Archives of Pathology & Laboratory Medicine
Lysozyme-induced nephropathy is a rare cause of acute kidney injury (AKI) in patients with chronic myelomonocytic leukemia (CMML). We report the case of an 85-year-old man with type II diabetes and hypertension who was being evaluated for an elevated serum creatinine of 2.27 mg/dL. Additional studies showed proteinuria (1 g), predominantly nonalbumin, along with an IgA λ monoclonal protein found on serum electrophoresis. His serum κ:λ ratio, however, was elevated and urinalysis showed free κ monoclonal protein. Further hematopathologic workup revealed CMML, and he also had progression of his AKI, for which a renal biopsy was performed. Light microscopy showed unremarkable glomeruli with dilated proximal tubules containing granular and strongly eosinophilic cytoplasm (Figure 2.82, A and B). Immunohistochemical staining for lysozymes showed strong positivity in the cytoplasm and nuclei of the proximal tubule cells (Figure 2.82, C). Electron microscopy showed expanded lysosomes with rounded, dense dots arranged in an annular “chocolate chip cookie” pattern ranging from 1.0 to 1.5 μm in diameter (Figure 2.82, D). No monoclonal proteins were detected by immunofluorescent stains in the renal biopsy. Plasma lysozyme level was >10.8 μg/mL (reference range, 2.6–6.0 μg/mL). Taken together, these data support the diagnosis of lysozyme-induced nephropathy likely secondary to overproduction of lysozymes from his CMML. He began treatment with azacitidine, and following 1 cycle of therapy, he had a reduction of his serum creatinine to 1.67 mg/dL after 1 month follow-up. Awareness and recognition of lysozyme-induced nephropathy as a cause of AKI in patients with CMML is important as it may have potential diagnostic and therapeutic considerations.
Mahalingam V, Abukhaled J, Zhang P. Lysozyme-induced nephropathy secondary to chronic myelomonocytic leukemia. Arch Pathol Lab Med. 2022 Sep;146(9):e94-e95. doi:10.5858/arpa.2022-0231-AB.