August 2007 QUIZ OF THE MONTH . . . Which of the statements about occupational asthma (OA) are true? Occupation-related asthma is involved in about 2% of asthma in adults. The absence of serum IgE antibodies against isocyanates rules out these agents as causes of OA Certain enzymes are allergens in Baker's asthma OA frequently persists for a sizable period of time after withdrawal of the patient from the offending inhalant The diagnosis of OA can be added by the measurement of non-specific bronchial responsiveness to inhaled methacholine Discussion OA is reportedly common, involved in 10-20% of those with adult asthma. Isocyanates, used in making polyurethane, are one of the common causes of OA. However, IgE antibodies against isocyanates are found in only about 25% of those with asthmatic reactions to isocyanate inhalation challenge. CD4+ lymphocyte reactions to isocyanates may be causing some of the IgE- negative cases. Proteins in grains used in baking are major allergens involved in Baker's asthma . However, new enzymes added in the baking process also appear to be potential allergens in Baker's asthma. It is not unusual for asthma to persist for weeks to months after withdrawal of the involved worker from prolonged exposure to the offending agent. A direct, blinded inhalation challenge with the suspect agent is the gold standard for diagnosing OA. However, a combination of evidence of IgE-mediated sensitivity to that agent and the presence of bronchial hyper-reactivity to methacholine is strong suggestive evidence of OA. References 1. Curr Opin Allergy Clin Immunol 2007;7:138-45 2. Curr Opin Allergy Clin Immunol 2007;7:152-5 3. Chest 2007;131:569-78 4. Curr Opin Allergy Clin Immunol 2007;7:96-10 Think you have the answers? Click here to find out if you're right! Please tell us what you think of this site. © Copyright 1997-2008 American Academy of Allergy, Asthma & Immunology All rights reserved