The Lysozyme Kidney

Introduction: Acute kidney injury (AKI) is a common complication of acute leukemias. Common causes include tumor lysis syndrome (TLS), leukemic kidney infiltration and injury due to nephrotoxic chemotherapy. Less recognized is lysozyme-induced nephropathy (LyN). Differentiating between common and less common causes of AKI in acute leukemia is critical for directing therapy. Case Description: A 37-year-old man with history of schizophrenia, and type 2 diabetes presented with chest pain and dyspnea. Vital signs were significant for tachycardia and hypoxemia and labs demonstrated WBC count of 204, hemoglobin 8.5 and platelets 61. He had severe AKI (creatinine of 3.06 mg/dl from baseline of 1 mg/dl five months prior), hypokalemia, hypophosphatemia and hyperuricemia. He was diagnosed with acute leukemia and nephrology was consulted with concern for TLS. Urine sediment exam revealed granular debris. Kidney ultrasound was negative for kidney enlargement or hydronephrosis. He was admitted to the medical ICU for cytoreductive therapy with cyclophosphamide and hydroxyurea followed by induction chemotherapy with midostaurin. Once his leukocytosis improved, his kidney function steadily improved as well and creatinine was 0.6 mg/dl at discharge. Given his presentation with acute leukemia, hypokalemia, hypophosphatemia without evidence of other kidney injury, a diagnosis of LyN was made. Discussion: Lysozyme is a small bactericidal enzyme that is freely filtered by the glomerulus. However, in acute leukemia due to the increased production, the reabsorbed enzyme becomes toxic to the proximal tubule, resulting in tubular injury characterized by hypokalemia, hypophosphatemia and often hyperuricemia. While rare, LyN should be considered in patients presenting with acute leukemia and AKI, especially when hypokalemia is present. If identified in time, treatment of primary malignancy results in resolution of kidney injury and may obviate the need for other therapies, including KRT.Creatinine trend