mutation as the
      proband demonstrate incomplete penetrance and variable expressivity.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients display a tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis, with severe clinical pictures that can be present even in children"
    explanation: >-
      The review documents the wide, variable range of liver-disease severity,
      supporting variable expressivity.
treatments:
- name: Carbamazepine and Ursodeoxycholic Acid
  description: >-
    Carbamazepine, an autophagy enhancer, combined with ursodeoxycholic acid
    has been reported to reduce aggregate-related hepatotoxicity and normalize
    transaminases in HFSD; supporting evidence is limited to case-level
    experience.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: carbamazepine
      term:
        id: CHEBI:3387
        label: carbamazepine
    - preferred_term: ursodeoxycholic acid
      term:
        id: CHEBI:9907
        label: ursodeoxycholic acid
  evidence:
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Data on medical management of HHHS are sparse; carbamazepine (CBZ) and ursodeoxycholic acid (UDCA) have been demonstrated to be beneficial in some cases"
    explanation: >-
      The review identifies carbamazepine and ursodeoxycholic acid as the
      reported, sparsely evidenced disease-directed management.
  - reference: PMID:33105716
    reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This drug is a well-tolerated anticonvulsive treatment, known to enhance autophagy, and its efficacy seems to be related to the normalization of ALT levels"
    explanation: >-
      The review explains the mechanistic rationale for carbamazepine
      (autophagy enhancement) and its observed normalization of transaminases.
- name: Supportive Care and Monitoring
  description: >-
    Most patients require monitoring of liver function and fibrinogen rather
    than active intervention; fibrinogen supplementation is reserved for the
    rare bleeding or perioperative situations.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:36055263
    reference_title: "One Hundred Years of Congenital Fibrinogen Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fibrinogen supplementation is the cornerstone of bleeding management in fibrinogen disorders."
    explanation: >-
      The review identifies fibrinogen supplementation as the mainstay only of
      bleeding management, which is rarely needed in HFSD.
references:
- reference: PMID:33105716
  title: Hereditary Hypofibrinogenemia with Hepatic Storage.
  findings:
  - statement: >-
      A serpin-like beta-strand pull-out mechanism has been proposed to explain
      the aberrant polymerization of HHHS-causing mutant fibrinogen.
    supporting_text: "The pull-out hypothesis offers a possible explanation for the pathogenic mechanism underlying HHHS-causing mutations."
    evidence:
    - reference: PMID:33105716
      reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
      supports: SUPPORT
      evidence_source: COMPUTATIONAL
      snippet: "The pull-out hypothesis offers a possible explanation for the pathogenic mechanism underlying HHHS-causing mutations."
      explanation: >-
        The review advances a serpin-analogy beta-strand pull-out model, derived
        from structural analysis, as the mechanism of mutant-fibrinogen
        polymerization.
  - statement: >-
      Aggregation of mutant fibrinogen may be triggered by xenobiotics, viral
      infection, or the acute-phase response, offering one explanation for
