title: Trisomy 7 mosaicism prenatally misdiagnosed and maternal uniparental disomy in a child with pigmentary mosaicism and Russell- Silver syndrome.
abstract: Prenatal diagnosis of true mosaic trisomy 7 is rare in amniotic fluid and can be misinterpreted as pseudomosaic. The phenotype is highly variable and may be modified by a maternal uniparental disomy of chromosome 7 leading to mild Russell-Silver syndrome (RSS). We report here the third postnatal case of mosaic trisomy 7 with maternal uniparental disomy of chromosome 7 in a boy presenting a mild RSS. Fetal karyotype performed in amniocentesis for intrauterine growth retardation was considered normal. Mosaic trisomy 7 was diagnosed after birth, on fibroblasts karyotype performed for blaschkolinear pigmentary skin anomalies and failure to thrive. Maternal uniparental disomy of chromosome 7 was observed in blood sample. Retrospectively, trisomic 7 cells were identified in one prenatal long-term flask culture revealing a prenatal diagnosis failure. This report emphasizes the difficulty of assessing fetal mosaicism and distinguishing it from pseudomosaicism in cultured amniocytes. It is important to search for uniparental disomy as an indirect clue of trisomy 7 mosaicism and a major prognosis element. Although there are only few prenatal informative cases, detection of trisomy 7 in amniocentesis appears to be associated with a relatively good outcome when maternal uniparental disomy has been ruled out.
authors.affiliation: Service de Génétique Clinique, Hôpital Jeanne de Flandre, CHRU, Lille, France. florence.petit@chru-lille.fr
authors.forename: F
authors.initials: F
authors.lastname: Petit
authors.forename: M
authors.initials: M
authors.lastname: Holder-Espinasse
authors.forename: B
authors.initials: B
authors.lastname: Duban-Bedu
authors.forename: S
authors.initials: S
authors.lastname: Bouquillon
authors.forename: O
authors.initials: O
authors.lastname: Boute-Benejean
authors.forename: A
authors.initials: A
authors.lastname: Bazin
authors.forename: V
authors.initials: V
authors.lastname: Rouland
authors.forename: S
authors.initials: S
authors.lastname: Manouvrier-Hanu
authors.forename: B
authors.initials: B
authors.lastname: Delobel
mesh_terms: D000649:Amniocentesis; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D005260:Female; D005317:Fetal Growth Retardation; D006801:Humans; D059785:Karyotype; D008297:Male; D009030:Mosaicism; D011247:Pregnancy; D011296:Prenatal Diagnosis; D056730:Silver-Russell Syndrome / Q000175:diagnosis* / Q000235:genetics; D014314:Trisomy / Q000175:diagnosis* / Q000235:genetics; D024182:Uniparental Disomy / Q000175:diagnosis* / Q000235:genetics