Probable Renal-Limited Sarcoidosis Presenting With Tubulointerstitial Nephritis Without Granulomas on Renal Biopsy: A diagnostic challenge

Sarcoidosis is an idiopathic multisystem inflammatory disorder characterised by non-caseating granulomas and a wide range of reported prevalence. Renal-limited sarcoidosis is a rare manifestation of sarcoidosis which remains a diagnostic challenge due to lack of extra renal manifestation and specific diagnostic criteria. We report a 37-year-old man who presented to a tertiary care hospital, Muscat, Oman, in 2024, with a two-month history of fever, weight loss, hypercalcaemia, high-to-normal 1,25-Vitamin D, high angiotensin-converting enzyme levels and acute kidney injury. His renal biopsy showed evidence of tubulointerstitial nephritis without granulomas or nephrocalcinosis. After exclusion of infectious, malignant, drug- related and autoimmune causes, a probable diagnosis of renal-limited sarcoidosis was considered. The patient received a course of steroids with subsequent improvement in his symptoms, renal function and renal biopsy inflammatory activity. This case highlights the diagnostic uncertainty and challenges in renal-limited sarcoidosis, particularly in the absence of granulomatous inflammation.