Prenatal diagnosis of mosaic distal 5p deletion and review of the literature.

Objective: To present the prenatal diagnosis of mosaic distal 5p deletion and a review of the literature.

Methods: A 37-year-old woman, gravida 2, para 1, underwent genetic amniocentesis at 17 weeks' gestation because of advanced maternal age. Cytogenetic analysis of the cultured amniocytes revealed mosaicism for a distal 5p deletion, mos 46,XX,del(5)(p15.1)/46,XX (23 colonies/23 colonies). Repeat amniocentesis showed a consistent karyotype of mos 46,XX,del(5)(p15.1)/46,XX (12 colonies/15 colonies). The parental karyotypes were normal. Prenatal ultrasound demonstrated microcephaly and cerebellar hypoplasia. The pregnancy was terminated at 21 weeks' gestation. Postnatally, the fetus displayed microcephaly, a triangular face, hypertelorism, epicanthic folds, down-slanting palpebral fissures, low-set ears, and micrognathia. A karyotype of mos 46,XX,del(5)(p15.1)/46,XX was found in the cord blood, liver, lungs, and skin, whereas the placenta had a different karyotype of mos 46,XX,dup(5)(qter-->p15.3::p15.3-->p10)/46,XX, and the karyotype of the amnion was mos 46,XX,del(5)(p15.1)/46,XX,dup(5)(qter-->p15.3::p15.3-->p10)/46,XX,trp(5)(qter-->p15.3::p15.3-->p10::p10-->p15.3)/46,XX. The deletion, duplication, and triplication of the terminal region of the short arm of chromosome 5 were confirmed by the studies of fluorescence in situ hybridization.

Conclusions: The cri-du-chat syndrome can be identified prenatally because of advanced maternal age, familial cri-du-chat syndrome, parental balanced translocations involving chromosome 5, sonographically detected fetal structural abnormalities, and/or an abnormal maternal serum test. Fetuses with the mosaic distal 5p deletion may be associated with the sonographic findings of microcephaly and cerebellar hypoplasia, and fetoplacental and fetoamnionic chromosomal discrepancies.