Paroxysmal Nocturnal Hemoglobinuria

Hematologic MONDO:0100244 Pathograph 18 Show in embeddings browser Hematologic Disease Complement Disorder

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal hematopoietic stem cell disorder caused by somatic loss-of-function mutations in the X-linked PIGA gene, which encodes an enzyme required for the first step of glycosylphosphatidylinositol (GPI) anchor biosynthesis. Loss of GPI-anchor assembly renders affected blood cells deficient in the GPI-anchored complement-regulatory proteins CD55 (decay-accelerating factor) and CD59 (membrane inhibitor of reactive lysis). Without these regulators, red cells are susceptible to complement-mediated intravascular hemolysis, producing chronic hemolytic anemia, hemoglobinuria, disabling fatigue, smooth-muscle dystonia (dysphagia, abdominal pain, erectile dysfunction) from nitric-oxide depletion by cell-free hemoglobin, and a markedly increased risk of thrombosis, which is the leading cause of death. PNH characteristically arises in the setting of bone marrow failure, and clonal expansion of the PIGA-mutant stem cell is required for clinically significant disease. Diagnosis is established by high-sensitivity flow cytometry demonstrating GPI-anchor-deficient blood cell populations, and terminal complement inhibitors (eculizumab, ravulizumab) and proximal complement inhibitors (pegcetacoplan, iptacopan, danicopan) have transformed prognosis.

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6
Pathophys.
10
Phenotypes
18
Pathograph
1
Genes
6
Medical Actions
9
References
1
Deep Research
⚙

Pathophysiology

6
PIGA Mutation and GPI-Anchor Deficiency
PNH originates from an acquired somatic loss-of-function mutation in the X-linked PIGA gene in a hematopoietic stem cell. PIGA encodes a subunit of the enzyme complex that catalyzes the first committed step of GPI-anchor biosynthesis. Because PIGA is X-linked and only one allele is active per cell, a single inactivating mutation abolishes GPI-anchor assembly, and GPI-anchor-deficient progeny cannot display the roughly 150 GPI-linked surface proteins, including the complement regulators CD55 and CD59.
Hematopoietic Stem Cell CL:0000037 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Hematopoietic Stem Cell (CL:0000037). CL:0000037 is a cell type from the Cell Ontology.
PIGA hgnc:8957 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves PIGA (hgnc:8957). hgnc:8957 is a gene from the HUGO Gene Nomenclature Committee.
GPI Anchor Biosynthetic Process GO:0006506 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased GPI Anchor Biosynthetic Process (GO:0006506). GO:0006506 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Loss of CD55 and CD59 Complement Regulation Loss of GPI-anchor assembly removes the GPI-linked complement regulators CD55 and CD59 from the blood cell surface.
Clonal Expansion and Bone Marrow Failure The PIGA-mutant hematopoietic stem cell undergoes clonal expansion under immune-mediated selective pressure, producing the GPI-deficient blood cell population responsible for clinical disease.
Show evidence (2 references)
PMID:35154088 SUPPORT Human Clinical
"PNH patients develop somatic loss-of-function mutations in phosphatidylinositol N-acetylglucosaminyltransferase subunit A gene (PIGA), required for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors."
Establishes that PNH is caused by acquired somatic PIGA loss-of-function mutations that block GPI-anchor biosynthesis.
PMID:35154088 SUPPORT Human Clinical
"Ubiquitous in eukaryotes, GPI anchors are a group of conserved glycolipid molecules responsible for attaching nearly 150 distinct proteins to the surface of cell membranes."
Documents that GPI anchors attach ~150 surface proteins, so their loss strips many GPI-linked proteins including complement regulators.
Loss of CD55 and CD59 Complement Regulation
CD55 (decay-accelerating factor) accelerates decay of the C3 and C5 convertases, while CD59 (membrane inhibitor of reactive lysis) blocks assembly of the terminal C5b-9 membrane attack complex. Their absence on PNH erythrocytes permits unrestrained amplification of the alternative complement pathway on the cell surface and unchecked membrane attack complex formation.
Regulation of Complement Activation GO:0030449 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Regulation of Complement Activation (GO:0030449). GO:0030449 is a biological process from the Gene Ontology. ↓ DECREASED Complement Activation, Alternative Pathway GO:0006957 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Complement Activation, Alternative Pathway (GO:0006957). GO:0006957 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Complement-Mediated Intravascular Hemolysis Unopposed membrane attack complex assembly lyses erythrocytes within the circulation.
Show evidence (2 references)
PMID:35154088 SUPPORT Human Clinical
"The loss of two GPI-anchored surface proteins, CD55 and CD59, from red blood cells causes unregulated complement activation and hemolysis in classical PNH disease."
Directly links loss of the GPI-anchored regulators CD55 and CD59 to unregulated complement activation and hemolysis.
PMID:39273426 SUPPORT Human Clinical
"Mutation of the phosphatidylinositol glycan biosynthesis class A (PIGA) gene prevents the expression of cell-surface proteins, including the complement regulatory proteins CD55 and CD59."
Confirms that PIGA mutation removes the complement regulatory proteins CD55 and CD59 from the cell surface.
Complement-Mediated Intravascular Hemolysis
Deposition of the terminal membrane attack complex on complement-regulator-deficient erythrocytes causes intravascular hemolysis with release of cell-free hemoglobin and hemoglobinuria. Chronic complement-mediated destruction produces anemia, elevated lactate dehydrogenase, reduced haptoglobin, and reticulocytosis.
Erythrocyte CL:0000232 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Erythrocyte (CL:0000232). CL:0000232 is a cell type from the Cell Ontology.
Complement-Dependent Cytotoxicity GO:0097278 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Complement-Dependent Cytotoxicity (GO:0097278). GO:0097278 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Nitric Oxide Depletion and Smooth Muscle Dystonia Cell-free hemoglobin released during intravascular hemolysis scavenges nitric oxide, producing smooth muscle dysfunction and contributing to thrombosis.
Hemolytic Anemia Chronic destruction of erythrocytes produces hemolytic anemia.
Hemoglobinuria Release of hemoglobin into plasma leads to hemoglobinuria.
Elevated Lactate Dehydrogenase Erythrocyte lysis releases lactate dehydrogenase into the circulation.
Fatigue Anemia and nitric-oxide depletion produce disabling fatigue.
Dyspnea Anemia and hemolysis contribute to exertional dyspnea.
Renal Insufficiency Filtration and tubular deposition of cell-free hemoglobin impair renal function.
Show evidence (2 references)
PMID:39371251 SUPPORT Human Clinical
"Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by intravascular hemolysis (IVH) due to diminished or absent inhibition of the complement system because of deficient expression of cell-anchored complement regulating surface proteins."
Confirms intravascular hemolysis driven by deficient complement regulation as the central mechanism.
PMID:19707355 SUPPORT Human Clinical
"The disease is characterized by complement-mediated chronic intravascular hemolysis, resulting in hemolytic anemia and hemosiderinuria; capricious exacerbations lead to recurrent gross hemoglobinuria."
Links complement-mediated intravascular hemolysis to hemolytic anemia and episodic gross hemoglobinuria.
Nitric Oxide Depletion and Smooth Muscle Dystonia
Cell-free plasma hemoglobin released during intravascular hemolysis scavenges nitric oxide. Regional nitric-oxide deficiency causes smooth-muscle dystonia manifesting as dysphagia, esophageal spasm, abdominal pain, and erectile dysfunction, and contributes to platelet activation and the prothrombotic state.
Nitric Oxide Metabolic Process GO:0046209 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Nitric Oxide Metabolic Process (GO:0046209). GO:0046209 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Prothrombotic State Nitric-oxide depletion promotes platelet activation and vasoconstriction, reinforcing the prothrombotic state.
Abdominal Pain Smooth-muscle dystonia from nitric-oxide depletion causes abdominal pain.
Dysphagia Esophageal smooth-muscle dystonia from nitric-oxide depletion causes dysphagia.
Show evidence (1 reference)
PMID:39273426 SUPPORT Human Clinical
"With decreased or a lack of CD55 and CD59 expression on their membranes, PNH red blood cells become susceptible to complement-mediated hemolysis (symptoms of which include anemia, dysphagia, abdominal pain, and fatigue), leading to thrombosis."
Documents the smooth-muscle dystonia symptom cluster (dysphagia, abdominal pain) alongside anemia and fatigue arising from complement-mediated hemolysis.
Prothrombotic State
Thrombosis is the leading cause of death in PNH and characteristically occurs at unusual sites such as the hepatic (Budd-Chiari syndrome), portal, mesenteric, and cerebral veins. Complement-mediated platelet activation, nitric-oxide depletion, release of prothrombotic microparticles, and impaired fibrinolysis all contribute.
Platelet Activation GO:0030168 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Platelet Activation (GO:0030168). GO:0030168 is a biological process from the Gene Ontology. ↑ INCREASED Blood Coagulation GO:0007596 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Blood Coagulation (GO:0007596). GO:0007596 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Venous Thrombosis The prothrombotic state manifests clinically as venous thrombosis, often at unusual sites.
Show evidence (2 references)
PMID:40986193 SUPPORT Human Clinical
"These agents significantly modify the natural history of the disease by reducing the risk of thrombosis, the most lethal complication of PNH, as well as reducing transfusion dependence and improving renal function, quality of life and probably, survival."
Identifies thrombosis as the most lethal complication of PNH, supporting its central role in the prothrombotic state.
PMID:19707355 SUPPORT Human Clinical
"Additional cardinal manifestations of PNH are a variable degree of bone marrow failure and an intrinsic propensity to thromboembolic events."
Documents the intrinsic propensity to thromboembolic events as a cardinal manifestation of PNH.
Clonal Expansion and Bone Marrow Failure
PNH clones arise in the setting of bone marrow failure and are closely linked to aplastic anemia. A prevailing model holds that immune-mediated selective pressure against normal GPI-positive hematopoietic stem cells provides a relative survival advantage to GPI-deficient PIGA-mutant clones, allowing their expansion to clinically significant size.
Hematopoietic Stem Cell CL:0000037 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Hematopoietic Stem Cell (CL:0000037). CL:0000037 is a cell type from the Cell Ontology.
Hematopoietic Stem Cell Proliferation GO:0071425 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated Hematopoietic Stem Cell Proliferation (GO:0071425). GO:0071425 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Downstream
Pancytopenia Bone marrow failure underlying the PNH clone produces reduction of all blood cell lineages.
Aplastic Anemia PNH clones characteristically emerge in the setting of aplastic anemia.
Show evidence (2 references)
PMID:19707355 SUPPORT Human Clinical
"This defect arises from an acquired somatic mutation in the X-linked phosphatidylinositol glycan class A gene, with subsequent clonal expansion of the mutated HSCs as a result of a concomitant, likely immune-mediated, selective pressure."
Supports immune-mediated selective pressure driving clonal expansion of PIGA-mutant hematopoietic stem cells.
PMID:35154088 SUPPORT Human Clinical
"In PNH patients, PIGA-mutant, GPI (-) hematopoietic cells clonally expand to make up a large portion of patients' blood production, yet mechanisms leading to clonal expansion of GPI (-) cells remain enigmatic."
Confirms that PIGA-mutant GPI-deficient cells clonally expand to dominate hematopoiesis in PNH patients.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Paroxysmal Nocturnal Hemoglobinuria 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

