AAV Involving Kidneys May Not Always Start in Glomeruli, Case Report Suggests

ANCA-associated vasculitis (AAV) can cause kidney damage without affecting the glomeruli, the filtering unit of the kidneys, a case report suggests.

Doctors should consider this possibility to avoid a late diagnosis and irreversible kidney damage, especially if anti-neutrophil cytoplasm antibodies (ANCAs) against myeloperoxidase (MPO) are present, according to the study, titled “ANCA vasculitis presenting with acute interstitial nephritis without glomerular involvement.” It was published in Clinical Nephrology – Case Studies.

AAV involving the kidneys usually starts in the glomeruli and only progresses to other kidney regions if not treated correctly. Therefore, doctors tend not to diagnose AAV in patients who have kidney damage that doesn’t involve the glomeruli.

Researchers at the University of Wisconsin presented the case of a 45-year-old female who developed AAV in regions of the kidneys other than the glomeruli.

She was first diagnosed with kidney disease at the beginning of 2011 based on proteins and blood in her urine. A kidney biopsy showed inflammation and scars in the tissue that supports the kidneys but no signs in the glomeruli; she also had high levels of ANCA antibodies against MPO.

By the end of the year, the levels of protein in the blood and creatinine increased, indicating further kidney damage. The woman started taking prednisone and azathioprine, which stopped the progression of kidney damage.

Over the course of that same year, the patient had complained of joint pain and sinusitis and was treated for pneumonia at one point due to lung obstruction.

A rheumatologist suggested that the woman might have arthritis and that the high levels of MPO-ANCAs might be related to AAV. However, the patient was not treated for AAV because there were no lesions in her glomeruli.

In 2013, the woman underwent a second kidney biopsy after lab exams showed that the kidney function had decreased.  The biopsy showed inflammation and scaring tissue but healthy glomeruli. Treatment with prednisone and cyclosporine improved kidney function.

The patient was hospitalized in 2014 due to abdominal pain and was diagnosed with Crohn’s disease. The doctors suspected that Crohn’s disease caused the damage to the kidney. Therefore, they tried to reduce and stop previous treatments.

Two years later, the patient stopped taking cyclosporine and only received treatment for Crohn’s disease, which improved the intestinal symptoms but led to a progressive decrease in the kidney function.

In 2018, the doctors performed a third biopsy, which showed damage involving 80% of the kidneys, acute inflammation, and regions of dead and scarred tissue. There was no glomerular disease, but the levels of MPO-ANCAs were high.

The woman was diagnosed with AAV and started treatment with mycophenolic acid and prednisone, and later received Rituxan (rituximab), but since the kidney damage was severe, the treatment did not result in significant improvement, and she had to start dialysis.

The investigators noted that the lack of damage to the glomeruli and the presence of confounding conditions, such as Crohn’s disease, might have prevented an earlier AAV diagnosis.

“In retrospect, the patient’s report of recurrent sinusitis, [joint pain], and pulmonary infiltrate treated as pneumonia during the year of presentation may have represented other systemic manifestations of MPO-AAV,” they said.

They concluded that “in patients with [kidney inflammation] and MPO-ANCA, strong consideration should be given to the possibility of AAV, even in the absence of glomerular lesions. Alternative explanations for interstitial nephritis should be considered with caution in the setting of high-titer ANCA positivity.”