PURPOSE: Lymphangioleiomyomatosis (LAM) is characterized by proliferation of abnormal smooth muscle-like cells (LAM cells) that leading to cystic lung destruction and LAM-associated lymphangionegesis. The cardinal physiologic and clinical consequences are impaired diffusing capacity and dyspnea on exertion. The precise mechanism for cystic destruction in LAM remains undetermined. Recently, quantitative analyses of pulmonary vascular alteration on CT images showed the strong correlation between emphysema and total cross sectional area (CSA) of small pulmonary vessels at sub-subsegmental levels in chronic obstruction pulmonary disease (COPD), the disease in which endothelial dysfunction is reported to be related with pulmonary vascular alteration and emphysema. In this context, we conducted quantitative CT analysis of small vascular alteration in LAM to examine whether the extent of cystic destruction correlates with vascular alteration.
METHODS: We measured CSA less than 5 mm2 and 5-10 mm2, and calculated the percentage of the total CSA for the lung area (%CSA<5, and %CSA5-10, respectively) using CT scans in 51 subjects. The extent of cystic destruction LAA%(-960) was calculated, and the correlations of %CSA<5 and %CSA5-10 with LAA%(-960) and results of pulmonary function tests (PFTs) were evaluated.
RESULTS: Although LAA%(-960) had significant negative correlations with FEV1/FVC (r = -0.78, p<0.01), FEV1 %predicted (r = -0.64, p<0.01), and DLCO/VA %predicted (r = -0.81, p<0.01), %CSA<5 and %CSA5-10 weakly correlated with DLCO/VA %predicted but not with LAA%(-960).
CONCLUSIONS: In contrast with COPD, cystic destruction had no correlation with small vascular impairment in LAM, indicating that the different mechanism for cystic destruction exists in LAM.
CLINICAL IMPLICATIONS: LAM lungs are characterized pathologically by the proliferation of LAM cells and abundant lymphatic vessels. The results in this study therefore may indicate that not only loss of parenchymal blood vessels but also acquisition of lymphatic flow influences the measurement of CSA and have physiologic consequences in LAM.
DISCLOSURE: The following authors have nothing to disclose: Katsutoshi Ando, Kazunori Tobino, Yoko Gunji, Makiko Kunogi, Yoshito Hoshika, Masatoshi Kurihara, Kuniaki Seyama, Kazuhisa Takahashi
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