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Abstract: SA-PO702

Pathological Value of Lysozyme Staining for Diagnosing Renal Sarcoidosis

Session Information

Category: Pathology and Lab Medicine

  • 1602 Pathology and Lab Medicine: Clinical

Authors

  • Sanada, Satoru, Japan Community Health Care Organization Sendai Hospital, Sendai, Miyagi, Japan
  • Yoda, Shohei, Japan Community Health Care Organization Sendai Hospital, Sendai, Miyagi, Japan
  • Sato, Toshinobu, Japan Community Health Care Organization Sendai Hospital, Sendai, Miyagi, Japan
Background

Sarcoidosis is a systemic inflammatory disease of unknown etiology. Pathological findings of the kidney show interstitial fibrosis with or without granulomatous formation, whereas low detection rates of granulomas make it difficult to diagnose renal sarcoidosis. We have found positive lysozyme staining of kidney tubular cells in sarcoidosis and assessed the diagnostic value of lysozyme staining for sarcoidosis.

Methods

Kidney biopsy specimens of 41 cases of pathological diagnosed tubulointerstitial nephritis (TIN) obtained in Japan Health Care Organization Sendai Hospital between 2013 to 2019 were analyzed retrospectively by immunohistochemistry. Diagnosis of sarcoidosis was made by clinical, radiational, and histopathological examinations. Samples of representative skin sarcoidosis were also stained by lysozyme. Three specimens from sarcoidosis, chronic myelomonocytic leukemia (CMML) and IgG4-related nephritis were analyzed by electron microscopy.

Results

All six cases of sarcoidosis showed positive staining of lysozyme in proximal tubular cells (100%), however, 25 TIN specimens, including drug-induced, IgG4-related, aristolochic acid toxicity, ischemia and Sjogren syndrome showed blunted stains (0%). The specimen of CMML-related TIN, representative of lysozyme-induced nephropathy, showed strikingly positive lysozyme staining in the proximal tubules. Among nine idiopathic TIN, two cases revealed lysozyme positive. These cases did not meet the diagnostic criteria of sarcoidosis clinically, but the possibility of sarcoidosis cannot be denied. In electron microscopy, an increased number of lysosomes in proximal tubules was observed in CMML and sarcoidosis, however, no lysosome was found in IgG4-related nephritis. In skin sarcoidosis, positive lysozyme staining was shown in basal layer of epidermis and dermis while no stain was found in skin samples from different subjects.

Conclusion

Lysozyme staining can aid in the diagnosis of renal sarcoidosis by distinguishing from sarcoidosis to other TIN diseases. Lysozyme induced tubular injury could be an underlying mechanism of TIN in sarcoidosis. In addition, this method could be a useful tool to detect clinically underdiagnosed sarcoidosis including skin and kidney lesions.