[A case of sarcoid granulomatous interstitial nephritis improved by steroid therapy].

We report a case of sarcoid granulomatous tubulointerstitial nephritis diagnosed by renal biopsy. A 60-year-old man presented with productive cough, and exertional dyspnea of 3 months duration. A chest X-ray film revealed diffuse reticulonodular infiltrates in both lung fields. A transbronchial lung biopsy specimen showed inflammation of the alveolar septum associated with non-caseating granulomas. The patient also had tubular proteinuria and glucosuria. Ga-scintigraphy demonstrated an abnormal accumulation of gallium in both lungs and kidneys. Renal function tests revealed tubular dysfunction. Tubulointerstitial nephropathy was suspected. A renal biopsy specimen exhibited tubulointerstitial nephritis associated with numerous non-caseating granulomas, similar to the findings of the lung biopsy specimen. No glomerular abnormalities were evident. Later, a scalene node biopsy confirmed the diagnosis of sarcoidosis. Prednisolone therapy yielded a favorable outcome for both the renal and pulmonary involvement. During the corticosteroid therapy, measurement of the urinary beta-2-microglobulin concentration proved a valuable monitoring tool for assessing the recovery of the tubular impairment.