Rash, Lymphadenopathy, and Nephritis: Is It Always Lupus?

Abstract

Background: IgG4-related disease (IgG4-RD) is a multisystem fibroinflammatory condition capable of affecting nearly any organ. Renal involvement, although recognized, remains uncommon and frequently leads to diagnostic uncertainty because of overlap with autoimmune, infectious, and lymphoproliferative disorders.

Case Presentation: A 34-year-old woman presented with a three-year course of intermittent painful purpuric plaques, chronic cough, Raynaud-like digital pallor, and episodic arthralgia. Examination revealed generalized non-tender lymphadenopathy. Laboratory studies showed anemia, eosinophilia, low complement levels, elevated IgG, and renal dysfunction. Autoimmune markers were negative. Imaging identified right-sided bronchiectatic changes and axillary lymphadenopathy. Skin biopsy showed leukocytoclastic vasculitis, while lymph node histology suggested reactive plasma cell-rich changes. A markedly raised serum IgG4 level (>53 g/L) prompted kidney biopsy, which demonstrated storiform fibrosis and abundant IgG4-positive plasma cells, confirming IgG4-related tubulointerstitial nephritis.

Discussion & Conclusion: The combination of renal, cutaneous, pulmonary, and lymph node abnormalities, together with serological and histopathological findings, established the diagnosis of systemic IgG4-RD and illustrated its ability to mimic a broad differential diagnosis.

Prednisolone therapy resulted in clinical and biochemical improvement, including normalization of renal function and improvement in complement levels. The patient remains in remission at 1 year.