IgA-nephropathy in children with alport syndrome

Abstract

BACKGROUND. The widespread use of genetic methods in clinical practice has shown that pathogenic variants in COL4A3, COL4A4, COL4A5 genes associated with Alport syndrome (AS) are detected in 10 % of sporadic and in 20 % of familial cases of IgA nephropathy (IgAN), which suggested a relationship between the two diseases. THE AIM was to determine the frequency and characteristics of the course of IgAN in children with AS. PATIENTS AND METHODS. A single-centre retrospective pilot study included 102 patients with AS. The inclusion criteria were: age 2-18 years, genetic and/or morphological confirmation of AS, availability of morphological data of pts. The comparison group included children and adolescents 2-18 years with morphologically confirmed primary IgAN; the exclusion criterion was the presence of AS-specific glomerular basement membrane changes. IgAN was classified according to the MESTC scale. Demographic (gender, age), clinical (arterial hypertension, AH) and laboratory data (proteinuria (Pr, mg/m2/day), (Schwartz eGFR, ml/min/1.73m2) at the time of the biopsy and at the last examination of patients were assessed. Arterial pressure ≥95‰ for sex, age, height was defined as AH. Pr >100 mg/m2/day, Pr≥500 mg/m2/day and Pr>1000 mg/m2/day were defined as proteinuria, high-level proteinuria and nephrotic level proteinuria, respectively. The statistic parametric and nonparametric methods were used ("Statistica 10", StatSoft Russia). RESULTS. IgAN was detected in 3 of 102 children with AS (q=0.03): 2 girls had heterozygous variants in COL4A3 and COL4A4, a boy had X-linked AS. Two patients had nephrotic proteinuria, 1 had SRNS at onset of IgAN. The comparison group included 25 children with IgAN (17M). Baseline patients age (9±4.2 vs 13±2.7 years), frequency of AH (q1=0.66 vs q2=0.28), eGFR decrease (q1=0.33 vs q2=0.44), eGFR level (91±24 vs 90.8±24 ml/ min/1.73 m2), morphological characteristics of IgAN did not differ significantly by groups; patients with AS were more likely to have nephrotic proteinuria (q1=1 vs q2=0.32, p=0.023). At follow-up (3.8±1.4 years), the groups were comparable in age (12.3±5.2 vs 15±1.8 years), AH frequency (q1=0.66 vs q2=0.5), eGFR level (87±16 vs 91±13 ml/min/1.73m2); children with AS had higher grade Pr (800[0;1150] vs 30[10;100] mg/m2/day, p=0.048) and more often had high-level Pr (q1=0.66 vs q2=0.06, p=0.006) at follow-up observation. The AS was associated with the development of nephrotic-level Pr at onset (r=0.41, p=0.008) and with high-level Pr (r=0.38, p=0.012) during follow-up. CONCLUSION. IgAN was detected in 3 % of children with AS. The presence of COL4A3, COL4A4, COL4A5 genes variants is associated with more pronounced proteinuria at the onset of IgAN and its preservation in the follow-up, and may be a risk factor for more severe course glomerulonephritis. The main limitations of the study: small sample size and duration of follow-up.