#1063 Presentation, treatment, and outcome of IgA nephropathy in children: comprehensive characterization of a Croatian single centre cohort
Authors: Lamot Lovro , Ivančić Jana , Kos Ivanka , Matić Toni , Brinar Ivana Vukovic , Ćorić Marijana , Vrljičak Kristina 
Published: May 2024

Abstract

Background and Aims
IgA nephropathy (IgAN) is a complex disease diagnosed only upon evaluation of a kidney biopsy. Since the threshold to perform this invasive procedure is higher and symptoms usually more indolent in children, the true prevalence might be underestimated, with fewer studies examining the presentation, treatment, and outcome of IgAN in paediatric population. Moreover, there is a substantial heterogeneity of clinical presentation and pathological features between geographical locations, with fewer data available for region of central and southern Europe. We therefore aim to provide a conscientious description of a paediatric IgAN cohort followed for an extended period of time in a centre caring for most of the Croatian paediatric patients.

Method
Single centre retrospective study of children newly diagnosed as IgAN since 2011 and followed for &gt;2 years in a tertiary referral centre for paediatric nephrology of the Republic of Croatia.

Results
Total of 15 paediatric (&lt;18 years) patients were included, of which 11 (73%) were male, 14 Caucasians and 1 of Roma origin. All the patients had proteinuria (&gt;150 mg/day) and hematuria (&gt;5 RBC/mm3 in uncentrifuged urine) at the time of the biopsy, with the mean age of 12.2 ± 3.6 years. The median eGFR was 87 (69 – 111) mL/min/1.73m2 and the median value of proteinuria 260 (150 – 370) mg/day. More specifically, 2 patients had mild proteinuria (&lt;20 mg/kg/day), 12 had moderate (20 – 50 mg/kg/day) and 1 had nephrotic range (&gt;50 mg/kg/day). The results of biopsy in terms of MEST-C score showed M1 in 4, E1 in none, S1 in 3, T1 in 4, T2 in 0, C1 in 2 and C2 in none of the patients. The IF was positive for IgA and C3 in all patients, and in 1 for C1q. There was no significant correlation between C3 intensity values (0-4+) and 24 h proteinuria (r = 0.49, p = 0.06) or eGFR (r = −0.22, p = 0.43). Hypertension (≥95 percentile for age) was present in 2 (13%) patients. The median risk of a 30% decline in eGFR or progression to end-stage renal disease 5 years after renal biopsy calculated by International IgAN prediction tool for use in paediatric patents was 8.03% (4.58 – 11.27). Initial presenting episode was treated with ACEi in 7 (47%) and with glucocorticoids in 4 (27%) patients. There was no significant difference in proteinuria (p = 0.19) or risk of decline in eGFR or progression to ESRD (p = 0.16) among treated and untreated patients. In all of the treated patients proteinuria reached a target of &lt;20 mg/kg during the median time of 11 (6 – 21) months. The median follow up was 6.5 (2.8 – 11.1) years. During the follow up 5 patients experienced first relapse of proteinuria, 3 had second and none had third relapse. None of the patients had adverse event related to medications. None were treated with renal replacement therapy or other immunomodulatory drugs. Tonsillectomy was performed in two patients with a substantial improvement of haematuria episodes reported by caregivers. Omega-3 polyunsaturated fatty acid was used in 1 patient. While none of the patients developed CKD during the follow up, none have reached complete renal remission defined as eGFR &gt;90 ml/min/1.73m2, proteinuria &lt;150 mg/day and RBC &lt; 5/mm3 in urinalysis.

Conclusion
All the patients in our cohort had indolent disease with proteinuria, along with low risk of decline in eGFR or progression to ESRD after biopsy. Almost half of them were treated with ACEi, and a quarter with glucocorticoids, all with beneficial response. Nevertheless, none of the patients in the cohort achieved full renal remission due to the persistent hematuria. While there are few well performed studies on the treatment of IgAN in adult patients, to date, there are no high-quality randomised studies on immunosuppressing and other drugs, as well as nutritional and other interventions in children with IgAN, prompting a case-to-case decision regarding the use of various therapeutic modalities. Therefore, well characterized cohorts from around the globe might provide further reassurance for physicians taking care of children with this intricating disease, support when deciding to commence the intervention and inform while selecting the most appropriate form.