Undescended testes or cryptorchidism is when one or both testes do not move down into the scrotum once developed. Found in 1.6 to 9.0% of boys, if left untreated, it can increase the risk of testicular cancer or infertility. We describe a family with four boys born with undescended testes. We identified a genetic change in the RXFP2 gene – present in two copies in the affected boys and in one copy in each unaffected parent. This genetic change causes the RXFP2 protein to lose its function. We conclude that changes to the RXFP2 gene can cause cryptorchidism in families. (By Dr. Katie Ayers, https://jmg.bmj.com/content/early/2019/06/05/jmedgenet-2019-106203 )