Noncaseating Granulomatous Nephritis Presenting with Fanconi Syndrome

Introduction: Fanconi syndrome is a defect in the renal proximal tubule resulting in urinary wasting of compounds normally reabsorbed. Causes include medications, dysproteinemias, heavy metal toxicity. Hypophosphatemia, glucosuria, hypouricemia, aminoaciduria and proximal tubular acidosis is seen. Renal Sarcoidosis usually presents with acute or chronic tubulointerstitial nephritis with acute kidney resulting from hypercalcemia or hypercalciuria. Case Description: 74-year-old male with a PMH of HTN, CKD 3b, Hodgkin lymphoma presented to the hospital for an AKI. Initial labs showed serum Cr 3.81 (1.6 baseline), Calcium (Ca) 13.8, phosphorous 1.9 mg/dL, bicarb 21, blood glucose 150, anion gap 10, urinalysis: 2+ protein, 3+ glucose, fractional excretion of phosphorous 72% and uric acid 70%, amino aciduria. Vitals signs positive for orthostatic hypotension. Bone marrow biopsy, Urine and Serum Protein electrophoresis and ANCA were unremarkable. He was given Intravenous fluids and pamidronate with improvement in renal function and calcium. He had low PTH, Vitamin D 25, elevated PTHrP and high-normal vitamin D 1,25. His labs supported the diagnosis of Fanconi syndrome. Renal biopsy showed chronic active non-caseating granulomatous nephritis and ACE level was elevated supporitng the diagnosis of sarcoidosis. He also had a prior CT chest showing calcified granulomata. He was reponsive to prednisone treatment and his creatinine improved dramatically to 1.3 mg/dL. Discussion: There are multiple causes of Fanconi syndrome but only 3 documented cases have been associated with sarcoidosis. The cause is thought to be from chronic interstitial nephritis leading to proximal tubular dysfunction.