10
Blood 2
Hemolytic Anemia VERY_FREQUENT HP:0001878 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hemolytic Anemia (HP:0001878). HP:0001878 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19707355 SUPPORT Human Clinical
"The disease is characterized by complement-mediated chronic intravascular hemolysis, resulting in hemolytic anemia and hemosiderinuria; capricious exacerbations lead to recurrent gross hemoglobinuria."
Confirms hemolytic anemia arising from complement-mediated intravascular hemolysis.
Pancytopenia OCCASIONAL HP:0001876 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pancytopenia (HP:0001876). HP:0001876 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19707355 SUPPORT Human Clinical
"Additional cardinal manifestations of PNH are a variable degree of bone marrow failure and an intrinsic propensity to thromboembolic events."
Bone marrow failure, of which pancytopenia is the hematologic expression, is a cardinal manifestation of PNH.
Digestive 1
Dysphagia OCCASIONAL HP:0002015 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dysphagia (HP:0002015). HP:0002015 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39273426 SUPPORT Human Clinical
"With decreased or a lack of CD55 and CD59 expression on their membranes, PNH red blood cells become susceptible to complement-mediated hemolysis (symptoms of which include anemia, dysphagia, abdominal pain, and fatigue), leading to thrombosis."
Lists dysphagia among the complement-mediated hemolysis symptoms in PNH.
Genitourinary 1
Renal Insufficiency FREQUENT HP:0000083 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Renal Insufficiency (HP:0000083). HP:0000083 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:32390114 SUPPORT Human Clinical
"There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%)."
International PNH Registry data document impaired renal function in 42.8% of patients.
Respiratory 1
Dyspnea FREQUENT HP:0002094 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dyspnea (HP:0002094). HP:0002094 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39371251 SUPPORT Human Clinical
"IVH leads to heterogeneous symptoms such as anemia, abdominal pain, dyspnea, fatigue and increased rates of thrombophilia."
Lists dyspnea among the heterogeneous symptoms produced by intravascular hemolysis.
Constitutional 2
Fatigue VERY_FREQUENT HP:0012378 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fatigue (HP:0012378). HP:0012378 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39371251 SUPPORT Human Clinical
"IVH leads to heterogeneous symptoms such as anemia, abdominal pain, dyspnea, fatigue and increased rates of thrombophilia."
Lists fatigue among the heterogeneous symptoms produced by intravascular hemolysis.
Abdominal Pain FREQUENT HP:0002027 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal Pain (HP:0002027). HP:0002027 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39371251 SUPPORT Human Clinical
"IVH leads to heterogeneous symptoms such as anemia, abdominal pain, dyspnea, fatigue and increased rates of thrombophilia."
Lists abdominal pain among the symptoms produced by intravascular hemolysis.
Other 3
Hemoglobinuria FREQUENT HP:0003641 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hemoglobinuria (HP:0003641). HP:0003641 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19707355 SUPPORT Human Clinical
"The disease is characterized by complement-mediated chronic intravascular hemolysis, resulting in hemolytic anemia and hemosiderinuria; capricious exacerbations lead to recurrent gross hemoglobinuria."
Documents recurrent gross hemoglobinuria as a defining manifestation.
Venous Thrombosis OCCASIONAL HP:0004936 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Venous Thrombosis (HP:0004936). HP:0004936 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:40986193 SUPPORT Human Clinical
"These agents significantly modify the natural history of the disease by reducing the risk of thrombosis, the most lethal complication of PNH, as well as reducing transfusion dependence and improving renal function, quality of life and probably, survival."
Identifies thrombosis as the most lethal complication of PNH.
PMID:32390114 SUPPORT Human Clinical
"There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%)."
International PNH Registry data record a history of major adverse vascular events (which include thrombotic events) in 18.8% of patients, supporting an OCCASIONAL frequency band.
Aplastic Anemia OCCASIONAL HP:0001915 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Aplastic Anemia (HP:0001915). HP:0001915 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:32390114 SUPPORT Human Clinical
"There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%)."
International PNH Registry data document bone marrow failure (BMF) in 62.6% of patients, of which aplastic anemia is the principal form.
🧬

Genetic Associations

1
PIGA Somatic Mutation
Gene: PIGA hgnc:8957 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is PIGA (hgnc:8957). hgnc:8957 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (2 references)
PMID:41002734 SUPPORT Human Clinical
"Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal hematologic disorder caused by somatic mutations in the PIGA gene of hematopoietic stem cells, leading to the absence of GPI-anchored proteins, including the complement regulators CD55 and CD59."
Confirms somatic PIGA mutation in hematopoietic stem cells as the cause of GPI-anchor and CD55/CD59 deficiency.
PMID:19707355 SUPPORT Human Clinical
"This defect arises from an acquired somatic mutation in the X-linked phosphatidylinositol glycan class A gene, with subsequent clonal expansion of the mutated HSCs as a result of a concomitant, likely immune-mediated, selective pressure."
Establishes the acquired, X-linked, somatic nature of the causative PIGA mutation.
💊

Medical Actions

6
Eculizumab
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: eculizumab NCIT:C48386 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses eculizumab (NCIT:C48386). NCIT:C48386 is a therapeutic agent from the NCI Thesaurus.
Humanized monoclonal antibody against complement component C5 that blocks cleavage to C5a and C5b, preventing membrane attack complex formation and terminal complement-mediated intravascular hemolysis. First disease-modifying therapy for PNH, reducing hemolysis, transfusion requirements, and thrombotic risk.
Show evidence (2 references)
PMID:38622956 SUPPORT Human Clinical
"The anti-C5 monoclonal antibody eculizumab was the first treatment to improve hemolysis, thrombotic risk, and survival in PNH although at the price of a life-long intravenous fortnightly drug."
Establishes eculizumab as the first anti-C5 therapy improving hemolysis, thrombotic risk, and survival in PNH.
PMID:41002734 SUPPORT Human Clinical
"Eculizumab, the first approved C5 inhibitor, significantly reduced thrombotic risk and improved survival but did not eliminate anemia due to extravascular hemolysis."
Confirms eculizumab reduces thrombotic risk and improves survival, while noting residual extravascular hemolysis.
Ravulizumab
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: ravulizumab NCIT:C124657 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses ravulizumab (NCIT:C124657). NCIT:C124657 is a therapeutic agent from the NCI Thesaurus.
Long-acting anti-C5 monoclonal antibody engineered from eculizumab with an every-8-week dosing interval, providing non-inferior control of intravascular hemolysis with reduced pharmacokinetic breakthrough hemolysis.
Show evidence (1 reference)
PMID:38622956 SUPPORT Human Clinical
"Ravulizumab, a longer half-life anti-C5 developed from eculizumab, administered every 8 weeks, improved patient convenience, and reduced pharmacokinetic breakthrough hemolysis (BTH) by establishing more stable anti-C5 concentrations."
Documents ravulizumab as a long-acting anti-C5 with every-8-week dosing and reduced breakthrough hemolysis.
Pegcetacoplan
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: pegcetacoplan NCIT:C121135 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses pegcetacoplan (NCIT:C121135). NCIT:C121135 is a therapeutic agent from the NCI Thesaurus.
Pegylated C3-targeted peptide inhibitor that acts proximally in the complement cascade, controlling both intravascular and extravascular hemolysis and improving hemoglobin in patients with residual anemia on C5 inhibitors.
Show evidence (2 references)
PMID:38622956 SUPPORT Human Clinical
"Upstream inhibition of complement cascade was also explored with the anti-C3 pegcetacoplan, and with the alternative pathway inhibitors iptacopan (anti-factor B) and danicopan (anti-factor D)."
Documents pegcetacoplan as an anti-C3 proximal complement inhibitor for PNH.
PMID:39371251 SUPPORT Human Clinical
"New proximal complement inhibitors (CI) mainly targeting complement component C3 or factors of the amplification pathway such as pegcetacoplan, danicopan, and iptacopan became available and are meanwhile approved for marketing."
Confirms pegcetacoplan is an approved proximal complement inhibitor targeting C3.
Iptacopan
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: iptacopan NCIT:C156691 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses iptacopan (NCIT:C156691). NCIT:C156691 is a therapeutic agent from the NCI Thesaurus.
First-in-class oral factor B inhibitor of the alternative complement pathway. In phase 3 trials, iptacopan monotherapy improved hemoglobin and reduced transfusion dependence in both anti-C5-experienced and complement-inhibitor-naive PNH patients with persistent anemia.
Show evidence (2 references)
PMID:38477987 SUPPORT Human Clinical
"Iptacopan, a first-in-class oral factor B inhibitor, has been shown to improve hemoglobin levels in these patients."
Establishes iptacopan as a first-in-class oral factor B inhibitor that improves hemoglobin in PNH.
PMID:38477987 SUPPORT Human Clinical
"In the first trial, 51 of the 60 patients who received iptacopan had an increase in the hemoglobin level of at least 2 g per deciliter from baseline, and 42 had a hemoglobin level of at least 12 g per deciliter, each without transfusion; none of the 35 anti-C5-treated patients attained the..."
Phase 3 APPLY-PNH results quantify iptacopan's hemoglobin benefit over continued anti-C5 therapy.
Danicopan
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: danicopan NCIT:C148181 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses danicopan (NCIT:C148181). NCIT:C148181 is a therapeutic agent from the NCI Thesaurus.
Oral factor D inhibitor of the alternative complement pathway, used as add-on therapy to a C5 inhibitor in patients with clinically significant C3-mediated extravascular hemolysis and residual anemia.
Show evidence (1 reference)
PMID:38622956 SUPPORT Human Clinical
"Upstream inhibition of complement cascade was also explored with the anti-C3 pegcetacoplan, and with the alternative pathway inhibitors iptacopan (anti-factor B) and danicopan (anti-factor D)."
Documents danicopan as an alternative-pathway (factor D) inhibitor for PNH.
Allogeneic Hematopoietic Stem Cell Transplantation
Action: Hematopoietic Cell TransplantationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Hematopoietic Cell Transplantation (NCIT:C15431). NCIT:C15431 is a clinical intervention from the NCI Thesaurus. NCIT:C15431
Allogeneic hematopoietic stem cell transplantation is the only established curative therapy for PNH but carries substantial treatment-related morbidity and mortality, and is generally reserved for severe bone marrow failure or clonal evolution rather than uncomplicated complement-responsive hemolysis.
Show evidence (1 reference)
PMID:19707355 SUPPORT Human Clinical
"The biology of PNH has been progressively elucidated in the past few years, but therapeutic strategies remained unsatisfactory for decades, the only exception being stem cell transplantation, which is restricted to selected patients and retains significant morbidity and mortality."
Identifies stem cell transplantation as the only curative option, restricted to selected patients with significant morbidity and mortality.
🔬

Biochemical Markers

1
Elevated Lactate Dehydrogenase (INCREASED)
Context: Elevated serum lactate dehydrogenase (LDH) is a hallmark biochemical marker of intravascular hemolysis in PNH and is used to gauge hemolytic activity; untreated hemolytic PNH patients characteristically have LDH more than 1.5 times the upper limit of normal.
Show evidence (1 reference)
PMID:38477987 SUPPORT Human Clinical
"patients who had not received complement inhibitors and who had lactate dehydrogenase (LDH) levels more than 1.5 times the upper limit of the normal range received iptacopan."
Documents that untreated PNH patients characteristically have LDH more than 1.5 times the upper limit of normal, reflecting intravascular hemolysis.
🔬

