The Principles of Clinical Cytogenetics - Extra Materials - Springer

530 Jin-Chen Wang
upd(21)pat
Two cases of paternal UPD for chromosome 21 have been reported (251,252). In both cases, UPD
resulted from de novo formation of a Robertsonian translocation (see Chapters 3 and 9). Both individuals
were phenotypically normal. Paternal UPD 21 does not appear to have an imprinting effect.
upd(22)mat
Maternal UPD for chromosome 22 not associated with mosaic trisomy 22 has been reported in
three cases (253–255). All three phenotypically normal individuals were ascertained via history of
multiple spontaneous abortions and were found to have balanced (22;22) Robertsonian translocations
(see Chapters 3 and 9). Another prenatally diagnosed case with nonmosaic trisomy 22 in placental
tissue and apparently nonmosaic normal 46,XY cells in newborn blood had severe IUGR, first-degree
hypospadias, and other features attributed to prematurity (256). There is no evidence that maternal
UPD 22 has an imprinting effect.
upd(22)pat
A single case of paternal UPD for chromosome 22 was reported in an abstract (257). Again, it was
observed in a phenotypically normal individual with a balanced (22;22) Robertsonian translocation
(see Chapters 3 and 9). Paternal UPD 22 is not likely to have imprinting effect.
upd(X)mat
Maternal UPD for the two X chromosomes in females has been reported in three cases (258,259).
The first two cases were detected by screening a normal population of 117 individuals. The third
patient had Duchenne muscular dystrophy resulting from homozygosity of a maternally inherited
deletion of exon 50 of the dystrophin gene. These observations indicate that maternal UPD for the X
chromosome might not have an imprinting effect.
upd(X)pat
A single case of paternal UPD for the two X chromosomes in the 46,XX cell line of a 14-year-old
girl with 45,X/46,XX mosaicism (see Chapter 10) has been reported (260). This patient had impaired
gonadal function and short stature. The presence of a 45,X cell line makes it difficult to determine if
the observed clinical features in this patient can be attributed to paternal UPD for the X chromosome.
Therefore, it is unknown at this time if paternal UPD X has an imprinting effect.
upd(XY)pat
A single case of paternal contribution of both the X and Y chromosomes in a male patient was
reported in an abstract (261). This patient was ascertained because he had hemophilia A, which was
transmitted from his father. No abnormalities other than hemophilia were described. Paternal UPD
for XY might therefore not have an imprinting effect.
Summary
In summary, of 47 possible maternal and paternal UPDs for whole chromosomes in humans, 34
have been reported. Among them, seven clearly have imprinting effects (6pat, 7mat, 11pat, 14mat,
14pat, 15mat, and 15pat), one potentially has an imprinting effect (16mat), one might have an
imprinting effect (2mat), 19 are unlikely to have imprinting effects [1mat, 1pat, 2pat, 4mat, 5pat,
6mat, 8pat, 9mat, 10mat, 12mat, 13mat, 13pat, 17mat, 21mat, 21pat, 22mat, 22pat, Xmat, and
(XY)pat], and the status is not known for 7pat, 8mat, 16pat, 20mat, 20pat, and Xpat at this time. A
better understanding of the effects of UPD will be possible as more data are accumulated.
Prenatal UPD analysis should be considered when the risk for UPD involving chromosomes with
known imprinting effects is increased. These include the following: