J Genet Med.  2009 Jun;6(1):95-99.

Prenatally Diagnosed Uncommon Mosaic Autosomal Trisomy

• Lee BY
• Park SY
• Lee MH
• Kim JW
• Park JY
• Choi EY
• Lee YW
• Oh AR
• Lee SY
• Kim MH
• Ryu HM

Abstract

Prenatal diagnosis of rare autosome mosaicism involvingchromosomes other than chromosome 13, 18, 21 or the sex chromosome is encountered prognostic dilemma during genetic counseling. We report four cases of level III uncommon mosaicism of trisomy 5, 16 and 20,diagnosed prenatally. In case 1 with mosaic trisomy 20, there was a higher mosaic ratio of trisomy 20 in the repeat amniocentesis (62.1%) than in the first (36.6%) with normal fetal ultrasound finding except for a relatively small aorta on a 3-vessel view of the fetal heart. Case 2 showed a low rate of mosaic trisomy 20 (5.25%) in cultured amniocytes but normal karyotype in the repeat amniocentesis, who delivered a normal healthy baby. Case 3 showed a 13.6% of trisomy 16 mosaicism in the 30 cells of cultured amniocytes. Sixty cells from a fetal blood sample at termination showed non-mosaic 46,XX normal karyotype, while skin fibroblasts had 22.5% trisomy 16 in 40 metaphases. The autopsy showed ventricular septal defect (VSD). Case 4 with low grade mosaicism (10.5%) of trisomy 5 resulted in elective termination, though the ultrasoumd showed growsly normal fetus. Although level III mosaicism is regarded as true mosaicism, it is difficult to predict the outcome of the fetus with rare mosaic autosome trisomy. Therefore mosaic autosome trisomy of fetus should be carefully interpreted with more various approaches including repeat sampling and targeted fetal ultrasound.

Keyword

Autosomal mosaicism; Trisomy 5; Trisomy 16; Trisomy 20

MeSH Terms

Amniocentesis
Aorta
Autopsy
Chromosomes, Human, Pair 13
Chromosomes, Human, Pair 16
Chromosomes, Human, Pair 20
Fetal Blood
Fetal Heart
Fetus
Fibroblasts
Genetic Counseling
Heart Septal Defects, Ventricular
Karyotype
Metaphase
Mosaicism
Prenatal Diagnosis
Sex Chromosomes
Skin
Trisomy
Chromosomes, Human, Pair 16
Chromosomes, Human, Pair 20
Mosaicism
Trisomy