Bird fancier's disease

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a complex syndrome caused by the inhalation of a variety of antigens in susceptible and sensitized individuals. These antigens are found in the environment, mostly derived from bird proteins and fungi. The prevalence and incidence of HP vary widely depending on the intensity of exposure, the geographical area and the local climate. Immunopathologically, HP is characterized by an exaggerated humoral and cellular immune response affecting the small airways and lung parenchyma. A complex interplay of genetic, host and environmental factors underlies the development and progression of HP. HP can be classified into acute, chronic non-fibrotic and chronic fibrotic forms. Acute HP results from intermittent, high-level exposure to the inducing antigen, usually within a few hours of exposure, whereas chronic HP mostly originates from long-term, low-level exposure (usually to birds or moulds in the home), is not easy to define in terms of time, and may occur within weeks, months or even years of exposure. Some patients with fibrotic HP may evolve to a progressive phenotype, even with complete exposure avoidance. Diagnosis is based on an accurate exposure history, clinical presentation, characteristic high-resolution CT findings, specific IgG antibodies to the offending antigen, bronchoalveolar lavage and pathological features. Complete antigen avoidance is the mainstay of treatment. The pharmacotherapy of chronic HP consists of immunosuppressive drugs such as corticosteroids, with antifibrotic therapy being a potential therapy for patients with progressive disease.

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.

Shortness of breath secondary to a pet cockatiel

A case of hypersensitivity pneumonitis in a 40-year-old patient secondary to a pet bird is presented. The clinical presentation, diagnosis, and management of hypersensitivity pneumonitis are reviewed.

Pigeon-breeder's lung. Extensive workup clarifies the clinical picture

Pigeon-breeder's lung should be included in the differential diagnosis when patients present with interstitial lung disease or intermittent cough and dyspnea. No single test confirms the diagnosis. Rather, careful attention must be given to results of history taking, physical examination, pulmonary function and precipitin testing, chest radiography, and, if indicated, lung biopsy. Symptoms usually resolve when exposure to suspected antigens is avoided.