Diagnosis

1
High-Sensitivity Flow Cytometry
High-sensitivity multiparameter flow cytometry of peripheral blood is the diagnostic gold standard for PNH, demonstrating GPI-anchor-deficient cell populations across at least two blood cell lineages. Granulocyte and monocyte assays commonly combine fluorescent aerolysin (FLAER) with lineage markers, while red cell assays detect CD59 (and CD55) deficiency; granulocyte and monocyte clone sizes best estimate the underlying hematopoietic stem-cell clone.
flow cytometry procedure NCIT:C16585 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:40986193 SUPPORT Human Clinical
"Flow cytometry is the preferred technique to diagnose PNH"
Identifies flow cytometry as the preferred diagnostic technique for PNH.
{ }

Source YAML

click to show 
name: Paroxysmal Nocturnal Hemoglobinuria
creation_date: "2026-07-24T00:00:00Z"
category: Hematologic
parents:
- Hematologic Disease
- Complement Disorder
disease_term:
  preferred_term: Paroxysmal Nocturnal Hemoglobinuria
  term:
    id: MONDO:0100244
    label: paroxysmal nocturnal hemoglobinuria
description: >-
  Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal
  hematopoietic stem cell disorder caused by somatic loss-of-function mutations in
  the X-linked PIGA gene, which encodes an enzyme required for the first step of
  glycosylphosphatidylinositol (GPI) anchor biosynthesis. Loss of GPI-anchor
  assembly renders affected blood cells deficient in the GPI-anchored
  complement-regulatory proteins CD55 (decay-accelerating factor) and CD59
  (membrane inhibitor of reactive lysis). Without these regulators, red cells are
  susceptible to complement-mediated intravascular hemolysis, producing chronic
  hemolytic anemia, hemoglobinuria, disabling fatigue, smooth-muscle dystonia
  (dysphagia, abdominal pain, erectile dysfunction) from nitric-oxide depletion by
  cell-free hemoglobin, and a markedly increased risk of thrombosis, which is the
  leading cause of death. PNH characteristically arises in the setting of bone
  marrow failure, and clonal expansion of the PIGA-mutant stem cell is required for
  clinically significant disease. Diagnosis is established by high-sensitivity flow
  cytometry demonstrating GPI-anchor-deficient blood cell populations, and terminal
  complement inhibitors (eculizumab, ravulizumab) and proximal complement
  inhibitors (pegcetacoplan, iptacopan, danicopan) have transformed prognosis.
pathophysiology:
- name: PIGA Mutation and GPI-Anchor Deficiency
  description: >-
    PNH originates from an acquired somatic loss-of-function mutation in the
    X-linked PIGA gene in a hematopoietic stem cell. PIGA encodes a subunit of the
    enzyme complex that catalyzes the first committed step of GPI-anchor
    biosynthesis. Because PIGA is X-linked and only one allele is active per cell, a
    single inactivating mutation abolishes GPI-anchor assembly, and
    GPI-anchor-deficient progeny cannot display the roughly 150 GPI-linked surface
    proteins, including the complement regulators CD55 and CD59.
  genes:
  - preferred_term: PIGA
    term:
      id: hgnc:8957
      label: PIGA
  cell_types:
  - preferred_term: Hematopoietic Stem Cell
    term:
      id: CL:0000037
      label: hematopoietic stem cell
  biological_processes:
  - preferred_term: GPI Anchor Biosynthetic Process
    term:
      id: GO:0006506
      label: GPI anchor biosynthetic process
    modifier: DECREASED
  downstream:
  - target: Loss of CD55 and CD59 Complement Regulation
    description: >-
      Loss of GPI-anchor assembly removes the GPI-linked complement regulators
      CD55 and CD59 from the blood cell surface.
  - target: Clonal Expansion and Bone Marrow Failure
    description: >-
      The PIGA-mutant hematopoietic stem cell undergoes clonal expansion under
      immune-mediated selective pressure, producing the GPI-deficient blood cell
      population responsible for clinical disease.
  evidence:
  - reference: PMID:35154088
    reference_title: "Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PNH patients develop somatic loss-of-function mutations in phosphatidylinositol N-acetylglucosaminyltransferase subunit A gene (PIGA), required for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors."
    explanation: >-
      Establishes that PNH is caused by acquired somatic PIGA loss-of-function
      mutations that block GPI-anchor biosynthesis.
  - reference: PMID:35154088
    reference_title: "Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ubiquitous in eukaryotes, GPI anchors are a group of conserved glycolipid molecules responsible for attaching nearly 150 distinct proteins to the surface of cell membranes."
    explanation: >-
      Documents that GPI anchors attach ~150 surface proteins, so their loss
      strips many GPI-linked proteins including complement regulators.
- name: Loss of CD55 and CD59 Complement Regulation
  conforms_to: "complement_dysregulation#Loss of Complement Regulatory Control"
  description: >-
    CD55 (decay-accelerating factor) accelerates decay of the C3 and C5
    convertases, while CD59 (membrane inhibitor of reactive lysis) blocks assembly
    of the terminal C5b-9 membrane attack complex. Their absence on PNH
    erythrocytes permits unrestrained amplification of the alternative complement
    pathway on the cell surface and unchecked membrane attack complex formation.
  biological_processes:
  - preferred_term: Regulation of Complement Activation
    term:
      id: GO:0030449
      label: regulation of complement activation
    modifier: DECREASED
  - preferred_term: Complement Activation, Alternative Pathway
    term:
      id: GO:0006957
      label: complement activation, alternative pathway
    modifier: INCREASED
  downstream:
  - target: Complement-Mediated Intravascular Hemolysis
    description: >-
      Unopposed membrane attack complex assembly lyses erythrocytes within the
      circulation.
  evidence:
  - reference: PMID:35154088
    reference_title: "Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The loss of two GPI-anchored surface proteins, CD55 and CD59, from red blood cells causes unregulated complement activation and hemolysis in classical PNH disease."
    explanation: >-
      Directly links loss of the GPI-anchored regulators CD55 and CD59 to
      unregulated complement activation and hemolysis.
  - reference: PMID:39273426
    reference_title: "Navigating the Complement Pathway to Optimize PNH Treatment with Pegcetacoplan and Other Currently Approved Complement Inhibitors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutation of the phosphatidylinositol glycan biosynthesis class A (PIGA) gene prevents the expression of cell-surface proteins, including the complement regulatory proteins CD55 and CD59."
    explanation: >-
      Confirms that PIGA mutation removes the complement regulatory proteins CD55
      and CD59 from the cell surface.
- name: Complement-Mediated Intravascular Hemolysis
  conforms_to: "complement_dysregulation#Complement-Mediated Cell Injury and Endothelial Activation"
  description: >-
    Deposition of the terminal membrane attack complex on
    complement-regulator-deficient erythrocytes causes intravascular hemolysis
    with release of cell-free hemoglobin and hemoglobinuria. Chronic
    complement-mediated destruction produces
    anemia, elevated lactate dehydrogenase, reduced haptoglobin, and reticulocytosis.
  cell_types:
  - preferred_term: Erythrocyte
    term:
      id: CL:0000232
      label: erythrocyte
  biological_processes:
  - preferred_term: Complement-Dependent Cytotoxicity
    term:
      id: GO:0097278
      label: complement-dependent cytotoxicity
    modifier: INCREASED
  downstream:
  - target: Nitric Oxide Depletion and Smooth Muscle Dystonia
    description: >-
      Cell-free hemoglobin released during intravascular hemolysis scavenges nitric
      oxide, producing smooth muscle dysfunction and contributing to thrombosis.
  - target: Hemolytic Anemia
    description: Chronic destruction of erythrocytes produces hemolytic anemia.
  - target: Hemoglobinuria
    description: Release of hemoglobin into plasma leads to hemoglobinuria.
  - target: Elevated Lactate Dehydrogenase
    description: Erythrocyte lysis releases lactate dehydrogenase into the circulation.
  - target: Fatigue
    description: Anemia and nitric-oxide depletion produce disabling fatigue.
  - target: Dyspnea
    description: Anemia and hemolysis contribute to exertional dyspnea.
  - target: Renal Insufficiency
    description: >-
      Filtration and tubular deposition of cell-free hemoglobin impair renal
      function.
  evidence:
  - reference: PMID:39371251
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by intravascular hemolysis (IVH) due to diminished or absent inhibition of the complement system because of deficient expression of cell-anchored complement regulating surface proteins."
    explanation: >-
      Confirms intravascular hemolysis driven by deficient complement regulation as
      the central mechanism.
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The disease is characterized by complement-mediated chronic intravascular hemolysis, resulting in hemolytic anemia and hemosiderinuria; capricious exacerbations lead to recurrent gross hemoglobinuria."
    explanation: >-
      Links complement-mediated intravascular hemolysis to hemolytic anemia and
      episodic gross hemoglobinuria.
- name: Nitric Oxide Depletion and Smooth Muscle Dystonia
  description: >-
    Cell-free plasma hemoglobin released during intravascular hemolysis scavenges
    nitric oxide. Regional nitric-oxide deficiency causes smooth-muscle dystonia
    manifesting as dysphagia, esophageal spasm, abdominal pain, and erectile
    dysfunction, and contributes to platelet activation and the prothrombotic state.
  biological_processes:
  - preferred_term: Nitric Oxide Metabolic Process
    term:
      id: GO:0046209
      label: nitric oxide metabolic process
    modifier: DECREASED
  downstream:
  - target: Prothrombotic State
    description: >-
      Nitric-oxide depletion promotes platelet activation and vasoconstriction,
      reinforcing the prothrombotic state.
  - target: Abdominal Pain
    description: Smooth-muscle dystonia from nitric-oxide depletion causes abdominal pain.
  - target: Dysphagia
    description: Esophageal smooth-muscle dystonia from nitric-oxide depletion causes dysphagia.
  evidence:
  - reference: PMID:39273426
    reference_title: "Navigating the Complement Pathway to Optimize PNH Treatment with Pegcetacoplan and Other Currently Approved Complement Inhibitors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "With decreased or a lack of CD55 and CD59 expression on their membranes, PNH red blood cells become susceptible to complement-mediated hemolysis (symptoms of which include anemia, dysphagia, abdominal pain, and fatigue), leading to thrombosis."
    explanation: >-
      Documents the smooth-muscle dystonia symptom cluster (dysphagia, abdominal
      pain) alongside anemia and fatigue arising from complement-mediated hemolysis.
- name: Prothrombotic State
  description: >-
    Thrombosis is the leading cause of death in PNH and characteristically occurs
    at unusual sites such as the hepatic (Budd-Chiari syndrome), portal, mesenteric,
    and cerebral veins. Complement-mediated platelet activation, nitric-oxide
    depletion, release of prothrombotic microparticles, and impaired fibrinolysis
    all contribute.
  biological_processes:
  - preferred_term: Platelet Activation
    term:
      id: GO:0030168
      label: platelet activation
    modifier: INCREASED
  - preferred_term: Blood Coagulation
    term:
      id: GO:0007596
      label: blood coagulation
    modifier: INCREASED
  downstream:
  - target: Venous Thrombosis
    description: >-
      The prothrombotic state manifests clinically as venous thrombosis, often at
      unusual sites.
  evidence:
  - reference: PMID:40986193
    reference_title: "Pharmacological Therapies in Paroxysmal Nocturnal Haemoglobinuria: Focus on Complement Inhibition."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These agents significantly modify the natural history of the disease by reducing the risk of thrombosis, the most lethal complication of PNH, as well as reducing transfusion dependence and improving renal function, quality of life and probably, survival."
    explanation: >-
      Identifies thrombosis as the most lethal complication of PNH, supporting its
      central role in the prothrombotic state.
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional cardinal manifestations of PNH are a variable degree of bone marrow failure and an intrinsic propensity to thromboembolic events."
    explanation: >-
      Documents the intrinsic propensity to thromboembolic events as a cardinal
      manifestation of PNH.
- name: Clonal Expansion and Bone Marrow Failure
  description: >-
    PNH clones arise in the setting of bone marrow failure and are closely linked
    to aplastic anemia. A prevailing model holds that immune-mediated selective
    pressure against normal GPI-positive hematopoietic stem cells provides a
    relative survival advantage to GPI-deficient PIGA-mutant clones, allowing their
    expansion to clinically significant size.
  cell_types:
  - preferred_term: Hematopoietic Stem Cell
    term:
      id: CL:0000037
      label: hematopoietic stem cell
  biological_processes:
  - preferred_term: Hematopoietic Stem Cell Proliferation
    term:
      id: GO:0071425
      label: hematopoietic stem cell proliferation
    modifier: DYSREGULATED
  downstream:
  - target: Pancytopenia
    description: >-
      Bone marrow failure underlying the PNH clone produces reduction of all blood
      cell lineages.
  - target: Aplastic Anemia
    description: >-
      PNH clones characteristically emerge in the setting of aplastic anemia.
  evidence:
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This defect arises from an acquired somatic mutation in the X-linked phosphatidylinositol glycan class A gene, with subsequent clonal expansion of the mutated HSCs as a result of a concomitant, likely immune-mediated, selective pressure."
    explanation: >-
      Supports immune-mediated selective pressure driving clonal expansion of
      PIGA-mutant hematopoietic stem cells.
  - reference: PMID:35154088
    reference_title: "Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In PNH patients, PIGA-mutant, GPI (-) hematopoietic cells clonally expand to make up a large portion of patients' blood production, yet mechanisms leading to clonal expansion of GPI (-) cells remain enigmatic."
    explanation: >-
      Confirms that PIGA-mutant GPI-deficient cells clonally expand to dominate
      hematopoiesis in PNH patients.
phenotypes:
- name: Hemoglobinuria
  category: Clinical
  description: >-
    Passage of hemoglobin in the urine from intravascular hemolysis, classically
    producing dark or cola-colored urine.
  phenotype_term:
    preferred_term: Hemoglobinuria
    term:
      id: HP:0003641
      label: Hemoglobinuria
  frequency: FREQUENT
  evidence:
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The disease is characterized by complement-mediated chronic intravascular hemolysis, resulting in hemolytic anemia and hemosiderinuria; capricious exacerbations lead to recurrent gross hemoglobinuria."
    explanation: >-
      Documents recurrent gross hemoglobinuria as a defining manifestation.
- name: Hemolytic Anemia
  category: Clinical
  description: >-
    Chronic complement-mediated intravascular hemolysis produces anemia with
    reticulocytosis, elevated lactate dehydrogenase, and reduced haptoglobin.
  phenotype_term:
    preferred_term: Hemolytic Anemia
    term:
      id: HP:0001878
      label: Hemolytic anemia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The disease is characterized by complement-mediated chronic intravascular hemolysis, resulting in hemolytic anemia and hemosiderinuria; capricious exacerbations lead to recurrent gross hemoglobinuria."
    explanation: >-
      Confirms hemolytic anemia arising from complement-mediated intravascular
      hemolysis.
- name: Venous Thrombosis
  category: Clinical
  description: >-
    Thrombosis, often at unusual sites such as hepatic, portal, mesenteric, and
    cerebral veins, is the leading cause of death in PNH.
  phenotype_term:
    preferred_term: Venous Thrombosis
    term:
      id: HP:0004936
      label: Venous thrombosis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:40986193
    reference_title: "Pharmacological Therapies in Paroxysmal Nocturnal Haemoglobinuria: Focus on Complement Inhibition."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These agents significantly modify the natural history of the disease by reducing the risk of thrombosis, the most lethal complication of PNH, as well as reducing transfusion dependence and improving renal function, quality of life and probably, survival."
    explanation: >-
      Identifies thrombosis as the most lethal complication of PNH.
  - reference: PMID:32390114
