Concurrent anti-neutrophil cytoplasmic antibody-associated glomerulonephritis and IgG4-associated tubulointerstitial nephritis with C3 glomerulonephritis: A case report.

RATIONALE

IgG4-related disease (IgG4-RD) is a slowly progressing inflammatory disease that can involve multiple organ systems. There is considerable overlap between IgG4-RDs and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Herein, we present an unusual case of IgG4-associated tubulointerstitial nephritis (IgG4-TIN) and ANCA-associated glomerulonephritis (ANCA-GN) co-occurring with C3 glomerulonephritis (C3GN).

PATIENT CONCERNS

A 72-year-old male was admitted to hospital because of fever and fatigue. He was diagnosed with elevated serum creatinine and IgG4 levels, and was positive for ANCA.

DIAGNOSIS

Initially, the pathology supported a diagnosis of IgG4-TIN and ANCA-GN; however, further examination revealed he also had C3GN.

INTERVENTIONS

The patient was treated with methylprednisolone and cyclophosphamide and received regular follow-up care.

OUTCOMES

After treatment, the patient no longer exhibited fever or fatigue and had no complications. The seven-month follow-up showed downward trends in IgG4 and MPO-ANCA levels and stable 24-hour urine protein, serum creatinine levels.

LESSONS

Anti-neutrophil cytoplasmic antibody-associated glomerulonephritis and IgG4-associated tubulointerstitial nephritis with C3glomerulonephritis rarely occur simultaneously. Laboratory analysis and pathology are both needed to ensure diagnostic accuracy. However, in this case, the three diseases overlapped to such a large extent that achieving a definitive diagnosis was particularly challenging. Timely and accurate diagnosis is crucial for selecting the best treatment course and optimizing patient outcome.