Recurrent hematuria and painful necrotic purpura induced by acquired Protein S deficiency associated with monoclonal immunoglobulin

Protein S deficiency is associated with an increased risk of thromboembolism, which may be caused by hereditary deficiency and several physiological and pathologic conditions, such as pregnancy, contraceptive use, liver diseases, inflammatory disease, and certain viruses infections. However, monoclonal immunoglobulin-mediated Protein S deficiency is rarely reported. Here we described a 49-year-old woman with a history of recurrent painful swelling in both lower extremities due to venous thrombosis for 7 years, accompanied by recurrent gross hematuria and multiple painful necrotic purpuras for 5 years, who was then diagnosed with acquired Protein S deficiency induced by the monoclonal immunoglobulin. Then she was successfully treated with rituximab combined with anticoagulation therapy. This case highlights the rare manifestations of Protein S deficiency and the influence of the monoclonal immunoglobulin produced by monoclonal B lymphocytes and monoclonal plasma cells on the activity of Protein S, which can be treated effectively with rituximab combined with anticoagulation therapy.