Henoch-Schonlein purpura nephritis in Croatian children: a retrospective study in five tertiary care centers

Introduction: Henoch-Schönlein purpura nephritis (HSPN) is the most severe complication of Henoch- Schönlein purpura (HSP) that can occur at any time of the disease process and includes isolated microscopic or macroscopic hematuria, mild or heavy proteinuria with or without nephrotic syndrome, renal failure and hypertension. Objectives: To determine a possible prognostic factor for earlier HSPN onset, to explore indications for kidney biopsy according to urine analysis and the correlation between 24-h urinary protein levels and biopsy findings, as well as biopsy findings and patient outcome. Methods: The cross-sectional study included all children with HSPN diagnosed by EULAR/PRES/PRINTO criteria from 2009 to 2017 at 5 tertiary care centres in Croatia. Results: Out of 540 patients diagnosed with HSP, 91 children who developed HSPN (16.85%) were included. The patient population with HSPN included 52 boys (57.14%) and 39 girls (42.86%). Median (range) age of HSP diagnosis was 8 years (1.5-17.5) and from the HSP diagnosis to HSPN onset was 1.5 (0- 60) months. Median (range) follow-up time was 44 (4-167) months. Nephritis was present in 18.68% of cases at the HSP onset. No statistically significant difference or correlation was found between the time of HSP diagnosis to HSPN onset and gender, age, purpura distribution, joint and gastrointestinal involvement. Kidney biopsy was done in 26 patients (28.57%). Among them, 3 patients had isolated persistent hematuria, 3 had isolated proteinuria and 20 patients had both hematuria and proteinuria. Median (range) 24-h urinary protein levels in patients who underwent biopsy was 1.28 (0-7.46) g/dU. The leading indication for biopsy was simultaneous hematuria and proteinuria (p1g/dU. No significant difference was found in patient outcome for different biopsy findings (p=0.214). Conclusion: Simultaneous hematuria and proteinuria was a statistically significant factor for kidney biopsy. However, while isolated proteinuria was not the sole determining factor, excessive levels of 24-h urinary proteins should be taken in consideration. Due to the small number of patients and no uniform classification generally used in grading biopsy findings, a statistically significant difference in regard to outcome could not be confirmed, indicating the need for both in future research.