Becker's nevus with ipsilateral breast hypoplasia: improvement with spironolactone.

Ipsilateral breast hypoplasia is a rare abnormality in Becker's nevus. The pathogenesis of the breast hypoplasia is not understood, but an increased level of androgenic receptor in the affected area may play a role. We report a case of Becker's nevus with ipsilateral breast hypoplasia. Spironolactone, an anti-androgenic agent, was tried for treatment of the hypoplasia, and, one month later, breast enlargement was seen in only the hypoplastic breast with Becker's nevus. This finding supports the theory that breast hypoplasia in Becker's nevus is related to an increase in androgenic receptor.