ANCA vasculitis presenting with acute interstitial nephritis without glomerular involvement.

Area of Science:

• Nephrology
• Immunology
• Rheumatology

Background:

• ANCA-associated vasculitis (AAV) typically presents with pauci-immune glomerulonephritis in renal involvement.
• Acute interstitial nephritis (AIN) is an alternative, less common renal manifestation of AAV.

Observation:

• A 45-year-old female with a history of Crohn's disease presented with recurrent AIN without glomerulonephritis.
• High titers of myeloperoxidase (MPO) anti-neutrophil cytoplasmic antibodies (ANCA) were consistently detected.
• Renal biopsies confirmed AIN with progressive fibrosis and tubular atrophy, despite various immunosuppressive treatments.

Findings:

• The patient's AIN was refractory to treatments targeting Crohn's disease and standard AAV therapies, including rituximab.
• Despite aggressive management, renal function continued to decline, necessitating consideration of dialysis.
• This case underscores AIN as a potential sole renal manifestation of MPO-ANCA vasculitis.

Implications:

• Delayed diagnosis of AAV-associated AIN can occur due to its atypical presentation.
• Clinicians must consider AAV in patients with AIN and positive ANCA, even without glomerulonephritis.
• Alternative causes of AIN, such as inflammatory bowel disease or proton pump inhibitor use, should be cautiously evaluated alongside ANCA status.