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Requests for reprints should be addressed to Masayuki Tanemoto, MD, PhD, Division of Nephrology, Department of Internal Medicine, International University of Health and Welfare School of Medicine, 13-1 Higashi-Kaigan-Cho, Atami, Shizuoka 413-0012, Japan.
Division of Nephrology, Department of Internal Medicine, International University of Health and Welfare School of Medicine, Atami, Shizuoka, JapanDialysis Unit, Shin-Kuki General Hospital, Kuki, Saitama, Japan
Division of Nephrology, Department of Internal Medicine, International University of Health and Welfare School of Medicine, Atami, Shizuoka, JapanDialysis Unit, Shin-Kuki General Hospital, Kuki, Saitama, Japan
Here, we present a case of isolated renal granulomatous disease with hypocalciuric hypercalcemia.
A 79-year-old male with chronic kidney disease developed hypercalcemia with an albumin-corrected serum calcium concentration (c[Ca]) of 11.1 mg/dL (normal range: 8.8-10.1 mg/dL) and was referred to our hospital. Because his serum creatinine concentration (s[Cr]) increased from 1.7 to 3.8 mg/dL within a month and urinalysis revealed high levels of β2-microglobulin (7688 µg/L; normal range: <289 µg/L) and N-acetyl-β-D-glucosaminidase (47.5 U/L; normal range: <11.5 U/L), a renal needle biopsy was performed.
Light microscopy examination of the biopsy samples revealed interstitial non-necrotizing granulomatous lesions containing multinucleated giant cells (Figure). Although sarcoidosis was suspected, computed tomography did not detect lymph node enlargement in the chest and abdomen, and serum levels of angiotensin-converting enzyme (18.4 U/L; normal range: 7.0-25.0 U/L) and 1,25OH-D (58 pg/mL; normal range: 20-60 pg/mL) were not elevated. Furthermore, urine calcium excretion was only 84 mg per gram of creatinine (mg/gCr), and plasma levels of intact parathormone (8 pg/mL; normal range: 10-65 pg/mL) and parathormone-related peptide (<1.1 pmol/L; normal range: <1.1 pmol/L) were not elevated.
FigureHistological findings of renal biopsy. Hematoxylin and eosin staining showing non-necrotizing granulomatous lesions with multinucleated giant cells (arrowheads). Scale bar: 100 µm.
Based on the histological findings, oral prednisolone therapy was initiated at a dose of 40 mg/d. One week later, urine calcium excretion increased to 271 mg/gCr and c[Ca] decreased to 10.5 mg/dL. Another week later, c[Ca] further decreased to 9.4 mg/dL and s[Cr] decreased to 1.7 mg/dL.
With no sign of extrarenal granulomatous disease, the patient was diagnosed with isolated renal granulomatous disease. As noted in our patient, hypercalcemia is frequently observed with normal serum 1,25OH-D levels in granulomatous diseases, including sarcoidosis, a systemic granulomatous disease.
In contrast to most granulomatous diseases, which have hypercalciuric hypercalcemia, this case had hypocalciuric hypercalcemia. This could be attributed to increased renal tubular calcium absorption. In this case, the 1,25OH-D converted by renal granulomas may have stayed intrarenally and increased renal tubular, but not gastrointestinal, calcium absorption.
A decrease in c[Ca] accompanied by an increase in urine calcium excretion through prednisolone therapy supported this presumption, even without confirmation of 1,25OH-D synthesis in the renal granulomas, which could not be confirmed due to a lack of molecular measures of local tissue vitamin D levels. While the glucocorticoid action of prednisolone may have increased urine calcium excretion and decreased c[Ca],
these findings suggest that renal granulomatous disease should be suspected in cases of hypocalciuric hypercalcemia wherein heredity is an unlikely cause.
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