A case of renal sarcoidosis: a special reference to calcium metabolism as a diagnostic and the therapeutic implications.

Sarcoidosis is a systemic granulomatous disease of unknown etiology and is associated with a wide variety of renal disorders including nephrolithiasis, hypercalciuria, hypercalcemia, nephrocalcinosis, tubular defect, glomerulonephritis, and granulomatous interstitial nephritis. We report a case of renal sarcoidosis in which we could not detect any evidence of extrarenal involvements that was diagnosed by renal biopsy and abnormal calcium metabolism incompatible with chronic renal insufficiency. On laboratory findings, decreased creatinine clearance, proteinuria, hypercalcemia, hypercalciuria, and mildly elevated serum angiotensin-converting enzyme (ACE) were seen. Serum intact parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D (1,α-25 vit D) were lower and higher than normal range, respectively, whereas the patient was already in chronic renal insufficiency. He was treated with oral corticosteroid. Serum ACE tended to fall, and 1,α-25 vit D level decreased with substantial fall of serum calcium and daily calcium excretion. In contrast, intact PTH increased slowly in accordance with a fall of serum calcium compatible with the level of renal impairment. Creatinine clearance and daily excretion of protein improved. The case reported here may propose that serial measurement of serum level of 1,α-25 vit D, calcium level, and magnitude of daily calcium excretion into urine is a simple and meaningful tool to detect the therapeutic response in sarcoidosis with abnormal calcium metabolism.