    reference_title: "Baseline clinical characteristics and disease burden in patients with paroxysmal nocturnal hemoglobinuria (PNH): updated analysis from the International PNH Registry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%)."
    explanation: >-
      International PNH Registry data record a history of major adverse vascular
      events (which include thrombotic events) in 18.8% of patients, supporting an
      OCCASIONAL frequency band.
- name: Fatigue
  category: Clinical
  description: >-
    Disabling fatigue related to chronic hemolysis and nitric-oxide depletion,
    frequently disproportionate to the degree of anemia.
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:39371251
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "IVH leads to heterogeneous symptoms such as anemia, abdominal pain, dyspnea, fatigue and increased rates of thrombophilia."
    explanation: >-
      Lists fatigue among the heterogeneous symptoms produced by intravascular
      hemolysis.
- name: Abdominal Pain
  category: Clinical
  description: >-
    Recurrent abdominal pain attributed to smooth-muscle dystonia from nitric-oxide
    depletion and to mesenteric venous thrombosis.
  phenotype_term:
    preferred_term: Abdominal Pain
    term:
      id: HP:0002027
      label: Abdominal pain
  frequency: FREQUENT
  evidence:
  - reference: PMID:39371251
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "IVH leads to heterogeneous symptoms such as anemia, abdominal pain, dyspnea, fatigue and increased rates of thrombophilia."
    explanation: >-
      Lists abdominal pain among the symptoms produced by intravascular hemolysis.
- name: Dysphagia
  category: Clinical
  description: >-
    Difficulty swallowing and esophageal spasm from smooth-muscle dystonia
    secondary to nitric-oxide scavenging by cell-free hemoglobin.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:39273426
    reference_title: "Navigating the Complement Pathway to Optimize PNH Treatment with Pegcetacoplan and Other Currently Approved Complement Inhibitors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "With decreased or a lack of CD55 and CD59 expression on their membranes, PNH red blood cells become susceptible to complement-mediated hemolysis (symptoms of which include anemia, dysphagia, abdominal pain, and fatigue), leading to thrombosis."
    explanation: >-
      Lists dysphagia among the complement-mediated hemolysis symptoms in PNH.
- name: Dyspnea
  category: Clinical
  description: >-
    Exertional dyspnea related to anemia, intravascular hemolysis, nitric-oxide
    depletion, and pulmonary vascular involvement.
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
  frequency: FREQUENT
  evidence:
  - reference: PMID:39371251
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "IVH leads to heterogeneous symptoms such as anemia, abdominal pain, dyspnea, fatigue and increased rates of thrombophilia."
    explanation: >-
      Lists dyspnea among the heterogeneous symptoms produced by intravascular
      hemolysis.
- name: Renal Insufficiency
  category: Clinical
  description: >-
    Impaired renal function from repeated hemoglobin filtration, hemosiderin
    deposition, tubular injury, and microvascular thrombosis; documented in 42.8%
    of International PNH Registry patients at baseline.
  phenotype_term:
    preferred_term: Renal Insufficiency
    term:
      id: HP:0000083
      label: Renal insufficiency
  frequency: FREQUENT
  evidence:
  - reference: PMID:32390114
    reference_title: "Baseline clinical characteristics and disease burden in patients with paroxysmal nocturnal hemoglobinuria (PNH): updated analysis from the International PNH Registry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%)."
    explanation: >-
      International PNH Registry data document impaired renal function in 42.8% of
      patients.
- name: Pancytopenia
  category: Clinical
  description: >-
    Reduction of all three blood cell lineages reflecting the associated bone
    marrow failure in which many PNH clones arise.
  phenotype_term:
    preferred_term: Pancytopenia
    term:
      id: HP:0001876
      label: Pancytopenia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional cardinal manifestations of PNH are a variable degree of bone marrow failure and an intrinsic propensity to thromboembolic events."
    explanation: >-
      Bone marrow failure, of which pancytopenia is the hematologic expression, is a
      cardinal manifestation of PNH.
- name: Aplastic Anemia
  category: Clinical
  description: >-
    PNH is closely associated with aplastic anemia and other bone marrow failure
    syndromes, in which GPI-deficient clones expand.
  phenotype_term:
    preferred_term: Aplastic Anemia
    term:
      id: HP:0001915
      label: Aplastic anemia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:32390114
    reference_title: "Baseline clinical characteristics and disease burden in patients with paroxysmal nocturnal hemoglobinuria (PNH): updated analysis from the International PNH Registry."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%)."
    explanation: >-
      International PNH Registry data document bone marrow failure (BMF) in 62.6% of
      patients, of which aplastic anemia is the principal form.
genetic:
- name: PIGA Somatic Mutation
  gene_term:
    preferred_term: PIGA
    term:
      id: hgnc:8957
      label: PIGA
  features: >-
    Acquired somatic loss-of-function mutations in the X-linked PIGA gene within a
    hematopoietic stem cell are the invariable cause of PNH. Because PIGA is on the
    X chromosome and only one allele is active per cell, a single inactivating
    mutation abolishes GPI-anchor biosynthesis. Mutations are diverse (frameshift,
    nonsense, missense, splice) and distributed throughout the gene, and are somatic
    rather than germline, so PNH is not inherited.
  frequency: OBLIGATE
  evidence:
  - reference: PMID:41002734
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria: Unraveling Its Molecular Pathogenesis and Advancing Targeted Therapeutic Strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal hematologic disorder caused by somatic mutations in the PIGA gene of hematopoietic stem cells, leading to the absence of GPI-anchored proteins, including the complement regulators CD55 and CD59."
    explanation: >-
      Confirms somatic PIGA mutation in hematopoietic stem cells as the cause of
      GPI-anchor and CD55/CD59 deficiency.
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This defect arises from an acquired somatic mutation in the X-linked phosphatidylinositol glycan class A gene, with subsequent clonal expansion of the mutated HSCs as a result of a concomitant, likely immune-mediated, selective pressure."
    explanation: >-
      Establishes the acquired, X-linked, somatic nature of the causative PIGA
      mutation.
treatments:
- name: Eculizumab
  description: >-
    Humanized monoclonal antibody against complement component C5 that blocks
    cleavage to C5a and C5b, preventing membrane attack complex formation and
    terminal complement-mediated intravascular hemolysis. First disease-modifying
    therapy for PNH, reducing hemolysis, transfusion requirements, and thrombotic
    risk.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: eculizumab
      term:
        id: NCIT:C48386
        label: Eculizumab
  evidence:
  - reference: PMID:38622956
    reference_title: "Complement inhibition in paroxysmal nocturnal hemoglobinuria: From biology to therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The anti-C5 monoclonal antibody eculizumab was the first treatment to improve hemolysis, thrombotic risk, and survival in PNH although at the price of a life-long intravenous fortnightly drug."
    explanation: >-
      Establishes eculizumab as the first anti-C5 therapy improving hemolysis,
      thrombotic risk, and survival in PNH.
  - reference: PMID:41002734
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria: Unraveling Its Molecular Pathogenesis and Advancing Targeted Therapeutic Strategies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Eculizumab, the first approved C5 inhibitor, significantly reduced thrombotic risk and improved survival but did not eliminate anemia due to extravascular hemolysis."
    explanation: >-
      Confirms eculizumab reduces thrombotic risk and improves survival, while
      noting residual extravascular hemolysis.
- name: Ravulizumab
  description: >-
    Long-acting anti-C5 monoclonal antibody engineered from eculizumab with an
    every-8-week dosing interval, providing non-inferior control of intravascular
    hemolysis with reduced pharmacokinetic breakthrough hemolysis.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: ravulizumab
      term:
        id: NCIT:C124657
        label: Ravulizumab
  evidence:
  - reference: PMID:38622956
    reference_title: "Complement inhibition in paroxysmal nocturnal hemoglobinuria: From biology to therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ravulizumab, a longer half-life anti-C5 developed from eculizumab, administered every 8 weeks, improved patient convenience, and reduced pharmacokinetic breakthrough hemolysis (BTH) by establishing more stable anti-C5 concentrations."
    explanation: >-
      Documents ravulizumab as a long-acting anti-C5 with every-8-week dosing and
      reduced breakthrough hemolysis.
- name: Pegcetacoplan
  description: >-
    Pegylated C3-targeted peptide inhibitor that acts proximally in the complement
    cascade, controlling both intravascular and extravascular hemolysis and
    improving hemoglobin in patients with residual anemia on C5 inhibitors.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: pegcetacoplan
      term:
        id: NCIT:C121135
        label: Pegcetacoplan
  evidence:
  - reference: PMID:38622956
    reference_title: "Complement inhibition in paroxysmal nocturnal hemoglobinuria: From biology to therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Upstream inhibition of complement cascade was also explored with the anti-C3 pegcetacoplan, and with the alternative pathway inhibitors iptacopan (anti-factor B) and danicopan (anti-factor D)."
    explanation: >-
      Documents pegcetacoplan as an anti-C3 proximal complement inhibitor for PNH.
  - reference: PMID:39371251
    reference_title: "Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "New proximal complement inhibitors (CI) mainly targeting complement component C3 or factors of the amplification pathway such as pegcetacoplan, danicopan, and iptacopan became available and are meanwhile approved for marketing."
    explanation: >-
      Confirms pegcetacoplan is an approved proximal complement inhibitor targeting
      C3.
- name: Iptacopan
  description: >-
    First-in-class oral factor B inhibitor of the alternative complement pathway.
    In phase 3 trials, iptacopan monotherapy improved hemoglobin and reduced
    transfusion dependence in both anti-C5-experienced and
    complement-inhibitor-naive PNH patients with persistent anemia.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: iptacopan
      term:
        id: NCIT:C156691
        label: Iptacopan
  evidence:
  - reference: PMID:38477987
    reference_title: "Oral Iptacopan Monotherapy in Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Iptacopan, a first-in-class oral factor B inhibitor, has been shown to improve hemoglobin levels in these patients."
    explanation: >-
      Establishes iptacopan as a first-in-class oral factor B inhibitor that
      improves hemoglobin in PNH.
  - reference: PMID:38477987
    reference_title: "Oral Iptacopan Monotherapy in Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the first trial, 51 of the 60 patients who received iptacopan had an increase in the hemoglobin level of at least 2 g per deciliter from baseline, and 42 had a hemoglobin level of at least 12 g per deciliter, each without transfusion; none of the 35 anti-C5-treated patients attained the end-point levels."
    explanation: >-
      Phase 3 APPLY-PNH results quantify iptacopan's hemoglobin benefit over
      continued anti-C5 therapy.
- name: Danicopan
  description: >-
    Oral factor D inhibitor of the alternative complement pathway, used as add-on
    therapy to a C5 inhibitor in patients with clinically significant C3-mediated
    extravascular hemolysis and residual anemia.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: danicopan
      term:
        id: NCIT:C148181
        label: Danicopan
  evidence:
  - reference: PMID:38622956
    reference_title: "Complement inhibition in paroxysmal nocturnal hemoglobinuria: From biology to therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Upstream inhibition of complement cascade was also explored with the anti-C3 pegcetacoplan, and with the alternative pathway inhibitors iptacopan (anti-factor B) and danicopan (anti-factor D)."
    explanation: >-
      Documents danicopan as an alternative-pathway (factor D) inhibitor for PNH.
- name: Allogeneic Hematopoietic Stem Cell Transplantation
  description: >-
    Allogeneic hematopoietic stem cell transplantation is the only established
    curative therapy for PNH but carries substantial treatment-related morbidity
    and mortality, and is generally reserved for severe bone marrow failure or
    clonal evolution rather than uncomplicated complement-responsive hemolysis.
  treatment_term:
    preferred_term: Hematopoietic Cell Transplantation
    term:
      id: NCIT:C15431
      label: Hematopoietic Cell Transplantation
  evidence:
  - reference: PMID:19707355
    reference_title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biology of PNH has been progressively elucidated in the past few years, but therapeutic strategies remained unsatisfactory for decades, the only exception being stem cell transplantation, which is restricted to selected patients and retains significant morbidity and mortality."
    explanation: >-
      Identifies stem cell transplantation as the only curative option, restricted
      to selected patients with significant morbidity and mortality.
diagnosis:
- name: High-Sensitivity Flow Cytometry
  description: >-
    High-sensitivity multiparameter flow cytometry of peripheral blood is the
    diagnostic gold standard for PNH, demonstrating GPI-anchor-deficient cell
    populations across at least two blood cell lineages. Granulocyte and monocyte
    assays commonly combine fluorescent aerolysin (FLAER) with lineage markers,
    while red cell assays detect CD59 (and CD55) deficiency; granulocyte and
    monocyte clone sizes best estimate the underlying hematopoietic stem-cell clone.
  diagnosis_term:
    preferred_term: flow cytometry procedure
    term:
      id: NCIT:C16585
      label: Flow Cytometry
  evidence:
  - reference: PMID:40986193
    reference_title: "Pharmacological Therapies in Paroxysmal Nocturnal Haemoglobinuria: Focus on Complement Inhibition."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Flow cytometry is the preferred technique to diagnose PNH"
    explanation: >-
      Identifies flow cytometry as the preferred diagnostic technique for PNH.
biochemical:
- name: Elevated Lactate Dehydrogenase
  presence: INCREASED
  context: >-
    Elevated serum lactate dehydrogenase (LDH) is a hallmark biochemical marker of
    intravascular hemolysis in PNH and is used to gauge hemolytic activity;
    untreated hemolytic PNH patients characteristically have LDH more than 1.5
    times the upper limit of normal.
  evidence:
  - reference: PMID:38477987
    reference_title: "Oral Iptacopan Monotherapy in Paroxysmal Nocturnal Hemoglobinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients who had not received complement inhibitors and who had lactate dehydrogenase (LDH) levels more than 1.5 times the upper limit of the normal range received iptacopan."
    explanation: >-
      Documents that untreated PNH patients characteristically have LDH more than
      1.5 times the upper limit of normal, reflecting intravascular hemolysis.
datasets:
references:
- reference: PMID:39371251
  title: "Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment."
- reference: PMID:38622956
  title: "Complement inhibition in paroxysmal nocturnal hemoglobinuria: From biology to therapy."
- reference: PMID:41002734
  title: "Paroxysmal Nocturnal Hemoglobinuria: Unraveling Its Molecular Pathogenesis and Advancing Targeted Therapeutic Strategies."
- reference: PMID:32390114
  title: "Baseline clinical characteristics and disease burden in patients with paroxysmal nocturnal hemoglobinuria (PNH): updated analysis from the International PNH Registry."
- reference: PMID:38477987
  title: "Oral Iptacopan Monotherapy in Paroxysmal Nocturnal Hemoglobinuria."
- reference: PMID:35154088
  title: "Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria."
- reference: PMID:39273426
  title: "Navigating the Complement Pathway to Optimize PNH Treatment with Pegcetacoplan and Other Currently Approved Complement Inhibitors."
- reference: PMID:40986193
  title: "Pharmacological Therapies in Paroxysmal Nocturnal Haemoglobinuria: Focus on Complement Inhibition."
- reference: PMID:19707355
  title: "Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents."
📚

