Babies with the rare Bannayan-Zonana syndrome (also known as the Riley-Smith syndrome) develop a large head, low muscle tone, intellectual delay, a speckled penis and multiple lumpy growths (hamartomas) on the skin and inside hollow organs (eg. intestine). There is a small risk of the hamartomas becoming cancerous.
The only treatment is surgical removal of the hamartomas that become troublesome. It is related genetically to Cowden disease.