Autosomal recessive Alport syndrome caused by disease-causing variants in COL4A3 and COL4A4 had a combined lifetime risk of 2.15 (1.64–2.79; European gnomAD), and 2.65 (2.24–3.12; worldwide gnomAD) per 100,000. Here, COL4A4 is linked to Alport syndrome.