References & Deep Research

References

9
PMID:39371251
Paroxysmal Nocturnal Hemoglobinuria, Pathophysiology, Diagnostics, and Treatment.
No top-level findings curated for this source.
PMID:38622956
Complement inhibition in paroxysmal nocturnal hemoglobinuria: From biology to therapy.
No top-level findings curated for this source.
PMID:41002734
Paroxysmal Nocturnal Hemoglobinuria: Unraveling Its Molecular Pathogenesis and Advancing Targeted Therapeutic Strategies.
No top-level findings curated for this source.
PMID:32390114
Baseline clinical characteristics and disease burden in patients with paroxysmal nocturnal hemoglobinuria (PNH): updated analysis from the International PNH Registry.
No top-level findings curated for this source.
PMID:38477987
Oral Iptacopan Monotherapy in Paroxysmal Nocturnal Hemoglobinuria.
No top-level findings curated for this source.
PMID:35154088
Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria.
No top-level findings curated for this source.
PMID:39273426
Navigating the Complement Pathway to Optimize PNH Treatment with Pegcetacoplan and Other Currently Approved Complement Inhibitors.
No top-level findings curated for this source.
PMID:40986193
Pharmacological Therapies in Paroxysmal Nocturnal Haemoglobinuria: Focus on Complement Inhibition.
No top-level findings curated for this source.
PMID:19707355
Paroxysmal nocturnal hemoglobinuria: pathophysiology, natural history and treatment options in the era of biological agents.
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Paroxysmal Nocturnal Hemoglobinuria: Disease-Characteristics Report
Edison Scientific Literature 41 citations 2026-07-24T16:26:25.944096

Paroxysmal Nocturnal Hemoglobinuria: Disease-Characteristics Report

Executive summary

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, non-Mendelian clonal hematopoietic stem-cell disorder. A somatic loss-of-function mutation—usually in PIGA—prevents biosynthesis of the glycosylphosphatidylinositol (GPI) anchor. Consequently, affected blood cells lack GPI-anchored complement regulators, especially CD55/decay-accelerating factor and CD59, and become susceptible to complement-mediated injury. The defining clinical spectrum comprises chronic or episodic intravascular hemolysis, thrombosis, and variable bone-marrow failure. Modern complement inhibitors have greatly improved survival, but residual anemia, breakthrough hemolysis, infection risk, adherence, marrow failure, and access remain important unmet needs. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, versino2024complementinhibitionin pages 2-2, colden2022insightsintothe pages 1-3)

The following table provides a compact knowledge-base summary; ontology accessions marked for validation should be checked directly against the current source ontology before production ingestion.

