Familial juvenile hypertrophy of the breast (JHB) is a rare condition characterized by gigantomastia in peripubertal females. The pathology is limited to the breast with otherwise normal growth and development (summary by Genzer-Nir et al., 2010). A syndrome has been described in which affected females display JHB in association with onychodystrophy/anonychia and abnormalities of the distal phalanges (ODP; see 106995), whereas males have only ODP (mammary-digital-nail syndrome; 613689). [from OMIM]