Simultaneous occurrence of idiopathic trachyonychia in dizygotic twins.

Trachyonychia (or twenty-nail dystrophy) is an uncommon chronic disorder manifesting as thin, flattened, brittle nails with excessive longitudinal ridging and loss of luster creating a "sandpaper-like" texture that most commonly presents spontaneously in childhood as an isolated phenomenon; however, it has been historically associated with numerous dermatoses. Rarely, trachyonychia has been reported to occur in families, suggesting a potential hereditary predisposition. We report trachyonychia occurring simultaneously in dizygotic twins, further supporting a possible underlying genetic basis of this idiopathic nail disorder.