Ten girls with idiopathic short stature (ISS) were clinically reviewed and cytogenetic analysis performed by GTG-banding. Two abnormal karyotypes were identified: mos 45,X/46,XX and mos 45,X/46,X, der(Xp)/46,X,r(X). In the latter, FISH analysis and microsatellite investigation, including intragenic SHOX CA repeat, confirmed the origin of the abnormal structural chromosomes and revealed haploinsufficiency for the SHOX gene. In the remaining 8 patients with a normal lymphocyte karyotype FISH analysis using an alpha centromeric X probe (DXZ1) in buccal smear cells (nuc ish) revealed two further cases of true X mosaicism (DXZ1x2/DXZ1x1). Clinical review of all four abnormal patients with the exception of patient with mos 45,X/46,XX revealed three or more clinical features commonly present in Turner syndrome (TS). Our results reinforce the importance of cytogenetic investigation in all patients with ISS. The SHOX molecular result sustains its correlation with most clinical signs of TS. In those cases where a normal karyotype was observed, cryptic mosaicism should be excluded. A precise etiologic diagnosis may be relevant for the indication of GH therapy in these girls.
Idiopathic short stature; X chromosome abnormalities; Turner syndrome; SHOX; FISH; Mosaicism