      incomplete penetrance.
    supporting_text: "the tendency of mutant fibrinogens to aggregate could also depend on xenobiotic intake (e.g., estrogen therapy, alcohol abuse), chronic or acute viral infections, or be secondary to cancer"
    evidence:
    - reference: PMID:33105716
      reference_title: "Hereditary Hypofibrinogenemia with Hepatic Storage."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the tendency of mutant fibrinogens to aggregate could also depend on xenobiotic intake (e.g., estrogen therapy, alcohol abuse), chronic or acute viral infections, or be secondary to cancer"
      explanation: >-
        The review lists external triggers (xenobiotics, viral infection, the
        acute-phase response) that may precipitate intrahepatic fibrinogen
        aggregation in mutation carriers.
- reference: PMID:31965886
  title: 'Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report.'
  findings:
  - statement: >-
      Excessive aggregation of variant fibrinogen in the hepatocyte ER is the
      central pathogenic event in HFSD.
    supporting_text: "Imbalanced homeostasis, caused by excessive aggregation of variant fibrinogen in the ER, is regarded as the central event in the pathogenesis of HFSD."
    evidence:
    - reference: PMID:31965886
      reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Imbalanced homeostasis, caused by excessive aggregation of variant fibrinogen in the ER, is regarded as the central event in the pathogenesis of HFSD."
      explanation: >-
        The case report frames ER fibrinogen aggregation as the central
        pathogenic event of HFSD.
  - statement: >-
      HFSD and congenital alpha-1-antitrypsin deficiency are ER storage diseases
      that share similar molecular mechanisms.
    supporting_text: "HFSD and another well-known disease, congenital alpha-1-antitrypsin deficiency, are ER storage diseases that share similar molecular mechanisms, due to gene mutations of the corresponding proteins that result in hepatocellular protein storage, defective secretion, and plasma deficiency."
    evidence:
    - reference: PMID:31965886
      reference_title: "Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "HFSD and another well-known disease, congenital alpha-1-antitrypsin deficiency, are ER storage diseases that share similar molecular mechanisms, due to gene mutations of the corresponding proteins that result in hepatocellular protein storage, defective secretion, and plasma deficiency."
      explanation: >-
        The case report draws the explicit mechanistic parallel between HFSD and
        alpha-1-antitrypsin deficiency as ER storage diseases.
- reference: PMID:36055263
  title: One Hundred Years of Congenital Fibrinogen Disorders.
  findings: []
notes: >-
  Scope/term note: this entry models hepatic fibrinogen storage disease (HFSD;
  also hereditary hypofibrinogenemia with hepatic storage, HHHS) as the
  mechanistically distinct, toxic gain-of-function FGG entity. The simple
  quantitative (Type I) loss-of-function form is curated separately as
  Congenital Hypofibrinogenemia (issue 2727, sister PR). The precise Mondo
  term for this entity, MONDO:7770747 (hepatic fibrinogen storage disease,
  added in Mondo via monarch-initiative/mondo#10239, merged 2026-05-13), does
  not yet resolve in the released OAK sqlite cache, so disease_term uses the
  resolvable parent MONDO:0018060 (congenital fibrinogen deficiency) with a
  specific preferred_term; the disease_term should be re-pointed to
  MONDO:7770747 once the OAK mondo cache refreshes.

