A 61-year-old woman experienced a high fever with anemia and APTT prolongation after suffering a herpes zoster virus infection. Physical examination revealed a large splenomegaly without lymphadenopathy. Laboratory evaluations were positive for lupus anticoagulant (LA) and monoclonal IgM-kappa protein. LA was associated with the presence of anti-beta2GPI antibody, anti-cardiolipin antibody, and anti-prothrombin antibody. Moreover, the results of factors IX, XI, and XII assays and CRP and FDP-E were disturbed. A splenectomy was performed, and a splenic marginal zone lymphoma (SMZL) was diagnosed. All hematological findings rapidly recovered after the splenectomy. No thrombotic events occurred after the splenectomy even though thrombosis prophylaxis was not performed. The clinical course suggested that the SMZL-producing antibody induced immunological abnormalities in the labolatory tests. Since the patient suffered disease progression soon after the splenectomy, an autologous peripheral stem cell transplantation with rituximab administration was performed.