Lymphangioleiomyomatosis (LAM) is a rare disease characterized by pulmonary cysts at computed tomography (CT) and proliferation of abnormal smooth muscle cells at lung biopsy. Almost all patients are female, and all have pulmonary cysts at high-resolution CT. Although the presence of cysts may be suggested at conventional CT or chest radiography, high-resolution CT is superior for cyst detection and is essential for diagnosis. The cysts are typically round; in most cases, the cyst wall is barely seen at thin-section CT. They are typically diffusely distributed throughout the central and peripheral lung parenchyma. The lung bases are affected in all patients. Some patients also have increased lung attenuation or a reticular pattern. Expiratory CT shows no air trapping between the cysts, and most of the cysts decrease in size. Pneumothorax, pleural effusion, and chylothorax are complications of LAM. Certain abdominal findings may provide additional corroborative evidence of the diagnosis. Renal angiomyolipomas, the most frequent abdominal lesions, usually manifest as asymptomatic, small, bilateral tumors of fat attenuation in the renal cortex. Lymphangiomas are cystic retroperitoneal masses that occur in up to 20% of patients. Other CT findings are hypo- or hyperattenuating lymph nodes, a dilated thoracic duct, and ascites.
Copyright RSNA, 2002