Domain Key facts Suggested ontology mappings* Key evidence
Identity / identifiers Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal hematopoietic stem-cell disorder characterized by complement-mediated hemolysis, thrombophilia, and variable bone-marrow failure; disease-level information here is derived from aggregated literature/registry resources rather than individual EHRs. Common synonyms: PNH; paroxysmal nocturnal haemoglobinuria. MONDO/OMIM/Orphanet/MeSH/ICD identifiers should be independently validated before KB ingestion if exact accession is required. MONDO: PNH [validate exact accession]; MeSH: [validate]; ICD-10/11: [validate] (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2, colden2022insightsintothe pages 1-3)
Cause / etiology Primary cause is acquired somatic loss-of-function mutation of PIGA in hematopoietic stem cells on Xp22.1, causing GPI-anchor deficiency. PIGA mutation is necessary but often considered insufficient alone for overt disease; clonal expansion is linked to immune-mediated marrow failure context, especially aplastic anemia. No Mendelian inheritance pattern for classic PNH. Gene: PIGA; CL: hematopoietic stem cell [validate exact CL term] (versino2024complementinhibitionin pages 1-2, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 2-4, versino2024complementinhibitionin pages 2-3, colden2022insightsintothe pages 1-3, chen2021advancesinthe pages 1-3)
Core mechanism / pathophysiology Loss of GPI anchors removes complement regulators CD55/DAF and CD59 from RBCs (and other blood cells), permitting alternative-pathway amplification, terminal complement activation, and MAC-mediated intravascular hemolysis. Upstream C3 deposition also drives extravascular hemolysis under C5 blockade. Free hemoglobin scavenges nitric oxide, contributing to smooth-muscle dystonia, vasospasm, platelet activation, endothelial dysfunction, thrombosis, renal injury, and pulmonary hypertension. GO: complement activation, alternative pathway [validate]; GO: membrane attack complex assembly [validate]; GO: hemolysis [validate]; GO: nitric oxide metabolic process [validate]; CL: erythrocyte [validate], platelet [validate], neutrophil [validate]; UBERON: bone marrow [validate], blood [validate], kidney [validate], lung vasculature [validate] (versino2024complementinhibitionin pages 3-4, risitano2008paroxysmalnocturnalhemoglobinuria pages 3-4, versino2024complementinhibitionin pages 2-3, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2, hillmen2024navigatingthecomplement pages 7-9)
Major phenotypes with frequencies Registry baseline burden (untreated at enrollment): fatigue 80.9–81%, dyspnea 45.3%, hemoglobinuria 45.0%, abdominal pain 35.2%, impaired renal function 42.8%, high disease activity 51.6%, bone-marrow failure 62.6%, RBC transfusion history 61.3%, major adverse vascular events 18.8%; thrombosis may affect up to 40% in some series/reviews and can be the first manifestation, often at unusual venous sites. QoL study (China): anxiety/depression problems 81.5%, pain/discomfort 69.9%, mean EQ-5D-5L utility 0.76, EQ-VAS 62.61. HPO: fatigue [validate]; dyspnea [validate]; hemoglobinuria [validate]; abdominal pain [validate]; anemia [validate]; thrombosis [validate]; bone marrow hypocellularity/failure [validate]; renal insufficiency [validate]; pulmonary hypertension [validate] (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, schrezenmeier2020baselineclinicalcharacteristics pages 1-2, schrezenmeier2020baselineclinicalcharacteristics pages 3-5, yu2024healthrelatedqualityof pages 1-2)
Diagnosis Gold standard is high-sensitivity flow cytometry demonstrating GPI-deficient populations across ≥2 blood cell lineages, typically using FLAER with lineage markers for granulocytes/monocytes and CD55/CD59 or related markers on RBCs. In the APPLY/APPOINT trial population, diagnostic eligibility required flow-confirmed affected red-cell and white-cell populations ≥10%. Screening is particularly relevant in aplastic anemia and unexplained persistent cytopenias. MAXO: flow cytometry assay [validate]; CL: granulocyte [validate], monocyte [validate], erythrocyte [validate] (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 2-4, almakadi2025clinicalcharacteristicsand pages 4-6, latour2024oraliptacopanmonotherapy pages 1-4)
Epidemiology / population Reported prevalence ranges roughly 10–20 per million globally; some reviews cite 13–38 per million. Incidence is commonly 1–1.5 per million/year; some sources report 0.08–0.57 per 100,000 person-years. Median age at diagnosis/onset is typically 35–40 years; no strong sex predilection is consistently observed. Italian real-world analysis estimated prevalence 17.6 per million adults (Dec 2021) and incidence 1.5 per million/year. MONDO: PNH [validate] (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2, schrezenmeier2020baselineclinicalcharacteristics pages 3-5, yu2024healthrelatedqualityof pages 1-2)
Current therapies Complement inhibition is standard of care for hemolytic PNH. Established agents: eculizumab (anti-C5; FDA 2007), ravulizumab (long-acting anti-C5; every 8 weeks), pegcetacoplan (C3 inhibitor; approved 2021), iptacopan (oral factor B inhibitor; FDA Dec 6, 2023), danicopan (factor D inhibitor; add-on/novel proximal inhibitor), and crovalimab (anti-C5; approved in 2024 in some jurisdictions per recent reviews). Supportive care includes RBC transfusion, anticoagulation when indicated, immunosuppressive therapy for marrow failure, and vaccination against encapsulated bacteria before complement inhibition; allogeneic HSCT remains the only curative option for selected fit patients, especially with severe marrow failure. MAXO: complement inhibition therapy [validate]; monoclonal antibody therapy [validate]; blood transfusion [validate]; anticoagulation therapy [validate]; hematopoietic stem-cell transplantation [validate]; CHEBI/drug mappings [validate separately] (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 6-8, perry2025theadvancinglandscape pages 3-4, schrezenmeier2020baselineclinicalcharacteristics pages 3-5, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2)
2023–2024 advances Iptacopan phase 3 (APPLY-PNH, APPOINT-PNH; NEJM 2024): in anti-C5-treated patients, 51/60 achieved Hb increase ≥2 g/dL without transfusion and 42/60 achieved Hb ≥12 g/dL without transfusion vs 0/35 on continued anti-C5; in complement-inhibitor–naive patients, 31/33 achieved Hb increase ≥2 g/dL without transfusion. 59/62 iptacopan-treated vs 14/35 anti-C5-treated patients avoided transfusion in APPLY; in APPOINT, no patients required transfusion. Reviews summarize ravulizumab as noninferior to eculizumab with fewer breakthrough hemolysis events and pegcetacoplan as superior to eculizumab for persistent anemia in PEGASUS, with PRINCE supporting first-line use. MAXO: oral small-molecule therapy [validate]; complement factor B inhibition [validate]; complement C3 inhibition [validate] (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 6-8, perry2025theadvancinglandscape pages 3-4, latour2024oraliptacopanmonotherapy pages 1-4, hillmen2024navigatingthecomplement pages 7-9)
Prognosis / outcomes Pre-complement era mortality was substantial; some retrospective analyses cited ~35% 5-year mortality and ~50% 10-year mortality. Complement inhibition markedly improves survival and reduces thrombosis. Review data cite 5-year survival 95.5% with eculizumab and thrombotic events decreasing from 5.6 to 0.8 per 100 patient-years. Thrombosis remains the leading cause of death in untreated disease and still occurs at lower frequency in the complement-inhibitor era. HPO: reduced survival [validate]; thrombosis [validate]; chronic kidney disease [validate] (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2, perry2025theadvancinglandscape pages 3-4, risitano2008paroxysmalnocturnalhemoglobinuria pages 3-4)
Model systems / comparative biology Mouse and rhesus macaque PIGA-loss models recapitulate GPI-AP-deficient blood cells, shortened erythrocyte lifespan, and complement sensitivity, but generally do not develop full human clinical hemolysis/thrombosis or sustained clonal expansion. These models suggest PIGA mutation alone is insufficient and that immune context/secondary factors are important. No strong evidence from collected sources for a naturally occurring veterinary analog was identified. CL: hematopoietic stem/progenitor cell [validate]; GO: erythrocyte homeostasis [validate] (colden2022insightsintothe pages 1-3, chen2021advancesinthe pages 1-3)
Important gaps / caution flags Exact disease identifiers (MONDO/OMIM/Orphanet/MeSH/ICD/HPO/GO/CL/UBERON/MAXO accessions) were not directly verified in the collected evidence and should be checked against the source ontologies before production use. Recent literature mentions additional somatic mutations and clonal hematopoiesis in marrow-failure contexts, but no robust disease-specific modifier set with validated clinical effect was established from the collected evidence. Omics/single-cell/spatial transcriptomic evidence was not clearly available in the retrieved material. All exact accession numbers: independent validation required (versino2024complementinhibitionin pages 2-3, colden2022insightsintothe pages 1-3, chen2021advancesinthe pages 1-3)

Table: This compact table summarizes core disease facts for paroxysmal nocturnal hemoglobinuria, including cause, mechanism, phenotypes, diagnosis, epidemiology, treatment advances, prognosis, and model systems. It also flags ontology mappings and identifiers that should be independently validated before database ingestion.

1. Disease information

Definition, identifiers, and synonyms

Preferred name: paroxysmal nocturnal hemoglobinuria. Synonyms: paroxysmal nocturnal haemoglobinuria, PNH, Marchiafava–Micheli disease, and Strübing–Marchiafava disease. The historical name is imperfect: hemolysis is not necessarily paroxysmal, nocturnal, or accompanied by visible hemoglobinuria.

Commonly assigned identifiers are OMIM 300818, Orphanet ORPHA:447, ICD-10-CM D59.5, and MeSH D006457. A commonly used MONDO mapping is MONDO:0012727, but all identifiers—particularly the current ICD-11 and MONDO releases—should be verified against the live terminology service before database release.

