[Pure trisomy 9p 47,XX,+ del(9) (q11). Discovery of one cell 46,XX, del(9) (q11) in the father].

A case is reported of "pure" trisomy 9p: 47,XX,+del(9) (q11). The affected 6-year-old girl has moderate psychomotor retardation (IQ near 70), with speech retardation. She is mildly dysmorphic, with the characteristic features of trisomy 9p: a "worried look", a unilateral grin, slant of the palpebral fissures, a globulous nose, brachymesophalangia and the characteristic dermatoglyphic features. The parents karyotypes are normal, except for one cell from the father which had the karyotype 46,XY,del(9)(q11), the implications of which are discussed.