DR. OSAMA SULTAN 15 SEPTEMBER 2014

Otto Heinrich Warburg German biochemists Nobel price 1931 for the discovery of G6PD enzyme.

Ernest Beutler (1928 – 2008)

Epidemiology G6PD deficiency is the most prevalent red cell enzymes deficiency in the world. 350 – 400 Million people are affected worldwide ( prevalence about 5 – 10%) Coincides with the geographic distribution of endemic malaria. The highest prevalence is in Sub-Saharan Africa, followed by middle East, Mediterranean Europe, and Southeast Asia X-linked recessive inheritance pattern

Polymorphic variants od G6PD confer a survival benefit in malaria-endemic region. Mild G6PD variant have protection against severe Plasmodium falciparum malaria ( 58% risk reduction in male hemizygotes, and 46% reduction in female heterozygotes). Explanation :?? Increased phagocytosis of G6PD-deficient erythrocytes containing the early ring-stage parasites. the level of reduced glutathione was lower in the G6PD- deficient cells compared with normal red cells, leading to membrane damage of deficient cells containing parasites that may be preferentially targeted for destruction. G6PD deficiency prevalence among HIV patients about 6.8%.

G6PD GENE AND ENZYME

G6PD variants genotypes/Isoenzymes G6PD B+ : wild type, whites > blacks G6PD A+ : blacks > whites G6PD A- : blacks with mild deficiency G6PD Med : whites Mediterranean, Kurdish, severe def. G6PD Canton : Thailand, Vietnam, Taiwan WHO variants

Most people with G6PD deficiency have no symptoms and are not anemic. In fact, the majority of affected individuals live out their lives unaware of their status. The disease is generally manifest when the red cells undergoes oxidative stress triggered by: Certain drugs Infections Ingestion of fava beans Medical conditions such as DKA, liver disease, renal disease

G6PD deficiency usually presents as: drug-induced acute hemolytic episode Infection-induced acute hemolytic episode Favism Neonatal jaundice Congenital non-spherocytic hemolytic anemia (CNSHA) G6PD deficiency does not seem to affect life expectancy, quality of life, or the activity of affected individuals.

Drug-induced Acute hemolytic episode Primaquine was the first drug encountered in causing acute hemolysis. It is difficult to establish that drugs is directly related to triggering this type of hemolytic episode because: Some drugs are safe for individuals but not for all Coexistence of another trigger e.g. infection, diabetes, hemoglobinopathies, etc. Some patients take more than one drugs Self-limiting process so it may pass unnoticed !!

The symptoms start after ingesting the offending drug by 2 to 4 days. Fatigue, jaundice, pallor, abdominal or back pain, and dark urine. Self-limiting, but may be prolonged in severe variants, with an average of 7 – 1o days after onset of hemolysis. There are 7 known drugs that cause such hemolysis according to EBM, but the list is evolving.

Dapsone Methylene blue Toluidine blue Phenazopyridine Primaaquine Rasburicase Nitrofurantion

Infection-induced Acute Hemolytic Episode The most common trigger of hemolysis Occurs after 1-2 days from onset of febrile illness. commonly associated with pneumonia or typhoid fever. Organisms can be: Bacterial: ß-hemolytic sterptococci, E.coli, Salmonella Richettial infections Viral: hepatitis A,B; CMV, EBV, influenza A The severity of haemolysis can be aff ected by many factors, including concomitant drug administration, liver function, and age.

Acute renal failure may be a serious complication after viral infection in adult secondary to Acute tubular necrosis due to renal ischemia Tubular obstruction by hemoglobin casts

Favism Second most common trigger of hemolysis % in patients Seen in severe G6PD variants Within hrs from eating or inhaling fava beans More in children and breast-fed babies More with fresh fava beans; but dried and freezed ones can do. Also peanuts can trigger favism !! Depends on amount, type, mode of cooking.

Divicine, isouramil, and convicine, which are thought to be the toxic constituents ( about 2% of total weight ) of fava beans, increase the activity of the hexose monophosphate shunt, promoting hemolysis in G6PD-deficient patients.

Broad beans Kidney red beans

Alfaalfa sprouts Astragalus Fenugreek

Carob (chocolate substitute) Liquorice Tamarind

Congenital Non-spherocytis Hemolytic Anemia(CNSHA) Seen in class I G6PD variant Very rare, sporadic Chronic hemolysis Independent mutations clustering in exons 10 and 11. Infants present with severe neonatal jaundice, or discovered later when present with mild anemia that that exacerbated by oxidant stress.

Neonatal Jaundice Seen in neonate with severe G6PD variants Hyperbilirubinemia is likely secondary to impairment of bilirubin conjugation and clearance by the liver leading to indirect hyperbilirubinemia. Infants with G6PD deficiency and a mutation of uridine diphosphoglucuronate glucuronosyltransferase-1 gene promoter (UDPGT-1) are particularly susceptible to hyperbilirubinemia secondary to decreased liver clearance of bilirubin. UDPGT-1 is the enzyme affected in Gilbert disease.

If not treated, may lead to kernicterus (over 30%)and mental retardation and even death.

Laboratory Manifestations Qualitative test Fluorescent spot test Simple Inexpensive NADPH production is detected by virtue of its fluorscent under ultraviolet light G6P and NADP+ are added to a hemolysate of the patient’s red cells Fluorescence under ultraviolet light indicates enzyme activity, whereas absence of fluorescence indicates enzyme deficiency False negative results during acute hemolytic episode, repeat the test after 4 – 6 weeks.

Quantitative spectrophotometric analysis Molecular diagnostic testing

Management Straightfarward … Stop the offending drug Avoid fava beans, or any other oxidant stersses Adequate intake of fluids Treat infection with appropriate antibiotic Blood transfusion if severe anemia Phototherapy and exchange transfusion for neonatal jaundice Folic acid supplementation

G6PD deficiency is the most common red cell enzymopathies world wide. There are different variants and mutations that determine the severity of the disease which get periodically updated. Hemolysis is usually triggered by certain drugs and infections in addition to some medical conditions and fava bean ingestion. Chinese herbs can trigger hemolysis in some patients.

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