Favism involves hemolytic anemia (breakup of red blood cells) after eating fava beans or being exposed to the pollen of the fava plant. This dangerous reaction occurs exclusively in people with a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), an X-linked genetic trait. However, not all G6PD-deficient families appear at risk for favism, indicating the additional need for a single autosomal (not X-linked) gene to create susceptibility to favism in G6PD-deficient people. The active hemolytic principle in fava beans is most likely DOPA-quinone. Differences in susceptibility to favism may be related to differences in the enzymatic system that converts L-DOPA to DOPA-quinone.