THE PREVALENCE AND RISK FACTORS FOR ARTERIAL HYPERTENSION IN CHILDREN WITH IDIOPATHIC NEPHROTIC SYNDROME

Abstract

Objective: Arterial hypertension (AH) is claimed to be an uncommon finding in children with idiopathic nephrotic syndrome (INS). The study aimed to analyze blood pressure, prevalence, and risk factors of AH in children with INS. Design and method: In 153 children with INS (9.32±3.84 years, 100 boys), we evaluated systolic and diastolic blood pressure (mm Hg, Z-scores), age at onset of the disease, anthropometric data, response to steroids, results of kidney biopsy, number of INS relapses, and medications. Results: The mean age at disease onset was 4.39±2.38 years; 67 patients had steroid-sensitive nephrotic syndrome (SSNS), 12 frequently relapsing nephrotic syndrome (FRNS), 58 steroid-dependent nephrotic syndrome (SDNS), and 16 steroid-resistant nephrotic syndrome (SRNS). Kidney biopsy was performed in 26: 5 – minimal change disease, 11 – mesangial proliferation, 10 – focal and segmental glomerulosclerosis. AH at disease onset was found in 10 (6.5%) patients in the following 11 (7.2%) after corticosteroid initiation. The observation period was 4.93±3.80 years, and AH was found in 31 (20.3%) – in 3 (4.5%) patients with SSNS, 2 (16.7%) with FRNS, 20 (34.5%) with SDNS, and 6 (37.5%) with SRNS. Patients with AH had lower height Z-score (-0.46±1.20 vs. 0.18±1.15, p=0.006), higher BMI Z-score (1.15±1.10 vs. 0.41±1.09, p<0.001), number of INS relapses (8.32±6.78 vs. 4.41±3.82, p<0.001), and current prednisone dose (0.49±0.67 vs. 0.18±0.29 [mg/kg/24h], p<0.001). Systolic blood pressure Z-score at the end of observation correlated with age (r=-0.192, p=0.017), BMI Z-score (r=0.368, p<0.001), and present prednisone dose [mg/kg/24h] (r=0.186, p=0.021), diastolic blood pressure Z-score with BMI Z-score (r=0.231, p=0.004), and number of INS relapses (r=0.163, p=0.044). In Cox Proportional Hazard presence of SDNS and SRNS were the only predictors of AH (SDNS: HR=4.80, 95CI(1.30-17.75), SRNS: HR=4.77, 95CI(1.06-21.53)). Conclusions: 1. Approximately one-third of patients with SDNS and SRNS develop arterial hypertension in the course of the disease. 2. Steroid dependence and steroid resistance are the strongest predictors of AH in children with INS. Other determinants of blood pressure elevation in this group of patients are high BMI and a high number of relapses.