Phenotypic discordance in monozygotic twins with 22q11.2 deletion.
We report on male monozygotic twins with 22q11.2 deletion and discordant phenotypes. The twins had twin-to-twin transfusion syndrome. Twin 1, the smaller of the pair, had Tetralogy of Fallot, a characteristic facial appearance, swallowing dysfunction, anal atresia, short stature, and mental retardation, whereas twin 2 had a characteristic facial appearance but no other signs of the 22q11 deletion syndrome. Fluorescence in situ hybridization analysis showed a microdeletion on chromosome 22q11.2 in both twins. Zygosity analysis gave a probability of monozygosity greater than 99.999%. These observations indicate that environmental factors or postzygotic events play a role in the phenotypic variability in the twins.
Yamagishi
H
H
Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan.
Ishii
C
C
Maeda
J
J
Kojima
Y
Y
Matsuoka
R
R
Kimura
M
M
Takao
A
A
Momma
K
K
Matsuo
N
N
D000015:Abnormalities, Multiple / Q000235:genetics*; D001824:Body Constitution; D002648:Child; D002872:Chromosome Deletion; D002892:Chromosomes, Human, Pair 22; D004062:DiGeorge Syndrome / Q000235:genetics; D004200:Diseases in Twins / Q000235:genetics*; D005145:Face / Q000002:abnormalities; D005260:Female; D005330:Fetofetal Transfusion; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008607:Intellectual Disability / Q000235:genetics; D007621:Karyotyping; D008297:Male; D010641:Phenotype; D011247:Pregnancy; D013771:Tetralogy of Fallot / Q000235:genetics; D014430:Twins, Monozygotic