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Kidney Week

Abstract: FR-PO226

Lysozyme Nephropathy: A Rare Cause of Progressive Kidney Disease

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Vaidya, Preyas, Lehigh Valley Health Network, Allentown, Pennsylvania, United States
  • Banach, Christopher T., Lehigh Valley Health Network, Allentown, Pennsylvania, United States
  • Ussai, Kathryn E., Lehigh Valley Health Network, Allentown, Pennsylvania, United States
  • Santoriello, Dominick, Columbia University Irving Medical Center, New York, New York, United States
  • Maynard, Sharon E., Lehigh Valley Health Network, Allentown, Pennsylvania, United States
Introduction

A progressive decline in renal function with sub-nephrotic proteinuria in a diabetic is usually attributed to DKD. Lysozyme nephropathy is a rare cause of progressive decline in renal function with only a few underreported cases in the literature mostly in patients with hematological malignancy. AKI is seen in one-third of patients with hematological malignancy and has a negative impact.

Case Description

An 84-year-old male with stage 4 chronic kidney disease, type 2 diabetes mellitus, and chronic anemia on ESA was admitted with an upper GI bleed. He had hemorrhagic shock leading to acute tubular injury. Urinalysis showed trace protein with no RBCs on the microscopic sediment exam. A serologic workup was negative except for positive ANA and hepatitis B surface antibody, which had been previously negative. He had anemia and severe leukocytosis (WBC > 65 K/mm3). His kidney function gradually improved over 2 weeks. Following hospital discharge, the patient was readmitted with worsening kidney function and a high anion gap metabolic acidosis. The urine sediment showed granular casts.
A kidney biopsy was performed, which showed moderate (30-40%) tubulointerstitial scarring and patchy proximal tubular degenerative changes, consistent with acute and chronic tubulointerstitial nephropathy. Refractile, hypereosinophilic intracytoplasmic protein droplets were noted in the proximal tubular cells, which showed immunohistochemical reactivity for lysozyme. Immunofluorescent staining for kappa and lambda was negative.

Discussion

Lysozyme, also called muramidase, is a basic, cationic protein, primarily produced by monocytes/macrophages, salivary gland acinar cells, Paneth cells, and other cell types. Lysozyme is filtered by the glomerulus and reabsorbed by the proximal convoluted tubule where tubular injury occurs.
Lysozyme nephropathy is seen with myeloid leukemias, myeloproliferative, myelodysplastic disorders, granulomatous disease, inflammatory bowel disease, and malignancy. This patient had leukocytosis with myelocytes on the smear which might have reflected underlying hematologic malignancy. A diagnostic evaluation was deferred as he was not a candidate for therapy based on age and comorbidities. Subsequently, his kidney function continued to decline. He opted for conservative management of end-stage kidney disease and hospice care.