  Module note: the fibrotic cascade is modeled as atomic nodes — "Hepatocyte
  Injury" -> "Hepatic Stellate Cell Activation"
  (conforms_to fibrotic_response#Mesenchymal Cell Activation) -> "Excessive
  Hepatic ECM Deposition" (conforms_to fibrotic_response#Excessive ECM
  Deposition) -> hepatic fibrosis/cirrhosis, mirroring the Wilson's Disease
  hepatic-fibrosis conformance pattern. The conserved TGF-beta/Smad
  mesenchymal-activation evidence is supplied by the fibrotic_response module
  itself; the disease-level evidence here documents the HFSD fibrosis-to-
  cirrhosis spectrum. A follow-up should additionally conform the
  ER-aggregation / ER-stress / hepatocyte-injury nodes to the
  er_protein_storage_disease module (in-progress in PR 2772) once that module
  lands on main, mirroring the Alpha-1 Antitrypsin Deficiency refactor in PR
  PR 2782. Tracker: issue 2727.
📚

References & Deep Research

References

3
PMID:33105716
Hereditary Hypofibrinogenemia with Hepatic Storage.
2 findings
A serpin-like beta-strand pull-out mechanism has been proposed to explain the aberrant polymerization of HHHS-causing mutant fibrinogen.
"The pull-out hypothesis offers a possible explanation for the pathogenic mechanism underlying HHHS-causing mutations."
Show evidence (1 reference)
PMID:33105716 SUPPORT Computational
"The pull-out hypothesis offers a possible explanation for the pathogenic mechanism underlying HHHS-causing mutations."
The review advances a serpin-analogy beta-strand pull-out model, derived from structural analysis, as the mechanism of mutant-fibrinogen polymerization.
Aggregation of mutant fibrinogen may be triggered by xenobiotics, viral infection, or the acute-phase response, offering one explanation for incomplete penetrance.
"the tendency of mutant fibrinogens to aggregate could also depend on xenobiotic intake (e.g., estrogen therapy, alcohol abuse), chronic or acute viral infections, or be secondary to cancer"
Show evidence (1 reference)
PMID:33105716 SUPPORT Human Clinical
"the tendency of mutant fibrinogens to aggregate could also depend on xenobiotic intake (e.g., estrogen therapy, alcohol abuse), chronic or acute viral infections, or be secondary to cancer"
The review lists external triggers (xenobiotics, viral infection, the acute-phase response) that may precipitate intrahepatic fibrinogen aggregation in mutation carriers.
PMID:31965886
Hepatic fibrinogen storage disease and hypofibrinogenemia caused by fibrinogen Aguadilla mutation: a case report.
2 findings
Excessive aggregation of variant fibrinogen in the hepatocyte ER is the central pathogenic event in HFSD.
"Imbalanced homeostasis, caused by excessive aggregation of variant fibrinogen in the ER, is regarded as the central event in the pathogenesis of HFSD."
Show evidence (1 reference)
PMID:31965886 SUPPORT Human Clinical
"Imbalanced homeostasis, caused by excessive aggregation of variant fibrinogen in the ER, is regarded as the central event in the pathogenesis of HFSD."
The case report frames ER fibrinogen aggregation as the central pathogenic event of HFSD.
HFSD and congenital alpha-1-antitrypsin deficiency are ER storage diseases that share similar molecular mechanisms.
"HFSD and another well-known disease, congenital alpha-1-antitrypsin deficiency, are ER storage diseases that share similar molecular mechanisms, due to gene mutations of the corresponding proteins that result in hepatocellular protein storage, defective secretion, and plasma deficiency."
Show evidence (1 reference)
PMID:31965886 SUPPORT Human Clinical
"HFSD and another well-known disease, congenital alpha-1-antitrypsin deficiency, are ER storage diseases that share similar molecular mechanisms, due to gene mutations of the corresponding proteins that result in hepatocellular protein storage, defective secretion, and plasma deficiency."
The case report draws the explicit mechanistic parallel between HFSD and alpha-1-antitrypsin deficiency as ER storage diseases.
PMID:36055263
One Hundred Years of Congenital Fibrinogen Disorders.
No top-level findings curated for this source.

Deep Research

1
Scanner ▸
Scanner Research Synthesis: Hepatic Fibrinogen Storage Disease (HFSD / HHHS)
claude-opus-4-7 2026-05-18T00:00:00Z

Scanner Research Synthesis: Hepatic Fibrinogen Storage Disease (HFSD / HHHS)

This report is a literature synthesis built strictly from the cached reference abstracts available in references_cache/ (PMID:33105716, PMID:31965886, PMID:36055263). No external deep-research provider was invoked; every statement below is grounded in one of these three cached sources, and PMIDs are cited inline. It is intended as a curation input for kb/disorders/Hepatic_Fibrinogen_Storage_Disease.yaml.

Disease Identity

  • Preferred name: Hepatic fibrinogen storage disease (HFSD); synonyms hereditary hypofibrinogenemia with hepatic storage (HHHS), fibrinogen storage disease (FSD) (PMID:33105716).
  • MONDO: MONDO:0018060 (congenital fibrinogen deficiency) used as the resolvable parent; the specific term MONDO:7770747 (hepatic fibrinogen storage disease) did not yet resolve in the released OAK sqlite cache at curation time.
  • Disease class: HFSD belongs to the ER storage diseases (ERSDs) — inborn errors of metabolism involving secretory proteins, characterized by hepatocellular storage in the rough ER and plasma deficiency of the relevant protein; ERSDs comprise alpha-1-antitrypsin, fibrinogen, and alpha-1-antichymotrypsin deficiencies (PMID:33105716).
  • Mechanistic contrast: Unlike simple Type I quantitative hypofibrinogenemia (a loss-of-function defect with a structurally normal liver), HFSD is a toxic gain-of-function disorder in which the mutant fibrinogen is assembled but secretion-incompetent, polymerizes, and aggregates spontaneously within the hepatocyte ER (PMID:33105716). The congenital fibrinogen disorders are formally classified by clottable and antigenic fibrinogen levels together with clinical phenotype and genotype (PMID:36055263).

