Nephrotic syndrome in a multiple sclerosis patient receiving long-term interferon beta therapy

Recombinant interferon α (IFN-α) and interferon β (IFN-β) are efficient drugs for clinical use in multiple sclerosis, hepatitis C virus infection, and malignant diseases. We report a case of a 40-year-old woman with relapsing-remitting multiple sclerosis who was treated with interferon beta-1b for several years before being admitted to our department with nephrotic-range proteinuria (protein excretion, 8.3 g/d) and serum albumin level of 2.9 g/dL without any clinical and laboratory change typical for a systemic autoimmune disease. The kidney biopsy led to the diagnosis of immune complex-mediated membranoproliferative glomerulonephritis with immunoglobulin and complement deposits visible by immunohistology, as well as subendothelial deposits and tubuloreticular inclusions evident by electron microscopy. Subsequently replacing interferon beta-1b with glatiramer acetate resulted in partial remission, with proteinuria decreasing to protein excretion of 1.0 g/d 2 months thereafter. The association of a focal mesangiocapillary glomerular change and immunoglobulin-complement deposits with tubuloreticular inclusions suggests lupus nephritis. To our knowledge, this is the first report of an interferon beta-1b-induced immune complex glomerulonephritis characterized by histologic, immunohistologic, and ultrastructural features that resembled lupus nephritis, but that occurred in a patient without evidence of systemic lupus erythematosus. Our review of experimental data and earlier case reports suggests a pathogenic role of recombinant IFN in some autoimmune diseases, especially those with the potency to induce systemic lupus erythematosus-like syndromes.