IgA nephropathy: clinical features and natural history--a pediatric perspective.

This review describes the spectrum of clinical features observed in pediatric patients with IgA nephropathy (IgAN) in different parts of the world. The typical clinical presentation consists of an episode of macroscopic hematuria within 24 to 48 hours of an upper respiratory infection. However, many children who present with macroscopic hematuria are subjected to a battery of urologic studies before the appropriate procedure is performed. This sequence highlights the lack of awareness of IgAN among pediatricians, family practitioners, and urologists. The finding of microscopic hematuria or, less commonly, proteinuria, in a urinalysis carried out as part of a school screening program is the most frequent "presentation" of IgAN in Japanese children. However, it is possible that many children with IgAN expressed as microscopic hematuria and/or mild proteinuria remain undiagnosed in this country because routine urinalysis is not done and many pediatric nephrologists are reluctant to perform renal biopsies when such children are identified. It is now recognized that some patients with IgAN and nephrotic range proteinuria exhibit a state of steroid responsiveness. The renal biopsy in such patients often reveals "minimal change." Several recent studies have shown progressive deterioration in approximately 10% of all pediatric patients found to have IgAN and in 15% to 30% of the subset of patients with more severe histologic findings. Hypertension and proteinuria are observed frequently in patients who progress to chronic renal failure. It is proposed that multicenter collaborative studies be designed to evaluate proposed therapies for children with IgAN associated with proliferative glomerular lesions, particularly those in whom hypertension, proteinuria, and depressed glomerular filtration rate are found.