Pathogenic variants in <i>PAX</i> genes underlie diverse congenital disorders such as aniridia (<i>PAX6</i>), renal coloboma syndrome (<i>PAX2</i>), otofaciocervical syndrome with immunodeficiency (<i>PAX1</i>), Waardenburg syndrome (<i>PAX3</i>), maturity-onset diabetes of the young (<i>PAX4</i>), and tooth agenesis (<i>PAX9</i>). Here, PAX4 is linked to immunodeficiency disease.