Eosinophilic bronchitis (EoB) is characterized by chronic cough and sputum eosinophilia. The diagnosis includes an evaluation of other causes of chronic cough, particularly asthma, cough-variant asthma, allergic rhinitis, gastro-oesophageal reflux and iatrogenic cough. The differential diagnosis is therefore a critical point and consists of assessing inflammatory cells in sputum and excluding abnormalities in functional respiratory explorations. Diagnosing EoB is important because inhaled corticosteroid (ICS) treatment is almost invariably effective (1). EoB can be considered as being a variant of occupational asthma when it is induced by work exposure (2).
Case reports of occupational EoB caused by latex (3), mushroom spores (4), acrylates (5) and epoxy hardener have been described. We herein report two cases of occupational EoB caused by welding fumes and formaldehyde. The main characteristics of the patients are presented in Table 1.
|Patient 1||Patient 2|
|Duration of symptoms (years)||3||1|
|Smoking habits||Ex-smoker (15 pack years)||Non-smoker|
|Chest auscultation||Bilateral sibilant ronchi||Normal|
|FEV1/forced vital capacity (%)||78||85|
|Sputum eosinophilia||Pre-SIC: 13.5% |
|Pre-SIC: 2.8% |
A 48-year-old man was employed for 12 years by a company that produced metallic parts. He used to weld aluminium and mild and stainless steel. Nine years after starting this work, a cough with sorrel expectoration, pharyngodynia, wheezing and mild dyspnoea appeared. These symptoms were present at the end of the workday and persisted throughout the night. An ICS therapy initiated by the family physician was useful and allowed him to work for two additional years.
Specific inhalation challenges (SIC) were performed in our laboratory and at the workplace. All SIC were negative (no significant changes in spirometry or in bronchial responsiveness). The subject therefore returned to work. At a follow-up visit, 1 month later, an increase in sputum eosinophilia was found (39%). To understand the possible association with the workplace, the patient was removed from exposure and induced sputum was repeated 1, 2 and 3 months later. Sputum eosinophilia decreased to 26.2, 26 and 14% respectively.
To confirm the diagnosis of occupational EoB, sputum cellularity was assessed after SIC. On two control days, sputum eosinophilia assessed 8 h after exposure, was 13.5 and 13.2% respectively. Four days later, he welded stainless steel for 30 min. Sputum eosinophilia increased to 50.8% by the end of the day. Increased specificity was ascertained by the decrease of sputum eosinophilia 1 week later (7.3%). Spirometry and methacholine tests performed after all SIC were negative. Diagnosis was confirmed by recurrence of symptoms and sputum eosinophilia (66.7%) as soon as he returned to work.
A 38-year-old woman worked in a laboratory for 10 years. Her work consisted of interpreting biologic samples and attending autopsies. Nine years after beginning this work, she reported chronic cough with off-white expectoration and chest tightness which exacerbated during the night. ICS therapy proved helpful. Sputum eosinophilia was found to be increased (18.8%). The patient was placed on sick leave. Two weeks later, respiratory symptoms improved and sputum eosinophilia decreased (11.3%). SIC with formaldehyde was then performed. On a control day (after having been away from work for 9 weeks), she was exposed to xylol diluent in the laboratory for 30 min. Sputum eosinophilia was assessed at 2.8%. On two subsequent days, she was exposed to evaporated formaldehyde for 30 and 120 min. Sputum eosinophilia increased to 4.2 and 22.3%, respectively, and a severe cough appeared. Spirometry and methacholine tests performed after all SIC were negative.
These two cases underline the relevance of monitoring airway inflammation by means of induced sputum in the investigation of occupational asthma. Removal from exposure remains a priority. Even if the outcome of occupational EoB is presently unknown, continued exposure might induce a chronic inflammation and consequently, could lead to the development of chronic airway obstruction, as described for non-occupational EoB (6).
Dr Mona-Rita Yacoub is a post- doctoral fellow supported by Asthma in the Workplace (Canadian Institutes of Health Research, Canadian Lung Association, Institut de recherche Robert-Sauvé en santé et sécurité du travail du Québec).