Also known as G6PD deficiency, G6PDH deficiency is a hereditary disorder. The main feature of the disorder is that your body cells do not produce enough of an enzyme known as glucose-6-phosphate dehydrogenase (G6PDH or G6PD). The enzyme is part of what biochemists call the pentose phosphate pathway, which is needed for cells to maintain high levels of a substance called nicotinamide adenine dinucleotide phosphate (NADPH), whose role is to carry electrons. This enables your cells to store up supplies of an antioxidant called glutathione. Red blood cells (RBCs, erythrocytes), in particular, depend on glutathione for protection against oxidative stress, a kind of stress caused by oxygen, which can cause the RBCs to break open, a process called hemolysis. In people with G6PD deficiency, hemolysis is triggered by various drugs such as trimethoprim-sulfamethoxazole, nitrofurantoin, and antimalarial drugs primaquine, chloroquine, pamaquine, and pentaquine. Hemolysis also can be triggered by agents in certain foods, such as fava beans.
G6PDH deficiency is the most common disease-producing enzyme disorder, affecting about 400 million people around the world, including women of child bearing age who may become pregnancy. Numerous genetic and chromosomal arrangements can cause the condition, and such arrangements are common in people with heritage around the Mediterranean Sea, tropical Africa, and New Guinea. Mediterranean and Middle Eastern people, such as Greeks, Italians, Sephardic Jews, and Arabs, and African Americans and others of African origin are at particular risk.
Genetically speaking, G6PDH deficiency is a recessive disease carried on the X-chromosome. This means that females more often are carriers, rather than people who have the diseases themselves. Thus, if G6PD deficiency runs in your family, most likely the significance if you become pregnant is that your male children have a high risk of ending up with G6PD deficiency. However, a female can develop G6PD deficiency if her father suffers from the condition and her mother is at least a carrier, since then she can end up with both of her X chromosomes having a defect that causes the disease.
The result of hemolysis is hemolytic anemia. If hemolysis occurs frequently, then RBCs do not live out their normal lifetime that averages about 120 days. Anemia is any decrease in RBC mass, or a decrease in the amount or concentration of hemoglobin (Hb) in the blood. This causes weakness, lightheadedness, and pallor, due to a decreased capacity of RBCs to deliver oxygen to body tissues. For the same reason, other symptoms such as fainting, headaches, and tinnitus (ringing in the ears) also are common. Clinical signs of anemia also may include tachycardia (fast heart rate), a systolic ejection murmur, and dyspnea (difficulty breathing), because the body tries to compensate for decreased efficiency of oxygen by increasing the rate of blood flow.
In the case of hemolytic anemia, the destruction of RBCs leads to elevations of lactate dehydrogenase and haptoglobin in the plasma. Haptoglobin is a protein that binds released hemoglobin, while the breakdown of hemoglobin produces bilirubin, which is elevated in the plasma as well, and patients exhibit jaundice. G6PDH deficiency is a manageable condition. Generally hemolytic crises can be avoided by having the patients avoid the agents that can trigger it, namely drugs such as trimethoprim-sulfamethoxazole and the antimalarial drugs primaquine, chloroquine, pamaquine, and pentaquine. In many cases, the condition will subside even if the drug is continued.
G6PDH deficiency is the most common disease-producing enzyme disorder, affecting about 400 million people around the world, including women of child bearing age who may become pregnancy.
For women who are not merely carriers, but do have G6PD deficiency, during pregnancy they may suffered an increased frequency of urinary tract infections, as well as a pregnancy complication called preeclamsia, which typically requires that your baby is delivered early. Newborns from mothers who have suffered hemolytic events due G6PD deficiency may develop what’s called neonatal jaundice, as well as a very serious, life-threatening condition called hydrops fetalis. Presence of G6PD deficiency in a mother also puts the fetus at risk of stillbirth.
All of this said, it is sometimes difficult to identify women who are truly G6PD deficient. This is because the condition is diagnosed based on levels of the enzyme G6PD in the mother’s blood. There are a range of G6PD blood levels and there haven’t been guidelines established for using a particular blood level of the enzyme as a cutoff for making a diagnosis. In other words, there is debate concerning what “low” levels of G6PD enzyme actually means in pregnant women. Consequently, all that you can really do is to play things safe. If you have roots in Mediterranean, Middle Eastern, or African regions, you should consult with a genetic counselor to determine whether G6PD deficiency runs in your family. If the condition does run in your family, then your obstetrician needs to be aware of it and your medications and diet need to be managed appropriately.
When it comes to breastfeeding and G6PD deficiency, an issue comes up in cases when the newborn has the condition. In such cases, the mother’s medications need to be monitored, along with her diet, to assure that she is not consuming anything that can pass into her breast milk and trigger hemolysis in a nursing infant.