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11 Cards in this Set
- Front
- Back
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Overview |
Inherited Over 300 variations reported Severe deficiency: Effects coding region for NADP+ binding domain Other mutations: Enzyme defiecency leading to haemolytic amaemia only under conditions of stress Affects 400 million people around the world X linked (Xq28) |
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Epidemiology |
Highest in countries that have high Malaria incidences Some prevalence in north and south America Thought to protect against Malaria |
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Glucose-6-phosphate Dehydrogenase |
Exists as a dimer-tetramer equilibrium -Monomer has 514 amino acids Each monomer has 2NADP+ binding sites -Co-enzyme sites -Structural sites occur at dimer interface considered to stabilise formation of the dimer Comparison of gene between organisms reveals 8 highly conserved aa linked to substrate binding site First step in pentose phosphate pathway -Important in erythrocytes Irreversible and a rate determining step Regulated by avalibility of NADP+ |
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Reaction Catalysed |
Glucose-6-phosphate to 6-phosphogluconate Requires NADP+ |
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Oxidative Stress on Erythrocytes |
HbFeII + O2 ---> Methaemoglobin FeIII + O2- Produces toxic superoxide Over 10^7 superoxide anions everyday Can destroy membrane lipids Can damage proteins by attaching SH groups |
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Heinz Bodies |
Presence of purple/blue inclusions after methyl blue stains Comprised of denatured and precipitated Hb Heinz bodies cells are DNA stained -ve |
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Deficiency |
2% chronic haemolysis 98% haemolytic episodes Precipitated by: -Infections -Drugs that induce oxidative stress -Fava beans Varients classified according to phenotype |
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Symptoms |
Fatigue Enlarged spleen Dark urine Yelloe colour Severe haemolysis may induce haemoglobinuria Anaemia |
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Diagnosis |
Fluorescence spot test -Not efficient in females -Based on conversion of NADP+ to NADPH Full Blood Count - anaemia Macrocytosis -Reduced folic acid Blood film Direct anti-globulin test Renal function LFT's Tests during an episode may not reflect true baseline values so must be performed when a patient is in remission (8-14 days post episode) |
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Treatment |
Stop drugs or fava beans Treat infection Transfuse RBC if needed |
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Favism |
Always G^PD deficient But not all G6PD deficient patiens develop haemolysis after eating fava beans Symptoms occur 5-24hrs after eating fava beans |
