A Rare Case of Renally Limited Sarcoidosis

Introduction: The most common manifestations of sarcoidosis involve the lung. The prevalence of renal involvement in sarcoidosis is variable, with some studies reporting approximately 6% of sarcoidosis case presenting with renal manifestations. However, the majority of these cases present with concurrent extrarenal manifestations. We present a case of sarcoidosis diagnosed with manifestation limited to the kidneys and the workup it entailed. Case Description: The patient is a 68 yo male with chronic low back pain, atrial fibrillation, CAD who presented to ED for evaluation of diarrhea. He was found to have renal insufficiency on that admission which was thought to be secondary to dehydration. In December 2020 he presented again with renal insufficiency and hypercalcemia. He underwent workup including kidney biopsy in January of the which showed noncaseating granulomatous interstitial nephritis. Autoimmune workup was negative, inflammatory markers unremarkable, BUN 54, Cr 3.67. Chest x ray was normal. He was initiated on dialysis. Patient’s review of systems was negative except for fatigue and chronic bilateral knee pain. Initially, kidney biopsy was thought to be drug induced noncaseating granulomatous interstitial nephritis from chronic NSAID use as patient did not have chronic hypercalcemia and pathology was not typical for renal sarcoidosis. Subsequently, patient was found to be recurrently hypercalcemic with elevated PTH RP, high ACE. He was treated in the acute setting with pamidronate infusion and prednisone daily He was found to have no other organ involvement of his sarcoidosis. He was subsequently evaluated for renal transplant. Discussion: Renally limited sarcoidosis is a rare presenstation and renal biopsy is essential for diagnosis. Typical findings on renal biopsy are noncaseating granulomas and giant cell formation, but athology findings on renal biopsy may vary and a broad differential should be considered. Workup should include chest radiograph and PFTs. Treatment typically consists of prednisone and if needed, supportive care with dialysis.