Pediatric hematuria screening with targeted NGS enables family cascade testing for COL4A nephropathies

Original abstract

BACKGROUND: Type IV collagen-related nephropathies comprise a spectrum of inherited glomerular disorders, with Alport disease representing the most severe phenotype. In children, these conditions often present with isolated hematuria, while progressive kidney disease typically develops later. Early diagnosis may therefore enable timely family-based risk assessment and preventive nephrological care. METHODS: We retrospectively analyzed data about 18 children with persistent microscopic and/or macroscopic hematuria who underwent targeted next-generation sequencing of COL4A3, COL4A4, and COL4A5, with variant classification according to ACMG criteria. Clinical data and family history were reviewed, and cascade testing of relatives was performed when feasible. RESULTS: Pathogenic COL4A5 variants were identified in 12 patients (67%) and likely pathogenic COL4A5 variants in two additional patients. Pathogenic variants in COL4A4 and COL4A3 were detected in one patient each, while two patients harbored only COL4A3 variants of uncertain significance. Glycine-substituting missense variants were the most frequent molecular defect (9/18 cases), whereas loss-of-function variants were identified in 7/18 patients, including variants in COL4A5, COL4A3 and COL4A4. Proteinuria was present in 44% of patients, while kidney function was preserved at diagnosis. A positive family history of kidney disease or hematuria was present in 61% of families, and kidney failure in adult relatives in 28%. Cascade testing identified additional genetically affected relatives in all tested families. CONCLUSIONS: Hematuria in pediatric age may represent an early manifestation of COL4A-related nephropathies and should prompt genetic evaluation. Molecular diagnosis in childhood facilitates identification of affected relatives and supports early surveillance and family-based preventive strategies.