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Glucose 6 phosphate dehydrogenase is the most common human enzyme defect being present in more than 400 million people worldwide. About 140 mutations have been described; Molecular characterization of G6PD deficiency variants is essential, especially since the biochemical characterization has lost its significance as a means of identifying variants.
Aim of the study: Genotyping of the most common mutations causing G6PD deficiency in Egyptian children, and Making genotype-phenotype correlation for the identified types of mutations affecting G6PD gene on Xq28.
Patients and Methods: the present study, included 100 G6PD deficient Egyptian children, attended hematology clinics at Ain shams University Hospital. A full medical record were reviewed as regard age at diagnosis, demographic data, the offending agent which precipitated the first attack, history of blood transfusion and g6pd level at diagnosis. the patients were investigated by CBC with retics, indirect bilirubin, MDA quantitative G6PD enzyme and detection of change of colour of urine) after intake of beans rather than fava beans, moreover all the samples went throught PCR-ARMS, ASO PCR, RFLP technique for detecting the different types of G6PD enzyme mutation.
Results: we were found G6PD Mediterranean mutation in 53% of cases (from which54.7% had G6PD 1311T silent polymorphism), Cairo mutation in(13%) of cases, African mutation in 16% of cases, Chatham mutation in 4% of cases, Santmaria in 1% of cases and Asahi mutation in 1%. One patient only is heterozygote Mediterranean (symptomatic carrier). 83 of patients were symptomatic; of these, 64 demonstrated acute haemolytic crisis and need blood transfusion induced mainly by ingestion of fava beans and 61 had neonatal jaundice. Acute haemolytic anemia was found in79% of subjects of Mediterranean variant, in 56% with the African variant, in 61.5% with Cairo variant, 50% with Chatham variant, 0% in santmaria variant and 0% in Asahi variant, no statistically significant difference between the studied groups in different types of mutation as regard blood transfusion requirement by using chi-square test. Enzymatic activity was shown to be a poor predictive parameter of acute hemolytic crises (moreover the G6PD level was declined in Mediterranean and African mutation while increasing in other mutation) and was not correlated with clinical features. we found no statistically significant difference between studied patients in different types of mutation and other variables(age at diagnosis, offending agents, g6pd level, [CBC with retics, indirect bilirubin and MDA after eating of legumes rather than fava beans taken in small amount (5-20 gm) per day for 3 successive days]) by using Kruskall Wallis test P value(>0.05). However, it should be noted that the MDA level measured in the cases was higher than those in the control.
Our results showed 6 variations. G6PD Mediterranean then African variant are the most common mutations in the studied patients followed by Cairo mutation. This is the first report of G6PD Santamaria, chatham and Asahi among our Egyptian population. The risk of all types of legumes rather than fava beans to cause haemolysis in G6PD deficient children will be further studied in higher quantities and for longer periods to detect the degree of haemolysis among different variants of G6PD.