FCN2 and autoimmune thrombocytopenic purpura: Furthermore, one of our PML risk variants (in the FCN2 gene) was found in PML cases (see Table 5, footnote b) with three different underlying diseases (MS, B cell lymphoma, and Behcet's disease with immune thrombocytopenia), but also representing exposure to three different PML-linked drugs (dimethyl fumarate, natalizumab, and rituximab).