Acute Tubulointerstitial Nephritis and Secondary Renal Amyloidosis: A Rare Complication of Atezolizumab

Lung cancer is the second most common malignancy in both genders and the most common cause of cancer related deaths worldwide. Broadly, lung cancer is divided into two types: small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Non-small cell lung cancer accounts for 85% of the diagnoses of lung cancer. It is necessary to check for any targetable mutations, which can help in deciding the treatment plan for the patients. The patient we are reporting is a 70-year-old male with multiple co-morbidities diagnosed with non-small cell carcinoma, favoring adenocarcinoma on histopathology. He was started on Atezolizumab/Bevacizumab/Carboplatin/Paclitaxel (ABCP). He was switched to maintenance Atezolizumab/Bevacizumab after four cycles due to poor tolerance to carboplatin and paclitaxel. The patient presented with neutropenic colitis and acute kidney injury (AKI), requiring admission. workup revealed nephrotic range proteinuria with a high urinary albumin-to-creatinine ratio. He underwent a renal biopsy to ascertain the cause of his proteinuria, which showed marked acute and chronic tubulo-interstitial nephritis (TIN), amyloidosis, and global glomerulosclerosis. Secondary (AA) amyloidosis is characterized by the extracellular deposition of misfolded proteins. Although interstitial nephritis is a reported side effect of immune checkpoint inhibitors, AA amyloidosis is a rarer side effect. So, to determine the exact cause and early therapeutic intervention in immune checkpoint inhibitor-related kidney injury, large retrospective or prospective studies should be done.