대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Subacute Hypersensitivity Pneumonitis (Probably Summer-type)

Radiologic Findings

Frontal chest radiograph shows diffuse nodular opacities in both lungs. Patchy consolidations are also seen in right lower and left middle lung zones. High resolution CT demonstrates diffuse centrilobular nodular and ground-glass opacities in both lungs, combined with patchy consolidations and ground-glass opacities in both lower lobes.

She also experienced flu-like symptoms in the summer months of last year. She lives in old wooden house mostly in the shade. Air culture from her house revealed growth of fungus (not definite, but suspicious for Trichosporon species). Her symptoms have gradually improved after institution of corticosteroid therapy and after cessation of rainy spell.

Brief Review

Hypersensitivity pneumonitis (HP) is an immunologically induced inflammation of the lung parenchyma resulting from the repeated inhalation of a variety of etiologic agents including organic dusts and chemicals. Diagnosis is frequently delayed because symptoms are nonspecific and a relevant exposure history may be absent. Elevated antibody titers to inhaled antigens can suggest the diagnosis. Lung biopsy is often necessary for confident diagnosis, and histopathologic features include cellular bronchiolitis, diffuse lymphocytic interstitial infiltration, and noncaseating granulomas.

Summer-type HP whose major causative agent is Trichosporon species is the most prevalent type in Japan, characterized by symptoms that appear during the summer months, repeated episodes during subsequent seasons for many years, provocation of symptoms when at home, familial occurrence, and other manifestations similar to those of other types of HP. The hot, humid summer season and living environment with traditional wooden house are very similar to those of Korea, and there are many articles reporting cases of summer-type HP occurring in Korea. There are no difference in radiologic findings between summer-type and other types of HP.

Although considerable overlap in the radiologic findings of acute and subacute HP can occur, diffuse homogeneous opacities are usually seen during acute phase, and heterogeneous or small nodular opacities that predominate in mid to lower lung zones are much more common in subacute phase. Characteristic HRCT findings of subacute HP are ground-glass and nodular opacities in a centrilobular distribution, and patchy ground-glass opacity or consolidation. Air trapping on expiratory scan is a helpful ancillary finding, reflecting associated bronchiolitis. In the appropriate clinical setting these findings strongly suggest the diagnosis.

References

1. Matar LD, McAdams HP, Sporn TA. Hypersensitivity pneumonitis. AJR Am J Roentgenol 2000;174:1061-1066.

2. Akira M, Kita N, Higashihara T, Sakatani M, Kozuka T. Summer-type hypersensitivity pneumonitis: comparison of high-resolution CT and plain radiographic findings. AJR Am J Roentgenol 1992;158:1223-1228.

3. Nakata H, Egashira K, Tsuda T, Hiraoka K, Kido M. High-resolution computed tomography of Japanese summer-type hypersensitivity pneumonitis. Clin Imaging 1991;15:185-190.

4. Kim KH, Kim CH, Kwon SS, et al. 5 cases of summer-type hypersensitivity pneumonitis. Korean J Med 1996;50:439-450.

Keywords

Lung, Non-infectious inflammation, HP,