Sequential sensitization to different occupational compounds in a young woman.

Background: Very few authors have reported sensitization to two or more different occupational sensitizers in a single patient.
Objective: To describe a subject with occupational asthma caused by sensitization to two different agents, exposure to which occurred in dierent time periods.
Methods: We studied a young woman with asthma-like symptoms predominantly in relationship to a sequential occupational exposure, first to methylene diisocyanate (MDI) and later to flour dust. In the first and second periods of occupational exposure, the patient was subjected to metbacholine challenge test (MCT), sputum analysis, and specific challenge test (SCT).
Results: At the first observation, MCT (PD20FEV1: 0.109 mg) and SCT with MDI were positive and induced sputum analysis showed a high percentage of eosinophils (32%). The patient reduced exposure to MDI but symptoms worsened with continuing occupational exposure. After one year, she started another job exposed to flour dust. After four years, asthma symptoms persisted despite treatment with inhaled corticosteroids and bronchodilators, and bronchial byperreactivity and sputum eosinophbilia were still present (PD2OFEV1: 0.067 mg; sputum eosinophils: 5.3%). The patient also developed rhinitis symptoms associated with dermatitis. A SCT with flour dust showed an immediate response (deltaFEV1: 33%). The subject left work and a year later was still symptomatic:pulmonary function was within normal limits under regular therapy and induced sputum showed absence of eosinophilia.
Conclusions: This was an unusual case of double sensitization to different occupational compounds to which the patient was exposed in different time periodsj suggesting the role of a pre-existing occupational aSthma in the development and/or worsening of sensitization to other occupational agents.