Core Pathophysiology

Genetic mechanism

HFSD is caused by heterozygous missense mutations located exclusively in exons 8 and 9 of FGG (the fibrinogen γ-chain gene); eight FGG mutations had been reported at the time of the cached review, seven non-conservative missense substitutions plus one 14-nucleotide deletion activating a cryptic splice site (PMID:33105716). All affected residues lie in the highly conserved C-terminal globular γ module (residues ~310–401), and all mutations occur in the heterozygous state, supporting an autosomal dominant trait and indirectly suggesting homozygous lethality (PMID:33105716). Variants are named after the proband's city of origin (e.g., Aguadilla, Brescia, Angers, Beograd, Ankara, Pisa); Aguadilla is the most common worldwide (PMID:33105716; PMID:31965886).

Molecular cascade

  1. Mutant γ-chain production — destabilizing FGG γ-module missense variant produced in the heterozygous state (PMID:33105716).
  2. Hepatocellular ER aggregation — mutant fibrinogen retains polymerization ability but cannot be secreted, so it aggregates spontaneously within the rough ER of hepatocytes as densely packed tubular inclusions (PMID:33105716). A proposed structural mechanism invokes a serpin-like β-strand "pull-out" from the central β-sheet of the γ module, permitting polymerization of destabilized fibrinogen (PMID:33105716).
  3. Histologic inclusions — circular eosinophilic intracytoplasmic inclusion bodies, fibrinogen-immunoreactive, classified ultrastructurally into type I (fingerprint tubular), type II (ground-glass), and type III (mixed) deposits (PMID:33105716); a concrete case showed "circular eosinophil inclusion bodies in the hepato-cytoplasm" (PMID:31965886).
  4. ER stress / impaired proteostasis — accumulated polymers impose proteotoxic ER burden; autophagy is the main pathway for intracellular fibrinogen clearance, and defects in protein-degradation pathways are candidate disease modifiers (PMID:33105716).
  5. Hepatocyte injury — ER accumulation "strongly predisposes to the development of chronic liver disease of variable severity, both in children and adults" (PMID:33105716).
  6. Stellate-cell-mediated fibrogenesis — the injury/regeneration cycle drives hepatic fibrosis; patients show "tremendous variability in the severity of liver disease, going from no signs of injury, to mild/moderate liver fibrosis, up to cirrhosis" (PMID:33105716). The conserved TGF-beta/Smad mesenchymal-activation axis is modeled by conforms_to linkage to the fibrotic_response module.
  7. Secondary hypofibrinogenemia — retention rather than secretion lowers circulating fibrinogen; HFSD is defined by "hypofibrinogenemia, as well as the retention of variant fibrinogen within the hepatocellular endoplasmic reticulum" (PMID:31965886).

Key liver biology

Fibrinogen is a 340-kDa hexamer (two sets of Aα/Bβ/γ trimers) coded by FGA, FGB, FGG on chromosome 4q31.3, assembled in the ER (with calnexin/calreticulin and ERp57 chaperones) and mainly expressed in liver (PMID:33105716). In HFSD the liver is the principal target organ; the coagulopathy is secondary and clinically minor (PMID:33105716).

Clinical Phenotype

  • Elevated hepatic transaminases — usual presenting feature; HFSD "is associated with mild and intermittent hypertransaminasemia" (mean ALT 191 ± 119 U/L, AST 147 ± 97 U/L) (PMID:33105716); a case showed elevated ALT 122 IU/L and AST 119 IU/L (PMID:31965886).
  • Hypofibrinogenemia — defining laboratory feature, secondary to impaired secretion (PMID:33105716; PMID:31965886).
  • Hepatic fibrosis / cirrhosis — variable, from no injury through mild/moderate fibrosis up to cirrhosis, sometimes in children (PMID:33105716).
  • Hepatomegaly — "Abdominal ultrasonography showed mild hepatomegaly" in an asymptomatic 4-year-old (PMID:31965886).
  • Hypo-apo-β (APOB) proteinemia — "HHHS has been associated with hypo-apo-β (APOB) proteinemia in several cases", with fibrinogen and APOB co-accumulating in the same ER inclusions; the absence of APOB/MTTP mutations indicates a secondary phenomenon (PMID:33105716).
  • Coagulopathy without bleeding — "HHHS patients usually show prolonged coagulation parameters ... but no hemorrhagic manifestations nor abnormal wound healing" (PMID:33105716).
  • Onset — first symptoms (usually transaminase elevation) at a young age (mean 13.1 ± 20.2 years); HFSD equally distributed between sexes (PMID:33105716).

