Development of bronchial sensitization to inhalant allergens in occupational asthma patients

Abstract

In cases of occupational asthma due to reactive chemicals, an appreciable number of patients have persistent asthmatic symptoms and airway inflammation even after several years' avoidance of the cause agents. A case of late respiratory systemic syndrome (LRSS) caused by phthalic anhydride is reported. The patient showed a progression of bronchial asthma due to house dust mite and developed a new bronchial sensitization to horse hair during the 5 year follow-up period. The patient was diagnosed in September 1990 as having LRSS due to phthalic anhydride. He was atopic and had worked in a factory preparing materials for paints for 8 years. After leaving his workplace and commencing treatment with anti-asthmatic medications, his asthmatic symptoms and airway hyper-responsiveness were much improved for 1 year (PC20 methacholine level was increased from 0.44 to 4.4mg/mL). For several months before the second admission (October 1992) his asthmatic symptoms were again aggravated and methacholine PC20 decreased to 1.1mg/mL without improvement in the following 3 years. The level of serum specific IgE antibody to phthalic anhydride has been gradually decreasing, while specific IgE to two types of house dust mite and horse hair has been increasing year by year during the last 3 years' follow-up period. These findings suggest that chronic exposure to inhalant allergens can induce the progression of allergen-induced airway inflammation, and result in new bronchial sensitization to inhalant allergens. Careful follow-up study is needed to detect new developments of allergen-induced bronchoconstriction in occupational asthma patients with persistent asthmatic symptoms.