Maria Pia Caforio

6-Phosphogluconate dehydrogenase deficiency in an Italian family

Abstract A rare case of hereditary erythrocyte enzymopathy, namely 6-phosphogluconate dehydrogenase (6PGD) deficiency, was found in an Italian family. The activity of the enzyme was reduced to 35% in the propositus and her mother, but was normal in the other three members of the family. The 6PGD deficiency was associated with a variable reticulocyte count and recurrent increased unconjugated bilirubinemia without anemia in the propositus, while no clinical or hematological symptoms were evident in her mother. Increased levels of erythrocyte pyruvate kinase (PK) activity and reduced glutathione (GSH) were observed, indicating a slight decrease in mean red blood cell (RBC) age and an activation of reducing systems. The episodic hemolytic events with jaundice observed in the propositus may be the result of a defective RBC ability to counteract conditions of marked oxidative stress. In this report the importance of 6PGD estimation for a proper analysis of glucose-6-phosphate dehydrogenase (G6PD) deficiency is also highlighted. In fact in the present study, the presence of 6PGD deficiency could be mistaken for a partial G6PD deficiency if the assay of G6PD activity was performed without correcting for 6PGD activity.

Identification of G6PD Mediterranean mutation by amplification refractory mutation system.

BACKGROUND Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common X chromosome-linked hereditary enzymopathy in humans. The authors have developed an amplification refractory mutation system (ARMS) to detect the G6PD Mediterranean mutation (nt. 563 C-->T) that is the most frequent among Caucasian population. METHODS Specific forward polymerase chain reaction (PCR) primers, within exon 6 of the G6PD gene, were designed: ARMS M complementary to the mutated DNA sequence and ARMS N complementary to the wild-type DNA. They were paired with a common reverse primer. The new method was validated using known DNA samples from 72 G6PD-deficient patients carrying the G6PD Mediterranean mutation ascertained by the restriction enzyme analysis. The ARMS test was performed on DNA extracted both from blood or saliva samples. RESULTS The ARMS test showed an excellent reproducibility and a complete concordance with the endonuclease cleavage reference method. At the same time, it is more rapid and less expensive. CONCLUSIONS The described molecular test may be a method of choice to identify the G6PD Mediterranean mutation. It could also be helpful to obtain a definite diagnosis of G6PD Mediterranean heterozygotes, which is not feasible by using red blood cell enzyme activity measurements.