Disease Modifiers / Variable Expressivity

The same FGG mutation can behave differently across individuals, even within a family. Proposed modifiers: (i) genetic defects in protein-degradation / autophagy pathways governing mutant-fibrinogen clearance; (ii) xenobiotic intake (estrogen therapy, alcohol); (iii) acute/chronic viral infection and the acute-phase over-production of fibrinogen "crowding" an already burdened ER (PMID:33105716). This is a documented mechanistic theme not yet modeled as a discrete pathophysiology node and is a candidate enrichment.

Genetics Summary

Gene HGNC Role Mutation class
FGG hgnc:3694 Causative Heterozygous missense in exons 8/9 (γ module, residues ~310–401); one cryptic-splice deletion (PMID:33105716)

Inheritance: Autosomal dominant; heterozygous only (PMID:33105716).

Treatment-relevant mechanisms

  • Carbamazepine (autophagy enhancer) + ursodeoxycholic acid — beneficial in some cases; CBZ is "known to enhance autophagy, and its efficacy seems to be related to the normalization of ALT levels" (PMID:33105716).
  • Supportive care / monitoring — fibrinogen supplementation is the cornerstone of bleeding management in fibrinogen disorders generally (PMID:36055263), but is only rarely required in HFSD given the minimal bleeding phenotype (PMID:33105716).
  • No HFSD-specific liver transplantation evidence is present in the cached abstracts (the prior PR review correctly flagged and removed an unsupported transplantation claim).

Content-Completeness Cross-Check vs. current YAML

Dimension Status
Phenotype coverage Adequate after enrichment — transaminase elevation, hypofibrinogenemia, hepatic fibrosis, cirrhosis, hepatomegaly, hypo-APOB proteinemia, subclinical coagulopathy all modeled.
Subtype completeness Adequate — single mechanistic entity; FGG city-named alleles are variant-level, not subtypes.
Pathophysiology Adequate — mutant γ-chain → ER aggregation → ER stress/autophagy → hepatocyte injury → stellate-cell activation (conforms_to fibrotic_response#Mesenchymal Cell Activation) → excessive hepatic ECM deposition (conforms_to fibrotic_response#Excessive ECM Deposition) → fibrosis/cirrhosis; secondary hypofibrinogenemia → subclinical coagulation abnormality. Modifier-gene/autophagy-capacity theme is noted in notes and remains an optional future node.
Treatments Adequate — CBZ+UDCA and supportive care, both with exact cached-abstract snippets.
Genetic Adequate — FGG causative, exons 8/9, heterozygous dominant.
Biomarkers/diagnostics Description-level only (immunohistochemistry/electron microscopy diagnosis); not formalized as structured biomarkers — optional enrichment.
References Three cached PMIDs; all snippets are exact whitespace-normalized substrings.

Notes for reviewers

  • This artifact is a transparent scanner cached-reference synthesis, not an external provider narrative; it follows the same format as the sibling approved PR for Congenital Hypofibrinogenemia (#2727).
  • The conserved TGF-beta/Smad mesenchymal-activation evidence is intentionally not duplicated as a disease-specific snippet (the cached HFSD abstracts do not mention TGF-beta or stellate cells by name); it is inherited through conforms_to: fibrotic_response#Mesenchymal Cell Activation, mirroring the Wilson's Disease hepatic-fibrosis conformance pattern.
  • disease_term should be re-pointed from MONDO:0018060 to MONDO:7770747 once the OAK mondo cache refreshes (tracked in the entry notes).