A girl with mosaicism for a dicentric X chromosome (45,X/46,X,dic(X) (Xqter to p22::p22 to qter)).

A 12-year-old girl was examined for growth retardation and a few very discrete dysmorphologic stigmata of Turner's syndrome; the genitalia were infantile yet both ovaries possessed functioning follicles. R- and C-banding techniques and Brdu treatment demonstrated a 45,X formula in 95% of lymphocytes, with 5% presenting a 46,X,dic(X) formula. Cytogenetic and clinical problems raised by this observation are discussed in relation to data from the literature.