Background: Hypercalcemia can occur in patients with granulomatous disorders such as sarcoidosis, and is commonly related to high serum 1,25-dihydroxyvitamin D (OHD) concentrations.
Case Report: We here report a 68-year-old man with a history of mild renal insufficiency who presented with hypercalcemia (serum calcium of 3.11 mmol) and normal 1,25-OHD levels (38 pg/ml, RIA/IDS, Boldon, UK, measuring both 1,25-OH D2 and D3). Imaging and laboratory investigations were suggestive of sarcoidosis. After hydration and prednisone therapy (40 mg/day) for 7 days, serum calcium dropped to 2.7 mmol and 1,25-OHD levels to 13.4 pg/ml. Six weeks after prednisone therapy, serum calcium was 2.41 mmol (normal) and 1,25-OHD 6.2 pg/ml (low). Computed tomography of the chest showed shrinkage of the right hilar mass.
Conclusions: This case illustrates that hypercalcemia can occur in granuloma-forming disorders such as sarcoidosis in the setting of inappropriately normal (and not elevated) 1,25-OHD levels. Contributing factors may include dehydration, increased uptake of oral calcium and/or decreased calcium excretion, especially in mild renal insufficiency. Therapy of choice are hydration and glucocorticoid (prednisone) therapy. In this setting, prednisone may lead to a decline of activated mononuclear cells (in the lung and lymph nodes) that are able to produce extrarenal PTH-independent 1,25-OHD.

Keywords: Calcitriol - blood, Calcium - blood, Hypercalcemia - etiology, Kidney Failure, Chronic - complications, Parathyroid Hormone - blood, Prednisone - therapeutic use, Sarcoidosis, Pulmonary - drug therapy, Vitamin D - blood