Chronic summer-type hypersensitivity pneumonitis: clinical similarities to idiopathic pulmonary fibrosis.
BACKGROUND
Chronic hypersensitivity pneumonitis (HP) eventually ensues to extensive lung fibrosis when exposure to the causative antigen continues. Differential diagnosis from idiopathic interstitial pneumonias is sometimes difficult especially in the advanced stage.


OBJECTIVE
To describe the clinical course of chronic summer-type HP, which is the most prevalent type of HP in Japan, in terms of early diagnosis and similarity to idiopathic pulmonary fibrosis (IPF).


METHODS
14 patients with chronic summer-type HP diagnosed between 2000 and 2005 were reviewed retrospectively.


RESULTS
KL-6, a mucin-like glycoprotein, and surfactant protein-D (SP-D) were elevated in most cases. Specific antibodies against Trichosporon asahii (T. asahii) and T. mucoides in sera and BAL fluids were positive in 12 of 14 cases. A lymphocyte proliferation test induced by Trichosporon related antigen was positive in all examined cases (n=5). On high-resolution CT, traction bronchiectasis and honeycombing were observed in more than 70% of cases. By video-assisted thoracoscopic surgery (VATS) and autopsy specimens, honeycombing, fibroblastic foci, centrilobular fibrosis, and bridging fibrosis between bronchiolar and subpleural areas were observed. Antigen avoidance by improving domestic environments kept patients stable without decline in vital capacity (VC). However, 3 of the 4 patients who did not remedy their houses died of respiratory failure after progression of this disease.


CONCLUSIONS
Correct diagnosis in the early stage is crucial, since chronic summer-type HP can result in a fatal outcome after continuous exposure to the causative antigen.
Inase
Naohiko
N
Department of Integrated Pulmonology, Tokyo Medical and Dental University, Tokyo, Japan.
Ohtani
Yoshio
Y
Usui
Yutaka
Y
Miyazaki
Yasunari
Y
Takemura
Tamiko
T
Yoshizawa
Yasuyuki
Y
D000368:Aged; D000542:Alveolitis, Extrinsic Allergic / Q000150:complications / Q000175:diagnosis / Q000276:immunology*; D018893:Bronchoalveolar Lavage; D002908:Chronic Disease; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011658:Pulmonary Fibrosis / Q000276:immunology*; D012189:Retrospective Studies; D012621:Seasons; D020775:Thoracic Surgery, Video-Assisted