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HEREDITARY MONOGENIC DISEASES

           

Glucose-6-phosphate dehydrogenase deficiency (G6PD)

G6PD deficiency (glucose-6-phosphate dehydrogenase deficiency) is an inherited condition in which the body doesn´t have enough of the enzyme glucose-6-phosphate dehydrogenase, or G6PD, which helps red blood cells (RBCs) function normally. This deficiency can cause hemolytic anemia, usually after exposure to certain medications, foods, or even infections. It is a disorder where the red blood cells are destroyed faster than the medulla can produce them.

Red blood cells transport oxygen throughout the body and G6PD protects these cells from the oxygen´s natural chemical products that accumulate when a person has a fever or takes certain medicines. If there are too many of these products, they can destroy the red blood cells, causing a hemolytic anemia. Those patients with glucose-6-phosphate dehydrogenase deficiency are more likely to develop acute hemolytic anemia after taking certain drugs (such as some antibiotics and medications used to treat malaria) or after eating broad beans (Vicia faba) or inhaling pollen from fava plants (a reaction called favism). This can be more serious in children or after eating raw and fresh broad beans.

G6PD deficiency is hereditary (a person is born with this deficiency) and is transmitted by females who have a copy of this gene on the X-chromosome to male children. The male children who receive this gene have G6PD deficiency and the females children who receive it will be healthy carriers (they usually display no symptoms). Those children (male and female) who do not receive the gene are not affected.

Certain ethnic groups have a higher incidence of G6PD deficiency than others; this condition occurs most frequently in certain parts of Africa, Asia, and the Mediterranean. It can be more or less serious depending on the different populations. In its most common form in the Afro-American population, the deficiency is less serious and hemolysis (destruction of red blood cells) mostly affects the older red cells. In Caucasians, G6PD deficiency is more serious as it also affects young red blood cells.

SIGNS AND SYMPTOMS

A list of the most common symptoms of hemolytic anemia follows. However, each individual may experience them in different ways.

  • Pale skin.
  • Jaundice, or yellowing of the skin, eyes, and mouth.
  • Dark-colored urine.
  • Fever.
  • Weakness.
  • Dizziness.
  • Confusion.
  • Trouble with physical activity
  • Enlarged spleen and liver
  • Increased heart rate
  • Heart murmur

The symptoms of hemolytic anemia may look like other medical problems. Always consult a health care provider for a diagnosis.

PREVENTION

In most cases, G6PD deficiency does not cause problems. Problems may occur if the patient is exposed to medicines or foods that may damage the blood cells. Depending on the gene flaw, it may be possible to handle a small amount of these exposures.

Certain medicines can produce oxygen´s natural chemical products in the body. Those persons with G6PD deficiency cannot protect their red blood cells from the accumulation of these products and the red blood cells are destroyed, causing a hemolytic anemia. Therefore, it is important to know which medicines can produce this effect and trigger anemia. Patients with G6PD should remember the following points when using medical drugs:

  • G6PD deficiency reveals genetic heterogeneity; the risk of medicine-related hemolysis varies. Therefore a drug that is harmless in one person may not be so in another.
  • Pharmaceutical companies do not systematically verify the effects of their products on persons with G6PD deficiency.
  • The risk and seriousness of hemolysis is almost always in relation to the dose taken.

The pharmaceutical products with a defined risk for the majority of G6PD deficiency patients are:

  • Dapsone and other sulfones (the higher dosis used in dermatitis herpetiforme generally causes more problems).
  • Methylene blue
  • Niridazole
  • Nitrofurantoin
  • Pamaquine
  • Primaquine
  • Quinolones (ciprofloxacin, moxifloxacin, nalidixic acid, norfloxacin and ofloxacin, among others)
  • Sulfonamides (cotrimoxazole). Some sulfa drugs, for example sulfadiazine, have been tested and do not produce hemolysis in many G6PD deficiency patients.

The pharmaceutical products with a possible risk for some G6PD deficiency patients are:

  • Aspirin or acetylsalicylic acid (used for relieving fever, pain, and swelling). Acceptable up to a minimum dose of 1 g/day for the majority of G6PD deficiency patients.
  • Chloroquine
  • Menadione, water soluble derivatives (for example, menadiol sodium diphosphase)
  • Probenecid (not available in British markets)
  • Quinidine
  • Quinine
  • Some non-steroidal anti-inflammatory medications (NSAIDs)

Napthalene in moth balls also produces hemolysis in G6PD deficiency patients.

GENE OR REGION STUDIED


  • G6PD