Granulomatous interstitial nephritis due to sarcoidosis following SARS-CoV-2 infection: a rare case report.

We report the first documented case of renal sarcoidosis developing after SARS-CoV-2 infection. The patient, a 59-year-old woman with no significant medical history, was diagnosed with COVID-19 after experiencing persistent fatigue and insomnia. Approximately three weeks after the infection, she developed a skin rash, prompting a biopsy that revealed epithelioid granulomas. A systemic evaluation using computed tomography identified enlarged bilateral hilar lymph nodes, and a needle aspiration biopsy confirmed the presence of epithelioid granulomas, leading to a diagnosis of sarcoidosis. Nine months after recovering from COVID-19, she was referred to the nephrology department due to progressive renal dysfunction. A renal biopsy demonstrated granulomatous interstitial nephritis with Schaumann bodies, consistent with renal sarcoidosis. Treatment with prednisolone (30 mg/day, 0.5 mg/kg/day) resulted in significant improvement in renal function, suggesting a potential link between SARS-CoV-2 infection and immune dysregulation. This case highlights the importance of monitoring renal function in patients with post-COVID-19 sarcoidosis, even in the absence of disease progression in other organs.