[en] We report magnetic resonance (MR) findings in a patient with histologically proven lymphangiomatosis with a history of chylothorax, diffuse lung infiltrates, spinal involvement, cystic lesions of the mediastinum, and mesentery thickening. The patient also had diffuse infiltration of the right brachial plexus, with similar imaging findings as the spinal lesions. Although osseous and extraosseous involvement may be seen frequently with lymphangiomatosis, involvement of the brachial plexus has not been previously reported