G6PD deficiency is a genetic disorder that most often affects males.G6PD deficiency is the most common enzyme deficiency in humans, affecting about 400 million people worldwide, with a high prevalence in persons of African, Asian, and Mediterranean descent.
Causes
G6PD deficiency occurs when a person is missing or does not have enough of an enzyme called glucose-6-phosphate dehydrogenase (G6PD). This enzyme helps red blood cells work properly. It also protects them from breakdown by oxygen reactive species called free radicals in the blood that could cause their destruction.
Too little of the enzyme, G6PD leads to the destruction of red blood cells. This process is called hemolysis. When this process is actively occurring, it is called a hemolytic episode. The episodes are most often brief. This is because the body continues to produce new red blood cells, which have normal activity.
In people with G6PD deficiency, either the red blood cells do not make enough G6PD or what they do make doesn’t work as it should. Without enough G6PD to protect them, the red blood cells break apart. When many red blood cells are destroyed, a person can develop hemolytic anemia. This can cause tiredness, dizziness, dark urine and other symptoms.
Red blood cell destruction can also be triggered by infections, certain foods (such as fava beans), and certain medicines. Other chemicals, such as those in mothballs, can also trigger an episode.
Symptoms
People with this condition do not display any signs of the disease until their red blood cells are exposed to certain chemicals in food or medicine.
Symptoms are more common in men and may include:
| Dark urine Fever Pain in abdomen Enlarged spleen and liver | Fatigue Pallor Rapid heart rate Shortness of breath Yellow skin color (jaundice) |
You are more likely to develop this condition if you are African-American, of Middle Eastern decent, male or have a family history of the deficiency.
A form of this disorder is common in whites of Mediterranean descent. This form is also associated with acute episodes of hemolysis. Episodes are longer and more severe than in the other types of the disorder.
Investigations
A blood test can be done to check the level of G6PD (Normal levels in adults; 5.5-20.5 units/g of Hb).Low levels are suggestive of a deficiency with the enzyme.
Other tests that may be done include: bilirubin level, complete blood count, hemoglobin – urine, haptoglobin level, LDH test, methemoglobin reduction test and reticulocyte count.
Treatment
Treatment may involve:
- Medicines to treat an infection, if present
- Stopping any drugs that are causing red blood cell destruction
- Transfusions, in some cases
Outcome (Prognosis)
In most cases, hemolytic episodes go away on their own.
Possible Complications
In rare case, kidney failure or death may occur following a severe hemolytic event.
When to Contact a Medical Professional
Call your health care provider if you have symptoms of this condition.
| SOME COMMON DRUGS TO AVOID IN G6PD DEFICIENCY | |||
| DEFINITE RISK OF HAEMOLYSIS | POSSIBLE RISK OF HAEMOLYSIS | ||
| Pharmacological Class | Drugs* | Pharmacological Class | Drugs* |
| Antibiotics | • Nitrofurans: –Nitrofurantoin Quinolones: – Ciprofloxacin –Moxifloxacin –Nalidixic acid –Norfloxacin -Ofloxacin •Chloramphenicol •Sulfonamides: – Co-trimoxazole (Sulfamethoxazole + Trimethoprim) – Sulfacetamide – Sulfadiazine – Sulfamethoxazole – Sulfapyridine – Sulfasalazine | Analgesics | • Acetylsalicylic acid (Aspirin) •Aminophenazone (Aminopyrine) • (Metamizole) • Phenylbutazone |
| Antibiotics | • Furazolidone • Streptomycin • Sulfonamides | ||
| Anticonvulsants | • Phenytoin | ||
| Antidiabetics | • Glibenclamide | ||
| Antidotes | • Dimercaprol (BAL) | ||
| Antihistamines | • Antazoline •Diphenhydramine | ||
| Antimalarials | • Mepacrine • Primaquine | Antihypertensives | • Hydralazine • Methyldopa |
| DEFINITE RISK OF HAEMOLYSIS | POSSIBLE RISK OF HAEMOLYSIS | ||
| Antimethemoglobinaemic Agents | • Methylene blue | Antimalarials | • Chloroquine & derivatives • Proguanil • Pyrimethamine • Quinidine • Quinine |
| Antimycobacterials | • Dapsone • Para-aminosalicylic acid | Antimycobacterials | • Isoniazid |
| Antineoplastic Adjuncts | • Doxorubicin • Rasburicase | Antiparkinsonism Agents | •Trihexyphenidyl (Benzhexol) |
| Cardiovascular Drugs | • Dopamine (L-dopa) • Procainamide • Quinidine | ||
| Diagnostic Agent for Cancer Detection | • Toluidine blue | ||
| Gout Preparations | • Colchicine • Probenecid | ||
| Nitrates | • Isobutyl nitrite | ||
| Vitamin K Substance | • Menadione •Phytomenadione | ||
| Vitamins | • Ascorbic acid (Vit C) (rare) | ||
| Others | • Arsine • Berberine (in Coptis chinensis) • Fava beans • Naphthalene (in mothballs) • Para-aminobenzoic acid(PABA) • Henna |
*Nomenclature based on INN (International non-proprietary name)
References
- Gregg XT, Prchal JT. Red blood cell enzymopathies. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018: chap 44.
- Lissauer T, Carroll W. Haematological disorders. In: Lissauer T, Carroll W, eds. Illustrated Textbook of Paediatrics. 5th ed. Philadelphia, PA: Elsevier; 2018: chap 23.
- Michel M. Autoimmune and intravascular hemolytic anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020: chap 151.
- https://www.medscape.com
- https://www.g6pd.org/en/Home.aspx
- https://kidshealth.org/en/parents/g6pd.html
Article by: Pharm.Magdalene Akanglah
Drug Information Unit
Pharmacy Department, KBTH
