Familial hematuria: A review

Area of Science:

• Nephrology
• Genetics
• Molecular Biology

Background:

• Familial glomerular hematuria is often caused by COL4A3/COL4A4 gene mutations leading to thin basement membrane nephropathy (TBMN).
• Alport syndrome, caused by COL4A5 gene mutations, is a significant cause of morbidity, characterized by hematuria, proteinuria, and often end-stage renal disease (ESRD).

Purpose of the Study:

• To review the genetic basis, clinical manifestations, and diagnostic approaches for TBMN and Alport syndrome.
• To discuss genotype-phenotype correlations and the influence of modifying factors in these collagen IV-related nephropathies.

Main Methods:

• Review of literature on COL4A3, COL4A4, and COL4A5 gene mutations and associated kidney diseases.
• Analysis of genotype-phenotype relationships in X-linked and autosomal recessive Alport syndrome.
• Discussion of diagnostic standards, including molecular genetic testing.

Main Results:

• COL4A3/COL4A4 mutations cause TBMN in heterozygous carriers and autosomal recessive Alport syndrome.
• COL4A5 mutations cause X-linked Alport syndrome, with genotype correlating to phenotype severity in males.
• Phenotype variability in females is attributed to X-chromosome inactivation; de novo mutations and mosaicism can occur.

Conclusions:

• Molecular genetic testing is essential for diagnosing TBMN and Alport syndrome.
• While genotype-phenotype correlations exist, undefined modifying factors impact disease expression.
• Current treatments, like ACE inhibitors, manage symptoms and delay ESRD, but no causal therapy is available.