This report concerns aggregated disease-level evidence from peer-reviewed studies, international registries, consensus literature, and trials. It is not derived from an individual patient’s EHR. The International PNH Registry analysis included 4,439 patients and is therefore population-level observational evidence. (schrezenmeier2020baselineclinicalcharacteristics pages 1-2)

2. Etiology, risks, and protective factors

Primary cause

Classic PNH is caused by an acquired somatic, not inherited, loss-of-function mutation in PIGA, an X-linked gene at Xp22. PIGA participates in the first step of GPI-anchor synthesis in the endoplasmic reticulum. Because only one active X chromosome is present in each hematopoietic cell, a single somatic hit can produce the phenotype. Hundreds of private mutations have been reported—including small insertions/deletions, substitutions, nonsense, frameshift, and splice-altering lesions—with no dominant hotspot; one sequencing series found 26 PIGA mutations among 33 patients and identified exon 2 as the most frequently affected region. (versino2024complementinhibitionin pages 2-3, chen2021advancesinthe pages 1-3)

PIGA mutation is necessary but generally insufficient for clinically overt PNH. Tiny GPI-deficient populations, approximately 0.001–0.005%, can occur in healthy people, whereas expanded clones occur in nearly half of patients with immune-mediated acquired aplastic anemia. The leading “escape” model proposes that autoreactive T-cell pressure suppresses normal hematopoiesis while GPI-deficient hematopoietic stem/progenitor cells enjoy relative survival—not an autonomous proliferative advantage. Mouse and macaque experiments support this interpretation because mutant cells reconstitute hematopoiesis but do not progressively dominate. (colden2022insightsintothe pages 1-3)

Risk and modifier factors

  • Strong clinical context: acquired aplastic anemia and other immune-mediated marrow-failure states. Clone evolution can occur during recovery after immunosuppression. (colden2022insightsintothe pages 1-3)
  • Clone size: larger granulocyte clones generally correlate with hemolysis, high disease activity, and thrombosis, although clinically important events occur even with clones below 10%. (schrezenmeier2020baselineclinicalcharacteristics pages 1-2)
  • Physiologic complement-amplifying conditions: infection, trauma, surgery, pregnancy, and other inflammatory states can precipitate pharmacodynamic breakthrough hemolysis. (versino2024complementinhibitionin pages 1-2, hillmen2024navigatingthecomplement pages 7-9)
  • Additional somatic variants: exploratory studies have reported variants in genes including TET2, CUX1, SUZ12, RBPJ, MUC4, MLL2/KMT2D, and others. Their causal or prognostic roles are not sufficiently validated for routine PNH risk stratification. RBPJ knockdown increased apoptosis and reduced proliferation in patient-derived cells in vitro, but in-vivo confirmation is lacking. (chen2021advancesinthe pages 1-3)
  • Thrombophilia alleles: factor V Leiden and MTHFR polymorphisms have been examined, but a disease-modifying causal effect remains unproven. (risitano2008paroxysmalnocturnalhemoglobinuria pages 3-4)

No reproducible dietary, lifestyle, occupational, toxin, infectious-agent, or environmental cause has been established. There are likewise no validated inherited protective alleles or lifestyle measures that prevent acquisition of PNH. Avoiding infection and promptly treating complement-amplifying conditions reduces complications rather than preventing the initial clone.

3. Phenotypes

PNH may present from childhood to late adulthood but is predominantly an adult-onset disease, with median diagnosis around 35–40 years. Severity is highly variable; manifestations are chronic with episodic exacerbations. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, yu2024healthrelatedqualityof pages 1-2)

Principal phenotypes and suggested HPO annotations

  • Coombs-negative intravascular hemolytic anemia: anemia, reticulocytosis, elevated LDH and indirect bilirubin, low haptoglobin, plasma-free hemoglobin, and hemoglobinuria/hemosiderinuria. Suggested HPO: Hemolytic anemia, Intravascular hemolysis, Reticulocytosis, Elevated lactate dehydrogenase, Hemoglobinuria. (versino2024complementinhibitionin pages 3-4)
  • Fatigue and exercise intolerance: fatigue occurred in 80.9–81% of registry patients; dyspnea occurred in 45.3%. Suggested HPO: Fatigue, Exercise intolerance, Dyspnea. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, schrezenmeier2020baselineclinicalcharacteristics pages 3-5)
  • Hemoglobinuria: reported by 45.0%; it may be episodic and is neither required nor always nocturnal. Suggested HPO: Hemoglobinuria. (schrezenmeier2020baselineclinicalcharacteristics pages 3-5)
  • Smooth-muscle dystonia: abdominal pain (35.2%), dysphagia, esophageal spasm, and erectile dysfunction arise largely from nitric-oxide depletion. Suggested HPO: Abdominal pain, Dysphagia, Erectile dysfunction. (versino2024complementinhibitionin pages 3-4, schrezenmeier2020baselineclinicalcharacteristics pages 3-5)
  • Thrombosis: venous events predominate and frequently involve unusual sites—hepatic/Budd–Chiari, portal, mesenteric, splenic, or cerebral veins. Thrombosis may be the first manifestation and historically affected up to approximately 40% of patients. Suggested HPO: Venous thrombosis, Budd-Chiari syndrome, Cerebral venous thrombosis. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2)
  • Bone-marrow failure/cytopenias: aplastic anemia, pancytopenia, neutropenia, and thrombocytopenia may precede, accompany, or follow hemolytic PNH. Bone-marrow failure was recorded in 62.6% of the large registry cohort. Suggested HPO: Bone marrow hypocellularity, Pancytopenia, Thrombocytopenia, Neutropenia. (schrezenmeier2020baselineclinicalcharacteristics pages 1-2)
  • Renal disease: acute kidney injury during hemolytic crises and chronic impairment from repeated hemoglobin filtration, hemosiderin deposition, tubular injury, and vascular dysfunction; registry impaired renal function was 42.8%. Suggested HPO: Renal insufficiency, Acute kidney injury, Hemosiderinuria. (schrezenmeier2020baselineclinicalcharacteristics pages 1-2, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2)
  • Pulmonary/vascular disease: pulmonary hypertension and dyspnea can follow NO depletion, hemolysis, and thromboembolism. Suggested HPO: Pulmonary hypertension. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2)

Clinical categories include classic hemolytic PNH, PNH associated with another marrow disorder, subclinical PNH, and a proposed ahemolytic/“white PNH” phenotype with a sizable clone but little biochemical hemolysis. Clone-size boundaries are descriptive rather than absolute treatment criteria. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 2-4)

Quality of life

A 2024 Chinese cross-sectional study of 329 patients found anxiety/depression problems in 81.5%, pain/discomfort in 69.9%, mean EQ-5D-5L utility 0.76, and mean EQ-VAS 62.61. Anemia symptoms, back pain, hemoglobinuria, thrombosis, sex, and income influenced HRQoL. Diagnostic burden is also substantial: fewer than 40% have historically been diagnosed within 12 months of symptom onset, while 24% waited at least five years. (yu2024healthrelatedqualityof pages 1-2)

4. Genetic and molecular information

Causal gene: PIGA; the relevant lesions are somatic variants in a multipotent hematopoietic stem cell. They are absent from the constitutional germline in ordinary PNH and therefore should not be interpreted using population carrier frequency or Mendelian penetrance concepts. Germline PIGA variants instead cause a distinct congenital disorder of GPI-anchor biosynthesis, not classic PNH.

Most pathogenic PNH variants produce partial or complete loss of function. Type III cells completely lack GPI-anchored proteins and are much more complement-sensitive; type II cells retain partial expression; type I cells are phenotypically normal. Flow cytometry—not germline variant classification—is the clinically decisive assay. (kelly2025pharmacologicaltherapiesin pages 1-2, versino2024complementinhibitionin pages 3-4)

No recurrent chromosomal abnormality defines PNH. Cytogenetic or myeloid-gene abnormalities may indicate associated MDS or clonal evolution and should be interpreted as comorbidity/modification rather than the defining lesion. WES/WGS may detect PIGA or secondary variants but is not first-line diagnostic testing.

Epigenetic, single-cell, spatial-transcriptomic, proteomic, metabolomic, and lipidomic signatures are not sufficiently standardized for clinical annotation. Current omics work is chiefly exploratory; no omics-based diagnostic has displaced flow cytometry.

5. Environmental information

PNH is not caused by a pathogen, toxin, diet, smoking, alcohol, radiation, or occupation. Infection, surgery, trauma, and pregnancy can increase complement activation and trigger hemolysis in an existing clone. These are triggers/modifiers, not primary causes. There is no zoonotic transmission or infectious reservoir. (versino2024complementinhibitionin pages 1-2, hillmen2024navigatingthecomplement pages 7-9)

6. Mechanism and pathophysiology

Upstream causal chain

  1. A somatic PIGA lesion occurs in a hematopoietic stem cell.
  2. Defective ER GPI-anchor synthesis prevents surface attachment of nearly 150 GPI-linked proteins.
  3. Descendant erythrocytes, granulocytes, monocytes, and platelets lack CD55 and CD59.
  4. CD55 loss impairs decay of C3/C5 convertases; CD59 loss permits C5b-9 membrane-attack-complex assembly.
  5. Constitutive alternative-pathway “tick-over,” factor B/factor D amplification, and terminal complement activation lyse PNH erythrocytes. (versino2024complementinhibitionin pages 2-3, colden2022insightsintothe pages 1-3)

Downstream injury

Intravascular hemolysis releases free hemoglobin, which scavenges nitric oxide. NO depletion causes vasoconstriction and smooth-muscle dystonia, explaining abdominal pain, dysphagia, erectile dysfunction, fatigue, and part of the pulmonary hypertension phenotype. Hemoglobin/iron filtration causes renal tubular hemosiderosis and dysfunction. (risitano2008paroxysmalnocturnalhemoglobinuria pages 3-4, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2)

Thrombosis is multifactorial: complement-mediated platelet and endothelial activation, procoagulant microparticles, leukocyte activation, tissue-factor and inflammatory signaling, impaired fibrinolysis—including possible loss of GPI-anchored uPAR—and NO depletion reinforce coagulation. The complement and coagulation systems form a bidirectional amplification loop. (risitano2008paroxysmalnocturnalhemoglobinuria pages 3-4, fattizzo2026thrombosisinparoxysmal pages 1-2, apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2)

Under C5 blockade, C3 fragments may accumulate on surviving PNH erythrocytes and mark them for hepatic/splenic phagocytosis, causing C3-mediated extravascular hemolysis. Proximal inhibitors at C3, factor B, or factor D address this mechanism. (kelly2025pharmacologicaltherapiesin pages 1-2, hillmen2024navigatingthecomplement pages 7-9)

Suggested annotations include GO GPI-anchor biosynthetic process, complement activation, alternative pathway, membrane attack complex assembly, erythrocyte homeostasis, nitric oxide metabolic process, and blood coagulation; CL hematopoietic stem cell, erythrocyte, monocyte, neutrophil, platelet, endothelial cell, and macrophage.

7. Anatomical structures affected

The primary compartment is bone marrow hematopoiesis and circulating blood. Directly affected cell lineages include erythrocytes, granulocytes, monocytes, and platelets. Secondary organs include the kidney, liver and splanchnic venous system, cerebral veins, lungs/pulmonary vasculature, spleen, and gastrointestinal tract. No lateralization applies. Subcellular compartments include the ER/Golgi GPI-biosynthetic pathway, plasma membrane, extracellular complement cascade, and MAC. Suggested UBERON mappings: bone marrow, blood, kidney, liver, spleen, lung, pulmonary artery, portal vein, hepatic vein, and cerebral venous system.

8. Temporal development

Onset is usually insidious in young-to-middle adulthood, although pediatric and geriatric disease occurs. The clone may remain small and asymptomatic, expand during immune marrow failure, produce chronic hemolysis with episodic crises, regress, or coexist with persistent aplasia. Small clones should be monitored because clinical burden is not zero: among clones below 10%, registry rates were 9.7% for hemolysis, 10.2% for major adverse vascular events, and 9.1% for high disease activity. (schrezenmeier2020baselineclinicalcharacteristics pages 1-2)

PNH is generally chronic. Spontaneous clonal contraction/remission can occur, but the timing is unpredictable. Critical intervention windows include active hemolysis, new thrombosis, pregnancy, major surgery, infection, transfusion dependence, and worsening marrow failure.

9. Inheritance, epidemiology, and population

PNH has no Mendelian inheritance pattern, carrier state, anticipation, founder effect, consanguinity association, or conventional germline penetrance. Familial recurrence is not expected, and routine cascade or reproductive genetic screening is inappropriate for classic PNH.

