Systemic lupus erythematosus is an autoimmune disease associated with mild valvular regurgitation. However, there have been no detailed reports of infective endocarditis in patients with systemic lupus erythematosus. Here, we describe a case of a 55-year-old woman without any cardiac abnormalities who was diagnosed with lupus nephritis by renal biopsy; she contracted infective endocarditis while receiving immunosuppressive therapy. Our case emphasizes that special consideration of the occurrence of infective endocarditis, and its early diagnosis and treatment are mandatory for patient survival. We propose that echocardiography should be performed before treating patients with systemic lupus erythematosus who have an uncertain cardiac status.

We report two cases of retroperitoneal fibrosis that emerged during a clinical course of moderate chronic kidney disease. In both cases, we observed an elevation in the serum CRP and IgG4 levels without an increase in the white blood cell count. The patients were treated with prednisolone. Their clinical conditions improved with a decrease in the serum IgG4 to total IgG ratio. The present cases suggest the importance of a differential diagnosis of retroperitoneal fibrosis in the medical care of chronic kidney disease patients, and we propose a useful biomarker for retroperitoneal fibrosis, which we suspect is associated with IgG4-related disease.