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Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

Pathophysiology description

2025-12-15
Falcon MONDO:0005775 Model: Edison Scientific Literature 18 citations

Pathophysiology description G6PD deficiency is an X-linked enzymopathy that reduces activity of the rate-limiting enzyme of the oxidative pentose phosphate pathway (PPP). In red blood cells (RBCs), which lack mitochondria, PPP-derived NADPH is the dominant source of reducing equivalents to maintain the glutathione system and broader redox homeostasis. In G6PD deficiency, diminished NADPH generation impairs glutathione reductase-mediated recycling of oxidized glutathione (GSSG) to reduced glutathione (GSH). This lowers cellular antioxidant capacity, promoting oxidative modification of hemoglobin (Heinz bodies), membrane lipid peroxidation, band 3 clustering, decreased deformability, and premature clearance or intravascular hemolysis. Oxidative stressors—especially certain drugs, infections, and oxidant foods such as fava beans—precipitate acute hemolytic anemia. Clinical phenotypes range from asymptomatic baseline to episodic hemolysis, neonatal jaundice, and in severe variants, chronic nonspherocytic hemolytic anemia (URLs: https://doi.org/10.3390/biom13081262, Aug 2023; https://doi.org/10.1155/2021/5529256, Apr 2021; https://doi.org/10.1016/j.tips.2021.07.002, Oct 2021) (orrico2023oxidativestressin pages 10-11, dore2021thecontroversialrole pages 1-2, garcia2021treatmentstrategiesfor pages 1-2).

1) Core Pathophysiology - Primary mechanisms - PPP/NADPH impairment: G6PD catalyzes the first, rate-limiting step of the oxidative PPP that produces NADPH; reduced enzyme activity lowers NADPH supply in RBCs (URLs: https://doi.org/10.3390/biom13081262; https://doi.org/10.1155/2021/5529256) (orrico2023oxidativestressin pages 10-11, dore2021thecontroversialrole pages 1-2). - Glutathione redox failure: Inadequate NADPH limits glutathione reductase recycling of GSSG to GSH, compromising detoxification of hydrogen peroxide and organic peroxides (URLs: https://doi.org/10.3390/biom13081262; https://doi.org/10.1016/j.tips.2021.07.002) (orrico2023oxidativestressin pages 10-11, garcia2021treatmentstrategiesfor pages 1-2). - RBC oxidative injury: Hemoglobin oxidative denaturation (Heinz bodies), membrane lipid peroxidation, and cytoskeletal alterations reduce deformability and promote hemolysis (URLs: https://doi.org/10.3390/biom13081262; https://doi.org/10.4314/sokjmls.v10i1.35) (orrico2023oxidativestressin pages 10-11, kwaifa2025pathophysiologyandcurrent pages 1-2). - Triggered hemolysis: Exposures that increase oxidant load—e.g., primaquine, sulfonamides, dapsone; infections; and fava bean metabolites (vicine/divicine)—precipitate acute hemolytic anemia in deficient individuals (URLs: https://doi.org/10.3390/biom13081262; https://doi.org/10.5195/ijms.2020.637) (orrico2023oxidativestressin pages 10-11, ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2). - Neonatal hyperbilirubinemia: In neonates with G6PD deficiency, unconjugated hyperbilirubinemia can occur rapidly, sometimes with minimal overt hemolysis, reflecting immature bilirubin conjugation/excretion superimposed on increased heme turnover and impaired antioxidant defenses (URL: https://doi.org/10.5195/ijms.2020.637) (ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2).

2) Key Molecular Players - Genes/Proteins (HGNC) - G6PD (HGNC:4421): X-linked enzyme catalyzing oxidation of glucose-6-phosphate to 6-phosphogluconolactone with reduction of NADP+ to NADPH (URLs: https://doi.org/10.1155/2021/5529256; https://doi.org/10.3390/biom13081262) (dore2021thecontroversialrole pages 1-2, orrico2023oxidativestressin pages 10-11). - GSR/glutathione reductase (HGNC:4635): NADPH-dependent enzyme for GSH regeneration; functionally impacted by NADPH deficit (URL: https://doi.org/10.1016/j.tips.2021.07.002) (garcia2021treatmentstrategiesfor pages 1-2). - Hemoglobin (HBB/HBA): Target of oxidation leading to Heinz bodies and precipitates (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11).

