An unusual case of systemic lupus erythematosus, lupus nephritis, and transient monoclonal gammopathy

Abstract

A 23-year-old female patient suffering from active systemic lupus erythematosus (SLE) was treated with azathioprine (2 mg/kg per day) and prednisone. Lupus nephritis class III with increasing proteinuria developed 28 months after disease onset. Treatment was switched to monthly pulse cyclophosphamide administered intravenously for 6 months (total dose 6.3 g), followed by oral azathioprine and low-dose prednisone to maintain partial remission. Eight months later, the patient developed an acute exacerbation of SLE with fever, proteinuria of 9.1 g/day, pancytopenia, and cerebral involvement with cephalgias and a grand mal seizure. She responded well to high-dose corticosteroids (500 mg prednisolone pulses over 3 days, i.v.) and was switched from azathioprine to methotrexate (12.5–15 mg per week). Under this treatment, lupus activity gradually decreased and the patient felt well again. Five years after the initial diagnosis of SLE, a rapidly increasing immunoglobulin G-kappa type (IgG-κ) monoclonal gammopathy developed, reaching a maximal serum paraprotein concentration of 73.5 g/l. Bone marrow biopsy revealed 15% of moderately abnormal, highly differentiated plasma cells arranged in small clusters and expressing IgG-κ. No bony lesions were detectable on skeletal radiographs. Pulses of dexamethasone (40 mg) were administered and led to a transient decrease of paraproteinemia to a minimum of 31.9 g/l, followed by an increase to 62 g/l. At that point, high-dose chemotherapy supported by autologous stem cell transplantation was considered. Due to an intermittent pneumococcal septicemia, methotrexate was discontinued and dexamethasone was replaced by 5–10 mg cloprednol. At this point, totally unexpectedly, the paraprotein decreased spontaneously without any further cytostatic treatment and was no longer detectable 1 year later. Concomitantly, plasma cell counts in bone marrow biopsies fell to below 5%. As SLE remained inactive, the patient became pregnant and gave birth to a healthy child. During late pregnancy, SLE activity flared up with rising proteinuria and blood pressure. Therefore, after delivery, cyclophosphamide (100 mg/day, orally) was readministered for 4 months, resulting in an improvement of kidney function with stable proteinuria of 1–2 g/l to date. Paraproteins are no longer detectable. In conclusion, this case report documents the rare event of transient paraproteinemia in a patient with SLE. A self-limiting regulatory defect in the control of a terminally differentiated B-cell clone may be the origin of this phenomenon.