We report on an 18-month-old boy with an interstitial deletion at 10q23.2-q24.1. This region includes the PTEN gene, mutations of which have been reported to cause Cowden disease. Our patient presented with manifestations of Bannayan-Riley-Ruvalcaba (BRR) syndrome. The BRR syndrome is a rare disorder which presents most commonly in childhood. Cowden disease is a disease of adulthood and is inadequately described in children. Because of the considerable phenotypic overlap between the two disorders, and the cytogenetic and molecular findings in our patient, we suggest that BRR syndrome and Cowden disease are allelic.