Utility of Urinary β2-Microglobulin for Detection of Renal Sarcoidosis Without Pulmonary Involvement: A Case Report.

Background and Clinical Significance: Sarcoidosis is a systemic inflammatory disorder characterized by noncaseating granulomas. While pulmonary involvement is common, isolated renal involvement is rare and diagnostically challenging. We report a case emphasizing the utility of urinary tubular markers for early detection. Case Presentation: A 60-year-old woman with a history of suspected ocular sarcoidosis presented with progressive renal impairment and constitutional symptoms. Initial workup for systemic sarcoidosis was negative, leading to a misdiagnosis of chronic fatigue syndrome. Her rising serum creatinine was initially attributed to dehydration. However, a marked elevation in urinary β2-microglobulin (33,736 μg/L) prompted a renal biopsy, which revealed granulomatous tubulointerstitial nephritis. Following prednisolone therapy, her renal function improved, and her fatigue resolved completely.

Conclusions

This case demonstrates that the kidney can be the primary site for histological diagnosis in the absence of pulmonary lesions. Incorporating urinary β2-microglobulin into routine monitoring may facilitate the early detection of renal sarcoidosis, preventing diagnostic delays.