Erythropoietin-driven proliferation of cells with mutations in the tumor suppressor gene TSC2.

Lymphangioleiomyomatosis (LAM) is characterized by cystic lung destruction, resulting from proliferation of smooth-muscle-like cells, which have mutations in the tumor suppressor genes TSC1 or TSC2. Among 277 LAM patients, severe disease was associated with hypoxia and elevated red blood cell indexes that accompanied reduced pulmonary function. Because high red cell indexes could result from hypoxemia-induced erythropoietin (EPO) production, and EPO is a smooth muscle cell mitogen, we investigated effects of EPO in human cells with genetic loss of tuberin function, and we found that EPO increased proliferation of human TSC2-/-, but not of TSC2+/-, cells. A discrete population of cells grown from explanted lungs was characterized by the presence of EPO receptor and loss of heterozygosity for TSC2, consistent with EPO involvement. In LAM cells from lung nodules, EPO was localized to the extracellular matrix, supporting evidence for activation of an EPO-driven signaling pathway. Although the high red cell mass of LAM patients could be related to advanced disease, we propose that EPO, synthesized in response to episodic hypoxia, may increase disease progression by enhancing the proliferation of LAM cells.

Pulmonary artery pressure in lymphangioleiomyomatosis: an echocardiographic study.

BACKGROUND: Exercise-induced hypoxemia is frequent in patients with lymphangioleiomyomatosis (LAM) and could be associated with pulmonary hypertension. The aims of this study were to determine the prevalence of pulmonary hypertension in patients with LAM, to identify physiologic parameters associated with its occurrence, and to evaluate the effect of oxygen on response to exercise. METHODS: Studies were performed in 120 patients. Complete data, including exercise echocardiography, pulmonary function testing, and standard cardiopulmonary exercise testing, were obtained in 95 patients. RESULTS: Resting pulmonary artery pressure (PAP) was 26+/-0.7 mm Hg (mean+/-SEM). Eight patients had pulmonary hypertension (43+/-3 mm Hg), and two patients had right ventricular dilatation. Ninety-five patients exercised (room air, n=64; oxygen, n=31) to a power of 58+/-2 W (49% of predicted) and an estimated peak oxygen uptake of 938+/-30 mL/min (56% of predicted). Sixty-one patients had a decline in arterial oxygen saturation (SaO2)>3%, and 56 patients had an elevation in PAP>40 mm Hg. Peak exercise PAP was negatively correlated with exercise Sao2 (p=0.0005). Multivariate analysis showed that exercise SaO2 was the best predictor of exercise PAP (p=0.012). CONCLUSIONS: Although resting pulmonary hypertension is rare in patients with LAM, a rise in PAP at low exercise levels occurs frequently, in part related to exercise-induced hypoxemia. Optimization of oxygen administration during activities of daily living should be undertaken in patients with LAM to prevent hypoxemia and exercise-induced pulmonary hypertension.

Pneumothorax after air travel in lymphangioleiomyomatosis, idiopathic pulmonary fibrosis, and sarcoidosis.

BACKGROUND: The prevalence of pneumothorax associated with travel in patients with interstitial lung diseases is unknown. In patients with lymphangioleiomyomatosis (LAM), in whom pneumothorax is common, patients are often concerned about the occurrence of a life-threatening event during air travel. The aim of this study was to determine the prevalence of pneumothorax associated with air travel in patients with LAM, idiopathic pulmonary fibrosis (IPF), and sarcoidosis. METHODS: Records and imaging studies of 449 patients traveling to the National Institutes of Health were reviewed. RESULTS: A total of 449 patients traveled 1,232 times; 299 by airplane (816 trips) and 150 by land (416 trips). Sixteen of 281 LAM patients arrived at their destination with a pneumothorax. In 5 patients, the diagnosis was made by chest roentgenogram, and in 11 patients by CT scans only. Of the 16 patients, 14 traveled by airplane and 2 by land. Seven of the 16 patients, 1 of whom traveled by train, had a new pneumothorax; 9 patients had chronic pneumothoraces. A new pneumothorax was more likely in patients with large cysts and more severe disease. The frequency of a new pneumothorax for LAM patients who traveled by airplane was 2.9% (1.1 per 100 flights) and by ground transportation, 1.3% (0.5 per 100 trips). No IPF (n = 76) or sarcoidosis (n = 92) patients presented with a pneumothorax. CONCLUSIONS: In interstitial lung diseases with a high prevalence of spontaneous pneumothorax, there is a relatively low risk of pneumothorax following air travel. In LAM, the presence of a pneumothorax associated with air travel may be related to the high incidence of pneumothorax and not to travel itself.

Computer-Aided Grading of Lymphangioleiomyomatosis (LAM) using HRCT.

Lymphangioleiomyomatosis (LAM) is a multisystem disorder associated with proliferation of smooth muscle-like cells, which leads to destruction of lung parenchyma. Subjective grading of LAM on HRCT is imprecise and can be arduous especially in cases with severe involvement. We propose a computer-aided evaluation system that grades LAM involvement based on analysis of lung texture patterns. A committee of support vector machines is employed for classification. The system was tested on 36 patients. The computer grade demonstrates good correlation with subjective radiologist grade (R=0.91, p<0.0001) and pulmonary functional tests (R=0.85, p<0.0001). The grade also provides precise progression assessment of disease over time.

Genetic and morphologic determinants of pneumothorax in lymphangioleiomyomatosis.

Lymphangioleiomyomatosis, a multisystem disease affecting women, is characterized by proliferation of abnormal smooth muscle-like cells in the lungs, leading to cystic destruction of the parenchyma and recurrent pneumothoraces. Clinical characteristics of lymphangioleiomyomatosis patients were analyzed to determine the relationship of pneumothoraces to disease progression. Patients were genotyped for polymorphisms in genes of extracellular matrix proteins collagen, elastin, and matrix metalloproteinase-1 to assess their association with pneumothoraces. Clinical data and polymorphisms in the genes for types I and III collagen, elastin, and matrix metalloproteinase-1 were compared with the prevalence of pneumothorax. Of 227 patients, 57% reported having had at least one pneumothorax. Cyst size on high-resolution computed tomography scans was associated with pneumothorax; patients with a history of pneumothorax were more likely to have larger cysts than patients who had no pneumothoraces. In patients with mild disease, those with a history of pneumothorax had a faster rate of decline in forced expiratory volume in 1 s (FEV(1); P = 0.001, adjusted for age) than those without. Genotype frequencies differed between patients with and without pneumothorax for polymorphisms in the types I and III collagen and matrix metalloproteinase-1 genes. Larger cysts may predispose lymphangioleiomyomatosis patients to pneumothorax, which, in early stages of disease, correlates with a more rapid rate of decline in FEV(1). Polymorphisms in types I and III collagen and matrix metalloproteinase-1 genes may cause differences in lung extracellular matrix that result in greater susceptibility to pneumothorax.