G6PD, galactosemia

Introduction

Glucose-6-Phosphate

Dehydrogenase deficiency

Glucose-6-Phosphate Dehydrogenase(G6PD) deficiency is the most common human enzyme deficiency; an estimated 400 million people worldwide are affected by this enzymopathy.

G6PD is caused due to a deficiency of a chemical enzyme called G6PD found in the red blood cells. This syndrome is more common in males than females, but females can carry it sometimes. This deficiency won’t show any symptoms. It causes severe injury to red blood cells by breaking the RBC’s down.

It is most prevalent in people of African, Mediterranean, and Asian ancestry. One benefit of having G6PD deficiency is that it confers a resistance to

malaria.

G6PD deficiency is also sometimes referred to as favism since some G6PD deficient individuals are also allergic to fava beans.

Galactosemia

History of galactosemia•Galactosemia was first "discovered" in 1908. Von Ruess, in a 1908 publication entitled, "Sugar Excretion in Infancy," reported on a breast-fed infant with failure to thrive, enlargement of the liver and spleen, and "galactosuria".

1917- "galactosuria" was a broadly recognized inherited disorder and was treated by removal of milk products from the diet. 1935- The disease was first recognized and described in detail in by Mason and Turner. Leloir worked out the metabolic pathway and the process of sugar-nucleotides and won the Nobel prize in Chemistry in 1970 for his work. He and coworkers elucidated the pathway for converting galactose to glucose in the early 50's.

1956- the defective gene that caused it was found. 1963- Another major break-through was when it was first found to be detectable through a newborn screening method. This method was developed by Guthrie and Paigen. Galactosemia was the second disorder found to be detectable through newborn screening methods by Robert Guthrie.

What is galactosemia??Galactosemia -is a rare genetic metabolic disorder that affects an individual's ability to metabolize the sugar galactose properly. Galactosemia is ussualy confused withlactose intolerance. But then Galactosemia follows an autosomal ressecive mode of inheritance that confers a deficiency in an enzyme responsible for adequate galactose degradation.

Three types:Type I – classic galactosemiaType II –galastokinase deficiencyType III –galactose epimerase deficiency, UDP-Galactose-4-epimerase deficiency

Glucose-6-Phosphate Dehydrogenase

deficiency

Incidence

The most common human enzyme defect inherited from a female who carries one defective X chromosome. The son of any female carrier who shall inherit the x-chromosome will have G6PD deficiency, while the daughter who receives the gene will eventually become a carrier without manifesting any of its sign or symptoms.

G6PD is present in more than 400 million people worldwide. This condition occurs most frequently in certain parts of Africa, Asia, and the Mediterranean. It affects about 1 in 10 African-American males in the United States.

RISK FACTORS

• The only known risk factor for having the disorder is a family history of G6PD deficiency.

• This is also common with blacks and with males.

• It occurs frequently in Asia, Africa and the Mediterranean

CAUSE

• The cause of G6PD is a defective G6PD gene found in the X-chromosome of the sex chromosome.

• The destruction of red blood cells can triggered by infections, severe stress, certain foods (such as fava beans), and certain drugs, including:Antimalarial drugs, Aspirin, Nonsteroidal anti-inflammatory drugs (NSAIDs), Quinidine, Quinine, Sulfonamides

Diagnostic Examinations

Reticulocyte CountA reticulocyte count measures the percentage of

reticulocytes (slightly immature red blood cells) in blood. The procedure is same with G6PD lever test. The blood sample is sent to a laboratory. A special stain is used to identify the reticulocytes.

The test is done to determine if red blood cells are being created in the bone marrow at an appropriate rate. The number of reticulocytes in the blood is a sign of how quickly they are being produced and released by the bone marrow.

The normal range depends on the level of hemoglobin, and the range is higher if there has been bleeding or red cell destruction.

Abnormal resultsA low reticulocyte count indicates that the

bone marrow is not producing a normal number of red blood cells. Low production may be caused by a lack of vitamin B12, folic acid, or iron in the diet; or by an illness affecting the bone marrow.

The reticulocyte count rises when the bone marrow makes more red cells in response to blood loss or treatment of anemia.

