Tubulointerstitial nephritis and uveitis in children during the COVID-19 pandemic: report of four cases.

Tubulointerstitial nephritis and uveitis (TINU) is a rare autoimmune disorder often triggered by drugs and infections. Since the onset of the COVID-19 pandemic, we have observed an unusual cluster of paediatric cases. Four children (3 females) were diagnosed with TINU (median age 13 years) following a kidney biopsy and ophthalmologic assessment. Presenting symptoms included abdominal pain (3 cases), fatigue, weight loss and vomiting (2 cases). At presentation, median eGFR was 50.3 ml/min/1.73m (range 19.2-69.3). Anaemia was common (3 cases) with median haemoglobin of 10.45 g/dL (range 8.4-12.1). Two patients were hypokalaemic and 3 had non-hyperglycaemic glycosuria. Median urine protein:creatinine ratio was 117 mg/mmol (range 68-167). SARS-CoV-2 antibodies were detected in 3 cases at presentation. All were asymptomatic for COVID-19 with a negative PCR. Kidney function improved following high-dose steroids. However, disease relapse was observed during steroid tapering (2 cases) and upon discontinuation (2 cases). All patients responded well to further high dose steroids. Mycophenolate mofetil was introduced as a steroid-sparing agent. At latest follow up (range 11-16 months), median eGFR was 109.8 ml/min/1.73m. All four patients continue on mycophenolate mofetil, with 2 patients applying topical steroids for uveitis. Our data suggest that SARS-CoV-2 infection might be a trigger for TINU.