Background

Favism is characterized as an enzymatic deficiency of glucose-6-phosphate dehydrogenase (G-6-PD).

It is believed to be one of the most common enzyme deficiencies worldwide, affecting nearly 400 million people.

G-6-PD deficiency can lead to jaundice, hemolysis (bursting of red blood cells), or acute hemolytic anemia or a chronic spherocytic type (premature destruction of red blood cells).

There are 5 classes of G-6-PD and they explain the polymorphism of this gene. These classes of G-6-PD deficiency exist based on enzyme activity levels, as follows: enzyme deficiency with chronic non-spherocytic hemolytic anemia, severe enzyme deficiency (<10 per cent), moderate-to-mild enzyme deficiency (10 ? 60 per cent), very mild-to-no enzyme deficiency (60 per cent), and increased enzyme activity. Glucose-6-phosphate dehydrogenase is present in every cell in the body. G-6-PD protects the cells from oxidants, chemicals that oxidize or break bonds between atoms in a molecule. G-6-PD has a crucial role in the control of oxidant stress in red blood cells. Oxidation causes lysis of the cell or, in the case of red blood cells, hemolysis; the cell membranes disintegrate, allowing the contents to leak out. Fava beans have pyrimidine aglycones, vicine, and convicine, possible causes of hemolytic anemia. These compounds have the capacity to oxidize the reduced glutathione (GSH) of G-6-PD deficient enzyme. Favism is found in many different regions of the world. Most commonly, favism is found in Mediterranean countries, South West Asia, and certain parts of Africa. Glucose-6-phosphate dehydrogenase is an inheritable X-linked genetic trait. In regions where the disorder is prevalent, pregnant women are advised to avoid consuming fava beans. Symptoms

Susceptible individuals include those who are exposed to as little as one fava bean seed or traces of pollen from the fava flowering plant. The degree of severity varies between individuals being asymptomatic in some cases but causing death in others.

Symptoms of fava bean ingestion usually occur five to 24 hours later. Pollen inhalation symptoms occur within minutes of exposure.

Importantly, the common route of exposure is through ingestion of fava beans and not through breathing in pollen particles. Typical symptoms of favism include tiredness, malaise, headache, dizziness, nausea, vomiting, chills, back pain (lumbar region), and increased heart rate, yellowing of the skin (jaundice), and fever.

Vicia faba

Fava, or faba bean, is a cultivated bean used in human food and animal feed. This vegetable is green or yellow and can be dried, fresh, or canned. In South West Asia, the Mediterranean region, and China it is a common breakfast food.

Diagnosis

If jaundice and anemia occur concurrently, a diagnosis of G-6-PD is investigated by blood tests. The volume of red blood cells is measured.

Specifically, tests for bilirubin to determine liver function and hemoglobin are important to determine if favism is the cause. Furthermore, other metabolic laboratory testing is conducted to confirm a diagnosis.

Treatment

The best available treatment is the avoidance of fava beans and pollen of the vicia fava plant. In addition, many drugs that precipitate hemolysis must be avoided, such as aspirin and non-steroidal anti-inflammatory drugs (NSAID). Therefore, current treatments are aimed at preventing the onset of hemolysis rather than treating the visible symptoms.

Non-traditional therapies have included the use of vitamin E, and other anti-oxidants to minimize hemolysis in patients.

For more information on favism, visit the Favism Association website.