Definition:

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked, hereditary disorder due to mutations in the G6PD gene, resulting in protein variants with different levels of enzyme activity, that are associated with a wide range of biochemical and clinical phenotypes. G6PD deficiency is the most common enzymatic disorder in humans. It is estimated that about 400 million people are affected by this deficiency. More than 400 biochemical variants of G6PD deficiency have since been defined, and grouped into five classes based on enzyme activity and clinical manifestations. The most common clinical manifestations are neonatal jaundice and acute haemolytic anaemia, which in most patients is triggered by an exogenous agent. A G6PD-deficient patient lacks the ability to protect red blood cells against oxidative stresses from certain drugs, infections, metabolic conditions, and ingestion of fava beans.