3) Biological Processes (GO annotations) - Pentose-phosphate shunt, oxidative branch (GO:0006098): Diminished flux due to G6PD deficiency (URLs: https://doi.org/10.1155/2021/5529256; https://doi.org/10.3390/biom13081262) (dore2021thecontroversialrole pages 1-2, orrico2023oxidativestressin pages 10-11). - NADPH regeneration (GO:0006739): Reduced capacity in RBCs (URL: https://doi.org/10.1016/j.tips.2021.07.002) (garcia2021treatmentstrategiesfor pages 1-2). - Glutathione metabolic process (GO:0006749) and response to oxidative stress (GO:0006979): Impaired GSH homeostasis increases susceptibility to ROS-mediated RBC injury (URLs: https://doi.org/10.3390/biom13081262; https://doi.org/10.4314/sokjmls.v10i1.35) (orrico2023oxidativestressin pages 10-11, kwaifa2025pathophysiologyandcurrent pages 1-2). - Hemolysis (GO:0002937): Triggered by oxidant stress in G6PD-deficient RBCs (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11).

4) Cellular Components - Cytosol: PPP enzymes and GSH/GSSG cycling occur in the RBC cytosol (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11). - RBC membrane/cytoskeleton: Oxidative damage to spectrin/ankyrin and band 3 promotes rigidity and splenic sequestration (URL: https://doi.org/10.4314/sokjmls.v10i1.35) (kwaifa2025pathophysiologyandcurrent pages 1-2). - Heinz bodies (inclusions): Oxidized hemoglobin precipitates attached to the inner membrane (URL: https://doi.org/10.4314/sokjmls.v10i1.35) (kwaifa2025pathophysiologyandcurrent pages 1-2).

5) Disease Progression - Initial trigger: exposure to oxidant drug (e.g., primaquine, sulfonamides, dapsone), intercurrent infection (inflammation-driven ROS), or fava bean ingestion (vicine/divicine) increases oxidant burden (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11). - Molecular defect: limited PPP flux reduces NADPH; GSH/GSSG ratio declines; peroxides accumulate (URLs: https://doi.org/10.1155/2021/5529256; https://doi.org/10.3390/biom13081262) (dore2021thecontroversialrole pages 1-2, orrico2023oxidativestressin pages 10-11). - Cellular injury: hemoglobin denaturation (Heinz bodies), membrane lipid peroxidation, band 3 clustering; decreased deformability (URL: https://doi.org/10.4314/sokjmls.v10i1.35) (kwaifa2025pathophysiologyandcurrent pages 1-2). - Clinical hemolysis: intravascular and/or extravascular hemolysis with anemia, jaundice, hemoglobinuria; in neonates, rapid unconjugated hyperbilirubinemia can develop with risk for bilirubin neurotoxicity if not promptly managed (URL: https://doi.org/10.5195/ijms.2020.637) (ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2).

6) Phenotypic Manifestations (HPO) - Acute hemolytic anemia (HP:0001878): fatigue, pallor, tachycardia following oxidative triggers (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11). - Neonatal hyperbilirubinemia (HP:0002904) and jaundice (HP:0000952): often early, can be severe, occasionally with limited overt signs of hemolysis (URL: https://doi.org/10.5195/ijms.2020.637) (ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2). - Hemoglobinuria (HP:0002905) during intravascular hemolysis; splenomegaly (HP:0001744) with recurrent/extravascular hemolysis; Heinz bodies (HP:0011893) on smear (URL: https://doi.org/10.4314/sokjmls.v10i1.35) (kwaifa2025pathophysiologyandcurrent pages 1-2).

Recent developments and latest research (2023–2024 priority) - RBC oxidative stress in health and disease (2023): Comprehensive review underscoring the central role of PPP-derived NADPH and glutathione in RBC redox control; details oxidative triggers of hemolysis in G6PD deficiency, including drugs, infections, and fava beans (URL: https://doi.org/10.3390/biom13081262, Aug 2023) (orrico2023oxidativestressin pages 10-11). - Systems and tissue perspectives (2022–2021): Although slightly older, state-of-the-art reviews in Cells and Trends in Pharmacological Sciences integrate PPP/NADPH biochemistry with clinical G6PD phenotypes and therapeutic concepts (URLs: https://doi.org/10.3390/cells11193041, Sep 2022; https://doi.org/10.1016/j.tips.2021.07.002, Oct 2021) (garciadominguez2022glucose6pdehydrogenase—an pages 5-6, garcia2021treatmentstrategiesfor pages 1-2).

Current applications and real-world implementations - Avoidance of oxidant drugs and triggers: Clinical management relies on patient education and screening to prevent exposure to high-risk drugs (e.g., primaquine, sulfonamides, dapsone) that precipitate hemolysis (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11). - Newborn screening and early diagnosis: Programs increasingly screen for G6PD activity to mitigate neonatal hyperbilirubinemia risk; prompt phototherapy and supportive care reduce neurotoxicity (URL: https://doi.org/10.5195/ijms.2020.637) (ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2). - Therapeutic concepts under evaluation: Small-molecule stabilization/activation of G6PD, augmentation of GSH pools (e.g., N-acetylcysteine), and compensatory NADPH pathways are discussed as future strategies (URL: https://doi.org/10.1016/j.tips.2021.07.002) (garcia2021treatmentstrategiesfor pages 1-2).

