Glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme that helps to protect red blood cells from being destroyed (hemolytic anemia) when a person is exposed to certain foods, drugs, or the stress of infection.

G6PD deficiency is the most common inherited human enzyme disorder [1], and is especially common in African-American males, and persons of Mediterranean, Middle Eastern, and Asian origin. The most severe cases of G6PD deficiency appear to occur in Asian and Mediterranean populations [2,3].

Symptoms and Signs

Males may present during the first few weeks of infancy with prolonged jaundice from anemia . Symptoms and signs in older persons may include:

Extreme tiredness
Abdominal and back pain
Pale skin
Jaundice (yellow skin or eyes)
Rapid heartbeat
Shortness of breath
An enlarged spleen
Dark, tea-colored urine

Diagnosis

The diagnosis of G6PD deficiency is made by measuring G6PD activity levels. Testing for G6PD deficiency may be negative in patients with recent hemolysis, because the older red blood cells with the greatest enzyme deficiency will have been destroyed.

The World Health Organization recommends screening all newborns in populations with a prevalence of 3 to 5 percent or more in males [5]

Other laboratory tests may show:

Anemia
Heinz bodies (denatured hemoglobin) within red blood cells on the peripheral blood smear.
Elevated reticulocyte count

Elevated bilirubin

Elevated serum LDH

Decreased haptoglobin

Negative Coomb's test

Hemoglobin in the urine (hemoglobinuria)

Substances That May Bring On Red blood Cell Destruction

Although the stress of infection most commonly brings about destruction of red blood cells in persons with G6PD deficiency other substances that may bring this about include [2,4]:

Drugs
- Aspirin
- Chloramphenicol
- Hydralazine
- High dose ascorbic acid
- Dapsone
- Mesalazine - 5-Aminosalicylic Acid (paraminosalicylic acid)
- Methyldopa
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Primaquine
- Phenazopyridine
- Quinidine
- Quinine
- Nalidixic acid
- Sulfonamides (antibiotics)
- Nitrofurantoin
Foods
- Fava Beans (also called broad beans)
Chemicals
- Naphthalene (mothballs)
- Methylene blue

Prenatal Diagnosis

The condition is transmitted by mutations in the G6PD gene located on the X chromosome and follows an X-linked recessive inheritance (sex-linked) pattern:

The normal random inactivation of one of the two X chromosomes that occurs in females may lead to a partial deficiency in female carriers which may not be detected using screening tests. Carrier detection using prenatal DNA analysis to detect specific mutations may be more suitable In patients with high risk for severe enzyme deficiency. Sequencing of the G6PD gene is available from Emory Genetics Laboratory