1.3 Kaposiform Lymphangiomatosis
Kaposiform lymphangiomatosis (KLA) is an aggressive lymphatic anomaly that is associated with significant morbidity and high mortality. KLA most commonly involves the thoracic cavity, bone and spleen [7]. Clinical presentation is typically severe, particularly at a young age, and progression occurs without treatment. Complications include organ compromise, pleural and pericardial effusions, ascites, pain, and functional issues. KLA is associated with a life-threatening coagulopathy characterized by severe hypofibrinogenemia, thrombocytopenia and bleeding [8]. Effusions and ascites are often hemorrhagic. Defining histopathological features are abnormal lymphatic channels with focal areas of spindle-shaped “kaposiform” endothelial cells, positive for D2-40 and PROX-1 [7]. Platelet trapping is also seen in KLA, suggesting that the pathogenesis of the coagulopathy is similar to Kasabach-Merritt phenomenon (KMP) occurring in kaposiform hemangioendothelioma (KHE) and tufted angioma (TA) [9]. Recently, RAS mutations were identified in affected tissue of patients with KLA [10].