Clinical features of recurrent and insidious chronic bird fancier's lung

Background: Chronic bird fancier's lung (BFL) can be subgrouped into two types. One subgroup of patients develops interstitial pulmonary fibrosis after recurrent acute episodes (recurrent BFL), and the other subgroup of patients has no history of acute episodes but has slowly progressive chronic respiratory disease (insidious BFL). Objective: To define the clinical characteristics of both types of BFL and to provide clues for diagnosis. Methods: We performed a retrospective review of the medical records of patients with chronic BFL who were evaluated between October 1992 and March 2001 at the Tokyo Medical and Dental University Hospital in Japan. Patients were evaluated for their clinical characteristics, including history, laboratory, and immunologic findings; imaging; bronchoalveolar lavage; and histologic findings. Results: Thirty-two patients with chronic BFL were included in this study; 15 patients had recurrent BFL and 17 had insidious BFL. The patients with recurrent BFL tended to breed dozens of pigeons in a loft, whereas the patients with insidious BFL were likely to be exposed to smaller birds kept indoors. Specific antibodies against pigeon dropping extracts or budgerigar dropping extracts were positive in 87% of the recurrent BFL cases and 35% of the insidious BFL cases. Antigen-induced lymphocyte proliferation was positive in more than 90% of both groups. The upper lung field was frequently involved in both groups as demonstrated by chest radiographic findings. In all of the patients with insidious BFL, the diagnosis was confirmed by positive laboratory-controlled inhalation test results. Conclusions: Insidious BFL may be misdiagnosed as idiopathic pulmonary fibrosis if a careful history is not taken and antigen-induced lymphocyte proliferation, careful imaging evaluation, and laboratory-controlled inhalation challenge testing are not conducted. In contrast, the clinical findings of recurrent BFL are consistent with hypersensitivity pneumonitis induced by other antigens.