• bakers;
  • basophil activation test;
  • induced sputum;
  • occupational eosinophilic bronchitis;
  • storage mites

Nonasthmatic eosinophilic bronchitis (NAEB) is a condition characterized by corticosteroid-responsive chronic cough, sputum eosinophilia and absence of symptoms or objective evidence of variable airflow obstruction and airway hyperresponsiveness (1). Like asthma, NAEB can be associated with exposure to occupational sensitizers (1), and the recognition of the offending agent is mandatory for diagnosis. Only few cases of occupational NAEB have been reported in bakers, because of enzymes and flour (1, 2). We describe the first case of occupational NAEB because of storage mites in which the offending agent was identified by means of the basophil activation test (BAT), a new tool that has never been proposed in diagnostic algorithms of occupational respiratory allergy (3, 4).

A 61-year-old ex-smoker atopic man came to our observation for work-related chronic cough. Since the age of 16, he suffered from perennial rhinoconjunctivitis, exacerbated in grass pollen period. He had been working as a baker since the age of 17, and 9 years later, he reported dry cough and throat hoarseness when bakering or going into flour storehouse, improving off work. Spirometry was normal, methacholine challenge test and bronchodilator test were negative. Skin prick tests (SPTs) and specific serum IgE (sIgE) results are reported in Table 1A. Blood eosinophils were 5.2% (0.28 × 109/l), total serum IgE 278 kU/l. Out of grass pollen period, the patient was asked to stay off work for 1 week, then restart baking 30 min/day for 1 week and afterward 2 h/day for another week, avoiding corticosteroid assumption. Induced sputum (IS) was collected at the end of each week (Table 1B). In winter season, the patient underwent specific inhalation challenge (SIC) (1). A control challenge with lactose induced significant variation neither in FEV1 nor in eosinophil percentage in IS, and nasal secretions (NS) collected before and after challenge (5). The following day exposure to wheat flour by occupational method elicited dry cough without any significant FEV1 variation. An increase in IS total cell count and in eosinophils was registered after challenge (Table 1B), but not in NS. Mch challenge test was negative 24 h after SIC. BATs results are reported in Table 1A. After discharge, to further exclude interference of common allergens in bronchial inflammation, patient avoided flour exposure for 5 weeks during grass pollen period, free of any therapy. At the end of this period, the patient was asymptomatic. IS challenge showed 0% eosinophils (Table 1B). A diagnosis of occupational NAEB because of storage mites was made (1).

Table 1.    (A) Results of skin prick tests (SPT), serum specific IgE (sIgE) and basophil activation test (BAT). (B) Induced sputum cell count in relation to wheat flour exposure
 SPTsIgE (kU/l)BAT [%* (SI†)]
Dermatophagoides pteronyssinus+++1.61NP
Dermatophagoides Farinae+++2.25NP
Acarus siro++0.1764.2 (40.1)
Lepidoglyphus destructor+++0.1947.3 (29.6)
Glycyphagus domesticus+0.4170.5 (44.1)
Tyrophagus putrescientiae+0.1453.1 (33.2)
Grass pollens+1.03NP
Wheat flour<0.100.9 (0.6)
Oats, barley, soy, rice<0.10NP
Ephestia kuhniellaNPNP
 Off work (1 week)At work (30 min/day)At work (120 min/ day)Off work (5 weeks‡)SIC
  1. NP, not performed; SIC, specific inhalation challenge; TCC, total cell count.

  2. *Percentage of CD63 positive basophils.

  3. †Stimulation index (percentage of CD63 with extract/percentage of CD63 with wash buffer).

  4. ‡Grass pollen period.

TCC (104/ml)4356147.63818159
Vitality (%)7086.47596.79092
Neutrophils (%)5.626.98.314.32.155
Eosinophils (%)1.88.758.501.815.2
Lymphocytes (%)1.660.603.21.4

The IS eosinophil increase after SIC, the negative or low percentage of IS eosinophils when not exposed to flour and the dose–response relationship between the duration of daily exposure and IS eosinophils were consistent with a work-related disease (1). Nevertheless, the negative SPT and sIgE to flour, and the discrepancy between SPTs and sIgE level for storage mites (Table 1A) required further investigation to identify the offending agent. BAT’s results, showing a high CD63 expression detected by flow-cytometry and an elevated stimulation index for all tested storage mites, proved the role of these agents and the absence of sensitization to wheat flour. Storage mites are known to be stored grain pests, but they have never been recognized as causative agent of NAEB. Compared with the determination of sIgE, BAT offers the additional advantage of being able to demonstrate functional responses (6). In our case, BATs solved the discrepancy between SPTs and sIgE results, therefore confirming storage mites as causal agents. Furthermore, our case proves that once the diagnosis of NAEB is established and the offending agent is recognized, a complete cessation of exposure is truly effective.


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