COL4A4 and kidney disorder: On the other hand, the female carriers of the XLS and the carriers of heterozygous COL4A4 and COL4A3 mutations have a better prognosis, featured by a spectrum of phenotypes ranging from a complete absence of signs and symptoms of kidney disease to isolated hematuria, up to progressive renal disease arising in a few cases (Jais et al., 2003; Matthaiou et al., 2020).