From clinical mimicry to accurate diagnosis: COL4A4-associated nephropathy hidden behind polycystic kidney disease.
Source: PubMed, NCBI / U.S. National Library of Medicine
Type IV collagen related nephropathy caused by heterozygous variants in the COL4A3 or COL4A4 genes shows a wide phenotypic variability, with asymptomatic individuals being relatively common. A cystic phenotype in these cases is uncommon and rarely presents with nephromegaly mimicking autosomal dominant polycystic kidney disease (ADPKD). We report a family with hereditary kidney disease showing an autosomal dominant inheritance pattern and marked phenotypic variability. Some family members were diagnosed with urate nephropathy, others met the Ravine-Pei criteria for ADPKD, and others were labeled as having chronic kidney disease of unknown etiology; five progressed to renal replacement therapy. The proband, who presented with bilateral renal cysts fulfilling ADPKD criteria, along with microhematuria and non-nephrotic proteinuria, tested negative for PKD1 and PKD2 variants after sequential genetic analysis. Meanwhile, another family member studied for persistent microhematuria and non-nephrotic proteinuria underwent a renal biopsy that revealed thinning of the glomerular basement membrane on electron microscopy, suggesting Alport syndrome. Genetic testing in both individuals identified the c.735+2T>C (p?) variant in the COL4A4 gene, classified as likely pathogenic due to its disruption of a splicing site. This case illustrates the phenotypic heterogeneity of heterozygous COL4A4-related Alport syndrome and highlights the importance of implementing genetic testing in the differen
Abstract
Type IV collagen related nephropathy caused by heterozygous variants in the COL4A3 or COL4A4 genes shows a wide phenotypic variability, with asymptomatic individuals being relatively common. A cystic phenotype in these cases is uncommon and rarely presents with nephromegaly mimicking autosomal dominant polycystic kidney disease (ADPKD). We report a family with hereditary kidney disease showing an autosomal dominant inheritance pattern and marked phenotypic variability. Some family members were diagnosed with urate nephropathy, others met the Ravine-Pei criteria for ADPKD, and others were labeled as having chronic kidney disease of unknown etiology; five progressed to renal replacement therapy. The proband, who presented with bilateral renal cysts fulfilling ADPKD criteria, along with microhematuria and non-nephrotic proteinuria, tested negative for PKD1 and PKD2 variants after sequential genetic analysis. Meanwhile, another family member studied for persistent microhematuria and non-nephrotic proteinuria underwent a renal biopsy that revealed thinning of the glomerular basement membrane on electron microscopy, suggesting Alport syndrome. Genetic testing in both individuals identified the c.735+2T>C (p?) variant in the COL4A4 gene, classified as likely pathogenic due to its disruption of a splicing site. This case illustrates the phenotypic heterogeneity of heterozygous COL4A4-related Alport syndrome and highlights the importance of implementing genetic testing in the differential diagnosis of hereditary kidney disorders to prevent diagnostic delays with potential clinical consequences.