Vitamin D Deficiency in Relapsing Idiopathic Nephrotic Syndrome in Children: Prevalence, Correlates, and Therapeutic Implications.

Background: Idiopathic nephrotic syndrome (NS) is a common cause of glomerulonephritis in children, often complicated by relapses and steroid dependence or resistance. Emerging evidence underscores the interplay between vitamin D metabolism and NS pathophysiology, particularly during relapse episodes. Objective: To investigate the prevalence of vitamin D deficiency in pediatric patients aged 2-12 years with relapsing idiopathic NS and to evaluate associations with proteinuria severity, relapse frequency, and steroid exposure. Methods: This cross-sectional study included 100 children diagnosed with idiopathic NS and at least one documented relapse. We enrolled all NS patients with completed follow-up for 1 year. Serum 25-hydroxyvitamin D (25[OH]D) levels were measured during relapse and six months later. Clinical and biochemical data, including proteinuria, albumin, creatinine, and corticosteroid usage, were analyzed. Results: At relapse, 84% of patients were vitamin D deficient, with only 7% reaching sufficiency after 6 months. A significant inverse correlation was observed between 25(OH)D levels and both proteinuria ( Conclusion: Vitamin D deficiency is highly prevalent among children with relapsing idiopathic NS and correlates with greater disease activity. Routine monitoring and timely supplementation of vitamin D may be essential components in managing NS flares and preventing long-term complications.