Complete Blood Count (CBC) TestOne of the most commonly ordered clinical

laboratory tests, a blood count, also called a complete blood count (CBC), is a basic evaluation of the cells (red blood cells, white blood cells, and platelets) suspended in the liquid part of the blood (plasma). It involves determining the numbers, concentrations, and conditions of the different types of blood cells.

The CBC test also provides specific information the size and hemoglobin content of individual red blood cells.

The test can reveal problems with red blood cell production and destruction.

Abnormal resultsAbnormal blood count results are seen in a variety of conditions. One of the most common is anemias, which are characterized by low RBC counts, hemoglobins, and hematocrits.

These abnormal red blood cells (RBCs) resemble targets. These cells are seen in association with some forms of anemia.

Haptoglobin TestThis test is done to help evaluate a person for hemolytic

anemia. Haptoglobin is a blood protein made by the liver. The haptoglobin levels decrease in hemolytic anemia. Hemolytic anemias include a variety of conditions that result in hemolyzed, or burst, red blood cells.

Hemoglobin is the protein in the red blood cell that carries oxygen throughout the body. Iron is an essential part of hemoglobin; without iron, hemoglobin cannot function. Haptoglobin's main role is to save iron by attaching itself to any hemoglobin released from a red cell.

When red blood cells are destroyed, the hemoglobin is released. Haptoglobin is always present in the blood waiting to bind to released hemoglobin. White blood cells (called macrophages) bring the haptoglobin-hemoglobin complex to the liver, where the haptoglobin and hemoglobin are separated and the iron is recycled.

In hemolytic anemia, so many red cells are destroyed that most of the available haptoglobin is needed to bind the released hemoglobin. The more severe the hemolysis, the less haptoglobin remains in the blood.

Haptoglobin is measured in several different ways. One way is called ratenephelometry. A person's serum is mixed with a substance that will bind to haptoglobin. The amount of bound haptoglobin is measured using a rate nephelometer, which measures the amount of light scattered by the bound haptoglobin. Another way of measuring haptoglobin is to measure it according to how much hemoglobin it can bind.

Normal results vary based on the laboratory and test method used. Haptoglobin is not present in newborns at birth, but develop adult levels by 6 months.

Beutler fluorescent spot test The Beutler fluorescent spot test is a rapid and inexpensive

test that visually identifies NADPH produced by G6PD under ultraviolet light. When the blood spot does not fluoresce, the test is positive; it can be falsely negative in patients who are actively hemolysing. It can therefore only be done 2–3 weeks after a hemolytic episode.

When a macrophage in the spleen identifies a RBC with a Heinz body, it removes the precipitate and a small piece of the membrane, leading to characteristic "bite cells". However, if a large number of Heinz bodies are produced, as in the case of G6PD deficiency, some Heinz bodies will nonetheless be visible when viewing RBCs that have been stained with crystal violet. This easy and inexpensive test can lead to an initial presumption of G6PD deficiency, which can be confirmed with the other tests.

Treatment and

management

Medication:• no medication needed Treatment:• Transfusions, in some cases• Exposing newborn to bright lights (bili lights) Alternative treatment:• Vitamin E• Folic acid• And both antioxidant

Prevention:• Avoid drugs that are causing RBC destruction• Avoid Fava beans• Or inhaling pollen fava plants

Nursing Management

for babies with G6PD

Mothers are advised to stop breast feeding their infants for a short period of time as breast milk might interfere with the liver’s ability to conjugate bilirubin.Both breast-feeding mother and child must avoid fava beans (broad beans). Fava bean remains the most common food to avoid for G6PD deficient individualsAlso avoid legumes, products containing sulfites, products containing blue food coloring, tonic water (contains quinine)Advised to choose milk formulas which have no traces of soya or soybeans

Advised that Soy products, blueberries and red wine are also trigger symptoms of G6PDAvoid exposure to naphthalene (a chemical found in mothballs and moth crystals)Be aware of the signs and symptoms like:– Paleness– rapid heartbeat– rapid breathing or shortness of breath– jaundice, or yellowing of the skin and eyes,

particularly in newborns– an enlarged spleen– dark, tea-colored urine