Congenital errors of lymphatic development can lead to primary pulmonary lymphatic disorders that include lymphangiomas and lymphangiomatosis, lymphangiectasis, and lymphatic dysplasia syndrome [183, 184] . Lymphangiomas are focal proliferations of well differentiated lymphatic tissue, and lymphangiomatosis describes the presence of multiple lymphangiomas. Most of these disorders are discovered in fetuses or during the early postnatal period. Lymphangiectasis is characterized by pathologic dilation of lymphatics. The term "lymphatic dysplasia syndrome" includes congenital chylothorax, and the yellow nail syndrome (a triad of idiopathic pleural effusions, lymphedema, and dystrophic nails) [185] . Secondary forms of lymphatic disorders result from a variety of processes such as chronic airway inflammation that impair lymph drainage and increase lymph production [186] . Diffuse alveolar hemorrhage syndromes Diffuse alveolar hemorrhage (DAH) syndromes are caused by the disruption of alveolar-capillary basement membrane as a consequence of injury to the alveolar septal capillaries, and less commonly to the arterioles and veinules. The hallmarks are intra-alveolar accumulation of red blood cells, fibrin, and hemosiderin-laden macrophages. It is important to point out that approximately one third of patients with DAH do not manifest hemoptysis, and BAL can be extremely helpful if this entity is suspected by showing the presence of siderophages or red blood cells within the alveoli. DAH can be observed in association with systemic findings or without evidence of associated diseases.