Hypersensitivity Pneumonitis Presenting as Fever of Unknown Origin-A Case Presentation and Review of the Literature

Hypersensitivity pneumonitis (HP) is a pulmonary disorder with symptoms of fever, dyspnea and cough resulting from exposure to an antigen to which the subject has been previously sensitized. The clinical symptoms are very similar to pyogenic infection. Detailed history-taking and a high index of suspicion are mandatory in aiding the diagnosis of HP. Herein, we reported a patient with HP with the initial presentation of intermittent fever, general malaise, and body weight loss. Comprehensive surveys for infectious diseases, autoimmune diseases and malignancies were carried out at a local hospital and a medical center, and yielded negative results. Despite undergoing open lung biopsy, no definite diagnosis was made. Bronchoalveolar lavage (BAL) was done at our hospital and lymphocytic alveolitis was suggested by the cytological smear of the BAL fluid (BALF). Based on the clinical presentation, contact history, cytological findings of the BALF and pathological findings of lung biopsy obtained from other hospitals, HP was highly suspected. The patient underwent pulse therapy with methyprednisolone and maintenance with a low-dose steroid. Fever subsided gradually and the follow-up chest radiograph demonstrated marked regression of the pulmonary lesions.