Masahide Yamazaki1^, Youichi Kawamura2^Takio Ohka2), Shoichi Katada3\ Katsuya Morita3M asaaki Nakagawa3), Eiko Kubo4), Aio Kawashima4), Hiroshi Shimizu5), Koji Nobata5), Shigeho Rikimaru5^Syugen Rin6), Hidesaku Asakura1^and Tamotsu Matsuda1Â 31-year-old womanpresented with hypertrophy of the left upper extremity and thrombocytopenia. Physical examination revealed splenomegaly, and laboratory investigation revealed thrombocytopenia, elevation of cross-linked fibrin degradation products (XDP), and thrombin-antithrombin III complex (TAT). A diagnosis of Klippel-Trenaunay-Weber (K-T-W) syndrome was established by the dermatologic findings and angiography of the extremities. A splenic cavernous lymphangiomawas diagnosed by ultrasonography and angiography, and was confirmed by pathology following splenectomy. Post-operatively, the platelet count increased, and hemostatic parameters normalized. Cavernous lymphangiomais a rare complication of KlippelTrenaunay-Weber syndrome. Splenectomy proved to be an effective therapy for both cavernous lymphangioma and consumptive coagulopathy in Klippel-Trenaunay-Weber syndrome. (Internal Medicine 33: 574-577, 1994)