[Collagen type IV nephropathy: from thin basement membrane nephropathy to Alport syndrome].

INTRODUCTION: Collagen type IV nephropathy includes the Goodpasture syndrome, thin basement membrane nephropathy and the Alport syndrome. Mutations in the coding Col(IV)A3/A4 and Col(IV)A5 genes are probable causes of the latter two. Thin basement membrane nephropathy is mostly familial and has an autosomal dominant inheritance, at least 40% of the families have hematuria that co-segregates with the Col(IV)A3 and/or Col(IV)A4 loci. 85% of Alport syndrome cases are transmitted as an X-linked semidominant form due to Col(IV)A5 mutations. About 14% of Alport syndrome cases exhibit autosomal recessive, and 1% autosomal dominant inheritance, both caused by mutations in the Col(IV)A3 or Col(IV)A4 genes in boys and in girls.

AIM: The co-segregation pattern of hematuria was examined in two families with thin basement membrane nephropathy and one family with the Alport syndrome, using short tandem repeat markers, spanning the Col(IV)A3/A4 and Col(IV)A5 loci to assess their linkage to the clinical symptoms and morphological alterations in the renal biopsy specimens.

METHODS: Markers: Col(IV)A3: CAll and D2S401; Col(IV)A4: HaeIII/RFLP; and Col(IV)A5: DXS456, 2B6 and 2B20.

RESULTS: The hematuria displayed autosomal dominant inheritance and co-segregated with Col(IV)A3 markers in one of the thin basement membrane nephropathy families. In the second, the hematuria did not segregate with the Col(IV)A3/A4 or Col(IV)A5 loci, suggesting the possibility of another genetic locus for the disease. The Alport syndrome exhibited autosomal recessive inheritance and did not link to Col(IV)A5 markers, and the Col(IV)A3/A4 markers were informative only in part.

CONCLUSION: Knowledge of the inheritance and genetic background of collagen type IV nephropathy will be very important in the diagnostics and genetic counseling in the future.