IgA nephropathy in children: before and after the start of COVID-19.

BACKGROUND: We describe the clinical course of children with IgA nephropathy (IgAN), diagnosed before and after the emergence of COVID-19. We hypothesized that COVID-19 vaccination and/or infection resulted in more children with IgAN to present clinically. METHODS: We conducted a retrospective cohort study of children with IgAN diagnosed on kidney biopsy from 2014-2020 (Period 1) and 2021-2022 (Period 2). Baseline characteristics, clinical presentation, investigations and treatments were compared between patients diagnosed in Period 1 and Period 2, as well as between patients with and without chronic changes on kidney biopsy. Continuous variables were compared using the Wilcoxon rank sum test. Categorical variables were compared using χ2 or Fisher exact tests. RESULTS: Nineteen children with IgAN were diagnosed by kidney biopsy, with 10 during Period 1 and 9 patients during Period 2 (an average of 1-2 patients/year and 4-5 patients/year in Periods 1 and 2, respectively). The most common indication for kidney biopsy is proteinuria with urine protein/creatinine ratio 1.4 (interquartile range [IQR] 1.2-9.0) vs. 0.8 (IQR 0.6-1.5) g/g (p = 0.064) at time of kidney biopsy for patients in Period 1 and 2, respectively. Clinical course was similar in both periods. No patient required acute or chronic kidney replacement therapy. CONCLUSIONS: The rate of diagnosing children with IgAN was higher since the emergence of COVID-19, suggesting that COVID-19 may trigger an immune response responsible for IgAN, similar to other mucosal infections.

Adenine phosphoribosyl transferase (APRT) deficiency and a novel sequence variant in APRT with phenotypic diversity and a literature review.

Adenine phosphoribosyl transferase (APRT) deficiency is an autosomal recessive disorder and a rare cause of urolithiasis due to mutations in APRT (OMIM #102600). APRT deficiency results in increased urinary excretion of 2,8-dihydroxyadenine (DHA) which can cause urolithiasis and kidney failure. However, with prompt diagnosis, patients with APRT deficiency can be treated with xanthine oxidoreductase inhibitors which decrease urinary DHA excretion and improve outcomes. We report a pair of siblings, an 11-year-old brother and his 14-year-old sister with compound heterozygous variants c.270del (p.Lys91Serfs*46) and c.484_486del (p.Leu162del) in APRT with variable clinical presentation of APRT deficiency. The brother presented at 17 months of age with urolithiasis and severe acute kidney injury. His elder sister remained well and asymptomatic with normal kidney function and did not develop renal calculi. Brownish disk or sphere-like crystals with both concentric and radial markings were reported on urine microscopy in the sister on screening. The sister's diagnosis was confirmed with further laboratory evidence of absent red cell lysate APRT activity with corresponding elevated levels of urinary DHA. In conclusion, we identified a novel mutation in the APRT gene in a pair of siblings with greater phenotypic severity in the male.

Risk factors for imaging abnormalities after the first febrile urinary tract infection in infants ≤3 months old: a retrospective cohort study.

OBJECTIVES: To assess the association of clinical factors and investigation results (blood and urine) with imaging abnormalities (ultrasound of the kidneys, ureters and bladder; dimercaptosuccinic acid scan; and/or micturating cystourethrogram) and recurrent urinary tract infections (UTIs) in infants ≤3 months old presenting with their first febrile UTI. METHODS: We conducted a retrospective cohort study of infants ≤3 months old with first febrile UTI admitted from 2010 to 2016. Multivariable logistic regression model was used to analyse the association of imaging abnormalities and recurrent UTI with covariates selected a priori: age at presentation, maximum temperature, duration of illness at presentation, interval between start of antibiotics and fever resolution, C-reactive protein, total white cell count on the full blood count, bacteraemia, white cell count on the urinalysis and non-Escherichia coli growth in the urine culture (non-E. coli UTI). RESULTS: There were 190 infants but 12 did not undergo any imaging. Median age at presentation was 63 days (IQR 41-78). Twenty-four patients had imaging abnormalities. Non-E. coli UTI (adjusted OR (aOR) 5.01, 95% CI 1.65 to 15.24, p=0.004) was independently associated with imaging abnormalities, while bacteraemia (aOR 4.93, 95% CI 1.25 to 19.43, p=0.022) and non-E. coli UTI (aOR 5.06, 95% CI 1.90 to 13.48, p=0.001) were independently associated with recurrent UTI. CONCLUSION: Non-E. coli UTI at the first febrile UTI in infants ≤3 months old may be useful in predicting imaging abnormalities while bacteraemia and non-E. coli UTI may be useful to predict recurrent UTI.