The elusive and heterogeneous pattern of type 2M von Willebrand disease: A diagnostic challenge.

ABSTRACT

Type 2M is a very heterogeneous form of von Willebrand disease (VWD) associated with impaired platelet and von Willebrand factor (VWF) interactions not due to a lack of large VWF multimers. OBJECTIVES: To investigate type 2M heterogeneity and to establish the most appropriate diagnostic flowchart. METHODS: Hemostatic and genetic VWF analyses were performed in 14 type 2M VWD patients carrying the p.G1324S, p.R1374H, p.R1374C, p.A1344_A1350del, or p.F1293L mutations. RESULTS: PFA-100 was always significantly prolonged, and ristocetin-induced platelet aggregation (RIPA) and VWF ristocetin cofactor (VWFRCo) greatly reduced or absent. Plasma VWF antigen (VWFAg) was reduced except in the p.G1324S patient, while platelet VWFAg was normal or near normal except in the p.R1374C patients. The ratio of collagen binding (VWFCB) to VWFAg was normal or near normal except in patients carrying the p.R1374H and p.A1344_A1350del mutations, whose large VWF multimers were slightly reduced. Multimer patterns were normal or lacking in large oligomers, or with larger than normal VWF components. CONCLUSIONS: Only PFA100, RIPA and VWFRCo were always abnormal. We thus propose a minimal diagnostic test battery RIPA (demonstrating the defective VWF-platelet interaction), VWFAg (exploring VWF synthesis), and VWFCB and its ratio (to explore multimer patterns). Other tests would only serve for confirmation, if necessary.