Deletions and duplications involving the BRCA1 gene can be found in a substantial proportion of families with inherited risk for breast and ovarian cancer. In this study, Pagnamenta et al identified two affected cousins from the 100,000 Genomes Project who shared a complex 178bp deletion in BRCA1. Due to its size and location, the deletion had escaped detection using multiple testing protocols that had been employed previously. Interrogation of an online database indicated this rare variant was restricted to families with Nepalese origin. The study also highlights the importance of using consistent approaches for deciding how to describe complex variants. (By Dr. Alistair T Pagnamenta, https://jmg.bmj.com/content/early/2024/12/11/jmg-2024-110422 )