A 51-year-old woman with metastatic ER positive, PR positive, HER2 negative breast cancer who previously received multiple lines of therapy, most recently sacituzumab govitecan, hypertension, diabetes mellitus, pulmonary embolism, and asthma, initially presented outpatient with three days of anorexia, non-bloody vomiting, large-volume watery diarrhea, and poor oral intake. No fever or chills. Home medications include amlodipine, apixaban, metformin, rosuvastatin, and levothyroxine. No proton pump inhibitor or non-steroidal anti-inflammatory drugs. She received IV fluids and was sent to the emergency department. Five days before the onset of symptoms, she received the second dose of first cycle of sacituzumab govitecan. In the outside hospital, she was found to have tachycardia, fever, normal blood pressure, respiratory rate, and oxygen saturation. Work-up revealed absolute neutrophil count 100, hemoglobin 10.2, platelet 112, sodium 125, potassium 4.2, serum creatinine 3.43, serum bicarbonate 17, anion gap of 19, normal lactate. Urine culture on admission was negative. She received cefepime and vancomycin, later deescalated to cefepime after blood cultures grew Proteus mirabilis. Vancomycin level was supratherapeutic at 30.4mcg/mL before it was discontinued. She received symptomatic treatment for nausea and diarrhea and was maintained on IV fluids. Non-contrast CT ruled out obstructive uropathy. However, her creatinine rose to 6.5 g/dL.

She was transferred to our hospital for further management. On presentation, she was confused, febrile, normotensive, and had atrial fibrillation in rapid ventricular response, requiring ICU admission. CT head showed no acute abnormality. She did not require pressors and blood pressure remained stable with IV fluids. Atrial fibrillation initially reverted to sinus rhythm with metoprolol. Cefepime was continued for neutropenic sepsis. IV sodium bicarbonate was started for severe metabolic acidosis. Despite supportive treatment, oliguric AKI continued to worsen; creatinine 7.32, and BUN 77, therefore continuous renal replacement therapy (CRRT) was started on hospital day 2. During CRRT, atrial fibrillation recurred, prompting amiodarone loading. Metabolic acidosis improved. CRRT was discontinued on hospital day 7. However, urine output remained minimal. IV furosemide and intermittent hemodialysis were started (Supplementary).

Work-up included elevated protein/creatinine ratio 4,584.2 mg/g, 24-hour urine protein 453 mg, negative anti-PLA2R antibody, negative dsDNA, ANA 1:80 titer, serum protein electrophoresis immunotyping without paraprotein, negative hepatitis panel, and negative ADAMTS13 activity. Kidney biopsy was performed on hospital day 11 (Supplementary) with result of ATIN. Prednisone 60 mg was given for two weeks with subsequent taper with famotidine as ulcer prophylaxis. Eventually, she no longer required hemodialysis. IV furosemide 80 mg daily was continued, further improving urine output. One week after discharge, serum creatinine was 1.58 and BUN 37 and three weeks later her kidney function was back to baseline normal levels. Further doses of sacituzumab-govitecan were withheld.