Reported estimates vary with ascertainment: prevalence is commonly 10–20 per million, with broader estimates of 13–38 per million; incidence is often approximately 1–1.5 per million/year. A 2024 review cited incidence 0.08–0.57 per 100,000 person-years and prevalence about 38 per million. There is no consistent sex, race, ethnicity, or geographic predilection, although ascertainment and access differ markedly. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2, yu2024healthrelatedqualityof pages 1-2)

In the 4,439-patient registry, 51.6% had high disease activity, 18.8% a major adverse vascular event, 62.6% marrow failure, 61.3% prior RBC transfusion, and 42.8% impaired renal function. (schrezenmeier2020baselineclinicalcharacteristics pages 1-2)

10. Diagnostics

Recommended approach

High-sensitivity multiparameter flow cytometry on peripheral blood is the diagnostic gold standard. Demonstrate deficient GPI-linked proteins in at least two lineages. Granulocyte/monocyte assays commonly combine FLAER with CD24, CD14, CD157, CD15, CD45, and/or CD64; RBC assays use CD235a gating with CD59 and sometimes CD55. Granulocyte and monocyte clone sizes best estimate the stem-cell clone because transfusion and hemolysis can underestimate RBC clones. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 2-4, almakadi2025clinicalcharacteristicsand pages 4-6)

Initial laboratory evaluation includes CBC/differential, reticulocytes, blood smear, LDH, bilirubin, haptoglobin, plasma-free hemoglobin, urinalysis, renal function, iron indices, and direct antiglobulin testing. Bone-marrow aspirate/biopsy and cytogenetic/myeloid NGS evaluation are indicated when aplastic anemia, MDS, or unexplained cytopenias are suspected.

Screen appropriate patients with acquired aplastic anemia; unexplained Coombs-negative hemolysis; hemoglobinuria; unexplained cytopenias; MDS with hypocellularity; thrombosis at unusual sites; or thrombosis accompanied by hemolysis/cytopenia. Historical Ham and sucrose-lysis tests are obsolete except in legacy reports.

Differential diagnosis

Exclude autoimmune hemolytic anemia, hereditary membrane/enzyme defects, microangiopathic hemolysis, cold-antibody disease, mechanical hemolysis, march hemoglobinuria, infection-associated hemolysis, and other marrow-failure/MDS syndromes. PNH is distinguished by a reproducible GPI-deficient clone across blood lineages.

WES, WGS, single-gene sequencing, CMA, FISH, karyotyping, mtDNA, and repeat-expansion tests are not routine confirmatory tests for PNH. Population, newborn, carrier, prenatal, and preimplantation screening are not indicated.

11. Outcomes and prognosis

Before complement inhibition, thrombosis was the leading cause of death and retrospective estimates included approximately 35% five-year mortality and 50% ten-year mortality. Contemporary complement therapy has transformed prognosis; a review cited 95.5% five-year survival with eculizumab and reduction in thrombotic events from 5.6 to 0.8 per 100 patient-years. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2, perry2025theadvancinglandscape pages 3-4)

Poor prognostic factors include prior thrombosis, large/expanding clone, severe hemolysis, transfusion dependence, renal impairment, pulmonary hypertension, persistent cytopenias, severe aplastic anemia, MDS/AML evolution, and inadequate complement control. Residual anemia may reflect extravascular hemolysis, breakthrough intravascular hemolysis, iron deficiency, renal dysfunction, or marrow failure.

12. Treatment and recent developments

Complement-directed therapy

  • Eculizumab, anti-C5 monoclonal antibody, FDA-approved in 2007, suppresses MAC-mediated intravascular hemolysis and substantially reduces transfusion, thrombosis, renal injury, and mortality. Limitations are intravenous dosing every two weeks, C3-mediated extravascular hemolysis, and breakthrough hemolysis. Suggested MAXO: complement-inhibitor therapy; monoclonal-antibody therapy. (versino2024complementinhibitionin pages 2-2, perry2025theadvancinglandscape pages 3-4)
  • Ravulizumab, recycled long-acting anti-C5 antibody, permits approximately eight-week dosing. Phase III studies established noninferiority to eculizumab; review data report transfusion avoidance of 73.6% versus 66.1% and breakthrough hemolysis of 4.0% versus 10.7%. (perry2025theadvancinglandscape pages 3-4)
  • Pegcetacoplan, subcutaneous C3/C3b inhibitor approved in 2021, inhibits proximal and terminal activation and controls both intravascular and C3-mediated extravascular hemolysis. PEGASUS showed superiority to eculizumab for persistent anemia; PRINCE supported use in complement-inhibitor-naïve disease. Injection-site reactions are common. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 6-8, hillmen2024navigatingthecomplement pages 7-9)
  • Iptacopan, oral factor-B inhibitor, received FDA approval on 6 December 2023. In 2024 APPLY-PNH, 51/60 patients switching from anti-C5 achieved a ≥2-g/dL hemoglobin increase and 42/60 reached hemoglobin ≥12 g/dL without transfusion, versus 0/35 continuing anti-C5. In APPOINT-PNH, 31/33 untreated patients achieved a ≥2-g/dL increase without transfusion. Transfusion avoidance was 59/62 versus 14/35 in APPLY; no APPOINT patient required transfusion. Headache was the most frequent adverse event. Trials: NCT04558918 and NCT04820530; published 14 March 2024, DOI https://doi.org/10.1056/NEJMoa2308695. (latour2024oraliptacopanmonotherapy pages 1-4)
  • Danicopan, oral factor-D inhibitor, is used as add-on therapy to anti-C5 in selected patients with clinically significant extravascular hemolysis/residual anemia. It targets alternative-pathway amplification while preserving established terminal blockade. (versino2024complementinhibitionin pages 1-2)
  • Crovalimab, a recycling subcutaneous anti-C5 antibody, showed noninferiority to eculizumab in the COMMODORE program and offers less frequent administration. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 6-8)

All complement inhibitors increase susceptibility to invasive infection—especially Neisseria meningitidis and, depending on the breadth of blockade, other encapsulated bacteria such as pneumococcus and Haemophilus influenzae. Vaccination should precede treatment when feasible; urgent therapy should not be delayed when clinically necessary, but antibiotic prophylaxis and local regulatory guidance should then be followed. Vaccination does not eliminate risk, so fever or meningococcal symptoms require emergency evaluation. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 6-8)

Treatment strategy

Treat clinically significant hemolysis, symptomatic anemia, thrombosis, organ injury, transfusion dependence, or high disease activity—not clone size alone. A C5 inhibitor remains appropriate for robust intravascular control; proximal inhibition is attractive for residual C3-mediated anemia or oral/subcutaneous convenience. There was no universally accepted evidence-based first-line algorithm in 2024; selection should incorporate marrow reserve, hemolysis type, thrombosis history, adherence, pregnancy, infection risk, route, availability, and cost. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2)

Supportive measures include phenotype-matched RBC transfusion, folate and iron replacement when deficient, treatment of infection, renal support, and careful avoidance of unnecessary corticosteroids. Anticoagulation is indicated for acute thrombosis, generally together with complement inhibition; duration should be individualized. Registry baseline use included transfusion in 61.3%, anticoagulation in 20.2%, and immunosuppression in 38.8%. (schrezenmeier2020baselineclinicalcharacteristics pages 3-5)

Allogeneic hematopoietic stem-cell transplantation is the only established curative therapy but carries substantial treatment-related morbidity and mortality. It is generally reserved for severe marrow failure, clonal evolution/MDS, or selected refractory disease rather than uncomplicated complement-responsive hemolysis. Suggested MAXO: hematopoietic stem-cell transplantation. (apostolidou2025paroxysmalnocturnalhemoglobinuria pages 1-2)

No validated pharmacogenomic genotype currently selects among complement inhibitors. PIGA variant class itself does not determine drug choice.

Pregnancy

Pregnancy raises hemolytic and thrombotic risk and requires specialist hematology–maternal-fetal care. A systematic review of 190 pregnancies found fetal survival of 82% with eculizumab versus 69% without it; miscarriage was twice as frequent without treatment, and preterm delivery occurred in 32% versus 44%. Evidence was predominantly observational/case-series level, so confounding remains. (manning2025paroxysmalnocturnalhaemoglobinuria pages 1-3)

13. Prevention

There is no primary prevention for the spontaneous somatic PIGA event. No population, newborn, carrier, or family screening program is appropriate.

Secondary prevention consists of timely flow-cytometric testing in high-risk clinical contexts, serial clone monitoring in aplastic anemia/MDS, and early treatment of active hemolysis or thrombosis. Tertiary prevention comprises complement inhibition, vaccination, infection education, thrombosis management, renal monitoring, perioperative planning, and management of pregnancy and inflammatory triggers. Genetic counseling should explain the acquired, non-heritable nature of classic PNH rather than offer familial predictive testing.

14. Other species and natural disease

No well-established naturally occurring veterinary counterpart of human clonal PNH was identified. PIGA and the GPI-anchor pathway are evolutionarily conserved, but classic PNH is not zoonotic and has no cross-species transmission. Mouse Piga and rhesus PIGA are the principal orthologous experimental targets; exact NCBI Gene and taxon identifiers should be validated directly before database ingestion.

15. Model organisms

Conditional/chimeric Piga-knockout mice, erythroid-specific knockout models, and CRISPR-edited rhesus macaques generate GPI-AP-deficient lineages. They reproduce shortened erythrocyte survival and increased complement sensitivity, making them useful for studying GPI biology, immune selection, and complement therapeutics. However, they generally fail to develop the sustained clone expansion, overt hemolysis, and thrombosis characteristic of human PNH. (colden2022insightsintothe pages 1-3, chen2021advancesinthe pages 1-3)

This limitation is mechanistically informative: the dedicated animal-model review concludes that “the PIG-A mutation is one of the several conditions required for PNH, but it alone is not enough to cause PNH.” Likewise, the 2022 review states that mutant cells “have no intrinsic growth advantage and do not clonally expand over time.” These are review-abstract quotations synthesizing mouse and nonhuman-primate evidence, not direct human clinical findings. (colden2022insightsintothe pages 1-3, chen2021advancesinthe pages 1-3)

Cellular systems include patient-derived CD59-negative blood/HSPC populations, engineered PIGA-null cell lines, and complement-sensitive erythroid assays. Their limitations include absence of marrow immune selection, whole-organism complement–coagulation interactions, and thrombosis. MGI, IMSR/MMRRC, NCBI Gene, and nonhuman-primate research repositories are appropriate model-resource starting points.

Evidence limitations and authoritative interpretation

The strongest human evidence comprises flow-confirmed clinical cohorts, the International PNH Registry, randomized complement-inhibitor trials, and recent expert reviews. Exact phenotype frequencies vary with referral pattern, clone threshold, therapy exposure, and geographic access. The 2024 expert position is that terminal inhibitors dramatically improve survival, whereas proximal inhibitors improve residual anemia and quality of life; nevertheless, long-term comparative effectiveness and first-line selection require more real-world data. (panse2024paroxysmalnocturnalhemoglobinuria pages 1-2)

Mechanistic statements about immune escape, secondary mutations, platelet/endothelial pathways, and animal models combine human observational, in-vitro, and model-organism evidence and should not all be assigned equal causal certainty. Robust PNH-specific spatial transcriptomic, single-cell atlas, epigenomic, lipidomic, or clinically validated multi-omic signatures remain unavailable in the retrieved evidence.

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