A Case of Concurrent IgG4-Related Kidney Disease and Lupus Nephritis

Abstract

A 74-year-old woman presented with a 1-year history of dry mouth. She had also noticed bilateral submandibular and parotid swelling 6 months before she visited the otolaryngology department of our hospital. Contrast-enhanced computed tomography showed multiple hilar and mediastinal lymphadenopathy, diffuse enlargement of the pancreas with partial narrowing of the main pancreatic duct, and multiple low-density areas in the bilateral kidneys. There was marked elevation of the serum IgG, IgG4, and IgE levels, together with tubulointerstitial dysfunction, compatible with IgG4-RD. Pancytopenia, positivity for antinuclear antibody and anti-double-stranded DNA antibody, and marked hypocomplementemia were also observed, all consistent with systemic lupus erythematosus (SLE). Percutaneous kidney biopsy revealed no significant abnormality in the glomeruli by light microscopy. In tubulointerstitial areas, well circumscribed areas of intense lymphoplasmacytic infiltration accompanied by mild fibrotic changes were evident, and immunohistochemistry demonstrated marked infiltration of IgG4-positive plasma cells. The immunofluorescence studies, however, revealed diffuse mesangial and capillary deposition of IgG, IgA, IgM, C1q, and C3c in the glomeruli, being typical of lupus nephritis. This case demonstrates the concurrent development of both IgG4-RD and SLE, suggesting the possibility of common pathophysiological mechanisms.