BACKGROUND Histological findings of kidney involvement have been rarely reported in pediatric patients with SARS-CoV-2 infection. Here, we describe clinical, laboratory, and histological findings of two pediatric cases with almost exclusive kidney involvement by SARS-CoV-2. RESULTS A 10-year-old girl with IgA vasculitis nephritis underwent kidney biopsy, showing diffuse and segmental mesangial-proliferative glomerulonephritis, and steroid therapy was initiated. After the worsening of the clinical picture, including an atypical skin rash, she was diagnosed with SARS-CoV-2. The re-evaluation of initial biopsy showed cytoplasmatic blebs and virus-like particles in tubular cells at electron microscopy. Despite SARS-CoV-2 clearance and the intensification of immunosuppression, no improvement was observed. A second kidney biopsy showed a crescentic glomerulonephritis with sclerosis, while virus-like particles were no longer evident. The second patient was a 12-year-old girl with a 3-week history of weakness and weight loss. Rhinitis was reported the month before. No medications were being taken. Blood and urine analysis revealed elevated serum creatinine, hypouricemia, low molecular weight proteinuria, and glycosuria. A high SARS-CoV-2-IgG titre was detected. Kidney biopsy showed acute tubular-interstitial nephritis. Steroid therapy was started with a complete resolution of kidney involvement. CONCLUSION We can speculate that in both cases SARS-CoV-2 played a major role as inflammatory trigger of the kidney damage. Therefore, we suggest investigating the potential kidney damage by SARS-CoV-2 in children. Moreover, SARS-CoV-2 can be included among infectious agents responsible for pediatric acute tubular interstitial nephritis.

中文翻译：

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两名儿科 COVID-19 患者的肾脏受累和组织学检查结果。

背景 在 SARS-CoV-2 感染的儿科患者中很少报道肾脏受累的组织学发现。在这里，我们描述了 SARS-CoV-2 几乎完全累及肾脏的两个儿科病例的临床、实验室和组织学发现。结果 10 岁女孩 IgA 血管炎肾炎接受肾活检，显示弥漫性和节段性系膜增生性肾小球肾炎，开始类固醇治疗。在包括非典型皮疹在内的临床症状恶化后，她被诊断出感染了 SARS-CoV-2。初始活检的重新评估在电子显微镜下显示管状细胞中有细胞质泡和病毒样颗粒。尽管 SARS-CoV-2 被清除并加强了免疫抑制，但没有观察到改善。第二次肾活检显示新月体肾小球肾炎伴硬化，而病毒样颗粒不再明显。第二名患者是一名 12 岁女孩，有 3 周的虚弱和体重减轻病史。前一个月报告了鼻炎。没有服用任何药物。血液和尿液分析显示血清肌酐升高、低尿酸血症、低分子量蛋白尿和糖尿。检测到高 SARS-CoV-2-IgG 滴度。肾活检显示急性肾小管间质性肾炎。类固醇治疗开始于肾脏受累完全消退。结论 我们可以推测，在这两种情况下，SARS-CoV-2 作为肾脏损伤的炎症触发因素都发挥了重要作用。因此，我们建议调查 SARS-CoV-2 对儿童的潜在肾脏损害。而且，