Renal sarcoidosis misdiagnosed as a “burned-out” kidney: diagnosis achieved during pre-transplant evaluation

Abstract Sarcoidosis is a systemic granulomatous disease of unknown etiology, characterized by non-caseating epithelioid granulomas in multiple organs. Renal involvement is uncommon and often under-recognized, particularly when biopsy is avoided due to renal atrophy or bleeding risk. As a result, the true prevalence of renal sarcoidosis remains uncertain and may be underestimated. In Japan, a notable proportion of patients undergoing dialysis or kidney transplantation are classified as having chronic kidney disease (CKD) of unknown etiology, highlighting the ongoing challenge of establishing a definitive diagnosis in advanced CKD. We report a case of renal-limited sarcoidosis diagnosed during pre-transplant evaluation in a patient initially labeled as having CKD of unknown etiology. This case illustrates how renewed imaging assessment can uncover treatable pathology, including mass-forming renal sarcoidosis, even in presumed “burned-out” kidneys.