Digenic Alport Syndrome in Children: A Systematic Review of Case Reports and Case Series

Abstract

Background: Alport syndrome comprises inherited heterogeneous disorders involving kidneys with varying combinations of ocular pathologies and hearing loss. Digenic Alport syndrome is a pathologic variant of Alport syndrome in which there is a mutation in two out of three mutations in type IV collagen (COL4A) genes, either COL4A5 with COL4A3/COL4A4, or pathogenic variants in COL4A3 with COL4A4. There are scarce data regarding the genotype–phenotype associations in children with digenic Alport syndrome. Objective: The present systematic review focuses on clinical presentations, genetic abnormalities, pharmacological management, and associated extrarenal manifestations in digenic Alport syndrome. Methods: A comprehensive search was done in major databases, such as PubMed and Google Scholar, using defined search terms encompassing case reports or case series on digenic Alport syndrome. The identified reports underwent screening by two different authors for inclusion and exclusion criteria. Results: Thirty-one cases were included, showing that the mean age at diagnosis was 6 years. Microhematuria was the most common kidney manifestation (80%), followed by nephrotic/nephritic range proteinuria (74%), while extrarenal features were a rare finding. The main diagnostic modality was genetic testing with specific findings on electron microscopy, such as thinning of the basement membrane (73.3%). Focal segmental glomerulosclerosis was the most common finding on light microscopy (50%). A missense mutation was the most common genetic mutation present in 64% of cases. The patients were primarily managed with medical management initially with no data regarding follow-up. Conclusion: The digenic phenotype of Alport syndrome presents with a mean age earlier than the other variants, with hematuria and proteinuria being the most common presentations, with rare extrarenal involvements. Furthermore, the most common genetic abnormality associated with the digenic variant of Alport syndrome is a missense mutation.

Keywords

• hearing loss
• hematuria
• kidney
• mutation in type iv collagen 3
• mutation in type iv collagen 4
• mutation in type iv collagen 5
• pediatric
• proteinuria