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The Red cell enzymopathies are a group of enzyme disorders which have been described in all the metabolic pathways, which includes or causes Haemolytic Anemia, Polycythaemia and methemoglobinemia , it occur in case of inheritance of one abnormal Red cell enzyme(Shiro Miwa,1996,p1). The most common enzymopathies or enzyme defects are the ones that cause Haemolytic Anemia (haemolysis) and it can be Acute Haemolytic Anemia or Chronic Haemolytic Anemia. The common enzyme defects that cause Haemolytic anemia (HA) are G6PD deficiency and Pyruvate kinase (PK) deficiency. There are others causing HA such as deficiencies of other glycolytic enzymes and Pyrimidine 5' nucleotidase deficiency but they are rare (Hoffbrand and Moss, 2011).
In the Red blood cell, enzymopathies which associated with Chronic Haemolytic Anemia (CHA) share the same laboratory findings but the degree of the haemolysis depends on the how much of the enzyme is deficient, for example if we have in one patient sever deficiency in Red Blood cell enzyme the rate of haemolysis will be high and Via versa.
The G6PD deficiency is an inherited condition can be passed to the child from either one or both parents and the gene responsible for this is coated in the X-Chromosome. The females are carriers for the G6PD deficiency which mean that they don't suffer from any clinical manifestations of the G6PD deficiency and only few cases have been reported that actual female carriers suffered from G6PD deficiency (Handin et al. 2003, p1924). This makes knowing family history of the patient really important and identifying if the patient have any of his parents have G6PD gene mutation.
The (G6PD) is the first enzyme reacts in the Pentose phosphate pathway which it's important for the production of energy (ATP) and it's known as the most common cause of enzymopathy. According to Luzzatto and Metha (1995) it have been estimated that the G6PD deficiency affect 400 million of the worldwide population which it's a great number. This makes G6PD enzyme screening tests are the first line of investigation in case of suspecting enzymopathies.
Now days laboratories have verity of methods and techniques to screen G6PD deficiency the most common tests are Dye Decolonisation, the principle of this test is simple according to Bernstein (1962) we add oxidising reagent to the sample which will oxidise Glucose-6-Phosphate to 6-phosphogluconate and then reduction of NADP to NADPH will produce blue colour, the rate of the colour reflects how much of the G6PD enzyme presence in the sample. The test is easy, quick to perform and cheap. Another screening test is Methemoglobin reduction test which is based on the G6PD reduction of Methaemoglobin and the rate of reduction is reflecting the G6PD activity in the blood , this test have allot of disadvantages such as it requires large sample volume , 3 hours incubation time (Sood, 2006).
The Beulter fluorescent spot test ''identifies the NADPH production by Glucose-6-phosphate Dehydrogenase under the ultraviolet light'' (Beulter, 1994) ,if the blood spot fluoresce that shows a negative results , if it didn't fluoresce that shows a positive results, this method is rapid with a reasonable price.
All of the previous techniques are simple screening tests for only detecting the presence of G6PD enzyme and they are useful in case of testing large number of samples for example if conducting research, however this tests have its limitations such as it should be done when the patients are in stable stage because it will give false negative results if we doing the tests when the patients are in stage or after acute haemolysis. This due to the fact that the new red blood cells contains higher concentration of G6PD enzyme which the bone marrow is producing to try and correct the anemic condition that occurred due to the haemolysis, I addition that this methods cannot detect G6PD deficiency in heterozygous women.
There are few tests can be used for confirmation of the G6PD deficiency such as PCR-based molecular diagnosis test which can detect any mutations in the G6PD gene, Bang-Ce et al. (2004) they have stated that this method can be used to detect all type of mutation including the G6PD deficiency in heterozygous women and the results of this test is extremely reliable and accurate however the technique have a major disadvantage which it is the fact that only one mutation can be detected with a signal primer while we have at the time being more than 140 mutations have been discovered by the scientists, we can use this method only if the DNA mutations are identified. In addition this test is extremely expensive and requires high experienced staff to run this test which makes it almost impossible to be done in poor countries.
Pyruvate Kinase (PK) is the second enzyme used in the Glycolytic Pathway for the production of energy in form of ATP. PK deficiency is an autosomal recessive inheritance disorder which means both of parent's must transfer defective PK gene to the child to develop PK deficiency.
According to Zenalla et al. (2005) there are about 180 different mutations have been identified so far and the severity of haemolysis in each one of them is different from the other. Acute deficiency in PK can cause hydrops fetalis (Gilsanz et al. 1993).
For the diagnosis of PK deficiency there is no specific morphological finding which leave for us only the methods or the techniques which can specifically identify enzyme defect such as doing enzyme assay using leucocyte depleted blood sample because leukocytes have 300 times more PK activity then what the red blood cells have , also can do PCR- based molecular diagnosis test for known DNA mutations but as we already said before this methods are really expansive and cannot be used in poor countries.
Both of G6PD deficiency and PK deficiency share some haemolytic anemia clinical features such as Full Blood Count (FBL) because they both cause Haemolysis we will most properly get Anemic picture due to the destruction of Haemoglobin, also we will have high retic count (Reticulocytosis) because the Bone Marrow is trying to produce as much Red cells as it can to increase the number of circulating red blood cells and compensate the loss which occur in haemolysis events, patients will usually have splenomegaly due to the excessive and early destruction of red blood cells, jaundice.
In G6PD deficiency will find haemoglobin abnormality known as Heniz bodies which we can see in blood smear its described by Harry Kaspar (1970) as molecule damage of the red cell haemoglobin mainly by oxidant, then the microphages will consider the red cells which contain Heniz bodies as antigen and will take it to the spleen which will take out or cut the part of the cell which contain the Heniz bodies then we will have what known as Bite cells in the blood film.
There are others red cell enzymopathies such as Pyrimidine 5' nucleotidase deficiency , Deficiencies of Enzymes Involved in Glutathione Metabolism, but they are extremely rare however that doesn't mean because they rare we should forget about them , some hospitals must provide detection of this types of red cell enzymopathies and the common types of enzymopathies screening tests must be provided in every hospital.