Disease states associated with lysozymuria, along with histological correlations

The spectrum of medical conditions associated with lysozymuria and the efficacy of urinary protein electrophoresis (UPE) in identifying lysosyme associated nephropathy (LyN) remain to be determined.

We retrospectively reviewed almost 3,000 UPE profiles from a decade of activity at a university medical center. Clinical data from patients with lysozymuria were collected, and kidney biopsies were examined for histological features consistent with LyN.

We identified a lysozymuria in nearly 1% of hospitalized patients who were tested. The medical conditions encompassed included sepsis, cancers, chronic myelomonocytic leukemia (CMML) and granulomatous disease. Of the 27 patients with lysozymuria on UPE, 9 underwent a kidney biopsy.

The 2 pathological signs suggestive of LyN (proximal tubular cytoplasmic inclusion and positive lysozyme immunostaining) were observed in 4 out of 9 biopsies with a positive UPE for lysozyme (2 sarcoidosis, 1 CMML and 1 vasculitis). The urinary lysozyme fraction was not associated with kidney function or the severity of the histological lesions. A negative UPE did not rule out the possibility of LyN, which was found in 7 of the 10 cases of granulomatous disease analyzed.

Retrospective design of the study CONCLUSIONS: Lysozymuria is prevalent among hospitalized patients and is associated with a variety of medical conditions, but the main diagnoses are CMML and granulomatous disease. UPE may have limited value in detecting histological cases of LyN, particularly when it is associated with a granulomatous disease. LyN is highly prevalent in granulomatous disease even with a negative UPE. Its impact on kidney function, disease progression and response to treatment remain to be established.