An acquired hemorrhagic disorder developed in two patients in association with postsplenectomy thrombocytosis and leukocytosis during the course of the myeloproliferative syndrome. The presence of acquired von Willebrand's disease in these individuals was demonstrated by a decrease or absence of the larger von Willebrand factor (vWF) multimers, alteration of the repeating vWF multimeric “triplet,” decreased ristocetin cofactor activity (vWF:RCo), and prolonged bleeding time. The bleeding stopped in both patients after treatment with either 1-deamino-[8-D-arginine]-vasopressin (DDAVP) or Cohn fraction I. Treatment with thrombocytapheresis and azathioprine or busulfan resulted in reduction of the elevated platelet and white cell counts and was associated with partial correction of the vWF abnormalities and remission of the hemostatic abnormalities. In five additional patients with the myeloproliferative syndrome, but without bleeding symptoms, large multimers of plasma vWF were diminished also. These findings suggest that acquired von Willebrand's disease should be considered when a bleeding diathesis develops during the course of the myeloproliferative syndrome.

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11.4 mg of a ceramide hexahexoside (B-I) and 16.4 mg of a ceramide octahexoside (B-II) as blood group B-active glycosphingolipids composed of glucose, galactose, N-acetylglucosamine and fucose (molar ratios 1:3:1:1 and 1:4:2:1 respectively) have been isolated from 6,400 ml of packed human B erythrocytes. This yield is greater by more than the 13-fold amount of B-I glycosphingolipid and the 20-fold amount of B-II glycosphingolipid which has hitherto been isolated from human erythrocytes. The B-active glycosphingolipids isolated represent about 0.04% of the erythrocyte membrane and in consequence must be regarded as the main representants of B properties of the erythrocytes as far as they have been investigated up to this time. This high yield was achieved by a simple and conservative erythrocyte membrane preparation without loss of serological activity and by the improvement of some chromatographical methods which permitted a high purification without the acetylation-deacetylation procedure. Purity was checked by gas-liquid chromatographical analysis of the sugars as their alditol acetates and by the hemagglutination inhibition technique. 1.7 x 10-8 g of each of these glycosphingolipids completely inhibit the agglutination of human B erythrocytes by 4 hemagglutination units of normal human anti-B sera. A ceramide tetrahexoside and a glycolipid fraction with a high H activity could also be isolated which possibly are blood group-intermediate substances. Lewis blood group-active glycosphingolipids characterized by the hemagglutination inhibition test and by passive hemagglutination are trace constituents of other glycosphingolipid fractions.

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