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FBC – Case F Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

FBC – Case F Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency. Tuan Tran Thi Trang Tu Nguyen. Patient History. Discussion Issues. Variations of G6PD Clinical features of G6PD Management of G6PD Potential adverse effects of patients medication (Bactrim and Aspirin) on his FMC

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FBC – Case F Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

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  1. FBC – Case FGlucose-6-Phosphate Dehydrogenase (G6PD) Deficiency Tuan Tran Thi Trang Tu Nguyen

  2. Patient History

  3. Discussion Issues • Variations of G6PD • Clinical features of G6PD • Management of G6PD • Potential adverse effects of patients medication (Bactrim and Aspirin) on his FMC • Other classes of medicines contraindicated in G6PD deficiency

  4. What is G6PD Deficiency? • G6PD deficiency is the most common human enzyme deficiency • Also known as Favism – since G6PD deficient patients are also allergic to fava beans • A genetic condition – inherited in an X-linked recessive gene • Most G6PD deficient patients have abnormality in the structure of the G6PD enzyme (Scriver et al., 1995)

  5. Variations of G6PD • G6PD genes is highly polymorphic • Over 300 variants resulting from a single-point mutationa are known to exist in different populations of the world • Several variants have significantly reduced activity and result in a condition called G6PD deficiency

  6. Clinical Features of G6PD • G6PD is 3 times the size of haemoglobin • Major carrier of oxygen • A deficiency results in lack of oxygen transport throughout the body causing; • haemolytic anaemia • neonatal jaundice • abdominal and/or back pain • dizziness • Headache • dyspnoea (irregular breathing) • palpitations (Cecil 1992)

  7. Clinical Features of G6PD • Most of the symptoms of G6PD deficiency are general symptoms often associated with other disease states • The two major pathologies associated with G6PD deficiency are; • haemolytic anaemia • neonatal jaundice (Cecil 1992)

  8. Haemolytic Anaemia • Induced in patients by; • Oxidative drugs • Result in the denaturation or unfolding of the hemoglobin molecule • Leads to the inability of the red blood cell to effectively transport oxygen throughout the body (Yoshida & Beutler, 1986) • Death occurs if the hemolytic episode is not properly treated

  9. Haemolytic Anaemia • Induced in patients by; • Fava beans (Favism) • The only food product to be implicated in inducing an anemic response in G6PD deficient individuals (Scriver et al. 1995) • Inhaling the pollen of the fava bean plant can also induce an effect • The abundant compounds vicine and isouramil, abundant in fava beans are suspected to be the causative agents of the hemolytic response (Beutler 1994).

  10. Haemolytic Anaemia • Induced in patients by; • Infections • Besides favism, infection is probably the most common cause of hemolysis in G6PD deficiency patients • Caused by oxidative metabolites produced by numerous bacterial, viral, and rickettsial infections • Important infections that can precipitate a hemolytic episode are viral hepatitis, pneumonia and typhoid fever (Cecil 1992).

  11. Neonatal Jaundice • Induced in patients by; • Infections • Besides favism, infection is probably the most common cause of hemolysis in G6PD deficiency patients • Caused by oxidative metabolites produced by numerous bacterial, viral, and rickettsial infections • Important infections that can precipitate a hemolytic episode are viral hepatitis, pneumonia and typhoid fever (Cecil 1992).

  12. Management of G6PD • Ensure body tissues are provided with enough oxygen by the red blood cells • Avoid trigger factors • Oxidative medications • Fava beans • Maintain good health to prevent attracting bacterial or viral infections • Infants with prolonged neonatal jaundice are placed under special lights, called bili-lights, which alleviate the jaundice

  13. Management of G6PD • Anaemic episodes are treated with nasal oxygen and are placed on bed rest, which may give symptomatic relief • Anemic patients are sometimes treated with human haptoglobin products (Ohga et al. 1995), and/or blood transfusions (Cecil 1992) • In acute hemolytic anemia, patients are administered with folic acid

