Histologic features--Lymphangiomyomatosis (LAM) is a rare disease characterized by progressive proliferation of spindle cells, resembling immature smooth muscle, in the lung parenchyma and along lymphatic vessels in the chest and abdomen. Proliferation of spindle cells along the bronchioles leads to air trapping and the development of emphysema and thin-walled lung cysts. Rupture of these cysts can result in pneumothorax. The spindle cell proliferation can also involve the hilar, mediastinal, and extrathoracic lymph nodes, sometimes resulting in dilation of intrapulmonary lymphatics and the thoracic duct. Involvement of the lymphatics can lead to chylous pleural effusion. Proliferation of cells in the walls of pulmonary veins may cause venous obstruction and lead to pulmonary hemorrhage.2, 90, 91
Clinical findings--The majority of patients present with dyspnea. Sixty percent develop chylous pleural effusions; 40% develop pneumothorax;92 and 30% to 40% develop blood-streaked sputum or frank hemoptysis. Almost all patients die within 10 years of the onset of symptoms. Recently, improved prognosis has been reported following treatment with progesterone or oophorectomy.2, 91
Lymphangiomyomatosis essentially occurs only in women of child-bearing age, usually between 17 and 50 years old.91 Rarely, however, it may be seen in postmenopausal women; the oldest patient described was 69 years of age. Caucasians are more commonly affected than other racial groups. Identical clinical, radiologic, and pathologic pulmonary changes may be seen in about 1% of patients with tuberous sclerosis.2, 90 Although tuberous sclerosis affects both sexes equally, the pulmonary changes have been described almost exclusively in women.
Radiographic findings--Chest radiographs: The plain radiologic manifestations of LAM include reticular, miliary, and honeycomb patterns (figure 22 -- 47KB). Lung volumes can be increased in patients with this disease. The radiologic findings may precede, accompany, or postdate other manifestations of the disease such as pneumothorax and chylous pleural effusion.93 In patients treated for recurrent pneumothoraces, extensive parenchymal abnormalities not visible on radiographs have been demonstrated at surgery.
HRCT: On HRCT, patients with LAM characteristically show numerous thin-walled cysts, surrounded by relatively normal lung parenchyma (figure 23 -- 79KB). These cysts usually range from 2 to 5 mm in diameter, but can be larger. Their size tends to increase with progression of the disease. Irregularly shaped lung cysts, as are seen in patients with EG, are uncommon.3, 94
In the majority of patients, the cysts are distributed diffusely throughout the lungs and no lung is spared; diffuse lung involvement is seen even in patients with mild disease. In most patients, the lung parenchyma between cysts appears normal on HRCT. Small nodules are occasionally seen, but are not a prominent feature of this disease as they are with EG.2, 3
Other features of LAM, which can be seen on HRCT, include hilar, mediastinal, and retrocrural adenopathy.90 Pleural effusion can also be seen, and is helpful in distinguishing LAM from EG.3
Next page: Conclusion & References
1 2 3 4 5 6 7 8 9 10 11
