Deficiency of platelet-activating factor acetylhydrolase is a severity factor for asthma

Asthma, a family of airway disorders characterized by airway inflammation, has an increasing incidence worldwide. Platelet-activating factor (PAF) may play a role in the pathophysiology of asthma. Its proinflammatory actions are antagonized by PAF acetylhydrolase. A missense mutation (V279F) in the PAF acetylhydrolase gene results in the complete loss of activity, which oc curs in 4% of the Japanese population. We asked if PAF acetylhydrolase defi ciency correlates with the incidence and severity of asthma in Japan. We fo und that the prevalence of PAF acetylhydrolase deficiency is higher in Japa nese asthmatics than healthy subjects and that the severity of this syndrom e is highest in homozygous-deficient subjects. We conclude that the PAF ace tylhydrolase gene is a modulating locus for the severity of asthma.