Expert opinions and analysis - Consensus across recent and foundational reviews emphasizes that in RBCs, “erythrocytes rely solely on PPP-derived NADPH” and that “G6PD deficiency thus impairs GSH regeneration, reducing disposal of oxidants and predisposing to oxidative membrane damage and hemolysis.” These mechanistic insights underpin current prevention-first clinical strategies and motivate development of enzyme-stabilizing therapies (URLs: https://doi.org/10.3390/biom13081262; https://doi.org/10.1155/2021/5529256; https://doi.org/10.1016/j.tips.2021.07.002) (orrico2023oxidativestressin pages 10-11, dore2021thecontroversialrole pages 1-2, garcia2021treatmentstrategiesfor pages 1-2).

Relevant statistics and data - Prevalence and genetics: G6PD deficiency is the most common human enzymopathy, with hundreds of variants producing a spectrum of residual activity and phenotypes; X-linked inheritance yields higher expression in males (URL: https://doi.org/10.5195/ijms.2020.637) (ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2). - Triggers and risk: Multiple commonly used drugs can trigger hemolysis in deficient individuals; infections and fava beans are frequent natural precipitants (URL: https://doi.org/10.3390/biom13081262) (orrico2023oxidativestressin pages 10-11).

Gene/protein annotations and ontology terms - Gene/Protein (HGNC): - G6PD (HGNC:4421) (dore2021thecontroversialrole pages 1-2, orrico2023oxidativestressin pages 10-11) - GSR (HGNC:4635) (garcia2021treatmentstrategiesfor pages 1-2)

Phenotype associations (HPO) - HP:0001878 acute hemolytic anemia; HP:0002904 neonatal hyperbilirubinemia; HP:0000952 jaundice; HP:0002905 hemoglobinuria; HP:0001744 splenomegaly; HP:0011893 Heinz bodies (orrico2023oxidativestressin pages 10-11, kwaifa2025pathophysiologyandcurrent pages 1-2, ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2).

Evidence items with PMIDs/identifiers, URLs, dates - Orrico F, et al. Oxidative Stress in Healthy and Pathological Red Blood Cells. Biomolecules. Aug 2023. URL: https://doi.org/10.3390/biom13081262 (mechanisms, triggers, RBC redox) (orrico2023oxidativestressin pages 10-11). - Dore MP, et al. The Controversial Role of G6PD Deficiency on Cardiovascular Disease. Oxid Med Cell Longev. Apr 2021. URL: https://doi.org/10.1155/2021/5529256 (PPP/NADPH overview in G6PD) (dore2021thecontroversialrole pages 1-2). - García-Domínguez E, et al. Glucose 6-P Dehydrogenase—Regulatory Functions. Cells. Sep 2022. URL: https://doi.org/10.3390/cells11193041 (systems implications; immune/redox) (garciadominguez2022glucose6pdehydrogenase—an pages 5-6). - Garcia AA, et al. Treatment strategies for G6PD deficiency. Trends Pharmacol Sci. Oct 2021. URL: https://doi.org/10.1016/j.tips.2021.07.002 (therapeutic concepts; GSH/NADPH) (garcia2021treatmentstrategiesfor pages 1-2). - Kwaifa IK, et al. Pathophysiology and current laboratory investigations. Sokoto J Med Lab Sci. Jun 2025. URL: https://doi.org/10.4314/sokjmls.v10i1.35 (mechanistic summaries; Heinz bodies, hemolysis) (kwaifa2025pathophysiologyandcurrent pages 1-2). - Ravikumar N, Greenfield G. G6PD Deficiency: A Review. Int J Med Students. Dec 2020. URL: https://doi.org/10.5195/ijms.2020.637 (clinical overview; neonatal jaundice) (ravikumar2020glucose6phosphatedehydrogenasedeficiency pages 1-2).

Notes on evidence strength and gaps - Mechanistic foundations (PPP/NADPH/GSH and RBC hemolysis) are consistent across reviews. The most recent RBC-focused review (2023) supports current understanding and clinical triggers. High-quality 2023–2024 primary mechanistic studies specific to neonatal bilirubin handling in G6PD deficiency were not retrieved in the provided evidence; therefore, neonatal mechanistic details are supported primarily by clinical overviews and prior reviews.

References

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