Pseudoisodicentric Xp chromosome [46,X,psu idic(X)(q21.1)] and its effect on growth and pubertal development.
BACKGROUND
Most isodicentric (Xp) and (Xq) chromosomes occur as a mosaic with a 45,X cell line. Patients with a nonmosaic 46,X,idic(Xq) are rare.


METHODS
The first girl was referred at 13 years with a short stature and pubertal delay (M1, P2, A1). Her height was 141.6 cm (-3.1 SDS). Ovarian failure was present. The second girl was referred because of her short stature at 12.5 years. Her height was 142.2 cm (-2.4 SDS). She had spontaneous puberty (M3, P1, A1).


RESULTS
In both girls, conventional karyotyping of lymphocytes revealed an aberrant X chromosome consisting of twice the short arm and a small part of the long arm of the X chromosome [nonmosaic 46,X,psu idic(X)(q21.1)]. FISH analysis of the aberrant X chromosome showed the presence of two centromeres, two copies of the XIST gene and two copies of the SHOX gene.


CONCLUSIONS
The presence of two XIST genes on the isodicentric X chromosome with Xq deletion indicates the inactivation of this chromosome. This inactivation also concerned the pseudoautosomal regions which caused haploinsufficiency of the SHOX genes. The girls were treated with growth hormones. The critical region (Xq23 to Xq28) for the ovarian function was deleted in both patients, but the gonadal function was variable. .
Department of Pediatrics, Leiden University Medical Center, Leiden, The Netherlands.
H J
HJ
van der Kamp
S G
SG
Kant
C A L
CA
Ruivenkamp
A C J
AC
Gijsbers
D
D
Haring
W
W
Oostdijk
D041321:Chromosomes, Human, X; D004392:Dwarfism / Q000235:genetics*; D005260:Female; D006128:Growth / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D009030:Mosaicism; D010053:Ovary / Q000503:physiopathology; D011627:Puberty / Q000235:genetics*; D062085:RNA, Long Noncoding / Q000235:genetics; D012729:Sex Chromosome Aberrations; D012741:Sexual Maturation / Q000235:genetics*; D000074122:Short Stature Homeobox Protein
D018398:Homeodomain Proteins; D062085:RNA, Long Noncoding; C106071:SHOX protein, human; D000074122:Short Stature Homeobox Protein; C077885:XIST non-coding RNA