Immunobullous dermatosis associated with Waldenström macroglobulinaemia treated with rituximab

Waldenström macroglobulinaemia (WM) is a chronic lymphoproliferative disorder characterized by the presence of a monoclonal IgM paraprotein. Specific cutaneous features of WM include neoplastic cell infiltrates, IgM storage papules and IgM bullous dermatosis. We report a patient with subepidermal bullous disease associated with WM. Immunofluorescence identified IgM deposition along the basement membrane zone (BMZ) with circulating anti-BMZ IgM antibodies reacting with the dermal side of salt-split skin. The autoantibodies did not react with type VII collagen or laminin 332. Following failed treatment with doxycycline, prednisolone, intravenous immunoglobulin and dapsone, the patient was successfully treated with a modified RCVP regimen (rituximab, cyclophosphamide and prednisolone). To our knowledge, this is the first reported case of IgM bullous disease of WM treated with rituximab.