Significant response to tocilizumab in a case of immune deposits-related membranoproliferative glomerulonephritis and tubulointerstitial nephritis complicated by multicentric Castleman's disease.

A 47-year-old woman with a 12-year history of anemia and high C-reactive protein (CRP) levels was admitted to our hospital with worsening fatigue and night sweats. She had high levels of immunoglobulin G (IgG; 4182 mg/dL), IgA (630.6 mg/dL), and CRP (7.44 mg/dL); a low hemoglobin level (8.9 g/dL); urinary protein (11.83 g/day); and urinary sediment (20 - 29 red blood cells per high power field). On the basis of the clinical findings and biopsied lymph nodes, we diagnosed multicentric Castleman's disease (MCD). Light microscopy of kidney biopsy samples revealed various nephropathies, including membranoproliferative glomerulonephritis with crescentic formation and focal segmental sclerosis and tubulointerstitial nephritis. Immunofluorescence and electron microscopy revealed IgG-positive deposits in the subepithelial areas, mesangial areas, and tubular basement membrane. The patient's clinical findings including kidney disease improved after treatment with tocilizumab. MCD is considered to be caused by abnormally high levels of interleukin (IL)-6. Tocilizumab, an IL-6 receptor antagonist, was effective in this patient, indicating that the immune complex-related kidney findings were also related to MCD.