[Pathological changes of lungs in patients with severity acute respiratory syndrome].
OBJECTIVE
To evaluate the progression in morphologic changes of lungs in SARS patients.


METHODS
Four cases of SARS with lung tissue samples available (including one for ultrastructural examination) were enrolled into the study. Histochemical study for VG, Masson, reticulin, orcein, PAS, sirius red stains and immunohistochemical study for vimentin, desmin, smooth muscle actin, HHF-35, CD34, F8, collagen types I and III were also performed.


RESULTS
According to the morphologic changes, lung lesions in SARS were subcategorized into 3 phases: acute exudative inflammation, fibrous proliferation and the final fibrotic stage. Two cases belonged to the acute exudative phase, in which the course was less than 20 days. The principal lesions consisted of acute alveolar exudative inflammation, hyperplasia of alveolar epithelium, necrosis, alveolar hyaline membrane formation, alveolar desquamation and focal fibroplasia. The acute exudative protein was PAS-positive. There was an increase in reticulin fiber formation. The reactive fibroblasts were highlighted by desmin and vimentin. One case belonged to the fibroproliferative stage, in which the course was around 25 days. Major lesions included proliferative interstitial pneumonia with early pulmonary fibrosis. There was also evidence of organizing pneumonia, with an increase in reticulin fiber formation, which had a glomeruloid appearance on special stain. The mesenchymal cells showed either myofibroblastic (which expressed desmin, HHF-35, smooth muscle actin and vimentin) or fibroblastic (which expressed vimentin only) differentiation. Fibroelastosis and fibroplasia was also noted. The remaining case belonged to the fibrotic stage, in which the course was around 75 days. The main features included diffuse fibrosis and honeycomb change, which were highlighted by sirius red stain. Immunohistochemistry showed mainly types I and IV collagen fibers. In all lesions, there was also an increase of number of CD68-positive macrophages.


CONCLUSIONS
The morphologic progression in lungs of SARS patients is characterized by the development of increased fibrosis. The primitive mesenchymal cells, hyperplastic alveolar epithelial cells and macrophages play an important role in the pathogenesis.
Lai
Ri-quan
RQ
Department of Pathology, General Hospital of Guangzhou Command, Guangzhou 510010, China.
Feng
Xiao-dong
XD
Gu
Ying-ying
YY
Lai
Huang-wen
HW
Liu
Fang
F
Tian
Ye
Y
Wang
Zhou-cai
ZC
Zhang
Wei
W
Chen
Guo-qin
GQ
Yang
Chuan-hong
CH
Yang
Tong
T
D000199:Actins / Q000378:metabolism; D000328:Adult; D024042:Collagen Type I / Q000378:metabolism; D003893:Desmin / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011658:Pulmonary Fibrosis / Q000473:pathology; D045169:Severe Acute Respiratory Syndrome / Q000378:metabolism / Q000473:pathology*; D014746:Vimentin / Q000378:metabolism
D000199:Actins; D024042:Collagen Type I; D003893:Desmin; D014746:Vimentin