Hypersensitivity pneumonitis in a fish-processing worker – use of specific inhalation challenge as a diagnostic tool

Objective: A fish-processing worker reporting symptoms consistent with HP during slaughtering of salmon was referred to our clinic. The 42 year old man, never smoker, no history of allergy or respiratory disease, reported job-related symptoms for the last 3 years (dyspnoe, coughing, flu-like symptoms and fever). The symptoms started 3-4 hours after start of work shift. He felt better next morning and during weekends. The last year he had had recurrent episodes of pneumonia. Aim: By the use of specific inhalation challenge (SIC), we aimed to describe the patient´s respiratory, clinical and immunological responses after inhalation of salmon proteins. Method: SIC is a method for diagnosing occupational asthma and a modified version of the protocol is used for diagnosing hypersensitivity pneumonitis (HP). The challenge with salmon proteins was conducted in a provocation chamber (13 m3) with the patient manually filleting salmon (20 min). Results: At baseline there was a tendency of low diffusion capacity for carbon monoxide (DLCO 74% of predicted), lung function verging a restrictive pattern (FVC 80% of predicted), and no specific IgEs towards fish allergens. In response to SIC, he got flu-like symptoms, further decrease in FVC (12.5%) and DLCO (11%), increase in neutrophils (12%) and decrease in lymphocytes (23%), as compared to pre-test values. Next day the patient was asymptomatic, and FVC and DLCO were normalized to pre-test values. Conclusion: The patient’s response to salmon proteins was compatible with HP according to Munoz X et al [Curr Opin Allergy Clin Immunol. 2013;13:151-8]. A better awareness of etiological factors of HP other than birds and mold is needed.