  14. New Development • Engineered fava beans • Eliminate the causative agents of hemolytic response from the fava beans • Fava beans are an important part of the diet in the Middle East, where the frequency of G6PD deficiency and favism is high

  15. Patient with G6PD + medication • Bactrim should not be given to patients with G6PD because megaloblastic anaemia can occur • Patient with G6PD deficiency are at increased risk of developing haemolytic anaemia when given oxidant drugs e.g. aspirin, anti-malarial…etc

  16. Bactrim… • Folic acid is important in the synthesis of nucleic acid i.e. required by rapidly dividing cells • Bactrim (trimethoprim & sulfamethoxazole) may prevents the convertion of folic acid in diet to the active form • Therefore, folic acid deficiency can lead to megaloblastic anaemia

  17. Megaloblastic anaemia • Megaloblastic anaemia presents with abnormal form of cells that are precursors of RBC • i.e. cells are large & nucleis fail to mature in normal way

  18. Megaloblastic anaemia continued… Adverse effect on laboratory findings: • Increase cytoplasmic mass & maturation  megaloblast • Macro-ovalocytic RBCs enter circulation • Ineffective erythropoiesis  reticulocytopenia • Hyperbilirubinemia & hyperuricemia • Leukopenia/thrombocytopenia may occur

  19. G6PD protects RBC from natural oxygen chemicals that may build up in people with fever or taking certain medications Therefore if this patient takes aspirin  unable to protect his RBC against the buildup of oxygen chemicals  blood cells are destroyed leading to haemolytic anaemia Aspirin…

  20. Haemolytic anaemia • Haemolytic anaemia = RBC are detroyed faster than the bone marrow can produce them • Abnormally shaped red cells presence in the blood

  21. Haemolytic anaemia continued… Adverse effect on laboratory findings: • Early stage = presence of Heinz bodies • Smear shows = anisocytosis & poikilocytosis • Reticulocytopenia & neutropenia • Thrombocytopenia & platelets are bizarre in shape & size • Shorten survival of the defective RBCs • Elevated LDH = shows sig. ineffective haemopoiesis &  haemolysis • End stage = haemoglobinuria & acute renal failure

  22. Infections • Patient suffering from overwhelming infections (likely this patient) can also experience  in leucocytes (i.e. WBC) • Because leucocytes are host defense against invading microorganisms

  23. Conclusion… • Bactrim  • Megaloblastic anaemia • Thrombocytopenia • G6PD + Aspirin  • Haemolytic anaemia • Thombocytopenia • Infections  • Haemolysis •  leucocytes

  24. Effect on patient’s FBC

  25. Other classes of drugs contraindicated in patients with G6PD deficiency • Many compounds reported to induce haemolysis in G6PD deficient individuals…however some unjustifiably labelled as haemolysis precipitants! • aspirin: in a review found that low dose 400mg aspirin in G6PD deficient pxs caused haemolytic episodes in 2 out of 40 cases….but open to much debate

  26. Medications with proven haemolytic potential • Currently available medications with proven haemolytic potential are relatively few in numbers. Known examples are: • primaquine • chloroquin • quinine

  27. Other drugs with haemolytic potential…. • Sulfonamides/sulfones • sulfamethoxazole • dapsone -> causes haemolytic anaemia when daily dose is greater than 200mg • Cytotoxic/antibacterials • chloramphenicol • cotrimoxazol

  28. Other drugs with haemolytic potential…. • Miscellaneous • vit K derivatives • hydralazine • probenecid • vit C (ascorbic acid): is an antioxidant and present in many foodstuff and food supplements. The problem arises when G6PD deficient persons take high doses

  29. Prescribing drugs for patients with G6PD defiency • 3 points to keep in mind • 1) G6PD deficiency is genetically heterogeneous, susceptibility to the haemolytic risk varies, thus a drug found to be safe in some G6PD deficient individuals may not be equally safe in others. • 2)Manufacturers do not routinely test drugs for their effects in G6PD deficient individuals. • 3) The risk and severity of haemolysis is almost always dose related.

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