# Renal Sarcoidosis With Increased 1,25(OH)2D3 Production via CYP27B1-Expressing Epithelioid Granuloma: A Case Report and Review

## TL;DR

A case of kidney sarcoidosis showed increased vitamin D production by granulomas, which may help monitor treatment.

## Contribution

This case report identifies CYP27B1-expressing granulomas as a source of 1,25(OH)2D3 in renal sarcoidosis.

## Key findings

- Renal sarcoidosis was associated with elevated 1,25(OH)2D3 levels due to CYP27B1-expressing granulomas.
- Glucocorticoid treatment reduced 1,25(OH)2D3 levels but they fluctuated with treatment tapering.
- Plasma 1,25(OH)2D3 may serve as a treatment indicator for renal sarcoidosis.

## Abstract

Sarcoidosis can cause acute kidney injury (AKI) through hypercalcemia and granulomatous interstitial nephritis. However, the detailed mechanisms linking intra-renal granuloma activity and AKI are not fully elucidated. A 69-year-old woman presented with AKI associated with elevated 1,25(OH)2D3 levels. A renal biopsy revealed tubulointerstitial nephritis with the presence of epithelioid granulomas and multinucleated giant cells. Immunohistochemistry showed that these cells expressed 25-hydroxyvitamin D-1 alpha hydroxylase (CYP27B1). Glucocorticoid therapy rapidly improved 1,25(OH)2D3 levels at initiation, but these levels fluctuated in relation to renal function during glucocorticoid tapering. Plasma 1,25(OH)2D3 may be produced by CYP27B1 expressed in renal granulomas and serves as an indicator for the treatment of renal sarcoidosis.