溶血性贫血_5课件.ppt

* * * * G-6PD deficiency is the most important disease of the Hexose monophosphate pathway and is responsible for two clinical syndromes an episode hemolytic anemia induced bu infections or certain drugs and a spontaneous chronic nonspherocytic hemolytic anemia This X-linded enzyme deficiency affects more than 200million people The deficency is caused by inheritance of any of a large number of abnormal alleles of the gene responsible for the synthesis of the G-6PD molecule. * After a patient has ingested a substance that has oxidant properties, insome patients ingestion of fava beans may slso produce an acute and severe hemolytic syndrome called favism. This results from oxidative products derived from two glucosidic compounds, ultimately producing hydrogen peroxide and other reactive oxygen products. Infection also may result in hemolysis and significant hemolysis may occur even when no exposure to drugs can be document. In the usual pattern of G6PD deficiency,symptoms develop 24-48h after a patient has ingested a substance that has oxidant properites The degree of hemolysis varies with the inciting agent, the amount ingested and the severity of the enzyme deficiency in the patient In severe cases, hemoglobinuria andjanudice result,a nd the Hb concentration may fall prcipitously and be life threatening Spontaneous hemolysis may occur in premature but not term infants,the dediciency of G-6PD is an important cause of hyperbilirubinemia and potential kernicterrus. When a pregant woman ingests oxidant drus, they may be transmitted to her G-6PD-deficient fetus, and hemolytic anemia and jaundice may be apparent at birth * The onset of acute hemolysis results in a precipitous fall in hb and hemotocrit If the episode is evere, the hemoglobin-binding proteins such as haptoglobin are saturated, and free hemoglobin may appear in the plasma and subsequently in the urine Unstained or supravital preparations of RBCsreveal Heinz bodies(precioitated hemoglobin) Because cell con