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

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.