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Lysozyme-induced nephropathy is a rare kidney manifestation mostly associated with hematologic diseases, especially Chronic Myelomonocytic Leukemia (CMML). This nephropathy is rare, underrecognized and underestimated in this population. Lysozyme is a 15 kDa cationic protein, produced mainly by monocytes and macrophages. The disease pathogenesis is not well understood; however, it is probably related to lysozyme's direct tubular injury after endocytic reabsorption by proximal tubules, leading to ischemic tubular damage. CMML patients with acute kidney injury (AKI) or chronic kidney disease (CKD) should be investigated for this entity. In this case report, we describe a patient with CMML and CKD, whose investigation disclosed a lysozyme nephropathy.
A 78-year-old man with CMML, with no other comorbidities, was investigated for a progressive CKD in the last 10 months (serum creatinine increased from 1.4 to 2.26 mg/dL); urinalysis displayed protein 0.3g/L, erythrocyte 1 and leukocyte 1; and 24-hour proteinuria 0.5g/24 h. Simultaneously, his hematological manifestations worsened: anemia (Hb 8.8g/dL), neutropenia (490 polymorphonuclear) and monocytic content increased (1066 monocytes). Despite this recent disease progression, he remained stable, and no specific treatment was initiated since the initial diagnosis in 2016. Laboratorial analyses were performed but did not elucidate the renal involvement. Thus, a percutaneous renal biopsy was indicated to investigate the progressive CKD.
Conclusions
We present a CMML patient with impaired kidney function associated with subnephrotic proteinuria, whose renal biopsy disclosed Lysozyme-induced nephropathy. In this context, correlation with serum Lysozyme levels may be useful and, it is important to recognize and discuss about treatment options because it is paramount to control monocytes’ lysozyme production.