Trisomy 12 mosaicism in amniocytes and dysmorphic child despite normal chromosomes in fetal blood sample

Abstract

Trisomy 12 mosaicism (44 per cent) was detected prenatally in cultured amniocytes. A cordocentesis was performed to confirm the result. Only normal cells were found in the fetal blood sample. The fetus was estimated to be at a low risk of having a chromosomal abnormality and the pregnancy continued. Eight days after birth, a congenital heart defect was detected in the child. Several dysmorphic features were also evident. Further karyotyping of different tissues revealed normal blood and urinary cells but trisomic cells in the placenta (100 per cent) and in skin fibroblasts (25 per cent). The child died at 5 weeks of age. In this case, the fetal blood sample failed to reveal the real chromosome constitution of the fetus.

Low-level mosaicism for both trisomy 15 and monosomy-X in amniotic fluid cells confirmed in fetal tissues

“…In our case, only metaphases with a normal karyotype were observed in the fetal lymphocytes. The present results, together with several other reports in the literature (e.g., von Koskull et al, 1989;Wyandt et al, 1990) clearly show that a normal chromosome complement in fetal lymphocytes does not exclude the existence of true fetal mosaicism in other tissues. In a recent review of rare trisomy mosaicism diagnosed in amniocytes, Hsu et al (1997), concluded that for less frequent trisomies, a cordocentesis is of limited value for further evaluation of true fetal mosaicism; except in cases of mosaicism for trisomy 8 and 9.…”

Four children with postnatally diagnosed mosaic trisomy 12: Clinical features, literature review, and current diagnostic capabilities of genetic testing

“…Eleven patients with mosaic trisomy 12 diagnosed prenatally have also been reported (Brosens, Overton, Lavery, & Thornton, ; Chen et al, ; Chen et al, ; Chen, Chang, Su, Chen, & Wang, ; Chen, Su, et al, ; Frohlich & Falk, ; Leschot, Wilmsen‐Linders, van Geijn, Samsom, & Smit, ; Meck et al, ; Spiro, Rita, Jazmines, Jones, & Booth, ; Staals, Schrander‐Stumpel, Hamers, & Fryns, ; Von Koskull et al, ). Table summarizes the clinical features in those patients.…”

Pallister‐Killian syndrome: A mild case diagnosed by fluorescence in situ hybridization. Review of the literature and expansion of the phenotype

“…Sometimes the i(12p) was misinterpreted as i(21q) [Hunter et al, 1982;Lopes et al, 1985;Kwee et al, 1984;Fryns et al, 19821 and in one case tetrasomy 12p was misinterpreted as trisomy of chromosome 20 [Pan et al, 19761. It is found in high percentage in skin fibroblasts [Kawashima, 1987;Narahara et al, 1988;Peltomaki et al, 1987;Priest et al, 1992;Reynolds et al, 1987;Soukup and Neidich, 1990;Speleman et al, 1991;Tejada et al, 19921, amniocytes, and bone marrow cells [Reeser and Wenger, 1992;Von Koskull et al, 1989;Ward et al, 19881. It is found in high percentage in skin fibroblasts [Kawashima, 1987;Narahara et al, 1988;Peltomaki et al, 1987;Priest et al, 1992;Reynolds et al, 1987;Soukup and Neidich, 1990;Speleman et al, 1991;Tejada et al, 19921, amniocytes, and bone marrow cells [Reeser and Wenger, 1992;Von Koskull et al, 1989;Ward et al, 19881.…”