Isochromosome consisting of terminal short arm and proximal long arm X in a girl with short stature

A 16-year-old girl with short stature, short neck, shield chest, and cubitu s valgus was studied. FISH analyses of her structurally altered X chromosom e showed a der(X)(wcpX+,TelXp/Yp+ +,SHOX++,STS++,KAL-, 37A12-,DXZ1+ ,XIST+,97L7++,300O13-,404F18-,417G15-,404F18-, 140A-,TelXq/Yq-), These results, t ogether with the high-resolution banding analysis, indicated her karyotype to be 46,X, der(X) (Xpter-->Xp22.3::Xq22.3--> cen-->Xq22,3::Xp22.3-->Xpter) . The der(X) was an isochromosome, consisting of duplicated terminal short arms and duplicated proximal long arms. This in turn suggested that the chr omosome was formed through pericentric inversion of an X chromosome, follow ed by isochromosome formation through sister chromatid exchange at Xp, clos e to the centromere, Replication R-banding analysis showed that the abnorma l X chromosome was late replicating, Analysis of digestion patterns with a methylation-sensitive restriction endonuclease of the phosphoglycerate kina se 1 gene, located in Xq13.3, indicated that its inactivation patterns were completely skewed. (C) 2001 Wiley-Liss,Inc.