Table 2.

Teaching points

1. X-linked Alport syndrome (XLAS) is the most common form of Alport syndrome, caused by mutations in COL4A5, residing at chrXq22.3.

2. Mosaic staining of type IV collagen alpha5 chain is frequently observed in renal biopsies of female patients with XLAS, but is atypical for male patients.

3. A karyotype analysis is performed to evaluate for concurrent Klinefelter syndrome in male patients with mosaic type IV collagen alpha5 chain staining.

4. Next generation sequencing of COL4A5 is performed to diagnose and confirm somatic mosaicism in male patients.