Mizoribine for renal sarcoidosis: effective steroid tapering and prevention of recurrence.

Sarcoidosis is a systemic disease of unknown etiology that is characterized by chronic non-caseating granulomatous inflammation with tissue destruction. It is an uncommon disease in children, and renal sarcoidosis in particular is very rare in adults and children. A 17-year-old boy with renal sarcoidosis was referred to our hospital with an initial diagnosis of pyelonephritis. Prior treatment with various antibiotics had not been effective, but tentative oral daily prednisolone (PSL) had partially ameliorated his symptoms, although the symptoms recurred during steroid tapering. We detected non-caseating granulomatous interstitial nephritis and numerous sclerotic glomeruli in a second biopsy specimen, compatible with the diagnosis of renal sarcoidosis. The patient was treated with pulsed methyl-prednisolone and oral daily doses of PSL and mizoribine (MZR). During the treatment with MZR, the PSL was successfully tapered, and the patient has since presented no signs of recurrence. Our treatment of this patient shows that treatment with MZR can allow steroid sparing and prevent recurrence in a patient with sarcoidosis.